ESE's works engine tuner

[Maxdelta]

What was that original pic Max? Not an RM250 as obviously oil injection. So guessing RG250. 1/2 Reed barrel so you don't need monster inlet area and you can get heaps normally. I'd concentrate on anything else.

Like re-engineering the crank to use better rods if you want to rev it a bit more.


Dave,
Its a Suzuki snow cylinder (Arctic Cat 580).

[Maxdelta]

Thanks Wob,
This cylinder has the C ports ducts that are fed right along the outside of the intake port, so there is minimal meat there to widen the port. Also, no room left to lower or raise the port. Hence my looking into the possibility of removing the bridge. The stock bridged intake port width is ~68% of bore. Maybe there's not much left that can be done to this port? I could square off the bottom corners to gain some more area, and I can widen approx. 1mm per side.

356886356887

[wobbly]

Depends on how the intake STA sits in comparison the the Blowdown , and the amount you would gain by increasing the Intake duration ( cut the skirt ) - against loosing bottom end.
Use JanBros spread sheet and analyze the ports.

[katinas]

.
356885

An interview with Dane Rowe, a hottie from the 60's

https://rocinantemecanico.blogspot.com/2012/04/surprise-guest-my-interview-with-dane.html

Great interview.

Thanks

[Frits Overmars]

An interview with Dane Rowe, a hottie from the 60's
https://rocinantemecanico.blogspot.com/2012/04/surprise-guest-my-interview-with-dane.htmlI always admired Dane Rowe and I enjoyed the interview but if I'm not mistaken your picture does not show Dane Rowe but Dutch sidecar passenger Anneke Mak.

[Maxdelta]

Depends on how the intake STA sits in comparison the the Blowdown , and the amount you would gain by increasing the Intake duration ( cut the skirt ) - against loosing bottom end.
Use JanBros spread sheet and analyze the ports.

I'm using Engmod. Basically i can't get enough intake STA. Blowdown and transfers are at ~120hp each. Intake is ~80hp. If removing the bridge isn't an option, then it seems my options are to square off the bottom corner radii and cut the piston skirt. Which leads me to ask....what's a reasonable amount you can remove from the skirt? Would 2.5-3mm be asking for trouble? Thanks for all the assistance.

[katinas]

I'm using Engmod. Basically i can't get enough intake STA. Blowdown and transfers are at ~120hp each. Intake is ~80hp. If removing the bridge isn't an option, then it seems my options are to square off the bottom corner radii and cut the piston skirt. Which leads me to ask....what's a reasonable amount you can remove from the skirt? Would 2.5-3mm be asking for trouble? Thanks for all the assistance.

I remember there was always a dilemma with piston ported engine intake, where to go from std, cut the piston or lowered intake port bottom or just lift the roof. But in any case dont remove the bridge as Wobb advised.
My last experience with piston ported engine was in 1998 with 340 cc single cylinder engine for road race with wide bridge, served as a C channel.
Best final results was nearly std intake ports roofs and bottoms just widened, but huge piston skirt cut ( step by step 3mm then 6 mm and finally 10mm).
I cant remember accurate duration aprox 190. Main advantage over port grinding ( bottom and roof) is that the piston skirt remains hidden from the suction flow for a longer period of time (similar to disc valve long cut).
And bridged port not only save engine, but allows you to make the bottom edges sharp, which, together with piston inside intake skirt sharp edge resist for reverse flow better.

[wobbly]

If you are using EngMod then its real easy to see the effect of cutting the skirt on bottom end power as you approach equality in STA with the Blowdown.
You can also adjust the intake length to see if power can be gained by increasing the air column and thus ram into the open port.

[JanBros]

Use JanBros spread sheet and analyze the ports.

sadly, there is nothing in it for the intake to analise. reedvalve only.

[wobbly]

Sorry JanBros , didnt realize.
But further on the intake scenario , the old TZ350 responded real well to cutting the skirt around 2mm and lengthening the tract 20mm with a plastic spacer from the 250 model.
And how close to the ring is the port top at BDC - can you ditch the bottom ring and grind that much upward - depends upon the skirt length a TDC.

[Peljhan]

I am wondering. If we have an engine with matching STAs let's say 30hp for each system (intake, transfers and exhaust) and we measure 30hp on a dyno.
Than we make-increase STA on one of the systems to 40hp. What would we measure teoretically?

[wobbly]

As long as everything in your sim is capable of achieving the 30 Hp of the STA prediction, depending upon the inertia of the vehicle components and the friction component, then you
will measure something like 14% less on a rear wheel Dynojet = 25.8RWHP.
EngMod calculates crank power - so if you now upgrade every part of the engine ( not just change the ports ) then the same applies to the new prediction.
Note the Exhaust STA is pretty much irrelevant ( except when using the duct exit radio button shortcut ), its the Blowdown that is highly important.

[katinas]

Sliding pipes from eighties. I just wonder when they really started using it.

From 21:21- https://youtu.be/2RZ86QoA-qI?si=ZuxwBLNCCw_762ih

From 0:35 https://youtu.be/D1e_vKt8Va0?si=lATwZp9HRV_D4QAw

[Jonny snatchsniffer]

I know most of you on here dont like air cooled 2 strokes because of thermal limitations, but i have what i have, its a 200cc lambretta piston ported no reed, the intake is only 153.5, exhaust angle 180, a and b transfers at 120, boost port 122.5, now im using a pipe from the 80's which has a long parallel header, also a 28mm pwk, the inlet is bridged, tz350, you probly know about the ported stuff, tho saying that most of us have been there done that, but my thing is Italian shopping bikes, and wobbly, when you worked with Jim did you do any of the scooter, like the jl3, jl4 lambretta pipes? And could they be improved upon?
I dont have engine mod and just threw it together with the above timings and thrashed the fuck out of it 140M to a rally but runs out of puff at 8000rpm @76mph gps
I know its over 60 yrs old but I'd like get more out of it
My 125 1966 vespa has 27 rwhp so surely I can get more out of a 200, thi over square at 58x66
So what should I be doing in my man cave to get it singing a bit more? I'm also stud limited and single chef hat exhaust port

[wobbly]

The scooter pipe thing happened after I left JL.

[Gradella23]

The scooter pipe thing happened after I left JL.

hello Wob, any sneak peek on the newcoming Kz R3? I saw Franco joined LKE, i was quite shocked

[Wos]

I know most of you on here dont like air cooled 2 strokes because of thermal limitations, but i have what i have, its a 200cc lambretta piston ported no reed, the intake is only 153.5, exhaust angle 180, a and b transfers at 120, boost port 122.5, now im using a pipe from the 80's which has a long parallel header, also a 28mm pwk, the inlet is bridged, tz350, you probly know about the ported stuff, tho saying that most of us have been there done that, but my thing is Italian shopping bikes, and wobbly, when you worked with Jim did you do any of the scooter, like the jl3, jl4 lambretta pipes? And could they be improved upon?
I dont have engine mod and just threw it together with the above timings and thrashed the fuck out of it 140M to a rally but runs out of puff at 8000rpm @76mph gps
I know its over 60 yrs old but I'd like get more out of it
My 125 1966 vespa has 27 rwhp so surely I can get more out of a 200, thi over square at 58x66
So what should I be doing in my man cave to get it singing a bit more? I'm also stud limited and single chef hat exhaust port

In germany there is a very good old scooter specific forum called german scooter forum (gsf)

If you ask your questions there even in english i am pretty sure you find specific help:2thumbsup

But its always worth to stay here, listen what others do in the big 2 stroke world ;)

https://www.germanscooterforum.de/

Grüße Wolfgang

[wobbly]

Grad, the R3 pipe /manifold/porting changes I worked on for a couple of months were sent of to Franko several months before the World Cup.
I heard nothing back - very unusual, then I received an email from the Flenghi brothers the day after the Cup finished, saying he was no longer at TM.
I got several spies on the job and found out he had gone to Lenzo.

Still no word from him at all - except a small pic of the new LKE Rev1 homologation stamp on Instagram.
He's now working in Mafia land big time, so should be very careful.
He has been beaten by independent tuners for some time now - maybe that is the root cause.

TM want me to sign an NDA , but I still have not seen any results from my new manifold or pipe testing.
They have agreed to pay me, thats some consolation, but being treated like a leper doesnt go down well - they simply ignor any conversation about what happened with Franco or the tests.
I do wonder if I designed the LKE pipe and didnt even know i did it.

[Flettner]

Grad, the R3 pipe /manifold/porting changes I worked on for a couple of months were sent of to Franko several months before the World Cup.
I heard nothing back - very unusual, then I received an email from the Flenghi brothers the day after the Cup finished, saying he was no longer at TM.
I got several spies on the job and found out he had gone to Lenzo.

Still no word from him at all - except a small pic of the new LKE Rev1 homologation stamp on Instagram.
He's now working in Mafia land big time, so should be very careful.
He has been beaten by independent tuners for some time now - maybe that is the root cause.

TM want me to sign an NDA , but I still have not seen any results from my new manifold or pipe testing.
They have agreed to pay me, thats some consolation, but being treated like a leper doesnt go down well - they simply ignor any conversation about what happened with Franco or the tests.
I do wonder if I designed the LKE pipe and didnt even know i did it.

Welcome to the club, at least you are getting paid.

[Frits Overmars]

... I received an email from the Flenghi brothers the day after the Cup finished, saying he was no longer at TM.
I got several spies on the job and found out he had gone to Lenzo. He's now working in Mafia land big time, so should be very careful.
I do wonder if I designed the LKE pipe and didnt even know i did it.Been there, know the feeling. About 20 years ago my friend Roland Holzner, after designing the Maxter kart engine, got an offer he couldn't refuse from Lenzo. He flew me in as well. When things got less pleasant, Roland's laptop, with my software on it, was stolen from his apartment. When he tried to rapport the theft to the local police, he was told that he couldn't, because he was not the rightful tenant of that apartment. He was shown a document stating that the apartment was rented out to Lenzo. The ink on that document was still wet and why would Lenzo rent an apartment that he already owned?
During this episode I had a whole hotel in the village of Brolo, Sicily (where Franco Drudi is staying now) to myself, owned by Lenzo and occupied by just me, the hotel staff and the biggest cockroaches you ever saw.

In case you're interested in the technical side of things, we worked on a cylinder that may look kinda familiar now. But at the time the local experts told us that it could never work because the auxiliary exhaust ports were twice as large as they had ever tested. And there was also a hump in the exhaust duct floor that 'confused the flow'.
Nice detail in the picture below: notice the broken-off M6 tap, top left. Just think what could have happened if the machine saw blade had hit that tap a little more head-on...
Anyway it paints a nice picture of the work quality.
356895

[Storbeck]

Been there, know the feeling. About 20 years ago my friend Roland Holzner, after designing the Maxter kart engine, got an offer he couldn't refuse from Lenzo. He flew me in as well. When things got less pleasant, Roland's laptop, with my software on it, was stolen from his apartment. When he tried to rapport the theft to the local police, he was told that he couldn't, because he was not the rightful tenant of that apartment. He was shown a document stating that the apartment was rented out to Lenzo. The ink on that document was still wet and why would Lenzo rent an apartment that he already owned?
During this episode I had a whole hotel in the village of Brolo, Sicily (where Franco Drudi is staying now) to myself, owned by Lenzo and occupied by just me, the hotel staff and the biggest cockroaches you ever saw.

In case you're interested in the technical side of things, we worked on a cylinder that may look kinda familiar now. But at the time the local experts told us that it could never work because the auxiliary exhaust ports were twice as large as they had ever tested. And there was also a hump in the exhaust duct floor that 'confused the flow'.
Nice detail in the picture below: notice the broken-off M6 tap, top left. Just think what could have happened if the machine saw blade had hit that tap a little more head-on...
Anyway it paints a nice picture of the work quality.
356895


Bit of a tangent, but your comment about being told that the large auxiliary exhaust ports were too large reminds me of a thing I've long wondered about. I've seen several examples of cylinders with super tiny auxiliary exhaust ports. Always wondered why on earth they would bother to add auxiliary ports and then make them so small. My assumption is that there is something that can be done "wrong" with auxiliaries to make them have negative affects, the designers of those cylinders unknowingly did that, and ended up testing smaller and smaller auxiliaries until that negative affect went away. But I have no idea.

[Frits Overmars]

... your comment about being told that the large auxiliary exhaust ports were too large reminds me of a thing I've long wondered about. I've seen several examples of cylinders with super tiny auxiliary exhaust ports. Always wondered why on earth they would bother to add auxiliary ports and then make them so small...In the beginning (let's give this a biblical twist) there were no auxiliary exhaust ports. Then Jan Thiel changed history, and others began to copy him, drilling small channels while trying to avoid the cylinder studs and the cooling system. Those local experts in Brolo, Sicily had never even tried decently-sized aux ports. They just went by what they had seen until then and from that they 'knew' that ours were too large.

You can go wrong with large auxiliary ports. Piercing the cooling system is not good practice and neither is combining effective aux ports with directionally unstable scavenging, or with piston skirts that open the aux ports around TDC. Smaller aux ports can avoid such problems but that's not the best solution if you want to make a powerful engine.

[wobbly]

Having not had any response from my many attempts to contact Franco , and receiving no feedback from the Flenghi brothers Filippo /Thomas I contacted a friend
Marc Marcelet.

He is also a very good friend of Roland and he has asked him to contact Filippo in person ( in Italian as he speaks little English ).
They have agreed to fulfil my normal " contract " for the R3 development work, but I fear I have been " tarred with the same brush as Franco " and am now PNG.

Really pisses me off, having started working with Claudio well over a decade ago and I have turned down work from others feeling loyalty to TM with such a long association.
We shall see what Roland can find out - I know he worked at TM, but Franco never had a kind word to say - nothing unusual about that though.

The latest info is that Franco was fired as he was spending all his time trying to get his own KZ engine homologated, ran out of time, and the Lenzo thing is just a stop gap.

[diesel pig]

When I read my copy of Jan Thiel's Book he hinted it was hard to work with the Italilans. But I now understand he was playing it down.

[Jonny snatchsniffer]

In germany there is a very good old scooter specific forum called german scooter forum (gsf)

If you ask your questions there even in english i am pretty sure you find specific help:2thumbsup

But its always worth to stay here, listen what others do in the big 2 stroke world ;)

https://www.germanscooterforum.de/

Grüße Wolfgang

I've been on gsf but translate is shite, mathias scherer use tovmake me pipes for the vespa, also having read all of the rsa thread, and all of this thread which after all is about buckets and, started by tz30 to explore the limitations and from getting to 30hp from his air cooled bucket
I intend to do the same but from something even older, as its a 2 stroke no matter my starting point surely all the rule apply, ask a simple question on say port roof angles or things like that, you get on the uk forums at least, the ones that dont know talk shit and the ones who do won't say, for example on 2 uk sites its been advised that the piston at bdc is ok at 2mm above the floor but dont ever have it lower, on here ideas are floated freely, (shame on ktm)
However having read all this, my memory is shit and forgotten 99% of it, its not big at 198cc but bigger than the 50s

[husaberg]

I am almost feeling guilty about bringing this up, as they are Italian.

But I am looking for a not so common Brembo caliper for a pre-89 project.

I know I can buy a new repo or get one close enough like a ktm60/65, but as I am in pretty deep now and a bit of an anorak.

As best as i can discover they were oem on a few bikes of the late 80s and early nineties they are a Brembo calipers As used on the TY250, Aprilia Climber, Montesa Cota, and I think a few others, like I possibly husky al ktm Gas Gas .and Fantic.


DR50 Big.

Grimeca and AJP later made a similar one used on a lot of debris, like the Senda and the early ubiquitous early 98 to 01 KTM 60/65. Which if i can't find a cheap one ,is what i will have to use.

Anyone have a lead on one or know other bikes that have them? i found a few but Shipping on eBay from the EU or US is almost criminal or the sellers dont want to?
I tried the usual cross matching through pads etc but they used similar pads on other Brembo and Grimecas?

They look very similar to a Yamaha RD350 caliper only smaller and not cast iron the Yamaha ones which i always thought was a licensed Lockheed Copy?
The Brembo also have square pads.

pic to be attached if KB lets me.
356896356897

[ranasada]

Having not had any response from my many attempts to contact Franco , and receiving no feedback from the Flenghi brothers Filippo /Thomas I contacted a friend
Marc Marcelet.

He is also a very good friend of Roland and he has asked him to contact Filippo in person ( in Italian as he speaks little English ).
They have agreed to fulfil my normal " contract " for the R3 development work, but I fear I have been " tarred with the same brush as Franco " and am now PNG.

Really pisses me off, having started working with Claudio well over a decade ago and I have turned down work from others feeling loyalty to TM with such a long association.
We shall see what Roland can find out - I know he worked at TM, but Franco never had a kind word to say - nothing unusual about that though.

The latest info is that Franco was fired as he was spending all his time trying to get his own KZ engine homologated, ran out of time, and the Lenzo thing is just a stop gap.


did you know that TM was sold to a fund, the same one that owns the OTK group (tonykart/vortex) & vegatyres?

[wobbly]

Several people with Tinfoil hats have said its a "Mafia " fund - just conjecture I imagine.

[crbbt]

I am wondering if anyone has experienced having a carb needle snap?

On my PWK. I've recently snapped two through a clip slot.

Seems to happen after landing a jump

I am guessing it's either a worn slide or the body.

But before I order another needle and a new slide. thought I would ask

[F5 Dave]

That's some weird shit. I had some debris fall in (trackside jetting) ans it caused the needlejet damage so it would scratch and hang up a needle (ie stick) had to turn up a new insert.
But snap??? That's weird. Genuine PWK not a clone?

[wobbly]

In the Dellorto 30mm carbs I use they have a washer sitting on the clip, and the screw in needle holder has a spring that pushes down on that washer.
Thus the needle can float.
It does of course and that wears the needle parallel and the tube, eventually making the transition and mid go rich.

The cure was to put a washer on both sides of the clip, insert the holder loosely and fit the slide.
Then push the slide up and down a few times and lock the holder.
This clamped the needle in place.

It did two things - eliminated the wear issue, and weirdly it reduced deto, allowing leaner mains and higher EGT.

[Wos]

I am wondering if anyone has experienced having a carb needle snap?

On my PWK. I've recently snapped two through a clip slot.

Seems to happen after landing a jump

I am guessing it's either a worn slide or the body.

But before I order another needle and a new slide. thought I would ask

There are many adtermarked and copy pwk in the universum Needles and clips too.
Some needles are of bronze / cusn with clips that look that they ar made of brass or copper berylium..

CUSN is not very break ressitant...and the brass clips loose tension very quick.

Mayby the clip slots have been worn out before breaking?

Steel clips as in keihin origina dont loose tension and keihin needles have best precision

Grüße Wolfgang

[Frits Overmars]

I am wondering if anyone has experienced having a carb needle snap? On my PWK. I've recently snapped two through a clip slot. Seems to happen after landing a jump. I am guessing it's either a worn slide or the body. But before I order another needle and a new slide. thought I would askA throttle slide tends to tilt slightly backward-forward due to the inlet flow pulsations it is subjected to. And as you guessed, this tilting becomes worse as the slide and/or the carb body become worn out.
In some throttle slide-needle combinations the needle fits so tightly in the slide that it cannot accommodate this tilting. The needle is then subjected to bending stresses and breaks at its weakest point: at one of the notches for the clip. The needle then remains in the throttle closed position while the slide is open, resulting in a lean mixture and a seizure.

You could enlarge the needle bore in the slide, but I'd leave a short piece of the original narrow bore, so the needle is still centered but can swivel just the same.

[crbbt]

Thank you for the replies.

Genuine Keihin, Yamaha needle

I've pulled the carb down. I can't see anything obvious.

The needle in carb in the other CR appears to have the same amount of movement (front, back, side to side)

Nothing money can't fix :rolleyes:

[TZ350]

.
356918 356919

1980 Suzuki GP125. Tried a power jet cut off on the old Suzuki. Used an air solenoid that was triggered at 11,500 rpm to collapse the fuel being drawn up the power jet tube.

Idea worked pretty well, red line. It will be interesting to see if the extra drive is noticeable on the track this weekend.

[ApolloMotoMoto]

Another interesting bit to add...

Attempting to do some further research and I tried to explicitly point google search AI at the kiwibiker.co.nz domain for a directed search and it returned this:

"The search returned no results, likely due to the website being unreachable or inaccessible at this time, as indicated by previous search results suggesting connectivity issues with the domain. I am unable to access the content of the forum to verify if the specific terms you requested are present."

Interesting, no?

[ApolloMotoMoto]

Tried a few different ways to get the google search API to reach Kiwibiker.co.nz, but apparently its innacessable, and apparently there are many other reports of innacessability to this domain from other users.

[bad'rule]

doing good from my part here in Malaysia , they happened to me before, usually it just coverage problems. Especially on school holidays, connection will go very lame or not moving at all.

Sent from my RMX1911 using Tapatalk

[pete376403]

This turned up on my FB feed this morning

[husaberg]

This turned up on my FB feed this morning
maybe Jan will add some translation ans text ad some more pis this is alli have
https://www.kiwibiker.co.nz/forums/album.php?albumid=4944

[JanBros]

maybe Jan will add some translation ans text ad some more pis thisis alli have

I'm a Jan :confused:
there is nothing technicaly interesting in the text, it is what we would call nowadays "clickbait" news : an article based on a photo that tell's you no more than what you can see in the picture.
I presume those days they already had some crowdfunding that raised 16.000 gulden (1 gulden is slightly less than half an euro) and there is some little talk about the successes of 1968-69-70 and the preparation for the next season.
what strikes me the most in the article is that at that time, aparently they didn't have an hydraulic press, for example to rebuilt cranks.

[Frits Overmars]

an article based on a photo that tells you no more than what you can see in the picture.Except: the picture is lying! Jan Thiel never intended to place the exhaust pipe above the engine but he did not want to give anything away at that stage, so for this photo he rotated the cylinder 180°, with the exhaust port on top.

[pete376403]

More from FB. The text accompanying it is obviously AI generated as this engine is described as a 350 twin (so I left that off)

[Peljhan]

I do some manual machining for my projects and I am wondering how were the outer radiuses on engine mounts made on this Jamathi engine?
I have some ideas, but want to know how it was made back in a day?

[wobbly]

Just as easy now as it was back then. The case supported thru the mounting hole in a 3 Jaw on a dividing head set vertically - with a long series cutter machining the whole surface in
several passes.

[husaberg]

Jamathi

https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131025140#post1131025140 (https://www.kiwibiker.co.nz/forums/showthread.php/145224-Race-chassis?p=1131025140#post1131025140)

https://www.elsberg-tuning.dk/jamathi.html

[Flettner]

I do some manual machining for my projects and I am wondering how were the outer radiuses on engine mounts made on this Jamathi engine?
I have some ideas, but want to know how it was made back in a day?

Cast them.

[husaberg]

I do some manual machining for my projects and I am wondering how were the outer radiuses on engine mounts made on this Jamathi engine?
I have some ideas, but want to know how it was made back in a day?


Cast them.

Go all Bert Munro and use a file.
note these conrods
356969356970
later ones were caterpillar axels heated up power hammered into a fillet holes machined and roughed out but then finished with handtools
i think he could knock out one in a weekend.
Early ones were i think from ford truck axles.

[ApolloMotoMoto]

Unintended Post

[ApolloMotoMoto]

I am attempting to track down an ignition coil that may not exist, or may be quite rare.... (or it might be very common but no one really knows what it is...).

I need CDI ignition coils for a project I am working on with ....really low.... inductance values.

I know Wayne uses high(ish) inductane Crane Cams PS91 coils for the 2-into-1 IgniTech DC-CDI setup to pump up the amps driven into the spark kernel.

But, I am playing with a different... expression... of the CDI circuit; and I am tuning for a faster rise time for the first high kV spike that "strikes the arc" (in addition to dumping some decent amps into the damped oscillation "tail"...)

The expression of the circuit I am playing with drives a requirement for ...medium... turns ratio in like the 30-60:1 range and LOW inductance....

Like uH scale primary and mH scale secondary. Anything over 1 Henry on the secondary is useless for my efforts...

IgniTech is one of the only people on the planet that publish inductance numbers with their coils; unfortunately no secondary inductance reported for the IC-CDI-F; but with its 80 uH primary inductance it is in a class of coils that are so rare they might as well not even exist.


Anyone of you know where I can find coil that are in the same "family" as the IgniTech IC-CDI-F, and by that I mean EXTREMELY low inductance?

I am really tring to see if I can find anything confirmed lower inductance than the IC-CDI-F ....anywhere on the planet..... before I go have custom coils wound.

[katinas]

Anyone of you know where I can find coil that are in the same "family" as the IgniTech IC-CDI-F, and by that I mean EXTREMELY low inductance?

I am really tring to see if I can find anything confirmed lower inductance than the IC-CDI-F ....anywhere on the planet..... before I go have custom coils wound.

Honda NS400\250 small type CDI coil MP 02, with primary 0,18 ohm, but secondary 4,1 k ohms.
https://www.ebay.co.uk/itm/183162158215?_skw=honda+ns+400+coil&epid
https://www.ebay.co.uk/itm/177335855786?_trkparms=amclksrc

[TZ350]

.

2Stroke Stuffing. Claims 26 HP on pump gas:- https://youtu.be/bRRIXnkRGwQ?si=mlPz2tbHtQNamVgD

[Sketchy_Racer]

26hp on pump gas is a bold claim! Seriously impressive if verified.

As someone who has built their own dyno, I can make it say what ever I like and you don't know what bullshit other "calculations" the software is doing in the background either. It would be a great move for Alex to take it to a known and respected dyno to verify.

[husaberg]

26hp on pump gas is a bold claim! Seriously impressive if verified.

As someone who has built their own dyno, I can make it say what ever I like and you don't know what bullshit other "calculations" the software is doing in the background either. It would be a great move for Alex to take it to a known and respected dyno to verify.
Seen your latest Video Glen, impressive. post it here to please.

[Sketchy_Racer]

Thanks Husa, link here for those interested.


https://youtu.be/TDSJnMOpniE?si=lUE6hioRmveY-Dxy
(https://youtu.be/TDSJnMOpniE?si=lUE6hioRmveY-Dxy)


I'm looking forward to getting the engine back together and progressing the EFI. The first tests with the acceleration enleanment (think inverted acceleration enrichment table) is showing to be incredibly responsive.

Cheers,
Glen

[SwePatrick]

26hp on pump gas is a bold claim! Seriously impressive if verified.

As someone who has built their own dyno, I can make it say what ever I like and you don't know what bullshit other "calculations" the software is doing in the background either. It would be a great move for Alex to take it to a known and respected dyno to verify.

I have invited him to my dyno, only a minor daytrip away.

[F5 Dave]

Thanks Husa, link here for those interested.


https://youtu.be/TDSJnMOpniE?si=lUE6hioRmveY-Dxy
(https://youtu.be/TDSJnMOpniE?si=lUE6hioRmveY-Dxy)


I'm looking forward to getting the engine back together and progressing the EFI. The first tests with the acceleration enleanment (think inverted acceleration enrichment table) is showing to be incredibly responsive.

Cheers,
Glen
Watching your updates with interest. Be freat to see it when it makes it to the track. Ruapuna short track would be fun.

[TZ350]

26hp on pump gas is a bold claim! Seriously impressive if verified. As someone who has built their own dyno, I can make it say what ever I like and you don't know what bullshit other "calculations" the software is doing in the background either. It would be a great move for Alex to take it to a known and respected dyno to verify.

357038

Here at Team ESE we run a Dynojet.

Richban and Team GPR built their own dyno and wanted to check it against ours by running up Richbans FXR150 on it.

357039357040

I think Richbans FXR was the first 4 Stroke Bucket to crack 25rwhp and they wanted to verify it on a known Dyno.

There are a number of home made dynos around. The impression I got, was that the people who were clever enough to make their own were also clever enough to calibrate them to display real horse power. Doing anything else made no sense.

A metric horsepower is <mark class="HxTRcb" jscontroller="DfH0l" jsuid="Q9E7ub_a" data-processed="true" style="color: rgb(0, 29, 53); border-radius: 4px; background-image: linear-gradient(90deg, rgb(211, 227, 253) 50%, rgba(0, 0, 0, 0) 50%); background-position: 75% 0px; background-size: 200% 100%; background-repeat: no-repeat; background-attachment: scroll; background-origin: padding-box; background-clip: border-box; padding: 0px 2px; animation: 0.75s cubic-bezier(0.05, 0.7, 0.1, 1) 0.25s 1 normal forwards running highlight-animation; font-family: &quot;Google Sans&quot;, Roboto, Arial, sans-serif; font-size: 16px;">the power required to lift a mass of 75 kilograms one meter high in one second</mark>, which is equivalent to approximately 735.5 watts. This is different from the imperial or mechanical horsepower, which is equivalent to about 746 watts. Metric horsepower is also known as a PS (Pferdestärke), CV (cheval-vapeur), or other variations. That basically read much the same as DIN.

[TZ350]

357041 357042

In the pursuit of ever more hp I made a triple exhaust port cylinder. Speedpro helped me with this with some clever milling of the eyebrows.

Initial dyno tests showed a big hole at the rpm where pipe reversion is out of sink. I became suspicious that the cutaways on the side of the Suzuki piston were allowing the pipe to interfere with the crankcase.

357043

So I fitted a Wiseco piston that did not have this problem.

357044

New Wiseco, red line. So, Suzuki piston side cutaways were not the problem?????

Blue line, the old single exhaust port cylinder. Also red and blue lines are offset because runs were inadvertently done in different gears. Blue = 5th, Red = 4th.
Observation, the triple exhaust cylinder ran much better, cleaner at 9,500 rpm than the single. 250cc Kawasaki F81.

Will have more of a look next week. Once I get it sorted, then onto the Nitro injection.

[Peljhan]

Talking about dyno figures, I had a huge issue or let's say dilemma this year when I bought new dyno software.

In my country Slovenia with 2M people there is not many dynos and 2t tuning-racing scene is mostly me and my 10 friends / schoolmates and we all know eachother. Me and 2 other tuners, so 3 different home made inertia dynos used dynomec software from Finland (https://www.dynomec.com/). My roller had 300kg and 4,8kgm^2 of inertia, other two had around 3,5. We were using this software (Dynomec WT and is not for sale anymore) for 15 years now and it was very simple and could not be more basic as it is.

In these 15 years we got out rear wheel horsepower figures like:
- Tomos D6 50cc pistonport 14hp @14200rpm
- 50cc freetech 23hp @16500rpm (also raced in Hockenheim)
- Tomos 50cc classic bike with bidalot50 and rotary intake 18hp @14500rpm
- Tomos 90cc aircooled '77 pistonport stock bike 9hp @6000rpm (same as claimed from factory)
- Stock aprilia RS125 24hp, later tuned to 30hp
- Cagiva Mito 125 '93, tuned to 33hp
- Yamaha 125 4t 2006 9hp :rolleyes:
- Yamaha YZ125 2015 stock 33hp
- Honda RS125 NX4 2003 40hp (two bikes)

So many bikes were measured. We also tested some on both dynos and measurements were the same or like 0,1-0,3hp difference.
Also one of the bikes Honda 250 4t was measured at Akrapovič facility and one of the dynos was checked with that bike (don't ask me about details how measurements were made)

This year I bought new software from DTec (http://dtec.net.au/) as it is major upgrade as EGT, temperatures, data analysis is much better to do, so many options, and price was good.

So I tested one bike and it was measuring 6hp instead of 9hp. Then tested another 3 known bikes and all measurements were lower for a factor of 1.3. I investigated and my old Dynomec had inside some random factor of 1.3 that I was suspicious of since I bought software in 2010.
So I tried to measure power with weight drop, suspended from 3m of height with rope winded around roller and 8x pulley sistem, but measurements were too slow and friction from the rope was not constant (logically) and did not made any conclusions from that.
I also tested electic bike with in wheel motor with nominal power of 1000W, I measured around 850W with new dyno. EM power could be stated-measured on many ways by factory so I also didn't find any answers.

At the end I adjusted inertia, multiplied it by 1.3 and called it a day. Why? So we can communicate with my friends about power we made and what we figured out. I can compare results with my old dyno and customers have bragging rights with same value if they measure at my place or on other dynos. Life is easier that way.

I know dyno is used for comparing between setups, finding small gains etc and hp number is not so important, but still, as an engineer, it doesn't give me piece of mind. And 30% difference is not small. So are all dynos showing too much, all freetech bikes have 18hp instead of 23hp, but how, 18hp was claimed in 1978 by many 50cc like Kreidlers, Tomos etc. Was it all just propaganda?

Any ideas, so I could sleep better?
Does anyone use some of theese softwares, Dynomec and Dtec and has some experience with similar problems?

[Sketchy_Racer]

Any ideas, so I could sleep better?
Does anyone use some of theese softwares, Dynomec and Dtec and has some experience with similar problems?

The dyno I built also uses Dtec and I have had exactly the same experience as you in regards to measured power outputs against calculated MOI.

That is what I was referring to earlier that I am almost certain that most dyno softwares are adding some level of "correction" that is not user adjustable.

Where I am, dynojet is the most popular commercial dyno around. There are two local to me that I have had bikes on and the outputs are similar. When I set up our Dtec dyno, the power numbers were very low, so I did the same as you and adjusted the MOI to get them as close as I could to the dynojet figures so that, whilst not perfect, there was some level of comparability.

[Frits Overmars]

Talking about dyno figures, I had a huge issue or let's say dilemma this year when I bought new dyno software.. all measurements were lower for a factor of 1.3. I investigated and my old Dynomec had inside some random factor of 1.3 that I was suspicious of since I bought software in 2010.
Any ideas, so I could sleep better?Yup. My FOS dyno software has a UNIT-option that offers the choice between Horsepower an KiloWatt. It caused one user to call desperately: "My engines suddenly produce a lot less power !" He had not noticed that somebody had changed his Horsepower-setting into a kiloWatt-setting :D.

[F5 Dave]

. . .

A metric horsepower is <mark class="HxTRcb" jscontroller="DfH0l" jsuid="Q9E7ub_a" data-processed="true" style="color: rgb(0, 29, 53); border-radius: 4px; background-image: linear-gradient(90deg, rgb(211, 227, 253) 50%, rgba(0, 0, 0, 0) 50%); background-position: 75% 0px; background-size: 200% 100%; background-repeat: no-repeat; background-attachment: scroll; background-origin: padding-box; background-clip: border-box; padding: 0px 2px; animation: 0.75s cubic-bezier(0.05, 0.7, 0.1, 1) 0.25s 1 normal forwards running highlight-animation; font-family: &quot;Google Sans&quot;, Roboto, Arial, sans-serif; font-size: 16px;">the power required to lift a mass of 75 kilograms one meter high in one second</mark>,. . .
Talking of Metric, quoting US sources results in spelling mistakes.
A Meter measures something. It is not a unit of length.

'Mericans. Don't use the Metric system, but can't let the opportunity slide to spell things differently to the rest of the world.

[lodgernz]

In the pursuit of ever more hp I made a triple exhaust port cylinder. Speedpro helped me with this with some clever milling of the eyebrows.

Initial dyno tests showed a big hole at the rpm where pipe reversion is out of sink. I became suspicious that the cutaways on the side of the Suzuki piston were allowing the pipe to interfere with the crankcase.



Rob, have you ever tried using the PrtScrn key to capture dyno runs, rather than photographing the screen?

[F5 Dave]

Windows key + Shift + S

Then select the area. Paste

[TZ350]

Talking of Metric, quoting US sources results in spelling mistakes. A Meter measures something. It is not a unit of length.
'Mericans. Don't use the Metric system, but can't let the opportunity slide to spell things differently to the rest of the world.

Left to my own devices the spelling and english would be even worse .....


Rob, have you ever tried using the PrtScrn key to capture dyno runs, rather than photographing the screen?

The dyno computer is an old relic. Not connected to the Internet or company's LAN. I had not thought of taking screenshots with it. The phone was easy, I might try a screen shot next time. Thanks.

[F5 Dave]

I should have known that. I was just wondering how the old dyno was fairing as I can't imagine it is still running Win 3.11.

[Frank S.]

I found out, that the rear wheel inertia has a quite measurable effect on dyno results.
On my homemade dyno I have only a 80kg roller, which is far from optimal,. So I had to use relatively long gearing to compensate.
In this specific case the inertia of the rear wheel has a huge effect on the measurement.
I don't remember exactly, didn'use it for years, but I had to add a big amount to the roller inertia.

[Frits Overmars]

I found out, that the rear wheel inertia has a quite measurable effect on dyno results. On my homemade dyno I have only a 80kg roller, which is far from optimal,. So I had to use relatively long gearing to compensate. In this specific case the inertia of the rear wheel has a huge effect on the measurement. I don't remember exactly, didn't use it for years, but I had to add a big amount to the roller inertia.It's not so much the rear wheel inertia that is to blame, but the ratio between rear wheel inertia and roller inertia, and that ratio won't change if you alter the gearing.
Increasing the roller inertia, as you did, is the only effective action.

[JanBros]

I think he had to use a very long gearring so that the pull would last long enough. if from low to max rpm lasts only 2 seconds, you have less points for an accurate graph and the engine/pipe won't reach the temperatures it would reach on the track.

[crbbt]

Hello Brains trust,

I am wondering if anyone can advise me on removing the powerjet tube that protrudes into carb bore?

specifically on a keihin spj.

The issue I have is that the tube's outlet/discharge is facing away from the carb slide and need to be rotated 180.

I am assuming they are a press fit but do not want to destroy the tubes or the carbs

Thank you!

[Peljhan]

That is what I was referring to earlier that I am almost certain that most dyno softwares are adding some level of "correction" that is not user adjustable.

Where I am, dynojet is the most popular commercial dyno around. There are two local to me that I have had bikes on and the outputs are similar. When I set up our Dtec dyno, the power numbers were very low, so I did the same as you and adjusted the MOI to get them as close as I could to the dynojet figures so that, whilst not perfect, there was some level of comparability.

I think Wobbly stated that DynoJet overcorrects for 15%
Do you know how much did you adjust the MOI from what it actually is?

Darren from Dtec said, their software is made on known basic equations and no additional factors are used.
Dynomec had some correction inside that was 1.30, exactly the difference with Dtec.

I also saw written on VHM page for their dyno tests:
- We measure on the rear wheel, but add a small correction factor (0.05PK/Kmh) for the crankshaft. So the graphs in the video's show the power on the crank.
What junk of correction is that? And definetly not small. For 50cc measured from 30-120km/h that is 1,5hp at bottom and 6hp at overrev. So for weak bikes it can double the power and for 1000cc bike is like nothing.

Thanks for suggestion Frits, but that was not the case as you can change from imperial to metric in the software. Downside is I can't choose HP/Nm/°C, only HP/lbsft/°F or kW/Nm/°C because we all speak in HP figures between friends.

[TZ350]

I am almost certain that most dyno softwares are adding some level of "correction" Where I am, dynojet is the most popular commercial dyno around.

It looks to me, that DynoJet's are a little bit optimistic but seem to give consistent results between individual units.

[F5 Dave]

At some point the horse(sorry) has bolted and something is so ingrained that we have to keep using it.
Dieters count in calories but really mean kilocalories and joules aren't in any conversation. Our wheels an TVs are inches. Although there was a Citroën that had metric wheels decades back apparently.
So I'm a wild hypocrite fervently defending the metric system and English language from being Americanised. But accepting some things like hp are probably best left fairly constant. It was bad enough with quoted hp being believed. Journalists are usually aware of this now, but still like waffling on about torque as if some mysterious motive force that is somehow produced independently and not mathematically constrained.
Anyway, rant for lunchtime. :rolleyes:

[Frits Overmars]

It looks to me, that DynoJet's are a little bit optimistic but seem to give consistent results between individual units.I once hooked my software onto the Dynojet of nearby Ten Kate (superbike world champ at the time), so each run on the Dynojet was simultaneously monitored by Dynojet software and FOS software. Clear outcome after a series of runs: when a bike delivers 100 hp on the dynojet drum, Dynojet claims it was 111 hp.

[F5 Dave]

Ok so let's play.
How would the 54hp of the RSA compare to either?

And is some of the conversion to bring it close to crank hp vs at the drum maybe?

[Sketchy_Racer]

It looks to me, that DynoJet's are a little bit optimistic but seem to give consistent results between individual units.


I once hooked my software onto the Dynojet of nearby Ten Kate (superbike world champ at the time), so each run on the Dynojet was simultaneously monitored by Dynojet software and FOS software. Clear outcome after a series of runs: when a bike delivers 100 hp on the dynojet drum, Dynojet claims it was 111 hp.

Yes, this is exactly my experience and conclusion.

We can all fool ourselves and enjoy seeing a larger 'measured' power output though....

[Frits Overmars]

Ok so let's play. How would the 54hp of the RSA compare to either?It wouldn't. The RSA power is measured at the gearbox exit shaft. So no varying losses through a chain that loses its lubrication over time and above all no wildly varying losses through the distortion of a tire on a drum, which will heat up the tire, which will raise the tire pressure, which will influence the distortion.
Measuring rear wheel power may be convenient for various purposes, but not for engine development.


And is some of the conversion to bring it close to crank hp vs at the drum maybe?If Dynojet would say so, I would be willing to accept that, even if their 11% exaggeration is neither a constant, because of the unpredictable tire losses, nor very realistic.
Total power losses between crankshaft and dyno drum will rather be in the order of 15%. But Dynojet just let you think that what you see on their software is the measured power.

[lohring]

By the way, one British horse power is 1.014 metric horse power. That's 33,000 ft pounds per minute vs 4500 kg meters per minute. Pounds and killograms are force, not mass for these definitions.

Lohring Miller

[JanBros]

started trying to make a very cheap DIY programmable ignition a french dude developed years ago :
https://www.youtube.com/shorts/tDq2E59a49A
works up to 20.050 rpm for now (that's as fast as my motor goes)

didn't wat to polute the topic with it too much, so opened a new topic about this :

https://www.kiwibiker.co.nz/forums/showthread.php/190568-cheap-DIY-programmable-ignition?p=1131242121#post1131242121

[ApolloMotoMoto]

started trying to make a very cheap DIY programmable ignition a french dude developed years ago :
https://www.youtube.com/shorts/tDq2E59a49A
works up to 20.050 rpm for nof (that's as fast as my motor goes)

didn't wat to polute the topic with it too much, so opened a new topic about this :

https://www.kiwibiker.co.nz/forums/showthread.php/190568-cheap-DIY-programmable-ignition?p=1131242121#post1131242121


Thats REALLY COOL.

Ignition system design and configuration is literally more "black magic" and "dark arts" than 2-stroke state of the art tuning theory is.

Its not horrendously complicated, nor does it require savant level electrical/ circuit knowledge...

But the "fundamental principles" and the "equivalent circuit" models that are best used to analyze and describe spark ignition systems are not ...well communicated... by the industry itself, or by those DIY'ers playing and sharing their work.

I am also doing a lot of work on "custom" ignition circuits that are open public knowledge.

I have a question for the other Guru's out there that have played with measuring and tinkering with ignition systems:


Is there a generally accepted "best setup" for an AC-CDI ignition dyno?

I want an electric motor that can spin, wall balanced and reliably, up to 20k RPM's.

I want some kind of "shaft rpm" readout because I wont always be testing with a full ignition system that would allow RPM reading off the tach-signal wire.

I want highly granular dynamic control of the RPM the motor is spinning at.


What motor/speed controller setups are people using out there for this kind of work?

[lohring]

I run electric RC model boats among others. Our electric motors easily spin much higher than that with over 3000 watts (4 hp) of power. What power or torque do you need? There are relatively inexpensive motors and speed controls available for lower powers. I use Castle Creations speed controls that have built in data loggers that read voltage, current, and rpm. With some more information I should be able to find you something for around $100 to $200 US.

Lohring Miller

[lohring]

After reviewing the other thread I see you don't need hardly any power. You could try drone motors and speed controls like these:

https://hobbyking.com/en_us/aircraft/drones/motors-accessories.html
https://www.amazon.com/Surpass-Hobby-S2810-Brushless-Racing/dp/B0CRQ15D5D?crid=1QJZDLR3BGHRK&dib=eyJ2IjoiMSJ9.2Ewn75QYUpBQK0m0ztIOowtuBN86yw-q_kIHRgVfiCJQTbYKSKvG_xwBje-Rl3tlSVfSbemKTHYUPlbvBm5ZTNMB0ua-EDUHCmS_8Jp_dW3534SS4Mb4EAFmMNHEjKy5yrWqrFG527JBiW-W0c_UjYzVQYcN42oDbxJsOqJpxxciuhaaSnMiKOR7yaKXqMr-LQVkKNIvcrsc8Ll4gnduBrM_w3ldjfdlTUwjKC22Um4m7iS29--8ywPrMkzCDAjOFVJ3AcW4Fm4O3pyIEft9xUeSF96SOnas3aie6 bPL6xM.wxXsCfzX9DQrrQMhHm-ah2EyntYhgMRckhJdhJj5p3Y&dib_tag=se&keywords=drone+motor&qid=1764782079&s=industrial&sprefix=drone+motor%2Cindustrial%2C176&sr=1-19
https://www.amazon.com/Brushless-Electronic-Components-Accessories-Helicopter/dp/B09DG18V6K?crid=3VNB94XPHA8A&dib=eyJ2IjoiMSJ9.aCRR17bFt3Wj4tabjW5Lv5ehPvmi8E8Iv OwAEkUdNCiY4nlidwCioyVWE4z63WG9pUpuahV9oIypkoKZ24W lCqRTBB5N0ZFiwixMayweKdQBAgR4VJjYf-WT5mgIvjDO87jLnCEnnZMq2d8ItDPOAfwInSiq7VNF2lf62vGd UFCWqRfJFPX81j8JNFsFOb1Hf6oH2orWUqw3_clE1i1IsXdVbC eWJuNIw_7RhfVS6fsNQsxj_BJSypzXYp3QUGmL4UobxPJynZns Easrv4Ghm3Vgc9dFvzKM7uuWYW36uEo.wLKoW908So4n5UGTNG pR9-3M3hfnFLHWijW4Pqi3TqU&dib_tag=se&keywords=drone+esc+and+motors&qid=1764782259&s=industrial&sprefix=drone+esc%2Cindustrial%2C193&sr=1-9
https://hobbyking.com/en_us/turnigy-plush-32-40a-2-6s-brushless-speed-controller-w-bec-rev1-1-0.html
https://www.amazon.com/VGEBY-Brushless-Controller-Airplanes-Accessory/dp/B08XZB9FX9?crid=3VNB94XPHA8A&dib=eyJ2IjoiMSJ9.nszCiy0O0mQZuyfQ154TrOb8oxQSY05JI mKBraJfPXpdG9Kio3Kmzns4ZQA_RSajMuna-Mm7YTSFbSYeJnpS6WeBAjaiUyHZEJuFdaTJGqqQpdh02fKL_5z bUyGwtfKm59ndKBS-9ZjRx2MxuePvN1vUY-t-78l1LKxygnsYxDGG5fVEC65LHjdlVbVNlhDFJV5e2zGBV5Jbux-DZl9eTcu2cmFxvlGySXNuACbgYZqSgqpEkdCTYMGfakvR-cyxCALP8PWtIIM8N-3wDDXv339s6zz-cWbsWlewo-4nas0.RnnGx8WLlhub3F7Ga24wiCfqvt2uJ-xlBgcGPN1wG9g&dib_tag=se&keywords=drone+esc+and+motors&qid=1764782349&s=industrial&sprefix=drone+esc%2Cindustrial%2C193&sr=1-10

The motor's no load rpm = input voltage x KV The actual rpm will be around 80% of that depending on the load. I would run around 12 to 16 volts from any source or battery that can supply up to 40 amps. You control the speed with a servo input to the speed control. See below for a servo tester to do that:

https://www.amazon.com/dp/B012LZKTDO?ref=ive_vfsp_pfo&_encoding=UTF8&pd_rd_w=w46gN&content-id=amzn1.sym.26dedd2b-540b-4bff-af75-7fea8d8f8913&pf_rd_p=26dedd2b-540b-4bff-af75-7fea8d8f8913&pf_rd_r=77JFTGZ35K51Q0JCN865&pd_rd_wg=leZSP&pd_rd_r=acbf1a89-2475-4b07-98c2-66345747ccca_vse-cards-ingress2

Lohring Miller

[diesel pig]

Hello Brains trust,

I am wondering if anyone can advise me on removing the powerjet tube that protrudes into carb bore?

specifically on a keihin spj.

The issue I have is that the tube's outlet/discharge is facing away from the carb slide and need to be rotated 180.

I am assuming they are a press fit but do not want to destroy the tubes or the carbs

Thank you!

I am not one of the Brains trust, But the only thing I can think of doing is use a industrail heat gun (not a Hair dyer as it would not get hot enough) to heat up the carb while it is in some kind of vise set up. Once as hot as you can get it use some soft nose piers to turn the tube. I am sure someone would tell us if that would work.

[katinas]

Thats REALLY COOL.

Ignition system design and configuration is literally more "black magic" and "dark arts" than 2-stroke state of the art tuning theory is.

Its not horrendously complicated, nor does it require savant level electrical/ circuit knowledge...

But the "fundamental principles" and the "equivalent circuit" models that are best used to analyze and describe spark ignition systems are not ...well communicated... by the industry itself, or by those DIY'ers playing and sharing their work.

I am also doing a lot of work on "custom" ignition circuits that are open public knowledge.

I have a question for the other Guru's out there that have played with measuring and tinkering with ignition systems:


Is there a generally accepted "best setup" for an AC-CDI ignition dyno?

I want an electric motor that can spin, wall balanced and reliably, up to 20k RPM's.

I want some kind of "shaft rpm" readout because I wont always be testing with a full ignition system that would allow RPM reading off the tach-signal wire.

I want highly granular dynamic control of the RPM the motor is spinning at.


What motor/speed controller setups are people using out there for this kind of work?

I use 1.5KW Air cooling Spindle Motor 24000rpm ER11 w/ 1.5KW Inverter VFD CNC, https://www.ebay.co.uk/itm/317553810908?, just older version.

But be careful if testing at home, loved ones can quickly leave you after constant testing !!!

[F5 Dave]

If you can get to the tube slide a section of nail in it in case you start to crush it. Leave a section of nail exposed for extraction.

[wobbly]

I have removed the PJ in that carb by clamping s piece of square steel in the vise, hold the PJ end square on the bar, and tap the body directly next to the pressed in ball.
The PJ tube and the ball easily came out doing this.

[wobbly]

Neels is still locked out - nothing has changed, the connection request times out.

[husaberg]

Neels is still locked out - nothing has changed, the connection request times out.


for clarity of the admins and mods
Neels is KB username Vannik
https://www.kiwibiker.co.nz/forums/member.php/34343-Vannik

[TZ350]

.
357106

Suggestions needed.

My good old new triple exhaust port methanol burning Kawasaki F81M 250 is suffering a serious bout of rough running around 8,000rpm.

Not a problem with the single exhaust port cylinder but a real issue with the tripple.

Things I have tried:-
Swapped out the Suzuki piston with the cutaway sides for a full skirt Wiseco one.
Reverted from my petrol/methanol carb setup back to a 100% methanol one.
Tried it with and without power jet.
Tried extreme richer and leaner main jetting. Jetting that makes best power also colours the plug and head. I would expect it to be clean.
Tried straight line ignition settings all the way from 5deg to 30deg BTDC. Over advanced can cause a patch of rough running.
Replaced the "R" retracted gap plug with a normal cold exposed tip one.
Tried plug gap settings from 010" to 030".
The coil is something that should be capable of throwing an arc across the room and welding heavy steel beams. Probably can create a spark underwater.
Both channels of the Race2 Ignitec discharge into the coil.
Checked that the Battery and generator can supply the ignitions current draw. About 4A at 10,000rpm.

Things that may be a problem:-
The scavenging stream is blowing the spark out.
The plug is slightly offset in the head and should be central.
Try it on petrol only. Although I want the methanol for cooling.

This was not an issue with the single exhaust port cylinder. The triple exhaust unit runs and sounds much better at 10,000 rpm than the single did.

Both my CHT and EGT gauges have chosen to go on the blink so not much help there.

Ideas???

[husaberg]

.
357106

Suggestions needed.

My good old new triple exhaust port methanol burning Kawasaki F81M 250 is suffering a serious bout of rough running around 8,000rpm.

Not a problem with the single exhaust port cylinder but a real issue with the tripple.

Things I have tried:-
Swapped out the Suzuki piston with the cutaway sides for a full skirt Wiseco one.
Reverted from my petrol/methanol carb setup back to a 100% methanol one.
Tried it with and without power jet.
Tried extreme richer and leaner main jetting. Jetting that makes best power also colours the plug and head. I would expect it to be clean.
Tried straight line ignition settings all the way from 5deg to 30deg BTDC. Over advanced can cause a patch of rough running.
Replaced the "R" retracted gap plug with a normal cold exposed tip one.
Tried plug gap settings from 010" to 030".
The coil is something that should be capable of throwing an arc across the room and welding heavy steel beams. Probably can create a spark underwater.
Both channels of the Race2 Ignitec discharge into the coil.
Checked that the Battery and generator can supply the ignitions current draw. About 4A at 10,000rpm.

Things that may be a problem:-
The scavenging stream is blowing the spark out.
The plug is slightly offset in the head and should be central.
Try it on petrol only. Although I want the methanol for cooling.

This was not an issue with the single exhaust port cylinder. The triple exhaust unit runs and sounds much better at 10,000 rpm than the single did.

Both my CHT and EGT gauges have chosen to go on the blink so not much help there.

Ideas???


Put a longer carb bellmouth stack or lengthen the intake to see if it shifs the rpm where it turns to shit.
Quick and easy, if its not that move on.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=251900&d=1322903746

[jonny quest]

TZ350, I just looked at your triple exhaust port shape.

I think you are having short circuit problems. This is showing an extreme case I've never seen, but it typically shows up in your area of dyno curve.

Fill in the bottom of those sub exhaust with epoxy, and hope you can make a quick dyno run before it blows out and see what happens

By bottom, I mean just the area that is inline with A port

[wobbly]

It sure as hell isnt the ignition system, but for the 10,000 th time, are you using a " proper " fine wire race plug that needs 1/2 the gap voltage to ionize.

First thing to look at is when the piston is at TDC, does the piston side cutaways expose a lump of Aux real estate , connecting the case to the Exhaust duct
thru the side port ducts. That will run like shit.
Its unlikely to be the A port short circuiting out the main port as it wasn't happening before - but sure you could be seeing vertical linking of the A port roof and the Aux floor if they are
separated by a very narrow septum width ( and this is why wide topped triangle Aux work so much better).

I have seen a similar thing happen if there is not a resistor cap and plug combination, or if the coil drive wires are not physically separated from any other in/out wires all the way
from the CDI plug end to the coil.
Also a possibility that the fueling is going haywire due to the much lower Blowdown residual pressure at TPO.
Remember that the mid range fuel curve is set by the needle/tube annulus area for low rpm/WOT.

[Frank S.]

To me this looks like a kind of resonance problem, because it only appears in a sharp band from about 8700 to 9700rpm. This is about 145 to160 Hz. Below and above this it runs fine.
Are there parts that can swing in resonance like carb, coil or something? Check the whole bike for loose parts.
Did you check the ignition timing with a strobo lamp at that rpm?

[ApolloMotoMoto]

.
357106

Suggestions needed.

My good old new triple exhaust port methanol burning Kawasaki F81M 250 is suffering a serious bout of rough running around 8,000rpm.

Not a problem with the single exhaust port cylinder but a real issue with the tripple.

Things I have tried:-
Swapped out the Suzuki piston with the cutaway sides for a full skirt Wiseco one.
Reverted from my petrol/methanol carb setup back to a 100% methanol one.
Tried it with and without power jet.
Tried extreme richer and leaner main jetting. Jetting that makes best power also colours the plug and head. I would expect it to be clean.
Tried straight line ignition settings all the way from 5deg to 30deg BTDC. Over advanced can cause a patch of rough running.
Replaced the "R" retracted gap plug with a normal cold exposed tip one.
Tried plug gap settings from 010" to 030".
The coil is something that should be capable of throwing an arc across the room and welding heavy steel beams. Probably can create a spark underwater.
Both channels of the Race2 Ignitec discharge into the coil.
Checked that the Battery and generator can supply the ignitions current draw. About 4A at 10,000rpm.

Things that may be a problem:-
The scavenging stream is blowing the spark out.
The plug is slightly offset in the head and should be central.
Try it on petrol only. Although I want the methanol for cooling.

This was not an issue with the single exhaust port cylinder. The triple exhaust unit runs and sounds much better at 10,000 rpm than the single did.

Both my CHT and EGT gauges have chosen to go on the blink so not much help there.

Ideas???


"Tried extreme richer and leaner main jetting. Jetting that makes best power also colours the plug and head. I would expect it to be clean. "

Okay, thats a PURE combustion efficiency problem right there, previously you had complete combustion at these jetting settins, now you cant (coloring the plug and head at lambda values that previously burned "clean")

You also swept up and down the stoich lambda curve and nothing "fixed it".

What does this mean?

Even when you sweep to the stoich value that is the "easiest" to ignite for the fuel you are using, spark initiation is still failing.

With the fuel you are burning (hard to ignite alcohol fuels) AND the increased BMEP the engine is making with tripple exhaust port; high dynamic in-cylinder pressure at the moment of spark firing = higher required breakdown voltage AND dV/dt.

delta Voltage divided by delta Time

You can have all the voltage potential in the world with the capability of throwing the gap from here to the moon in a steady state, with UNLIMITED time to achieve breakdown....

But, that is not what Paschen says happens in a dynamic townsend regime that includes a "time-domain" function.

Literature (lab studies of plasma formation at internal combustion engine cylinder pressures/conditions) suggests that the required breakdown voltage to initiate the spark gap MUST BE ACHIEVED within 1-5 uSecs (0.001 - 0.005 seconds) or breakdown formation "LAG FACTORS" overcome the rising kV potential comming from the high voltage transient discharge from the CDI, through the COIL and into the spark gap.

This means:

If your systems RISE TIME for the first HIGH VOLTAGE transient pulse that is meant to "jump the gap" is TOO SLOW, it doesn't matter if you have 100,000 kV of open-circuit, open air POTENTIAL; you will fail to achieve breakdown for real in-cylinder conditions that maybe only need 20-30kV of VOLTAGE at the gap because you built your potential (rising rate) too slow.


Okay, thats problem number one.


Problem number two:

Lets assume you DID achieve breakdown, you DID jump the gap, and you DID establish a "nascent kernel".

Why is combustion proceeding so slowly and inneficiently around where the engine makes peak power/ peak cylinder pressure/ and probably peak MSV Turbulence....???

Turbulent conditions after the nascent kernel forms are "quenching" it before the CDI's discharg regime "catches up" and dumps the remaining energy stored in the discharge caps as lower volts and higher amps.

Once breakdown forms the kernel, the plasma channel becomes nearly superconductive; what was once an infinite resistance air-gap is now a highly conductive plasma channel, the volts required to sustain the arc are more like 800 - 1000V, so the remaining energy flows at higher relative current and lower relative volts.

This "post breakdown" current flow stabilizes the nascent kernel, grows its diameter, and delivers heat energy to this kernel.

It is CRITICALLY IMPORTANT that this post breakdown current is delivered in a window around 0-200 uSecs after breakdown occurs.

You dont want ALL of the current dumping in this quickly, but you MUST have SOME meaningful current delivered in this time window to stabilize the nascent kernel, or turbulence can ABSOLUTELY "blow out" the already established nascent kernel.

IDEALLY, you have a front-loaded current delivery window that dissipates a good margin in the first 200 uSecs, with a still meaningful "tail" that delivers energy over ~800 to 1,200 uSec total "spark energy delivery window".

None of this is necessary for a "simple" petrol burning engine at low to moderate BMEP and combustion chamber design "turbulence factors".

For an alcohol burning engine that wants RICH stoich values for best power, tuned to a high BMEP state, using a well optimized combustion chamber producing ...high... "turbulence factors", on the other hand:

This "time-domain" factor now becomes a lot more important to tune for in your ignitions discharge regime.


Attached is a document you have probably seen 100 times before from Frits, but it really does seem to match the condition you see on your dyno VERY well, especially the "saw tooth" pattern within the "power hole".



Now, you are using Wayne Wrights recommended CDI setup for this EXACT scenaio: jungle juice near impossible to light fuels at high engine BMEP with high turbulence head designs:

IgniTech 2 cylinder DC-CDI box with the outputs paralleled into one coil.

The questions I have are the same as Waynes:

1. Are you using the recommended NGK Race Plug?

Double fine-wire (laser welded fine-wire ground strap), Double rare-earth (irridium electrode, platinum ground strap)

NGK R7376 or equivalent.


2. Are you using the Crane Cams PS91 Ignition Coil Wayne ALSO says to run with this setup???


The "time domains" that I described above are mostly controlled by the natural resonant frequency of the CDI/Ignition Coil combination.

The capacitor(s) in the CDI and the "inductor" represented by the ignition coil (in addition to the resistive/inductive/capacitive contribution of the coils windings and the full circuits wiring loop) form an "LC Tank" equivalent circuit with a time-domain defined by the RLC of the combined components in the circuit loop.

This is one of the reasons Wayne recommends the Crane Cames PS91 coil specifically, when paired with the dual/parallel IgniTech DC-CDI setup, the natural resonant requency produced establishes a set of "discharge event time domains" that ACTUALLY WORK.


If you go arbitrarily trading out pieces of this setup, like for example, the ignition coil; for a different part with inductance/resistance/stray capacitance values that are much different than the Crane Cams PS91, then its entirely possible you skew the time domains into a region where you make PLENTY of power, just too late for it to actually mean anything to the spark kernel as its getting blasted by in-cylinder pressure and turbulence.



Wayne ALREADY HAS a setup that is KNOWN to work under these conditions.

If it IS a spark-loss condition, my FIRST recommendation would be to replicate Wayne's setup EXACTLY if you have not already done so.

[TZ350]

If it IS a spark-loss condition, my FIRST recommendation would be to replicate Wayne's setup EXACTLY if you have not already done so.

Thanks. I think I have the right coil and I have one of those plugs. I will check through the system and do my best to replicate Wobblys setup.

[F5 Dave]

I thought he was going to conclude by saying Tap the plug on the side of the head and close the gap up a bit:pinch:. At least check it I suppose but unlikely to be wrong thee days on million dollar plug. Funny fuel seems to play by odd rules.

[wobbly]

Using the prescribed plug/coil/DCCDIP2 arc welder ignition was developed for a World Champ mini hydro 125 making well over 60 Hp @ 14000 on straight Methanol with 20:1 compression.
Man, if it can fire that up easily , the little Kawasaki is a walk in the park.

Edit - I even asked Jiri the tech at Ignitech if it was possible to program a delay into the twin spark setup, to increase the overall burn period in the gap.
He tried it, and replied that it kept blowing the output capacitors apart, he thought due to the coil ringing and the caps seeing nulls - and worse, huge superposition voltages.

[Hoebra]

I got a question about finding proper jetting dimensions for Powerjetaplications, espacially for wobbly cause i know he used these components alot.

I got a electrical Mikuni powerjet, wich i want to use with my ignitechs pwm function to keep egt longer up after peak power. So i asked myself if there is a kind of "rule of thumb" how big to choose the powerjet nozzle. If it is bigger and you turn off after Peak Power, a bigger amount of fuel dissapears an egt will rise/keep up in a bigger value. But fore shure theres a "to much", "less then possible" and a "sweet spot".
So lets say in an non Powerjet Szenario you found a mainjet with "100" flowrate as perfect. Is there a relationship to say it would be a good starting point to choose for example 25% of this mainjet flowrate as powerjet flowratesize? Of course the mainjet in the Powerjetaplication would have to become less big, becaus of the extra amount of fuel the powerjet is adding. I guess it isnt as simple as saying 100-25=75... so theres maybe some testing, starting richer (like about 85?) and testing down leaner until you reach about the same egt/peak power like with the 100 mainjet.
From there starting with shutting Powerjet off via PWM. Could you show such a PWM table in the ignitech software, becaus until now I have no real idea how to start. Thanks!

[TZ350]

If it IS a spark-loss condition, my FIRST recommendation would be to replicate Wayne's setup EXACTLY if you have not already done so.

357294

Damm expensive plug, about 80-120 NZD each.

357295

Lead and cap 9,6k Ohm

357296

FireBall PS92N

357297

Ignitec DC_CDIP2_Race with both the white and orange wires paired and going to the coil.

357300

[TZ350]

.
357298


It sure as hell isnt the ignition system, but for the 10,000 th time, are you using a " proper " fine wire race plug that needs 1/2 the gap voltage to ionize.

I am a pensioner so No, not been but I have one and will try it. The NGK R7376-10 is so damned expensive.


First thing to look at is when the piston is at TDC, does the piston side cutaways expose a lump of Aux real estate , connecting the case to the Exhaust duct
thru the side port ducts. That will run like shit.

357299

Looking at the old Suzuki piston in the single exhaust cylinder it looks very possible that the side exhaust ports may be opening into the crankcase at TDC.

I will have to take the good cylinder and piston off to check ........

Cylinder off will be the first move.

[wobbly]

The best place to buy the NGK plugs is JDM Planet - very reasonable shipping as well. But here is another idea I have been using for some time now.
A NGK R0373A is the 10mm version of the R7376 , and is cheaper, plus it enables a minimal boss intrusion into the chamber when using a Toroidal dome
to reduce the shadow or masking effect on the loop flow across the dome face.
This idea was proven ( though sworn to secrecy ) via a World Champ winning big bore snowmobile project.
The small resistor caps to suit are cheaper as well - I got a bunch from a British Bike parts place in ChCh I think.

And yea, if your Aux are linked to the case - the jetting goes completely to shit.
Same thing happened when I cut the skirts short on a " stock " World Champ Jetski with a 2: 1 pipe setup.
The fuel curve went out the window completely, and it was only due to having pumper carbs with Aux venturi's that allowed the thing to be dialed back in.
Made a shit ton of top end power, and won a title with zero chance of any tech seeing what had been done.

[Larry Wiechman]

357296

FireBall PS92N







PS91 or PS92, 3 Ω or .82 Ω, which one is preferred?
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=357190&d=1765144544

[Hoebra]

About the dip in the powercurve: Maybe not thge spark is lost in this rpms, but AFR is crazy wrong? Looking at the curve it is about the rpm of maximum torque. Have you made any changes to your scavening or your diffusorcreation? Once your scavening is less stiff than before, or your main Depression pulse is much stronger so sthe scavening colapses as it hits, leaving a lot of burned gases inside, as the this maindepression pulse gets weaker scavening becomes stiff enough again and AFR gets back to normal.
Had such phännomena by testing diffusor dimensions on non full race cylinders. Got good good curves with mild diff anngles, by increasing them torque an power rised, until a point of 18°+ main diff angle, curve startet at the same RPM with even higher torque, dipped than completly around max torque rpm and after this again went on with more torque than before, but in the region of the heavy main depression pulse great dip in the torque/powercurve, so to much Depression for the stiffness of this scavening.

[wobbly]

The coil I used was a PS92N, built for Nascar CDI systems.

[ken seeber]

The man says:

"Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one."

Just maybe it's true:

357439

[wobbly]

Kentastic, that was a line from a Joni song - she's older than me, but I would hope some much younger ladies would like that version of me, due to obvious physical enjoyment.

[husaberg]

Picture albums they have multiple pages at the bottom

Aprilia GP bikes https://www.kiwibiker.co.nz/forums/album.php?albumid=4839
Cagiva GP bikes https://www.kiwibiker.co.nz/forums/album.php?albumid=4842
Honda NSR500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4837
Suzuki RGV500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4848
Yamaha YZ500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4845
Honda NSR500V https://www.kiwibiker.co.nz/forums/album.php?albumid=4953
Swissauto ELF pulse 500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4833
Honda Rs125 RS250 https://www.kiwibiker.co.nz/forums/album.php?albumid=4841
Suzuki RGV250 GP bikes https://www.kiwibiker.co.nz/forums/album.php?albumid=4938
Yamaha TZ250-350 https://www.kiwibiker.co.nz/forums/album.php?albumid=4882
Yamaha TZ750 https://www.kiwibiker.co.nz/forums/album.php?albumid=4932
BSL500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4865
Rotax and other tandems https://www.kiwibiker.co.nz/forums/album.php?albumid=4840
Patton https://www.kiwibiker.co.nz/forums/album.php?albumid=4849
Roberts 3s https://www.kiwibiker.co.nz/forums/album.php?albumid=5025
Honda RS and NS500 https://www.kiwibiker.co.nz/forums/album.php?albumid=4861
Kawasaki H1R and H2R https://www.kiwibiker.co.nz/forums/album.php?albumid=4964

plus many others
there are about 100 albums most are open
https://www.kiwibiker.co.nz/forums/album.php?u=28036

[diesel pig]

Damn you Husberg! I now know what I will be doing this Xmas.

I got a little weirded out when I check out the JDM Planet site it's a car parts site but they do have all types of NGK plugs for reasonable prices.

[crbbt]

I have removed the PJ in that carb by clamping s piece of square steel in the vise, hold the PJ end square on the bar, and tap the body directly next to the pressed in ball.
The PJ tube and the ball easily came out doing this.

Thank you!

this worked. Now to find your post about putting the 0.2mm hole into tube to atomize the fuel coming out of the PJ

[husaberg]

..............

Thank you!

this worked. Now to find your post about putting the 0.2mm hole into tube to atomize the fuel coming out of the PJ


Here's a mod I have done on many Yamaha racebikes with the electronic solenoid PJ - move the PJ to the top of the bellmouth and shorten the dump tube so it
only protrudes around 15mm into the bore . I cut the tube end at 45* facing the reeds as this atomizes the fuel stream much better than the stock small hole does.
The slide has to be well past the tube end for flow to begin , having a low down tube richens the fuel curve way too much in the midrange.

The only other way is to use a truth table in the ecu to switch the flow depending upon TPS and rpm , but this is problematic to tune , causing jerking response on part throttle , mid corner.
Cutting the tube short works on Lectrons as well , when having to use large PJ flow ( 50 + ) to get the top end tune correct without shagging the midrange jetting.


Re the tiny bleed hole in the TZ powerjet tube - I always thought that this was a good idea to emulsify the fuel as it exited the dropper.
But years ago i did some wet tests on the flowbench with a VCR video camera ( pretty trick shit stuff back then ).
The Mikuni was a horror scene when played back slo mo,with huge "gobbs" of fuel exiting the main and powerjet.
We then stuck on a Lectron - wow, lovely fine mist of fuel from the back of the flat needle face - and it flowed 12% more air - size for size with a venturi 2mm smaller behind the slide.

Next is the current state of TeeZees GP125, here is the latest dyno curve digitised with 16% added to simulate crank power.
Then there is the sim with an actual RS early model pipe.
Then there is the new pipe of my design.
Of most interest is that in this case the sim is giving slightly too much crank power - but the shape and peak point are all but perfect.
I would be confident now that any change in the sim, would be reflected in reality on the dyno.
In my experience the later Dynojets like a twin roller 168 with Eddy current load control to slow the acceleration rate down ,seem to read around 5 to 10% lower
so this would put the sim and the dyno reading very close, as the shape is spot on now.


When using a simple powerjet nozzle the tip position matters in that no flow will occur until the slide is well past the exit hole, and there is sufficient airflow
to drag fuel up the feed tube above the bowl level.
With the aftermarket add ons and the ones as used by Lectron you can shorten the dump tube so that the flow will only occur at high slide openings,as well as high air flow.
These also have a built in "lag "control in that it takes time for the fuel to rise up the tube and dump out the exit into the air stream.
With a solenoid controlled setup all this is pretty much irrelevant as the flow can only occur when the solenoid is not powered up, and this
is TPS as well as rpm dependant inside the ECU program..
The carbs as used on the MX bikes has the dump tube very low in the bore as they added and subtracted fuel at low slide positions in those bikes.
For a race engine I bend the tube up to around 1/2 bore, as this is where the exit is on the Kehin SPJ carb for RS125/RS250 Honda.
And the general setting is the solenoid is powered up ie no flow below 4000 and 60% TPS and is powered up again at around 12400 to lean off the mixture and increase revon.
This causes a problem with Ignitechs that are used with only a capacitor, as at startup the solenoid is powered up, dragging all the voltage out of the ECU, so I convert the ECU output
to a 3 step truth table, and have the setting such that below 1500rpm the solenoid isnt powered.

[crbbt]

Thank you Husa,

I gave up after an hour.
Not sure where I recall the 0.2mm hole from however

[wobbly]

First off, still nothing has been achieved to get Neels ( Vannick ) from being unblocked on here.
C'mon guys this is getting ridiculous.

The hole in the PJ dump tube idea came about when I first got access to Robert Taylors new portable dynojet.
I wanted to make something similar to the newly available Dialajet , and Intelajet setups from Thunder Products that had a fixed fuel jet, but made it adjustable by bleeding a variable amount of air
into a small volume sitting on top of the PJ tube.
This operated just like a normal main or idle air corrector, bending the fuel curve such that as the bulk air flow increased, the fuel flow was gradually decreased, countering a 2T carbs
natural tendency to run richer and richer - even though power is decreasing.
The other advantage was that bleeding air into the PJ circuit also helped to reduce droplet size due to better emulsification.
The short story was that I could never get that system to make any better power.

But during the dyno session I looked at the PJ's on a late model TZ250 and it had a tiny hole in front of the PJ tube - doing that made better top end overev power.
At the time I was also cutting the engine side of the emulsion tube shrouds off at an angle, making the top of the shroud a small radius facing the airflow, tapering down at an angle to no cut on
the carb floor facing the engine.
This was tested and proven during the dyno work at ZipKart on the Rotax 256.
So at the last minute I filled the 0.2mm front hole in the PJ and cut its end off at 45* facing the engine - this was better everywhere.

[TZ350]

.

357473 357474 357475

Ok, at first glance. Uncovering the exhaust ports at TDC does not look like it is the issue.

But a more careful look may be warranted as the cylinder could be slightly rotated and that may expose an edge of an exhaust boost port.

357476

[crbbt]

Thanks for the insight Wob!

I'll get some more tubes made up and go for the 45 angle on the discharge

[Frits Overmars]

357474
at first glance. Uncovering the exhaust ports at TDC does not look like it is the issue. But a more careful look may be warranted as the cylinder could be slightly rotated and that may expose an edge of an exhaust boost port.I can't say for sure that your problems are caused by transfer short-circuiting, but it seems certain that you do have short-circuiting, unless you have used piston plugs.

[husaberg]

It would be pretty easy to say super glue some cork plugs as a trial to see if that is the major issue it only needs to last a few minutes soak the ends in an epoxy or similar, if they break off little harm done.

[F5 Dave]

Re Neels
I know nothing about website access issues but can he create a new account with a different email perhaps?

[husaberg]

Re Neels
I know nothing about website access issues but can he create a new account with a different email perhaps?
Use a proxy with a NZ location?

[wobbly]

I will suggest that to Neels.

TeeZee, if you find you do have Aux/A port linking, the way this was solved in the kart engines to enable running no plugs, was a full triangle shape on the Aux, such that only the very small top corner
radius of the Aux was in play, for only a very short time.
The top edge of the Aux can be much longer, utilizing the high Blowdown Pressure Ratio at APO
The other thing I see is the off the wall Aux shape dead in front of the A port - absolutely incurring short circuiting around BDC when the port depression is greatest .
I have used Hi Temp Ceramic paste in the Exhaust duct when testing the exit reduction idea, it never failed on the dyno - JB Weld make one.

[wobbly]

Neels very grumpy reply - " I cannot access the kiwibiker at all, not even as non-user. "

[TZ350]

The other thing I see is the off the wall Aux shape dead in front of the A port - absolutely incurring short circuiting around BDC when the port depression is greatest .
I have used Hi Temp Ceramic paste in the Exhaust duct when testing the exit reduction idea, it never failed on the dyno - JB Weld make one.

357490

The exhaust duct tunnel was dug at the bottom of the axillary port because that brought it out between the cylinder fins. I will have to think about how I can change this.

[TZ350]

TeeZee, if you find you do have Aux/A port linking, the way this was solved in the kart engines to enable running no plugs, was a full triangle shape on the Aux, such that only the very small top corner radius of the Aux was in play, for only a very short time. The top edge of the Aux can be much longer, utilizing the high Blowdown Pressure Ratio at APO.

357491

After doing lots of fancy difficult measurements trying to work it out. I figured the easiest and best way to check for port/cylinder rotation was to assemble it all up and draw a line across the piston at TDC.

357492

Then disassemble it, pop the piston back in at TDC, align the pen marks and look inside.

357493 357494

Simple as, after wasting time doing it the hard way. A quick check and there is no exhaust or Ex axillary port exposed at TDC.


I can't say for sure that your problems are caused by transfer short-circuiting, but it seems certain that you do have short-circuiting, unless you have used piston plugs.

357496357495



Piston pin plugs might be the next move. Last time I tried them they rattled loose and the transfer port shaved them away until they were just a ball of ally rattling around in the end of the piston pin.

[wobbly]

As I said you dont need pin hole bushes, a proper triangle Aux shape fixes both vertical and horizontal linking/short circuit issues.
More especially in your case due to having nothing like the RSA bmep, you dont need to even go close to bore center.

[TZ350]

I have used Hi Temp Ceramic paste in the Exhaust duct when testing the exit reduction idea, it never failed on the dyno - JB Weld make one.

I will see what I can find. I should be able to fill part of the auxiliary port to get a more triangular shape.

I have to say no more HP but with the auxiliary exhaust ports, over rev was greatly improved. It would run out past 10,000 rpm with ease.

[Wos]

The auxiliary seem to act very late after main exhaust opening !?
Most of the job seems to be done by main and its blowdown area

Maybe better to keep auxiliary small, away from transfers, away from center of bore and set them higher, let them only act in blowdown area

[jonny quest]

TZ350

Do you have capabilities for a wide band AFR? In real-time in dyno run?

When I originally replied I thought it was more of a short circuit thing between A and your odd shaped auxiliary ports.

You may see that with AFR.

If your carb needle is too rich, this will show up on dyno like this too.

What does bike sound like holding a steady state with slide in needle operating range? Does is blubber and not zing right through the RPM's?

Make a marker line on piston and show us the A transfer angle

[TZ350]

357499 Piston pin plugs.

357500 Reference cylinder.


TZ350 When I originally replied I thought it was more of a short circuit thing between A and your odd shaped auxiliary ports. Make a marker line on piston and show us the A transfer angle

357501 Port discharge angles.

357502 357503

Alloy welding wire indicates placement of axillary port duct which is between the fins. My method to make the duct was to drill through between the fins. That initial drilling came out in the cylinder between the A and Ex ports. The upper part of the axillary port was cut into the wall of the cylinder with a mill. Speedpro handled the tricky milling job. I dug out the cylinder to connect the two parts, port and duct.

Yes. Quite a difference between the reference cylinder and mine in the area between the Exhaust port and A port. Might be a clue about where I am going wrong.


TZ350 Do you have capabilities for a wide band AFR? In real-time in dyno run?

Not now but I did use one and a data logging program with my 2Stroke EFI project.

[Hoebra]

wobbly, can you give me some advice about my PJ question from second last post on site 2740? Especially about the design of a PWM table in the ignitech? Thanks!

[wobbly]

Sorry I missed that PJ post completely.
Not the answer you want to hear, but the Mikuni solenoid PJ does not take kindly to PWM at all.
The tip wears , due to the constant hammering it gets from being cycled at 10Hz or so, and a " step " appears on the tapered end very quickly.
The Aprilia used a different solenoid for PWM, taken from a Fiat carburetor, that was originally an idle air control valve of some sort I believe ( and way cheaper as well ).

Anyway the PJ sizing depends upon the fuel used, for race or leaded gas where the overall jetting is run very lean ( simply because it can ) then the PJ size has to be quite small.
Using the Mikuni powerjets, this is in the range of 32 to 38 so that the amount of fuel being reduced is small, as the peak power EGT is already hot - well over 1200*C.
Unleaded or pump gas settings that are usually run richer with less compression and more advance, need approx twice the PJ size , up around 70 to 80.
This leans off the mixture alot more over the pipe, as its already inherently much richer.
These sizes are independent of the main used, and they work, even in a Lectron with no actual main jet at all.


As for the hard switch point, a good place to start is around 2/3 rpm between peak torque and peak power.
The fuel curve needs to start leaning of at this point due to the fact Scavenging and Trapping Efficiency start dropping immediately past peak torque, even though
the Delivery Ratio is still increasing.
But this effect is ameliorated alot by pulling out advance as the rpm rises, thus increasing the wave speed in the pipe.

Using PWM, the 0% point is closer to peak torque, and ramps to 100% ( ie no fuel ) somewhere again around 2/3 the way to peak power rpm.
Maybe Frits could confirm this, as I have never actually seen the RSW/RSA PWM table.

[Hoebra]

thanks alot, sounds very logic, I will start playing around with it and the Mik Powerjet I actually have becaus its still unused and not worn out, if the results look promising I can go looking for such a Fiat Solenoid or maybe Frits knows exactly wich typ they are from.

[Frits Overmars]

Not the answer you want to hear, but the Mikuni solenoid PJ does not take kindly to PWM at all. The tip wears , due to the constant hammering it gets from being cycled at 10Hz or so, and a " step " appears on the tapered end very quickly.
The Aprilia used a different solenoid for PWM, taken from a Fiat carburetor, that was originally an idle air control valve of some sort I believe ( and way cheaper as well ).Yeah, well, sort of. The first programmable Aprilia power jet was not a solenoid at all but a threaded needle, the same kind that you'll find as an air screw in most carbs. This needle was screwed in or out by a stepper motor that was originally designated to regulate the idle rpm of some Fiat car engine. It was soon replaced by a real solenoid that was easier to control and could also withstand the 13 Hz pulse width modulation. Imagine how Dellorto felt when their precious RSA carburettor was fitted with a solenoid from Honda-daughter Keihin.....
The pics below show the priceless RSA125 carb and the not quite so expensive Dellortos on its big brother, the rare RSA250.


Anyway the PJ sizing depends upon the fuel used, for race or leaded gas where the overall jetting is run very lean ( simply because it can ) then the PJ size has to be quite small. Using the Mikuni powerjets, this is in the range of 32 to 38 so that the amount of fuel being reduced is small, as the peak power EGT is already hot - well over 1200*C.
Unleaded or pump gas settings that are usually run richer with less compression and more advance, need approx twice the PJ size , up around 70 to 80.
This leans off the mixture alot more over the pipe, as its already inherently much richer. These sizes are independent of the main used, and they work, even in a Lectron with no actual main jet at all.
As for the hard switch point, a good place to start is around 2/3 rpm between peak torque and peak power.
The fuel curve needs to start leaning of at this point due to the fact Scavenging and Trapping Efficiency start dropping immediately past peak torque, even though the Delivery Ratio is still increasing. But this effect is ameliorated alot by pulling out advance as the rpm rises, thus increasing the wave speed in the pipe.
Using PWM, the 0% point is closer to peak torque, and ramps to 100% ( ie no fuel ) somewhere again around 2/3 the way to peak power rpm.
Maybe Frits could confirm this, as I have never actually seen the RSW/RSA PWM table.I haven't seen those mappings either in quite a while; they must be hiding somewhere in the mass of papers here. They form a multidimensional map with rpm, throttle position, gear selection an deto signal inputs, and ignition, power valve and power jet outputs
What I can do, is give you the settings of the very RSA that unleashed those 54 horses on the dyno, if you promise not to tell anyone.
You must have some Italian by now Wob, so I will leave you to it :msn-wink:.

357505357506357504
l=========================================
DRVE4734.PC:
2006-10-30; Gilera DRD 071030, LD 120, squish .74,
tubo G10/07 Sam.n°2.BN, tail 23, collettore 36, silenziatore 25,
Denso 34, accensione Poker, carb 42, AU286T2P264Max192m53-4f-P120, benzina Agip +4% Elf 909, disco 152.5°/90°.
=========================================
On second thought, this Italian was quite idiomatic so you could probably do with some clues: main jet 264, power jet 120.

[wobbly]

Thanks Frits, I had seen those small cylindrical PJ solenoids before but never made the connection to Keihin, I just looked at a carb here and yes they are identical to those
fitted to Keihin SPJ off an RS125 or RS250 Honda as of 1998.

Mikuni, in a tune up paper I have for the solenoid kits they sold, say to use a PJ/Main combination of 25/75% - thats not far off the Dellorto combination quoted.
Dellorto mains, you would think, represent mm diameter, but the dont.
For example I have a full range of pinned jets from 125 out to 195 ( 125,126,127,128 etc ) - every one of them
is very near 0.1mm different that the stamped number. ie a 150 pins at 1.6mm.
There QC is atrocious , a 150 can pin at anything from 1.58 to 1.62, and mine were all double confirmed in a diesel injector flow machine.

Super surprised to see the valve open time at 152.5*, way more than other sources have quoted at 140* thereabouts.
I will have to test that once Neels has removed every last strand of hair fighting with the coding.

[Frits Overmars]

Thanks Frits......Super surprised to see the valve open time at 152.5*, way more than other sources have quoted at 140* thereabouts.
Opening an inlet disk at about 140° before TDC is generally considered a practical value. At that point, a slight depression begins to develop in the crankcase, to which the carburettor responds favourably, i.e. changes in the carburettor settings directly result in changes in engine behaviour. And that's very nice when you are adjusting your settings.
However, that slight depression in the crankcase is going to slow down the transfer flow. And if you want to squeeze every last bit of power out of an engine, you don't want anything to hinder that transfer flow.
At low revs, the crankcase pressure has had more time to drop, so you could open the disk even earlier, in some cases even before BDC. But to be able to use that in practice, you need Neil Hintz's wonderful disk valve inlet system with its variable opening and closing points.
Of course Neil, having his Transfer Port Injection, doesn't need to fiddle with carburettor settings anyway. The man is brilliant. But you are right about his ugly knees, Wob :D.

[husaberg]

Far more common than Honda RS parts the Kawasaki KX125 and 250 and likely other bikes ran the Solenoid PJ at arround 1999 it'd the "shortie version" as well like a RS body. they also have built in TPS The 125 is the 36mm the 250 has the 38mm.
Wob has detailed how to mod the outlet on the PJ before.

the solenoid is still available $78USD
357510
https://www.cmsnl.com/kawasaki-kx125k5-1998-europe-fr-as_model11926/solenoid_211881005/

[jonny quest]

Far more common than Honda RS parts the Kawasaki KX125 and 250 and likely other bikes ran the Solenoid PJ at arround 1999 it'd the "shortie version" as well like a RS body. they also have built in TPS The 125 is the 36mm the 250 has the 38mm.
Wob has detailed how to mod the outlet on the PJ before.

The Yamaha YZ250 has had it continuously since around 2021, YZ125 now has it too, since '24 I believe.

[jonny quest]

Forgot to mention, Kawasaki is coming out with a new line of big bike 2 stroke motocross bikes again. '27 models is the rumor. No other information.

There is a ad for them I believe you can find on YouTube

[F5 Dave]

I spent 1/2 my life trying to extract as much power out of 50 and 100cc commuting bikes. Or original rules were purposefully quite restricted and the bikes didn't evolve much past 1970..

Anyway the 300cc 'big bore' (but not really) dirtbikes I ride now are fantastic for other reasons.

If your body will allow it, please buy one and enjoy a ripping 2 stroke while they still exist. We all get old. Do it if you still can.

[TZ350]

.
356395 356394 170/88 ... Red Line on graph.

70cc. The crazy inlet timing started easy enough and made more power and even idled but I did not put any effort into trying to tune it. Flagged it for something more traditional timing wise.

[wobbly]

The large number of MX bikes since about 2000 that have the solenoid PJ carb and some have the built in TPS, beware , many are the so called AirStriker versions.
These do exactly what they were designed to do, better throttle response, off the very bottom.
But on the flow bench and on the dyno, the curved guides in venturi floor completely fuck the cfm and the Hp up the front side and around peak.
Yes they are cheap if found in bike breakers, and yes you can knock out the PJ and remove the guides, but in a back to back the SPJ simply makes more power.
Up to 2Hp in a race 125.
Been there, done the research.

[jonny quest]

Power spread is exactly what MX bikes need.

I made a post a few months ago about faster opening power valves made quite a bit more power on dyno. Problem was, bike had to be geared taller otherwise it hit too hard on track. Wheel spin, abrupt hit on faces of some jumps. Had to tame with gearing.

I ended up trying slower opening valve, shorter gearing... what a difference. Able to ride bike for faster lap times hands down.

MX style motors are an art in itself. Trials bike power/road race power on top. We would like to have it all... but it ain't happening. We have to compromise everything, but be smart about it. Such a balancing act.

[Frits Overmars]

I made a post a few months ago about faster opening power valves ....Do you mean faster opening, as in fewer crankshaft degrees from fully closed to fully open, or do you mean earlier opening, as in starting to open shorter after BDC?

[jonny quest]

Do you mean faster opening, as in fewer crankshaft degrees from fully closed to fully open, or do you mean earlier opening, as in starting to open shorter after BDC?


Ball bearing governor with a spring attached to a arm for PV movement.

It will control both faster/earlier opening vs slower/later opening.

The slower/later opening combined with shorter gearing was definitely the faster way around the track even though it makes less HP from PV opening on up on the dyno.

[wobbly]

So the slower/later timing softened the " hit " making it easier to control tire spinup, and the shorter gearing made it accelerate faster due to the torque multiplication.
A better set of compromises, in that application.
Yes, MX is a special case with a special set of requirements to be fast, but you gotta realize the vast majority of members on here don't give a monkeys what happens well under the pipe.

[katinas]

KTM used Keihin carbs from MX Suzuki RM 250 for semi mass production Red Bull cup, when they was on the right way with 2T Al frame 125. Original PJ and TPS, but working must be different from MX.

[Flettner]

So the slower/later timing softened the " hit " making it easier to control tire spinup, and the shorter gearing made it accelerate faster due to the torque multiplication.
A better set of compromises, in that application.
Yes, MX is a special case with a special set of requirements to be fast, but you gotta realize the vast majority of members on here don't give a monkeys what happens well under the pipe.


I give a monkeys,

[jonny quest]

Wobbly, I know you know power off the pipe is always beneficial. Always.

The moral to my story (which was brought up because of Airstriker mention) mechanical gearing advantage in my case trumped all out power.

Bottom end power, strangely, is more beneficial the bigger an engine gets for faster lap times.

[F5 Dave]

I know I was dribbling on about Enduro bikes before which are largely used below peak, off pipe. Yesterday I was out on the Trials bike. Still good clean 2 stroke fun. . . but I don't think it has any on-pipe power:msn-wink:

[Larry Wiechman]

Wobbly, I know you know power off the pipe is always beneficial. Always.



What if my monkeys think like kart racers and use a slipper clutch that gradually engages just before peak torque? On a small displacement motor (Freetech 50 or Bucket), that would help cover up gearbox ratio gaps and the power dip at 2/3 RPM.

[jonny quest]

What if my monkeys think like kart racers and use a slipper clutch that gradually engages just before peak torque? On a small displacement motor (Freetech 50 or Bucket), that would help cover up gearbox ratio gaps and the power dip at 2/3 RPM.


Every motorcycle with a gearbox and clutch has a slipper clutch. It's your left hand. Good offroad riders constantly slip clutch in corners.

[diesel pig]

KTM used Keihin carbs from MX Suzuki RM 250 for semi mass production Red Bull cup, when they was on the right way with 2T Al frame 125. Original PJ and TPS, but working must be different from MX.

Of couse. The Red Bull bikes were meant to be all the same ( I am sure someone here would let us know if that was actually true or not) So they all should here been giving up the same amount of power with all them having the same bad carburation. So what Wobbley posted still holds water I think.

[ApolloMotoMoto]

Every motorcycle with a gearbox and clutch has a slipper clutch. It's your left hand. Good offroad riders constantly slip clutch in corners.


1000X this.

My Single-Speed Direct-Drive Kart track racing machines have a manually operated friction clutch. A carefully manuplated clutch hand converts this into a slipper clutch. All the fastest racer are apply controlled slip in certain areas around the course to maximize drive and generally keep the engine within its useful power-delivery band given my use has NO TRANSMISSION of any kind.

Yeah I care about "under the pipe" features, but only because our engines and vehicles are not yet really optimized for the use case.

We keep changing gearing to shift the RPM range relative to vehicle speed "UP" such that we can get the bike "above the torque hole" comming out of the slowest corners.

As it stands right now, we still have to use RPM's that are below 2/3rds of the torque peak, which means accelerating through the 2/3rds torque hole.

Everything that addresses while still requiring the vehicle to operate in this band is mostly a band-aid.

Really, gear ratio must be such that the vehicle never drops into that 2/3rds of peak torque "torque hole" band, with an effective power range wide enough for the application;

That means in my case, if I am going to make peak torque between 9-10k PRM in a ~90-100cc engine, I cant really be using RPM's below 7k RPM's, and with a required power range for single-speed direct-drive of 3.0+ (ideally more like 4.3-3.6...) that means this engine needs to have usable over-rev to 20k RPM's, or I am going to be forced to use the dreaded "torque hole" range.

As it stands right now, our setups are not optimized, over-rev to 15k is barely consistently achievable, engine RPM comming out of the slowest corners is 4-5k RPM's, and there is a LOT of 'manual slipper clutching".

Its mildly interesting how much of a race is decided on "cltuch games" VS. the other elements of the competition; clear evidence that the setups have quite a bit more optimization required.

It can be deceptive how much better a bigger rear sprocket can be. You think you are going to give up terminal velocity, be the way the engine is loaded will allow over-rev to extend further than intuitionally expected when you slap the bigger rear sprocket on the bike, and the torque multiplications wins everywhere else can produce an unexpected range of ideal gearing if these larger rear sprockets are never fully explored.


This is a persistent argument within my own race team and across the paddock, and everytime we put a new "biggest ever used" rear sprocket (or smaller front sprocket, or anything else that drives the ration in this direction) lap times come down, and we dont loose the terminal velocity we would expect to loose given the change.

[wobbly]

Quoting different Apple and Oranges scenario's, like direct drive karts, Gyrocopters, MX/VMX or whatever are all special, specific cases where off the pipe power does matter.
And the people doing those things imho are in the minority on here as a group.

All I am saying, for example, is that if you take any MX 125 engine where power under the pipe is so important that people even clutch the things off the slowest corners, then fit that engine to a kart the
fastest setup then needs no power at all below 9500, but has to run the shortest gear possible and thus it needs to rev to 14500 and beyond.

In this case having a carb that has fantastic throttle connection at 4500 is completely useless, especially if that carb wreaks the front side, peak and overev power.
Thus I would never use that carb in a Roadrace or LSR end use.
Same with FreeTech 50's, the fastest bikes in video's I have seen will easily rev to 16,000, and they never drop off the pipe, or if they do they get beaten by correctly tuned engines that dont.

Bucket racing, that this forum was initiated because of , is in the same category.
If you are off the pipe or slipping the clutch, a correctly tuned/ well setup bike will blow your doors off.
Quite happy to be corrected on that.

[Flettner]

Quoting different Apple and Oranges scenario's, like direct drive karts, Gyrocopters, MX/VMX or whatever are all special, specific cases where off the pipe power does matter.
And the people doing those things imho are in the minority on here as a group.

All I am saying, for example, is that if you take any MX 125 engine where power under the pipe is so important that people even clutch the things off the slowest corners, then fit that engine to a kart the
fastest setup then needs no power at all below 9500, but has to run the shortest gear possible and thus it needs to rev to 14500 and beyond.

In this case having a carb that has fantastic throttle connection at 4500 is completely useless, especially if that carb wreaks the front side, peak and overev power.
Thus I would never use that carb in a Roadrace or LSR end use.
Same with FreeTech 50's, the fastest bikes in video's I have seen will easily rev to 16,000, and they never drop off the pipe, or if they do they get beaten by correctly tuned engines that dont.

Bucket racing, that this forum was initiated because of , is in the same category.
If you are off the pipe or slipping the clutch, a correctly tuned/ well setup bike will blow your doors off.
Quite happy to be corrected on that.


In Vinduro, it's extremely difficult to be 'on the pipe' all the time. In fact the only place 'on the pipe' is used is between sections, but, I don't want to lose that between sections top end power.
So I want best top end I can muster with electronic devices to enhance the mid (and some bottom end) as best I can. Clearly powervalves, sliding gib and my vairable rear cone 'device'.
Would be EFI also, if it wasn't outlawed. Quad injector TPI would have been my choice.

[husaberg]

Mmmm., I suggested the Carbs of the mx bike primarily as a source of parts rather than raiding a somewhat limited supply of Honda RS125 parts.
TBH I never looked into the air striker thing meant I assumed it was additional air bleeds and those funny wings?

He looks at pics
357525357526
^^^^^^^
SPJ as in RS125 NX4 $$$$
Actually looks even shorter than the PWKS?
a lot of difference also in the slide config (looks more Mikuni)

is it the same slide as a PWM?



357529
^^^^^^^^^
KX125 arround 99 PWK short with a TPS and E PJ


357527357528
^^^^^^
above what is called airstiker PWK in short with tps but no E PJ or to the right as totally bare no TPS or E PJ

[wobbly]

Its the " funny wings" that generate extra venturi velocity at low slide heights, but they also completely wreak the rest of the powerband.

[Wos]

I know I was dribbling on about Enduro bikes before which are largely used below peak, off pipe. Yesterday I was out on the Trials bike. Still good clean 2 stroke fun. . . but I don't think it has any on-pipe power:msn-wink:

The needs of trial bikes is to have torque and driveability from deepest rpms...

Big cross or enduro 2t bikes need a compromise between trial and road race...yes ;)

Big 300 cross and trial bikes often use ex timing under 185 degree and ignition timing curvr is Completely diffrent from road racers, for example to avoid hard hitting response on short geared bikes

Think its an advantage to know best of every diffrent world ...

Grüße Wolfgang

[JdG]

I have a jetting question: Say that you go from 2% oil in the fuel to 4%. For instance after seeing Frits’s RS125 data that says 4% Elf HTX909 was being used by world champion bikes.

Should you then blindly jet 2% richer to compensate for the fuel that is displaced by the oil that burns less good and to maybe prevent detonation? I can imagine that the higher oil percentage lowers the octane value of the mix and that the oil in the mix makes the engine “see” a leaner mixture.


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[JdG]

RS125 should be RSA 125. Sorry Frits [emoji51]


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[wobbly]

The only properly conducted oil ratio test I have done was testing HTX 909 on the dyno several years ago when we still used KT100 Yamaha's.
As no one would ever use 2% in any race engine the test started at 32:1 = 3.124% , then 25:1 = 4%, then 20:1 = 5% , then 16:1 = 6.25%.
The tests were all immediately back to back, and the tune was monitored with a CHT clamped to the case determining the warmed up start temp, and the EGT determining the final run temp.

The only result that was of interest at the time was did more oil make more power.
The answer was yes, each change from 32 to 25 then 20:1 all made small increments in power, 0.75 Hp in 16Hp when changing the oil ratio to 20:1 from 32:1.
At 16:1 it made no more power.

In all cases the final EGT was practically identical, within 5*C of the final temp of 650*C thus no jet change was needed nor attempted.
It may seem " logical " that more oil, displaces fuel in the mix - thus making it run leaner, but what many dont realize is that there is also more energy value in the oil, than in the fuel.
If there was any change in the jetting needed, the EGT value would have immediately been obvious, there was none.
So just maybe the combination of less friction, and more fuel energy contributed to the small power increase in that air cooled engine.

I have also tested, over extended time frames, using more oil in the KZ engines, in this case using Vrooam semi castor - a super clean burning oil, or Maxima 927.
On the dyno changing from 32 to 25 to 20:1 made no discernable difference in power, nor the jetting needed ie less than 2/10Hp in 50Hp with absolutely identical EGT - but the piston skirt wear rate, and the wear on the big end washers silver plating is easily measurable and visually better at 20:1.
In this case the parts are changed at the same run hours on the data logger, but imho its making the engine safer and holds up its as dyno'd power longer.

[F5 Dave]

That's real interesting and introspective empirical information, so thank you.
But why did you spell realised with a 'z'? I assume autocorrect.

[JdG]

Thanks a lot for the detailed information Wobbly!

Very interesting to know that one can vary quite a lot with the oil : fuel ratio without having to change the jetting.

Also like you said: no race engine should run 50:1, but there’s still heaps of people around that think that more oil reduces power (because of less fuel, if you don’t consider the oil to be a good fuel also) and who are scared that their engine will foul in no-time because of the additional oil.


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[lohring]

On our 26 cc race engines we found doubling the manufacturer's recommended ratio to 16:1 increased power significantly. Power still increases up to around 10:1 and the big end bearings live longer at 16 to 19,000 rpm. More oil doesn't seem to increase power further. We tested several different oils at the same ratio and there was no power difference. All this i believe comes from better sealing on our 36 mm, single ring pistons. I would expect this to make less difference on larger pistons. Below is our fuel test data.

Lohring Miller

357531

[wobbly]

The other side benefit of the 20:1 oil mix was that due to extra oil cushioning, having the reed corner tips fretting with constant serious overev was eliminated in the KZ engines.

[lodgernz]

The only properly conducted oil ratio test I have done was testing HTX 909 on the dyno several years ago when we still used KT100 Yamaha's.
As no one would ever use 2% in any race engine the test started at 32:1 = 3.124% , then 25:1 = 4%, then 20:1 = 5% , then 16:1 = 6.25%.
The tests were all immediately back to back, and the tune was monitored with a CHT clamped to the case determining the warmed up start temp, and the EGT determining the final run temp.

The only result that was of interest at the time was did more oil make more power.
The answer was yes, each change from 32 to 25 then 20:1 all made small increments in power, 0.75 Hp in 16Hp when changing the oil ratio to 20:1 from 32:1.
At 16:1 it made no more power.

In all cases the final EGT was practically identical, within 5*C of the final temp of 650*C thus no jet change was needed nor attempted.
It may seem " logical " that more oil, displaces fuel in the mix - thus making it run leaner, but what many dont realize is that there is also more energy value in the oil, than in the fuel.
If there was any change in the jetting needed, the EGT value would have immediately been obvious, there was none.
So just maybe the combination of less friction, and more fuel energy contributed to the small power increase in that air cooled engine.

I have also tested, over extended time frames, using more oil in the KZ engines, in this case using Vrooam semi castor - a super clean burning oil, or Maxima 927.
On the dyno changing from 32 to 25 to 20:1 made no discernable difference in power, nor the jetting needed ie less than 2/10Hp in 50Hp with absolutely identical EGT - but the piston skirt wear rate, and the wear on the big end washers silver plating is easily measurable and visually better at 20:1.
In this case the parts are changed at the same run hours on the data logger, but imho its making the engine safer and holds up its as dyno'd power longer.

Wobbly, do you think that similar results would be observed with a fully synthetic oil such as Motul 800? I realise that HTX909 is only partially synthetic, partly bean.

[ApolloMotoMoto]

Aprilia RSA 125 Electronics Question....

Does anyone here have any familiarity with the electrical specifications of the AC Magneto system on the Aprilia RSA125?

Picured here;

It "appears" to be a similar configuration to the KTM 50 AC Magneto;

Bi-Symetrical rotor magnet (inner rotor style).

Exciter coil "pairs" with the exciter coils wrapped around a stator "pole piece" which face/engages the rotor magnets flux through the air gap.

I am ASSUMING (but would love confirmation) that the exiter coils are wired in PARELLEL such that each exciter coil "pair" behaves similarly to a single coil with a number of winding turns equal to the summed turns of the pair, but with HALF (roughly) the effective inductance.

This dual exciter coil "pair" configuration allowing for half the inductance for the same voltage output slope, yielding more efficienct charging of the main charge/discharge capacitor in the CDI.

I am ASSUMING this is the configuration used in the Aprilia RSA125....


Furthermore, the Aprilia Stator has an ADDITIONAL pair of exciter coils (compared to the KTM 50 example) that are 90 degrees opposed to the first pair.

This leads me to assume (given the assumed bi-symetrical 2-pole rotor magnet) the out-put waveform from the Aprilia RSA125 magneto stator would show TWO electrical cycles per engine revolution;

Essentially doubling the "charge availabe per revolution".



Picutred along with the Aprilia RSA125 magneto is the KTM 50 magneto (1x pair of black potted coils) and the magneto from my engine system (1x single coil wrapped on red winding bobbin).


Does anyone know the specifics electrical specifications for the RSA125 magneto or enough to answer/ confirm my suspicions?





357532357533357534357535

[wobbly]

Lodger, part of the answer lies in the introduction of many fully synthetic race oils, they all started to appear around the time that GP racing converted to Unleaded fuel.
Motul 800 Elf 976 etc.
Unleaded is best when operated rich, with less compression and more timing.
Up to that time the most widely used oil was semi castor Castrol 927, in fact I know for sure that many teams with oil sponsors actually secretly substituted this so as not to upset anyone.

In the tests I did ALL the fully synthetic oils LOST power when run in the KT100 up at an EGT of 650*, no matter what the oil ratio was, compared to the HTX 909.
What you have to realise is that all the synthetics, when tested in a Timken/Falex machine, have huge oil film strength, but the instant they loose this film and are overheated, they break down into their component
constituents, that are NOT actual lubricants at all.

The very old R30 castor oil has probably 1/10th of the film strength, but when its overheated and breaks down, those component chemicals still operate as lubricants.
And I know some experts have rubbished the Falex machine as being unrealistic in a 4T, but empirical evidence in a 2T shows exactly the same characteristics as the machine demonstrates.
When a synthetic film is broken down, it tears the shit out of everything, a Castor type fails sooner, but the wear pattern is perfectly smooth on the test shaft.

In the KT100 test at very high run temps, I was seeing really premature piston skirt wear using Motul 800 and several other full synthetics - plus the obvious power losses.
I had used Maxima 927 in the USA with 110 race gas in World Champ Jetski's, as the HTX909 was not compatible and would separate out very quickly.
Both are semi castor mixes, and that seems to be the holy grail in 2T race engines operated out at the limits.
HTX909 separates real quick in AvGas, the Maxima doesnt, but both those oils are perfectly fine in pump gas, or the unleaded fuels mandated for CIK or FIA racing.

[TZ350]

It may seem " logical " that more oil, displaces fuel in the mix - thus making it run leaner, but what many don't realize is that there is also more energy value in the oil, than in the fuel.

Yes, that is what I found with my 2S EFI project. After a hard full throttle pull on the Dyno. I could completely shut all the fuel off but with the electric oil injection pump still going. The motor would keep running just burning the oil and it would pickup on the throttle again for another pull. I wanted very good oiling on over run and it seemed it was enough to keep the motor running on very small throttle openings.

[Flettner]

A rubbish post, deleted.

[Flettner]

Another rubbish post, I deleted it also.

[husaberg]

Aprilia RSA 125 Electronics Question....

Does anyone here have any familiarity with the electrical specifications of the AC Magneto system on the Aprilia RSA125?

Picured here;

It "appears" to be a similar configuration to the KTM 50 AC Magneto;

Bi-Symetrical rotor magnet (inner rotor style).

Exciter coil "pairs" with the exciter coils wrapped around a stator "pole piece" which face/engages the rotor magnets flux through the air gap.

I am ASSUMING (but would love confirmation) that the exiter coils are wired in PARELLEL such that each exciter coil "pair" behaves similarly to a single coil with a number of winding turns equal to the summed turns of the pair, but with HALF (roughly) the effective inductance.

This dual exciter coil "pair" configuration allowing for half the inductance for the same voltage output slope, yielding more efficienct charging of the main charge/discharge capacitor in the CDI.

I am ASSUMING this is the configuration used in the Aprilia RSA125....


Furthermore, the Aprilia Stator has an ADDITIONAL pair of exciter coils (compared to the KTM 50 example) that are 90 degrees opposed to the first pair.

This leads me to assume (given the assumed bi-symetrical 2-pole rotor magnet) the out-put waveform from the Aprilia RSA125 magneto stator would show TWO electrical cycles per engine revolution;

Essentially doubling the "charge availabe per revolution".



Picutred along with the Aprilia RSA125 magneto is the KTM 50 magneto (1x pair of black potted coils) and the magneto from my engine system (1x single coil wrapped on red winding bobbin).


Does anyone know the specifics electrical specifications for the RSA125 magneto or enough to answer/ confirm my suspicions?





357532357533357534357535

I have no idea if they are the same rotor but this is the size.

357538357655
They look the same 02-23
You can get programble ignition kits for them as well

a mini albulm for the GP Aprilia ignition https://www.kiwibiker.co.nz/forums/album.php?albumid=5248
a mini albulm for the GP Aprilia Carbs https://www.kiwibiker.co.nz/forums/album.php?albumid=5249

[fpayart]

Hi,

There are clearly several versions.
Here's what I have available:
Mine is a SELETTRA.
The stator has four coils, I can't determine how they are connected.
The output connector only has two pins.
The rotor has six poles.
The Aprilia RSA125's output signal is generated by a sensor located on the engine casing.
This sensor is activated by a notch in the crankshaft.


Regards.
Francis.

[ApolloMotoMoto]

Thank you so much guys!

A lot can be infered from what you have shared, and that Aprilia GP ignition album is gold. Wow, they used every coil configuration imaginable on the RSA it seems! Single coils configurations with large pole area wrap around the magnet rotor. Dual coil configurations essentially identical to the KTM 50. Quad coil configurations noted to have only two discrete output wires, a clear indication that all 4 coils are in electrical parallel (or series until the wiring is confirmed, but parallel would make the most sense to me...). The note about your rotor magnet having 6 poles on it is also highly interesting and confirms some suspicions I have; that a 'simple' 2 pole rotor magnet was clearly not the only thing used on an RSA either. That is a whole FAMILY of AC magneto configurations.


...It's almost like they were hunting for more charge energy transfer into the main charge/discharge capacitor in the CDI over and over and over again, by any means necessary. I wonder what could possibly drive such a persistent development of higher order complexity magneto configurations....

The CDI can only deliver an amount of energy to the spark plug that is equal to (and likely some amount less) than what was initially stored as charge on that capacitor, even with 100% transfer efficiency from CDI to plug gap (not happening) 100% of "not enough energy" for a given cylinder condition is still going to be "not enough".

But, what is it that drives you into "not enough" ignition territory?

I remember a story about a confligration of leaves being turbulently scattered by the winds of a hurricane.

"It is not that the MSV is too high, it's that the ignition cant keep up."


A very interesting story to ponder.

[husaberg]

these two stand out as being distinct from the others
one is on the 500 twin.
357649
the other on a late looking 250 twin
357650

in the carb album a few late looking bikes including Marcos one seem to have the powerjet solenoid blanked off?
357654357653357652357651

[fpayart]

Hi,

The rotor has six poles.

Sorry, it was a typo, I should have written 4 poles instead of 6.

[lodgernz]

Lodger, part of the answer lies in the introduction of many fully synthetic race oils, they all started to appear around the time that GP racing converted to Unleaded fuel.
Motul 800 Elf 976 etc.
Unleaded is best when operated rich, with less compression and more timing.
Up to that time the most widely used oil was semi castor Castrol 927, in fact I know for sure that many teams with oil sponsors actually secretly substituted this so as not to upset anyone.

In the tests I did ALL the fully synthetic oils LOST power when run in the KT100 up at an EGT of 650*, no matter what the oil ratio was, compared to the HTX 909.
What you have to realise is that all the synthetics, when tested in a Timken/Falex machine, have huge oil film strength, but the instant they loose this film and are overheated, they break down into their component
constituents, that are NOT actual lubricants at all.

The very old R30 castor oil has probably 1/10th of the film strength, but when its overheated and breaks down, those component chemicals still operate as lubricants.
And I know some experts have rubbished the Falex machine as being unrealistic in a 4T, but empirical evidence in a 2T shows exactly the same characteristics as the machine demonstrates.
When a synthetic film is broken down, it tears the shit out of everything, a Castor type fails sooner, but the wear pattern is perfectly smooth on the test shaft.

In the KT100 test at very high run temps, I was seeing really premature piston skirt wear using Motul 800 and several other full synthetics - plus the obvious power losses.
I had used Maxima 927 in the USA with 110 race gas in World Champ Jetski's, as the HTX909 was not compatible and would separate out very quickly.
Both are semi castor mixes, and that seems to be the holy grail in 2T race engines operated out at the limits.
HTX909 separates real quick in AvGas, the Maxima doesnt, but both those oils are perfectly fine in pump gas, or the unleaded fuels mandated for CIK or FIA racing.

Thank you Wobbly. Excellent reply as always

[wobbly]

So as Neels STILL hasn't access allowed here on KB, he has asked me to post this new video.
Can Admin please spend some Xmas time and get this sorted for him.

https://www.youtube.com/watch?v=zItXBc0gRvw&t=13s

[lodgernz]

Ha ha, I already use what is called a Hyper Coating,a thermal barrier coating usually used for retaining heat in exhaust systems.
See here :http://www.hpcoatings.co.nz/ExhaustHeatManagement.aspx#HiPerCoat_Extreme.
I just happened to see the inside of a special race engine at TM that had a black " coating " of some sort.
The legality could strictly be questioned, as a basic rule of the class is " no added material ",but the coating has never been questioned by tech.
Let alone the clear thermal barrier coating in the combustion chamber, that you cant see when oil residue is burnt onto its surface.

JanBros - the big problem with trying to replicate the STA and or bmep of the Aprilia is that this engine was R&D'd to death on both the dyno and the flow bench.
The STA numbers nowhere near match,as the Blowdown Cd is hugely affected by the port exit geometry,and this works way better than the raw numbers generated by the simply calculated area.
Then you have a plethora of tiny details ( such as PWM powerjet operation ) and unless you replicate all of this synergy,the numbers you are trying to simulate in your own project are stuff of daydreams.

Wobbly, please forgive me for reviving a very old post. Can I just ask if you have ever used HiperCoat Extreme to line the combustion chamber?

[wobbly]

I have used the thermal barrier coating in several scenario's - after successfully HPC doing the pipes on my GT R35.
The testing I did on the piston and combustion chamber surfaces immediately gave a huge deto increase on the dyno, something I had not envisioned at all.
After the shock, I did some serious dreaming about the issue, and finally came up with the fact ( after prompting from Mr Overmars ) that the coating, in doing its job
of preventing heat from transitioning thru to the base material, was creating a super hot boundary layer surface in the squish band.
Thus causing much worse deto than before.

So - easy new test, stick both items in the lathe and remove the coating from the squish area with wet and dry.
Boom, instantly hotter EGT, power increase, and no more deto than previously.

This was used for the first time in the " Stock " Jetski class at the Havasu Champs.
The tech guy looked at the pistons with a very black oil layer in the middle and said " Wow, no wonder you guys won, that piston has been hot as hell ".
Never thinking to check if some cheating bastard hadnt cut the skirts short on one side as well.

So, yes coating the piston center only, reduces the thermal loading, and coating the combustion chamber only reduces the thermal transfer of heat energy into the water.
Sadly ceramics are specifically outlawed in KZ racing, so I have never actually done that - though how the hell anyone could detect a clear coated surface I dont know.

[lodgernz]

I have used the thermal barrier coating in several scenario's - after successfully HPC doing the pipes on my GT R35.
The testing I did on the piston and combustion chamber surfaces immediately gave a huge deto increase on the dyno, something I had not envisioned at all.
After the shock, I did some serious dreaming about the issue, and finally came up with the fact ( after prompting from Mr Overmars ) that the coating, in doing its job
of preventing heat from transitioning thru to the base material, was creating a super hot boundary layer surface in the squish band.
Thus causing much worse deto than before.

So - easy new test, stick both items in the lathe and remove the coating from the squish area with wet and dry.
Boom, instantly hotter EGT, power increase, and no more deto than previously.

This was used for the first time in the " Stock " Jetski class at the Havasu Champs.
The tech guy looked at the pistons with a very black oil layer in the middle and said " Wow, no wonder you guys won, that piston has been hot as hell ".
Never thinking to check if some cheating bastard hadnt cut the skirts short on one side as well.

So, yes coating the piston center only, reduces the thermal loading, and coating the combustion chamber only reduces the thermal transfer of heat energy into the water.
Sadly ceramics are specifically outlawed in KZ racing, so I have never actually done that - though how the hell anyone could detect a clear coated surface I dont know.

No such restrictions in Bucket Racing of course. When you say "the centre of the piston" do you mean just the area of the dome that is inside the squish band area?
Do you think the coating will last in the relatively benign conditions of a 100cc 2T Bucket turning out bugger all more than 22HP? And is it worth the trouble?

[wobbly]

Yes, keep the coating out of the squish band.
Technically reducing the thermal load on the piston, as well as reducing thermal loss to the water, is going to increase the energy in the combustion space.
I used the ceramic thermal barrier coating for pistons from HPC - no issues at all with adhesion or efficiency.

[lodgernz]

Yes, keep the coating out of the squish band.
Technically reducing the thermal load on the piston, as well as reducing thermal loss to the water, is going to increase the energy in the combustion space.
I used the ceramic thermal barrier coating for pistons from HPC - no issues at all with adhesion or efficiency.

Thanks Wobbly.

[wobbly]

And dont forget the test I did for Jan, ceramic coating the Exhaust duct.
His boss, the great leader, insisted that retaining the heat energy in the exiting Exhaust gasses would increase power - Jan disagreed.
When I finally got to do this experiment, the deto level went thru the roof and the 48Hp KZ125 engine lost 1.5 Hp.
But to stop the dangerous deto level, it would have to be jetted hugely richer - loosing way more power.
As it turned out WankerVeen was still convinced of his own superior cleverness with hot Exhaust ducts, but history tells a slightly different story with the absolutely pitiful performance of his
infamous 125GP engine project failure.

[diesel pig]

And dont forget the test I did for Jan, ceramic coating the Exhaust duct.
His boss, the great leader, insisted that retaining the heat energy in the exiting Exhaust gasses would increase power - Jan disagreed.
When I finally got to do this experiment, the deto level went thru the roof and the 48Hp KZ125 engine lost 1.5 Hp.
But to stop the dangerous deto level, it would have to be jetted hugely richer - loosing way more power.
As it turned out WankerVeen was still convinced of his own superior cleverness with hot Exhaust ducts, but history tells a slightly different story with the absolutely pitiful performance of his
infamous 125GP engine project failure.

While you are talking about heat and exhaust ducts, I thought I would run an idea I had after reading frits and your take on two stroke cooling. This is my idea. Take the coolant coming out of the bottom the of the cooling radiator and feed 50% of it into the area around the C port or ports, have this cooling tranfers and then using blanking plates have it travel into the cylinder head and then out of the engine. At the same time feed the other 50% of the coolant into the intake cooling jacket/s at the bottom of the exhaust port/ports like on Two stroke dirt bikes and using the same blanking plates mentioned before to direct this coolant down the exhaust port to a length equal to 150% of the bore diameter and then have it leave from it's own exit duct at the end of the exhaust duct. Only having it combine with the other coolant in the pipe work going to the top of the cooling radiator. Does this idea have any merit? or am I missing something?

[wobbly]

That idea has merit, absolutely.
But another similar idea , that has just been finished in CAD as we speak, is to feed all the cold water in above the C port, and arrange the combustion insert such that nothing flows up anywhere into the head.
The cold water, having done its initial job, then flows forward over the entire Exhaust duct length, out to my suggested 150% of the bore.
It then exits this point, and externally, via a short hose enters the front side of the head, above the insert, crosses the chamber and exits out at the rear, directly above the cold inlet spigot in the cylinder.

Thus the warmest water crosses the combustion chamber, reducing the temp delta stealing heat energy from the inner combustion wall.
Cold water can also be plumbed to enter the bottom of the case, to cool the vertical channel, separating the gearbox, then upward as normal thru restrictor drillings underneath the Exhaust duct.
A concept proven in the latest winning KZ engines.
Another detail is that water , not only cools the space between the bore and the Transfer inner walls, but is also flowing completely around the Transfers outer walls within the cylinder - travelling
forward toward the ducts end exit hose.

The twin parallel circuit concept I proved worked perfectly , and easily , in the successful Jet Ski projects.
That is cold water in the cylinder with its own low temperature regulated outlet, and a second separated head circuit at more than double the cylinder exit temperature.
Doing essentially the same thing in series, I believe, is also a simple and achievable viable solution that relies on a single radiator cooler.

[JdG]

https://youtu.be/aJ_0zwsa4mw?si=NtOVWalPjtVhSLXm

Most of you must already know this man and maybe Jan and Frits have some nice stories to tell about this remarkable man.

The video isn’t perfect regarding the technical information and mentioned (power) numbers, but that aside, I can’t have anything but huge respect for the skills of this man.


Verzonden vanaf mijn iPhone met Tapatalk

[Frits Overmars]

https://youtu.be/aJ_0zwsa4mw?si=NtOVWalPjtVhSLXm Most of you must already know this man and maybe Jan and Frits have some nice stories to tell about this remarkable man. The video isn’t perfect regarding the technical information and mentioned (power) numbers, but that aside, I can’t have anything but huge respect for the skills of this man.I share your respect for Gabriele Gnani. Here is a collection of his videos:

https://www.youtube.com/watch?v=3tJupBvcIQs

https://www.youtube.com/watch?v=XTCWU78CjBw

2021:

https://youtu.be/xJPYXG1oGl4

dyno:

https://www.youtube.com/watch?v=Lxq-9tPxWc8

2016:

https://www.youtube.com/watch?v=ONS0elyCX8s&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=BEeMHT0E1m8&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=4Rh6J6stfMQ&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=7ys5PfS___g&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=i_VWzz7HMn0&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=mwX8qCTT2nQ&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=c5Df3ICSy48&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=EgynmhCn2wM&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=LCm5ZCyy4Gc&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=irw9-pK-tT0&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=I8aZR-c1V2A&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=wdDPvVVrVBM&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=e_j5Yjm7-0E&ab_channel=cristiancorticchia

2017:

https://www.youtube.com/watch?v=_WxgXOe5ma4&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=wQmrG8u_ijE&t=147s&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=cbSracHHIvw&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=SGjpDo6yp2U&ab_channel=cristiancorticchia

[diesel pig]

https://youtu.be/aJ_0zwsa4mw?si=NtOVWalPjtVhSLXm

Most of you must already know this man and maybe Jan and Frits have some nice stories to tell about this remarkable man.

The video isn’t perfect regarding the technical information and mentioned (power) numbers, but that aside, I can’t have anything but huge respect for the skills of this man.


Verzonden vanaf mijn iPhone met Tapatalk

A video well worth watching. A very impressive Man.

[diesel pig]

That idea has merit, absolutely.
But another similar idea , that has just been finished in CAD as we speak, is to feed all the cold water in above the C port, and arrange the combustion insert such that nothing flows up anywhere into the head.
The cold water, having done its initial job, then flows forward over the entire Exhaust duct length, out to my suggested 150% of the bore.
It then exits this point, and externally, via a short hose enters the front side of the head, above the insert, crosses the chamber and exits out at the rear, directly above the cold inlet spigot in the cylinder.

Thus the warmest water crosses the combustion chamber, reducing the temp delta stealing heat energy from the inner combustion wall.
Cold water can also be plumbed to enter the bottom of the case, to cool the vertical channel, separating the gearbox, then upward as normal thru restrictor drillings underneath the Exhaust duct.
A concept proven in the latest winning KZ engines.
Another detail is that water , not only cools the space between the bore and the Transfer inner walls, but is also flowing completely around the Transfers outer walls within the cylinder - travelling
forward toward the ducts end exit hose.

The twin parallel circuit concept I proved worked perfectly , and easily , in the successful Jet Ski projects.
That is cold water in the cylinder with its own low temperature regulated outlet, and a second separated head circuit at more than double the cylinder exit temperature.
Doing essentially the same thing in series, I believe, is also a simple and achievable viable solution that relies on a single radiator cooler.

Very interesting! I must abmit I was under the mistaken impression the whole engine would need the coldest coolent possible but now you mentioned it I can understand why the combustion chamber would not need to be as cooled as much as the transfer or exhaust ports

[husaberg]

Very interesting! I must admit I was under the mistaken impression the whole engine would need the coldest coolent possible but now you mentioned it I can understand why the combustion chamber would not need to be as cooled as much as the transfer or exhaust ports
IMO cases should get the coolest....

357657357658
You need to avoid that hot gearbox oil heating the cases as well as het from the cylinders.
if water cooling the cases is impractical Frits friend has a ceramic insulated paint work around. EMOT
although reading this Patrick has another diy solution


Wob, what do the tech minions say about painting? Surely they can't object to that, can they?
Now there happens to be a paint that is not too good at conducting heat. In fact it was developed to heat-protect Soviet satellites. But it works in two-strokes too.
If you coat the crankcases and the transfer ducts internally, the temperature of the gearbox oil and the wall temperature of the transfer ducts won't matter any more.
You can get the stuff at http://emot.nl/contact.php.
336012

An older project i´ve got has this mod actually.
But i blended my own coating.
It is a ceramic weldingspray that protects from weldsputter that i blended up with some ordinary 2k paint.
Then brush painted it onto the crankhousing.

I testpainted first on a aluminium sheet and heated it up from behind with a torch, it worked =)
But cant rememer any numbers sadly enough :(

Edit: i tested with a IR gun.

[diesel pig]

Interesting stuff, husaberg. I just checked out EMOT's site and they don't appear to list this Hi-temp paint anymore. As a typically Buckeeter I was thinking more about my cooling mod's as relates to a existing set of crankcase's but if one had a blank design sheet, I too would go for a cooling jacket between the gearbox and the crankwell. I am starting to look at the cooling of the lower half of a Two Stroke like how boy racer's think of there intercooler's on there turbo engine's.

[husaberg]

Interesting stuff, husaberg. I just checked out EMOT's site and they don't appear to list this Hi-temp paint anymore. As a typically Buckeeter I was thinking more about my cooling mod's as relates to a existing set of crankcase's but if one had a blank design sheet, I too would go for a cooling jacket between the gearbox and the crankwell. I am starting to look at the cooling of the lower half of a Two Stroke like how boy racer's think of there intercooler's on there turbo engine's.
Swede Patrick mentioned he made his one mixing welding anti-splatter ceramic coat and paint

This stuff is likely very close to what the emot was using not sure how it would cope with petrol
https://insulationcoatings.com.au/the-science-behind-super-therm-insulation-coating/

https://www.u-buy.co.nz/product/8BKHJDQK-thermacels-insulating-paint-additive-1-gallon-package?srsltid=AfmBOoppbKB3elMmzBm53jMl-LA-HM7SUK1-hESQ874tB1sdOpvTaFmo

this can be purchased down to 1.5 lters
https://www.carboline.com/products/product-details/Thermaline-4900-Aluminum/



https://www.tegrastate.eu/p/inral-spray-paint-ceramics-high-gloss-coating-ral9003-white-glossy/

but I would get a can of ceramic splatter and a can of high temp exhaust paint and spray 50-50 into a lid and voila....

[diesel pig]

It's good to know there are options. I would like to know wobbley's opinion on Hi-temp coatings. As he strikes me as a man who doesn't put up with things that look like they work but are more show than go.

[Frits Overmars]

I just checked out EMOT's site and they don't appear to list this Hi-temp paint anymore. As a typically Buckeeter I was thinking more about my cooling mods as relates to a existing set of crankcases but if one had a blank design sheet, I too would go for a cooling jacket between the gearbox and the crankwall. I don't know whether Martijn Stehouwer ever offered that Russian insulation varnish on his EMOT website. It's rather specialized stuff and most people who might be interested in it know Martijn personally, so there was no need to advertise it. There are bound to be other useful items that aren't listed on his website; it can't hurt to send an email.

A cooling jacket between the crankcase and the gearbox is definitely a good idea. But it doesn't necessarily have to be a liquid jacket.
Most plastics have poor heat conductivity, especially compared to aluminium. I once worked on a 125cc Rotax kart engine, which was actually a 250cc engine into which Rotax had placed a 125 cc crankshaft. There was plenty of space around the crankshaft in the crankcase, which I filled with a plastic ring that I had cut from a 4-inch water pipe.
It worked great. Not because of the reduction in crankcase volume (which was actually more favorable for power than the small crankcase volumes of the “real” 125 cc engines of the time), but because it significantly reduced contact between the fuel/air mixture and the hot crankcase walls.
357660

[diesel pig]

I don't know whether Martijn Stehouwer ever offered that Russian insulation varnish on his EMOT website. It's rather specialized stuff and most people who might be interested in it know Martijn personally, so there was no need to advertise it. There are bound to be other useful items that aren't listed on his website; it can't hurt to send an email.

A cooling jacket between the crankcase and the gearbox is definitely a good idea. But it doesn't necessarily have to be a liquid jacket.
Most plastics have poor heat conductivity, especially compared to aluminium. I once worked on a 125cc Rotax kart engine, which was actually a 250cc engine into which Rotax had placed a 125 cc crankshaft. There was plenty of space around the crankshaft in the crankcase, which I filled with a plastic ring that I had cut from a 4-inch water pipe.
It worked great. Not because of the reduction in crankcase volume (which was actually more favorable for power than the small crankcase volumes of the “real” 125 cc engines of the time), but because it significantly reduced contact between the fuel/air mixture and the hot crankcase walls.
357659357660

Thanks for the idea about the plastic pipe as a heat gap, Frits. There are larger cc versions of the engine I am looking at using, which get the cc's by longer stroke's which should mean more room in the crankwell for a larger crankshaft so hopefully making room for the shorter (and hopefully smaller diameter) stroke crank I want to use and the plastic pipe heat gap.

P.S. I may well send Martijn Stehouwer a email about the paint but I will wait until the new year.

[wobbly]

Frits friend Roland Holzner when he designed the Modena KZ engine, engineered a " plastic " insert that completely lined the intake surfaces from the reed block mount face , all
the way thru the case up to the Transfer duct entries.
Thus the inducted A/F never actually contacted the hotter metal, except down the sides of the crank.
It somehow got through the CIK tech inspection of the 50 units for homologation, but quickly the CIK banned it from any future engines.

EDIT - easily replicated using 3D printed fuel resistant polymers.

The ceramic coatings I have used were developed to prevent heat from migrating through to the metal substrate - I have not had a look or had any experience with coatings that do the reverse
ie ,preventing heat from migrating from the substrate out to the coatings surface - mind you, the coating used on the inside of 4T headers is so effective the pipes are only warm to the touch on the outside at idle.

[wobbly]

I loved the fact that Gnani , in the second video, demonstrated his own home made Timken/Falex 2T oil testing machine.
This method of oil test has been completely rubbished by the self proclaimed 4T lubrication experts - Lake Speed Jnr being the worst and most " loud mouth Yank " annoying.
But in the dyno testing I did of Synthetic Vs Castor and oil mix ratio's, the piston skirt wear rate and form, was absolutely analogous between reality and the machines results.

[TZ350]

There was plenty of space around the crankshaft in the crankcase, which I filled with a plastic ring that I had cut from a 4-inch water pipe.
It worked great. Not because of the reduction in crankcase volume (which was actually more favorable for power than the small crankcase volumes of the “real” 125 cc engines of the time), but because it significantly reduced contact between the fuel/air mixture and the hot crankcase walls.
357660

If our new water cooled crankcase idea springs leaks and is too difficult we will try the plastic liner idea.

357663

We are about to test a 50cc motor that has water circulating through the casting cavities around the crankcase.

[pete376403]

I loved the fact that Gnani , in the second video, demonstrated his own home made Timken/Falex 2T oil testing machine.
This method of oil test has been completely rubbished by the self proclaimed 4T lubrication experts - Lake Speed Jnr being the loudest and most " loud mouth Yank " annoying.
But in the dyno testing I did of Synthetic Vs Castor and oil mix ratio's, the piston skirt wear rate and form, was absolutely analogous between reality and the machines results.

Many years ago (like 30-40 years) Dirt Bike magazine did a big dyno shootout of various oils, using a DT1 Yamaha, which got a fresh piston and rings after each test. IIRC the autolube was disconnected and they ran premix. Castrol R came out near or on top.

[diesel pig]

If our new water cooled crankcase idea springs leaks and is too difficult we will try the plastic liner idea.

357663

We are about to test a 50cc motor that has water circulating through the casting cavities around the crankcase.

Do you mean you are going to run coolant throu the cavities that attach the engine mounts that are normally empty air? if not, what do you mean? I abmit I do not follow what you mean with this picture.

[JdG]

I share your respect for Gabriele Gnani. Here is a collection of his videos:

https://www.youtube.com/watch?v=3tJupBvcIQs

https://www.youtube.com/watch?v=XTCWU78CjBw

2021:

https://youtu.be/xJPYXG1oGl4

dyno:

https://www.youtube.com/watch?v=Lxq-9tPxWc8

2016:

https://www.youtube.com/watch?v=ONS0elyCX8s&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=BEeMHT0E1m8&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=4Rh6J6stfMQ&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=7ys5PfS___g&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=i_VWzz7HMn0&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=mwX8qCTT2nQ&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=c5Df3ICSy48&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=EgynmhCn2wM&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=LCm5ZCyy4Gc&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=irw9-pK-tT0&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=I8aZR-c1V2A&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=wdDPvVVrVBM&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=e_j5Yjm7-0E&ab_channel=cristiancorticchia

2017:

https://www.youtube.com/watch?v=_WxgXOe5ma4&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=wQmrG8u_ijE&t=147s&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=cbSracHHIvw&ab_channel=cristiancorticchia

https://www.youtube.com/watch?v=SGjpDo6yp2U&ab_channel=cristiancorticchia

Thanks Frits! Saves a lot of time, filtering YouTube [emoji1303]


Verzonden vanaf mijn iPhone met Tapatalk

[TZ350]

Do you mean you are going to run coolant through the cavities that attach the engine mounts that are normally empty air?

Yes, trying to see if we can run coolant through casting cavities that are normal empty air.

[diesel pig]

Yes, trying to see if we can run coolant through casting cavities that are normal empty air.

OK, Cool, Good luck with that, Don't get me wrong I think that it may be possible. It would take lot and I mean alot of plumbing to get that to work. I would be very interested to see how you get on with this.

[TZ350]

OK, Cool, Good luck with that, Don't get me wrong I think that it may be possible.

I have high hopes for the idea. My biggest concern is the very narrow sealing surfaces, water tightness could be a problem.

[husaberg]

Yamaha and others use a fix that is awesome I have seen on a modern "450 oiler "to use but likely a little time consuming to machine. :)
That said they don't rip don't leak and are reliable and only need matching /inserting once.
357664357665357666

I am pretty sure if you had a mini cnc and a scan of the gasket ai could maybe get it close. or at least close enough to run a simulation of the tool path with a pen.

Whilst I don't currently have a NSR500 on the bench, I can see the witness marks as well as the grooves in these pictures
357667357669357670
Team ESE is practically NZ's version of HRC so i cant see them not having the technical capacity....

[diesel pig]

I think husaberg has the right idea. O-rings fail a lot less than paper gaskets. But it would depend on wrether you have access to a CNC mill.

[Flettner]

Yes, trying to see if we can run coolant through casting cavities that are normal empty air.

I do, with the AG. One surface is less than a millimeters wide. I use high temp sealastic. So far so good.

While I have your attention, where can I access the current Bucket Engine rules.

[husaberg]

I do, with the AG. One surface is less than a millimeters wide. I use high temp sealastic. So far so good.

While I have your attention, where can I access the current Bucket Engine rules.
here https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-W.pdf

[Flettner]

So what's that telling me, twostroke up to 104cc ?
Auckland buckets telling me up to 107cc, ?

[husaberg]

So what's that telling me, twostroke up to 104cc ?
Auckland buckets telling me up to 107cc, ?

why stop there appendix A says 110cc
https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-A.pdf

my understanding was if you went over 104cc liquid cooled it was to be 24mm carb area restricted?
pretty sure most of the rules changes have came from ESE ideas....
if the crept up the cc for 2t to 106 or so H100/MB100 could use kt pistons without destroying.

[Flettner]

So, 104cc is it then. I don't want the intake restriction.

[TZ350]

I do, with the AG. One surface is less than a millimeters wide. I use high temp sealastic. So far so good.

Good to know, very encouraging, thanks.


While I have your attention, where can I access the current Bucket Engine rules.


here https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-W.pdf

As I remember it, 110cc overbore allowance came in for the 100cc guys to be able to use 52mm KT100 pistons. So they could keep their old two strokes going as good original pistons were getting very hard to get. And the 24mm carb rule for two strokes over 104cc stayed in place. Someone has proposed to MNZ this year to do away with that rule. But the new rules don't seem to have come out yet, so I am not sure what is happening there if anything.

Team ESE were very imaginative with the 110cc thing and in the tradition of Bucket racing. To get away from air cooling Team ESE destroked their engines so they could use water cooled cylinders like from NSR125/250 or TZR250's ETC.

The poor old two strokes are getting left behind by the big modern four strokes. This year there were some proposals like changing to unlimited carburettor and 125cc water cooled. To try and level the playing field a bit. We would still be limited to using non competition cylinders etc. Just the same as always, so anything homemade is Ok.

[F5 Dave]

We dynod a stock RS125 Aprilia roadbike at 30hp.
That would be silly to allow as a starting point.

Oh and happy new year. .

[Peljhan]

I don't know whether Martijn Stehouwer ever offered that Russian insulation varnish on his EMOT website.
He had it on EMOT website or atleast on his FB page, but later stopped selling it, I asked him and he said it is Russian stuff and also gave me link where to buy it (no chance I can find it today as this was like 8+ years ago).

Today I use Cerakote for coating 4t turbines, headers, 2t exhausts, carb bodies etc.

[lodgernz]

As I remember it, 110cc overbore allowance came in for the 100cc guys to be able to use 52mm KT100 pistons. So they could keep their old two strokes going as good original pistons were getting very hard to get. And the 24mm carb rule for two strokes over 104cc stayed in place. Someone has proposed to MNZ this year to do away with that rule. But the new rules don't seem to have come out yet, so I am not sure what is happening there if anything.

Team ESE were very imaginative with the 110cc thing and in the tradition of Bucket racing. To get away from air cooling Team ESE destroked their engines so they could use water cooled cylinders like from NSR125/250 or TZR250's ETC.

The poor old two strokes are getting left behind by the big modern four strokes. This year there were some proposals like changing to unlimited carburettor and 125cc water cooled. To try and level the playing field a bit. We would still be limited to using non competition cylinders etc. Just the same as always, so anything homemade is Ok.

The new rules are out, that's what Appendix W is. And no, the open carb rule didn't get through. I don't know why. I guess the diesel guys are scared of 30 year old 2Ts. The extension of water-cooled 2Ts to 125 was also rejected.

[Flettner]

The extension of water-cooled 2Ts to 125 was also rejected.[/QUOTE]

A pitty, but not unexpected
I'll stick to building Vinduro engines I think, open engine rules, my kind.
Truth is I've got a friend that was a road racer and is keen to try bucket racing, at your next round.
If he likes it ... we will be building a twostroke bucket, with as much modern twostroke tech as we can squeeze into it, to get as wide a power spread as we can.

[TZ350]

We dynod a stock RS125 Aprilia roadbike at 30hp.
That would be silly to allow as a starting point.

I have heard of a possible Aprilia/TS125 project in Wellington. Of course, being water cooled they have to reduce it to 110cc or less and use a 24mm carb so I guess it won't be 30hp after that. But a pretty good F4 Bucket never the less. Pity Aprilia 125's are like hens teeth here in NZ or I might give it a go myself.

[lodgernz]

A pitty, but not unexpected
I'll stick to building Vinduro engines I think, open engine rules, my kind.
Truth is I've got a friend that was a road racer and is keen to try bucket racing, at your next round.
If he likes it ... we will be building a twostroke bucket, with as much modern twostroke tech as we can squeeze into it, to get as wide a power spread as we can.

Neil, the first round of the AMCC Bucket Champs is at Tokoroa on 23/24 January.
I suggest your friend drops in to see how it all works, or maybe enter if he's ready.

[Flettner]

Neil, the first round of the AMCC Bucket Champs is at Tokoroa on 23/24 January.
I suggest your friend drops in to see how it all works, or maybe enter if he's ready.

Might be already entered, on a fourstroke unfortunately, we aim to remedy that in the future.

[TZ350]

.

F4 and F5 Miniature Road Racing. (Buckets)

MNZ Rules. (Motorcycling New Zealand)

Appendix W - Minature Road Race https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-W.pdf

Appendix A - Championship classes https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-A.pdf

Appendix X - Technical https://mnz.co.nz/wp-content/uploads/2025/12/Road-Technical-Appendix.pdf

Fuel is covered in Technical 12 and Nitro in Technical 12e. So Pump gas and/or Av gas for F4 F5 and not Ethanol, Methanol or Nitro. Total party poopers.

Appendix D - Fuel specifications https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-D.pdf

[husaberg]

.

F4 and F5 Miniature Road Racing. (Buckets)

MNZ Rules. (Motorcycling New Zealand)

Appendix W - Minature Road Race https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-W.pdf

Appendix A - Championship classes https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-A.pdf

Appendix X - Technical https://mnz.co.nz/wp-content/uploads/2025/12/Road-Technical-Appendix.pdf

Fuel is covered in Technical 12 and Nitro in Technical 12e. So Pump gas and/or Av gas for F4 F5 and not Ethanol, Methanol or Nitro. Total party poopers.

Appendix D - Fuel specifications https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-D.pdf

I don't think i will ever understand the MNZ thought process.
they have classic classes but change the capacity to be outside of what was in the rules in those eras.
like allowing GP 250cc 2 stokes in F3 when the periods only allowed 125cc.
For f1 there is no allowance for 4t twins vs 4t 4's so its 1300cc 4's against 1300cc twins when thse era rules were 750cc 4 's vs 1000 twins

[lodgernz]

.
F4 and F5 Miniature Road Racing. (Buckets)
Fuel is covered in Technical 12 and Nitro in Technical 12e. So Pump gas and/or Av gas for F4 F5 and not Ethanol, Methanol or Nitro. Total party poopers.
Appendix D - Fuel specifications https://mnz.co.nz/wp-content/uploads/2025/12/Road-Appendix-D.pdf

Rob, where does it say that ethanol is not allowed for buckets?

[TZ350]

Rob, where does it say that ethanol is not allowed for buckets?

Good question, I may be wrong but I thought the specs (Appendix D) specified the amount of Ethanol permitted in petrol. So Ethanol at 100% is not permitted. Best fact check me about this.

Persionaly I would be happy with no fuel restrictions at all for Buckets.

[husaberg]

Rob, where does it say that ethanol is not allowed for buckets?


Good question, I may be wrong but I thought the specs (Appendix D) specified the amount of Ethanol permitted in petrol. So Ethanol at 100% is not permitted. Best fact check me about this.

Persionaly I would be happy with no fuel restrictions at all for Buckets.

Pump gas max 10% Ethanol is specified.

[jamathi]

When I read my copy of Jan Thiel's Book he hinted it was hard to work with the Italilans. But I now understand he was playing it down.

I ALWAYS worked very well with the Italians, except rumi, who was a real piece of SHIT..... and the most dishonest person I ever met..........

[Flettner]

No, rules say the maxim amount of ethanol in unleaded petrol is 10%.
It is there for allowed to run 85% ethanol in 15% LEADED petrol.
Ethanol is not banned outright, as I was led to believe, although methanol is.

[Frits Overmars]

Persionaly I would be happy with no fuel restrictions at all for Buckes.Personally I think the less restrictions the better. But what if someone discovers a fuel that delivers 5% more power and costs 500% more than regular petrol? In the end everybody who does not want to be left behind has the same power again but now everybody has to pay five times the price. A fuel rule can protect you from situations like this.

Having said that, I am a huge fan of E85: more power than just about every racing gasoline I know of and at the same time easier on the engine and cheaper than regular petrol.
Too bad you seem to have to mix it with leaded fuel, which I detest.

[Rudex]

Yes, the Modena KK1 is very interesting. But it's only used on the reed valve and intake ports, not around the crankshaft. I always wonder if it would provide more power, at least noticeably.


https://www.youtube.com/watch?v=U09mE-xcUxM&t=32s







Frits friend Roland Holzner when he designed the Modena KZ engine, engineered a " plastic " insert that completely lined the intake surfaces from the reed block mount face , all
the way thru the case up to the Transfer duct entries.
Thus the inducted A/F never actually contacted the hotter metal, except down the sides of the crank.
It somehow got through the CIK tech inspection of the 50 units for homologation, but quickly the CIK banned it from any future engines.

EDIT - easily replicated using 3D printed fuel resistant polymers.

The ceramic coatings I have used were developed to prevent heat from migrating through to the metal substrate - I have not had a look or had any experience with coatings that do the reverse
ie ,preventing heat from migrating from the substrate out to the coatings surface - mind you, the coating used on the inside of 4T headers is so effective the pipes are only warm to the touch on the outside at idle.

[Flettner]

Personally I think the less restrictions the better. But what if someone discovers a fuel that delivers 5% more power and costs 500% more than regular petrol? In the end everybody who does not want to be left behind has the same power again but now everybody has to pay five times the price. A fuel rule can protect you from situations like this.

Having said that, I am a huge fan of E85: more power than just about every racing gasoline I know of and at the same time easier on the engine and cheaper than regular petrol.
Too bad you seem to have to mix it with leaded fuel, which I detest.


I also detest leaded fuel.
Unfortunately this is how the rules are written, the wording will be changed presently I'm sure.
I ask, when the fuel rules are changed, let E85 be allowed for 100 fourstroke supercharged, like it used to be.
Continue the ban on methanol and I'd be all for a ban on leaded fuel also, outright.

[katinas]

Having said that, I am a huge fan of E85: more power than just about every racing gasoline I know of and at the same time easier on the engine and cheaper than regular petrol.


Yes, absolutely agree about E85. Apart more power, you can adjust bike all day in exhaust fumes and still feel good.

More power not only with a two strokes. I've tried E85 on 4t Yamaha R6, VFR 750 (RC24 RC36), VFR 800 and Suzuki GSX 400 Bandit. With the right adjustments all goes faster.
Yamaha R6 2003 original injectors for gasoline has 4 holes, but with E85 real difference in power comes with 12 holes injectors from Mitsubishi Lancer 2. (shape is the same like on R6 2003). Injectors with 6 and 8 holes from 1300cc bikes still too lean.

But, as many time was discuses, E85 does not mix with fully synthetic racing oils. I haven't found a single that will mix without separation. Add photo with just few of them. The worst was autolube oil, separate after few minutes.
All castor base oils I've tried mixed very well with E85. The only exception Castrol A747, separation not as clear like with the fully synthetic, but it seems that 747 synthetic additives insoluble in ethanol.
And vice versa, only few castor base oils mix with usual gasoline.

[diesel pig]

I ALWAYS worked very well with the Italians, except rumi, who was a real piece of SHIT..... and the most dishonest person I ever met..........

My Apologies, The dangers of trying to read between the lines.

[diesel pig]

I have ever had anything to do with E85, so don't have a opinion on it. But the little I have had to do with methanol makes me think for practical reasons at a track, that it would be best to keep methanol out of bucket racing.

[TZ350]

.

A link to everything you wanted to know about the Aprilia RSA 125 engine. Words with Pictures:- https://forums.kartpulse.com/t/peak-2t-aprillia-rsa125/9958/3

[Flettner]

My design package, plus some wood from the wood shed. Best bit is when it's complete, its cast into a usable alloy component. At minimal cost.

[reefmuncher]

Good Day all,

I hope you don't mind my jumping in. I used to skim through this forum and Pit Lane maybe 10+ years ago for 2 stroke related learning. About a year ago I started designing on CAD a Honda 2 stroke cylinder which ended up having an experienced and talented 2T fiend join in to help produce something quite sweet. We had a few cast, he machined, had plated and recently he has started testing.

It the time January a year ago when I mentioned doing the cylinder design he suggested doing one for the Yamaha v 80 type engine which is very popular where I am from. So about 4 - 5 months ago I began designing a cylinder around the 3 duct to make a 4 transfer port / 3 boost port type cylinder with a bridged exhaust. As these engines have a massive C port and duct normally I wanted to take advantage of this port rather than stretch the B ports around dramatically towards the C port.

The goal is not to make a firebreathing GP cyl (lol) but to have a much higher performance cyl than was is currently used with the ability to work with the "chopped out" non expansion chamber pipes many use but also workable with the guys that use expansion chambers as street going bikes. I have given the ext port a generous top radius, curving about 3mm from top to edges from memory to ensure for a wide power curve that works with the 3 speed gearboxes. The timing is currently at 130 / 190. I have been using Frits axial angle formula to begin setting the A / B and C ports

The one aspect of the 3 boost ports which I can call the pair of C ports and centerline D port is the effect of changing the pair of C ports axial angles. I set them to converge to mimic the hook typically on the B ports. I have looked at Bidalot cylinders and they look to keep the axial angle similar to the B ports, where Voca, DEA and others have the angles of the "C" ports angled close or the same as the D port. Ultimately I'll want porting that encourages a broader port curve and my gut feeling is to have the ported angled upwards towards the head rather than across the piston.

Cheers

[reefmuncher]

Good Day all, just recently joined the forum was wanting to discuss design considerations around cylinder design with "C" ports with side boost ports incorporated into the design so the "C" port becomes in effect a "D" port. I have been working on a cyl design project for a street bike and due to cyl stud spacing and existing duct layout and sizes decided to adopt this approach. I have noticed some firms such as Bidalot keep the axial angle shallow likely similar to the B port axial angles and other firms, VOCO, DEA and a few others pitch them at close or the same as the typical C port angle. Ultimately I want to achieve a wide powerband with a large sweetspot as the bikes in question are 3 speed. I've attached an image of the current design layout. 357690

[lodgernz]

As usual, I'm seeking advice.
My water-cooled Honda 50, with a 26mm carb, has EO 192, the ex port extended to twice the bore and water-cooled, with the Wobbly reduction to 90% at the flange. The CR is 14.0:1, running on 98 pump fuel with Motul 800 at 30:1.

I designed and built a pipe using a planned peak power RPM of 13000, using guessed EGT of 470⁰C. This gave SoS of 546m/s, and Lt = 672mm.

After much racing with this pipe, a dyno session showed the peak power RPM to be at 11800.
Of course, with a single ex port, blowdown is compromised, but there is reasonable over-rev (see graph), so I don't think the low RPM is due to that.

Calculating back, with known Lt and peak Power RPM, the actual average SoS is only 496m/s, suggesting an average EGT of only 340⁰C.

If I now make a new pipe, using this EGT and SoS, and still aiming for 13000RPM peak, Lt will be 610mm.

But maybe the higher peak power RPM would produce a higher EGT, so the pipe would then be too short.

So should I compromise somewhere between the two values of Lt for the new pipe?

357691

[wobbly]

Jan , thats sad to hear of Rumi - he obviously ripped you off personally.
I always thought his 125 engine design looked really well thought out, with a dead straight inlet above cylinder.
Unlike Vankerveens 45* bent intake on his horribly uncompetitive cylinder down later design.
He probably had no water cooling around the Exhaust Duct as well, as you well know he was adamant that was " better ".

[husaberg]

Jan , thats sad to hear of Rumi - he obviously ripped you off personally.
I always thought his 125 engine design looked really well thought out, with a dead straight inlet above cylinder.
Unlike Vankerveens 45* bent intake on his horribly uncompetitive cylinder down later design.
He probably had no water cooling around the Exhaust Duct as well, as you well know he was adamant that was " better ".

years ago i posted a pic of the jan wittenturd engine.
i cant be assed looking for it but he just got a kart engine and flipped it even the gearbox some plug was left on an upside down position.

[husaberg]

Well i could be assed


TBH i had forgotten about the disc valve rumi
357694357696357695

Am i the only one that gets excited about chromate finish on engines?

Yep, here is the Rumi "upside down " reed engine with dead straight inlet ie done right, unlike Mr Ws half arsed attempt.
Then there is the Rumi rear valve - not alot done wrong there, but I dont know the detail.


Who knows the RUMI details ?
Frits your turn


Here is another shot I found on EMOT



This was the engine i was meaning it seems by the simple expedient of turning an existing kart upside down a "new Engine" was thus created.
If you look at the oil Breather/Filler housing and surround on the Kart engine (right pics in compliation), and compare then it to the Maxtra Haojue engine Drain plug, you will see what i mean.:lol:

The Rumi engines have there own thread on pitlane.

357693



Here's some more photos of the Rumi GP

http://2stroker.createforumhosting.com/viewtopic.php?f=5&t=2652&start=0&&view=print

Here's a relevant quote too from Jan Thiel: (auto translation from Dutch)


Rumi The engine was not a success but there were still some nice things, and also
some big drawbacks. The gearbox was designed by an artist who also
has signed a number of F1 engines. This tank had no seeger rings and washers and you
could him after removal of the cover without tools apart. There were also 3
different primary ratios, you could cover the primary disassembly without the ignition
rotor disassembly. The crankcase halves and the lids were sealed with O-rings. The engine is the cylinder downwards designed for 2 reasons. Rumi wanted an engine that was different from all others (no good reason) I myself had to Garelli once did a test with a kilo of lead in the tip of the keel of the fairing. Gresini found that the motor thus better sent, so I thought the cylinder down like a good idea. The carburetor was thus rightly at the place where normally the radiator sits. I thought this to fix the radiator in a different place to put behind us, under the tank. Something like the British did. The frame was made ​​by Nico Bakker, with even a monoarm swingarm for more space for the exhaust. The frame is also made ​​but were not collected nor paid. Rumi had a frame in Italy, with the radiator in the traditional place. Thus came the carburetor between 2 radiator little to worry about as a result poor cooling, hot air inlet and no place for a good airbox. Also, it was very difficult to place the outlet to find the thick part came up right where the footrest Sat We solved through a hole in the frame to make the exhaust was then in an s-curve before the rear wheel backwards along with the muffler under the seat. This went well but was very difficult to make. On the test bench to ensure no power cost. There were also problems with the mechanical Niese water pump 3.5 HP cost. A elektriese pump made ​​the ignition after a while too little power and the engine was badly began to walk. Rumi began increasingly to technology to interfere where I think he totally did not know, was also the organization of the team unimaginably bad. then also pay my salary a growing backlog was I decided only to disband, after eighteen months work.

Last but not least, another set of photos through the Rumi pits:
http://www.2t-special.it/forum/viewtopic.php?f=11&t=3333&start=10

Finally, an upside down pavesi :P
http://www.motoripavesi.it/img/motore_moto_6_big.jpg



ps. I have mentioned it before, but it is possible to search any pic through google images. it usually leads to more relevant photos and info. :)


Sure. Much has already been said in Jan's Google-translated story above. But I'm not sure I would have understood one word of that Googletalk if I hadn't been there myself at the time and could reconstruct ill-translated Dutch words and expressions.
But I've got a problem: I can neither see nor post PNG-pictures on Kiwibiker. I run Windows 7 with Internet Exporer 8. On a friend's computer with Windows 7 and Google Chrome I can at least see the PNGs. Suggestions anyone?


There you go Frits!

http://www.winhelponline.com/articles/202/1/PNG-images-are-not-displayed-on-Web-sites-in-Internet-Explorer.html

Win Vista > same kernel as Win7, Vista~=7.
Why not also try the IE 9, which is a much better and faster browser than IE8?


Thanks dinamik, but I get this: "Cannot import C:\Users\FOS\Desktop\pngasso_vista.reg: Not all data was successfully written to the registry."
The problem with PNGs refusing to show only occurs when I'm visiting Kiwibiker; all other programs function OK.

Why not IE9? Because Microsoft won't let me install it, saying I should first substitute my beta-version of Windows7 with the final version.
You don't happen to know a way around that, do you?

[aljaxon]

hi everyone, ive been awol for a long time. good..... i hear some of you saying.

for years i was of the understanding that it was the crankcase and crankcase compression that delivered fuel up through the transfers into the cylinder.
then a couple of years ago i read on here or on pit lane biz that on modern designs the crankcase was only of use for starting the motor and once running it was down to the exhaust pipe to draw fresh charge up.

i just searched on google to find this and cant see it anywhere. is this belief still so? has it been shot down? or did i imagine reading this? old age and memory etc
cheers

[wobbly]

Crankcase compression is only a direct factor for transfer charging flow in a lawnmower.
In modern engines with a " proper " expansion chamber it is the diffuser that creates a depression around BDC that pulls mixture from the case, thru the transfer ducts
and into the cylinder. If the axial and radial angles of the transfers are correct, this negative pressure ratio at the port creates a coherent intake charge column that is angled back toward the rear wall,
and this then loops across the cylinder head and down toward the Exhaust port.
The larger the depression, and the better the transfer design, the higher the Scavenging and Charging Efficiency within the cylinder.

[aljaxon]

Crankcase compression is only a direct factor for transfer charging flow in a lawnmower.
In modern engines with a " proper " expansion chamber it is the diffuser that creates a depression around BDC that pulls mixture from the case, thru the transfer ducts
and into the cylinder. If the axial and radial angles of the transfers are correct, this negative pressure ratio at the port creates a coherent intake charge column that is angled back toward the rear wall,
and this then loops across the cylinder head and down toward the Exhaust port.
The larger the depression, and the better the transfer design, the higher the Scavenging and Charging Efficiency within the cylinder.

excrellent thanks wobbly. glad i'm not losing my marbles after all.

[ApolloMotoMoto]

As usual, I'm seeking advice.
My water-cooled Honda 50, with a 26mm carb, has EO 192, the ex port extended to twice the bore and water-cooled, with the Wobbly reduction to 90% at the flange. The CR is 14.0:1, running on 98 pump fuel with Motul 800 at 30:1.

I designed and built a pipe using a planned peak power RPM of 13000, using guessed EGT of 470�C. This gave SoS of 546m/s, and Lt = 672mm.

After much racing with this pipe, a dyno session showed the peak power RPM to be at 11800.
Of course, with a single ex port, blowdown is compromised, but there is reasonable over-rev (see graph), so I don't think the low RPM is due to that.

Calculating back, with known Lt and peak Power RPM, the actual average SoS is only 496m/s, suggesting an average EGT of only 340�C.

If I now make a new pipe, using this EGT and SoS, and still aiming for 13000RPM peak, Lt will be 610mm.

But maybe the higher peak power RPM would produce a higher EGT, so the pipe would then be too short.

So should I compromise somewhere between the two values of Lt for the new pipe?

357691


If I were to channel my inner "wobbly" and attempt to throw down a hand at 'long distance troubleshooting roullette'


My first question is, why so cold, Batman?

Targetting 470c with the pipe design???

That should be ~600c if you want to make real power.

Only achieving a derived (not directly measured with high speed EGT probe....) 340c?

Re-running the pipe design for 340c would NOT be my first advice.

I would first wonder why your pipe is so cold to begin with, assuming it truly is.

The most likely culprit from a general theory perspective would be the tailpipt outlet diameter. Often termed "D_restrictor" in some pipe formulas....

If you have the exact diameter in your pipe on the bike from the formula you used, and you are that far under the formulas target EGT, I would have questions about the engine actually meeting the input parameters that went into the pipe calculator, or the pipe calculator itself, is it the FOS formula?

You should be closer to 600c EGT for an incredibly general ideal.

Being cold either means you are not delivering the heat energy that the calculator assumes you would have been delivering to the pipe or the tailpipe diameter on your actual pipe is larger than the calculator actually spit out.

Making the tailpipe restrictor diameter smaller WILL increase the pipes EGT, and if you are currently "too large", making it smaller WILL bring with it an increase in power up until the point where you go "too small" and you burn holes in your piston, so there is a balance point to be found, and the pipe formula wont give you the EXACT perfect number for your engine. It SHOULD give you a generally safe place to START, and you tune it from there.

Generally speaking shrinking the tailpipe diameter is going to increase the EGT.

Inreasing the EGT will increase the net temperature of the pipe.

Increasing the temperature of the pipe will make the speed of sound within it FASTER.

Faster speed of sound = faster wave travel.

Faster wave travel = pipes natural "resonant frequency" goes up.

Well look at that:


1. You pipe is too cold (not metting the formula number).

2. Your pipe is peaking at too low an RPM (resoanant frequency LOWER than formula number).

So, logic says:

Make the pipe hotter (decrease tailpipe restrictor diameter) and you will see an attendent increase in pipe resonant frequency, maybe even landing exactly where the formula said you would be once you actually achieve the 470c EGT you entered into the formula.

[husaberg]

Frits, Wob, could you give us an insight, into how one can use the big volume of the crankcase effectively, in a high performance design? Would there be any rules connecting crank volume with ducts volume or pipe volume?

I simulated two different ratios in EngMod, and the higher comp/smaller volume was up by 1+hp. Both with the same tfr duct volumes (~78cc).
I did a hasty overlay of the pressure waves of the intake and exhaust:

256943

256944

The higher comp case caused the reeds to open less. Tfr pressure was higher from Ex open until just-before Tfr closed. Crankcase pressure was higher too.
On the exhaust part, difference was mainly betweet Tfr open and close, both for cylinder and exhaust pressure - higher comp produced the higher pressure.
Also, delivery ratio was much bigger in the high-comp, while TubMax was slighly less.

edit: I don't know whether I am missing something here, but EngMod kind of shows what you told us about 'pipe sucking from tfr ducts and that vol being important'.
I run the same as above, with 1.45 crank comp ratio, to see a number of 30.4kw. Then, with longer TFR passages (new vol about 100cc), with 1.3 CCR it showed 33.2kw, while with 1.45 it rised to 33.6kw.
I think it favorises a little the high primary comp ratios.


A layman's (mine) view of the effect case volume has is that a larger volume has a smaller drop in pressure given any particular volume transfer up the transfer ducts. As it is the pressure differential between the cylinder and the case that causes the transfer flow having the largest possible pressure differential for as long as possible will result in the maximum volume flow possible. As with anything in pesky 2-strokes there is a trade-off and therefore an optimum value of crankcase volume given any particular application.

You could go for smaller volume, higher compression, crankcases but that would only benefit initial transfer flow before the crankcase pressure dropped. However there may be some advantage in this setup with smaller transfer ducts if the energy in the initially rapidly moving mass in the transfer ducts could be used.

Maybe.


I have tried all kinds of crazy things but I never had the guts to try 32° straight line ignition advance in the powerband of any engine with a decent BMEP.
Flat lining at 15° would be a safe way to start your ignition quest. Subsequently you can run flat lines with even less advance, en finally carefully try more advance at the rpm points that suffered from retarding.

Now that is something you can safely try. You may be generating ignition and fueling numbers that are of no use whatever in a properly setup engine, as Wob says, but I would not call it a complete waste of time. It will be educational either way and you won't have to get rid of broken engine parts afterwards.

I've long been a proponent of low compression ratios. In my experience, a low-compressed engine reacts much more clearly to changes. But to take advantage, you'll need an exhaust pipe that deals extremely efficiently with the energy contained in the exhaust gases of such an engine. And the engine will need a transfer layout that can handle that amount of pipe suction.


It was considered large compared to what had been done before.
The Aprilia RSW had a TDC crankcase volume of 650 cc and a Crankcase Compression Ratio of 1,238 .
The Aprilia RSA had a TDC crankcase volume of 675 cc and a CCR of 1,227, which gave a power improvement over its predecessor.
But is 1,227 the optimum? I don't know and Jan Thiel doesn't know either. You won't discover a border until you cross it, and Jan retired before it came to that.


No, balancing the pressures above and below the piston is not a point of consideration. You want a downward-moving piston to push on the con rod as much as possible, so you do not want the crankcase pressure to slow down a downward-moving piston. But after BDC the piston must be accelerated upwards, which requires negative work via the con rod; now you want the crankcase pressure to help accelerate the piston as much as possible.
In short: when the piston is moving down, you want a low crankcase pressure, i.e. a large crankcase volume, and when the piston starts moving upwards, you want a high crankcase pressure. But when the crankcase volume is small, the crankcase pressure will drop fast because of the rising piston, so that is one more argument in favour of a large crankcase volume.
However, all the above factors are unimportant against the requirement for mixture transfer: a large crankcase volume from which the exhaust pipe can suck up as much mixture as possible.

Above the piston, things are much simpler. Let's just look at an engine without ignition and combustion. On its way towards TDC the piston is slowed down by the compression pressure, so this pressure is applying negative energy. But after TDC that same compression pressure is accelerating the piston downward, applying just as much positive energy. In short: compression pressure above the piston is energy-neutral.

Of course, with combustion, things become more biased: a low compression ratio equals a low expansion ratio, leaving more energy in the exhaust gas. And this energy is used by the exhaust pipe in the same way that a turbo would: the more the better.


That depends on how you define the transfers. They are not only the ducts in the cylinder but also the sweeping curves in the crankcase. In any case it is not a matter of mixture drawn into the cylinder, but of mixture drawn through the cylinder. Some of it stays there, some of it exits and then comes back, some of it may be lost, especially at revs outside the optimum range. By the way, I like the distinction you make between mixture mass and mixture volume.

Correct. Blowdown should be finished by the time the transfers open, but it takes a certain time.area and if this time.area has not been reached by the time the transfers open, the exhaust gas just abuses the transfers as extra exhaust ports.

Maybe we should be more aware of the ambiguity of blowdown. It starts at the angle where the exhaust begins to open, but where does it end? It should end at the opening point of the transfers, but at low revs that is more blowdown time.area than we need, and at high revs the blowdown may carry on past the opening point of the transfers. Usually we take the opening point of the transfers as the end point of the blowdown because we have no simple way of knowing at what crank angle the cylinder and transfer pressures are equal.

You're thinking in the right direction but I'd like to rephrase your thoughts. Blowdown time.area is the product of port timings and port areas, divided by revs. If you don't alter the cylinder, the blowdown angle.area and time.area stay the same, irrespective of crankcase pressure. Blowdown should allow the cylinder pressure to drop to the level of the transfer pressure just before the transfers open. So a higher crankcase pressure means that the cylinder pressure does not have to drop quite so far.
In other words, a higher crankcase pressure requires less blowdown time.area.

That's right, but for real power you cannot vary the exhaust timing too much; it has to be about 180° effective or you'll get no true resonance.

Yes; that is the main reason that the exhaust timing has to be about 180° effective for true resonance; we want superposition of the old and the new +pulses.

They cover both; the variation of the crankcase volume during one crankshaft revolution should not exceed the permissible cylinder capacity, so both suction and primary compression are coupled to piston displacement. In addition, any mechanical device that creates positive boost, is forbidden (an exhaust pipe does that, but it is not considered a mechanical device).


hi everyone, ive been awol for a long time. good..... i hear some of you saying.

for years i was of the understanding that it was the crankcase and crankcase compression that delivered fuel up through the transfers into the cylinder.
then a couple of years ago i read on here or on pit lane biz that on modern designs the crankcase was only of use for starting the motor and once running it was down to the exhaust pipe to draw fresh charge up.

i just searched on google to find this and cant see it anywhere. is this belief still so? has it been shot down? or did i imagine reading this? old age and memory etc
cheers....................................

Frits overmars

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ujet: Re: [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked) https://2img.net/i/fa/icon_minitime.gifJeu 13 Juin 2013 - 17:12






By '2 mm clearance' I assume you mean 1 mm either side between crank and case, and 1 mm between outer crank radius and inner case radius. Viscous drag increases strongly below 1 mm clearance; enlarging the clearance beyond 1 mm has only a limited effect on viscous drag. So if increasing the clearances beyond 1 mm improves power, I would assume that this improvement was caused by the increased crankcase volume. It could also have been caused by improved inlet flow, but I cannot comment on that without knowing your engine so I will leave this aside for now.

The most striking example of crankshaft clearance I saw in the old Rotax-124 kart engine that I worked on from 1978 onward. It was really a 250 cc motocross engine with a 125 cc crank in it. If I remember correctly the case diameter was about 12 mm larger than the crank diameter! But it was easily the fastest engine of that era, and the most susceptible to tuning modifications. It was also the grandfather of the Aprilia RSW125 Grand Prix engine.

How did you arrive at this value, Speedslut?
The Aprilia RSA125 has a TDC crankcase volume of 675 cc. That gives a primary compression ratio of 675 / (675 - 125) = 1,23. Rather different from your value.

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ot only, Graham. I've said lots of things that seem hard to swallow. Here is an anthology:


'The part of the exhaust port area beneath the transfer port level is a waste of real estate'.


'A high secondary compression ratio improves power in a four-stroke;
in a two-stroke with an efficient exhaust system it is the other way around'.


'Two-stroke rpm is limited by blowdown and scavenging angle.areas, not by crankshaft reliability issues'.


'Comparisons of differently sized engines should be based on mean piston speed, not on rpm'.


'Piston clearance, coolant flow rate, radiator size and ambient temperature are practical limits to engine cooling,
but in theory there is no such thing as too much cooling'.


'Top speed is the most unimportant thing in racing. Keeping your minimum speed high is the most important'.


The above collection should be sufficient to earn me a reserved place in an asylum, don't you think, Graham?
I'm not sure. Too many forums... The idea is that a large expansion ratio takes away exhaust gas energy that could otherwise be more useful supercharging the cylinder, so the next bang will be bigger, and the bang after that bigger still, and... you'll get the picture.
A low secondary compression/expansion ratio provides for more exhaust gas energy; it also provides for a larger cylinder volume above the exhaust port so the exhaust pipe has an easier time shoving washed-through fresh charge back into the cylinder because the resulting cylinder pressure rise will be smaller.
In theory it would be best to connect the transfer ports directly to the outside world. Then the engine could breathe cool mixture through short tracts with low dynamic flow resistance. Don't worry about the 'swing'; transfer tracts, cylinder volume and exhaust pipe form a compound Helmholtz resonator that will swing just fine without the crankcase attached.


When the crankcase volume gets really big, fuel may separate from the air. Direct injection would solve this, but for now the time available for direct injection in a competition engine is too short to form a homogeneous mixture.


I once made an experimental cylinder with carburetors bolted left and right against it. But starting was a problem and lubricating the big end was an even bigger problem, so for practical reasons we still use the crankcase.

en Seeber a écrit:
I would think that the pressure in the transfer passages would mainly be a function of the exhaust system, port timing and the rpm. I would suggest that if a well balanced (not crankshaft) engine was running at its optimum "tuned"speed that there would be no blowdown into the transfers and that no carbon would form. Outside the "tuned window" then it could be well possible, as evidence the formation of carbon. As always, I could be wrong though.
Not this time Ken; you are quite right Wink.
But rev any engine high enough and the blowdown time.area will become too small. Or use 'normal' revs with the throttle almost closed and the crankcase pressure will be so low that even with ample blowdown the cylinder pressure will not drop below the crankcase pressure before the transfers open. The latter situation was notorious on the racing Aprilias: they never detonated under full power but they could detonate like hell at 10% throttle.
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I was musing something less mechanical more pneumatic as a side note. More in the reed cavity area, more a bypass.
One of the guys that used to work with Helmet was Ferry Brouwer (not sure of the spelling) he allegedly used to remove so much of the rear skirt of the piston on the (I think TR2) that the inlet closing became simultaneous with the transfer opening, this was pre reed days of course. Not sure what would make of the inlet duration or the primary compression on piston ports.


My old mate Ferry spells his name the same way you do, but I doubt if the late Helmut Fath would trade his first name for a headgear description.

Ferry and I did a lot of silly things. With about 134° transfer timing his piston shortening would give an inlet timing of 226°.
It was not uncommon in those days; Bultaco did it too on their TSS250. Remember: back then the carburettors were tiny by current standards.
A more drastic mod by Ferry was raising the inlet ports until they opened at BDC. That's right: C-transfer ports directly connected to the carbs; no reed interference (but quite a lot of Read interference; dear Phil MBE was not the easiest person to get along with).

atributed to Frits

Everything has to fitWhat makes a two-stroke engine a high-performance engine? The exhaust.
The vacuum from Exh Opening first empties the cylinder. When the exhaust gases are out, the transfers open
and fresh gas flows out of the crankcase via the scavenging channels in the cylinder.
The exhaust continues to suck, and part of that fresh gas passes through the cylinder to the exhaust manifold.
If speed, exhaust length and speed of sound all match, then before the port closes again and at the same time
changes the flow in the exhaust manifold, the direction of flow and the escaped fresh gas is pushed back in the
cylinder.
Finally the piston closes the exhaust port again, so that the pushed back fresh gas in the cylinder is trapped.
There are two cases where speed, exhaust length and sound velocity do not all fit together: If the engine speed is
too high (or the exhaust is too long, or the sound speed too low). Although still fresh gas sucked in the mani-
fold, the return flow begins too late for this speed: the outlet slot closes again before all this fresh gas is pushed
back.
That’s what causes overrev performance to fall.
On the other hand, if the engine speed is too low (or the exhaust too short, or the speed of sound too high), the
engine behaves even grumpier.
Although the cylinder is sucked empty and rinsed, and sufficient fresh gas comes in the manifold to be able to
charge the cylinder afterwards, the return flow starts much too early for this speed, if the transfers are still open.
The overpressure which is generated by the return flow into the cylinder (via the exhaust port), escapes immedi-
ately through the scavenging channels back into the crankcase. When the exhaust port finally closes, there is no
overpressure (“supercharging”) in the cylinder. There is overpressure in the crankcase, which is not helpful for
the next intake cycle.
And the backflow not only starts too early, but comes to a standstill too early and then changes the flow direction
again (Helmholtz). The little fresh gas that still remained in the cylinder is subsequently sucked out again. And
then finally, but far too late, the piston closes the exhaust port.
No wonder that there is then a huge torque hole. In addition, the engine is now drinking extra fuel: per horse-
power, it consumes a lot more gasoline and a significant part of it disappears unburned through the tailpipe.
Burning speed and expansion
There are two ways to adjust the exhaust to high or low speeds: change the exhaust length or change the speed of
sound. Exhausts with sliding manifolds like a trombone have been used, and also exhausts where the end cone
was able to slide. That may work, but it requires a lot expenditure.
The speed of sound is easier; this works over the exhaust gas temperature. The maximum temperature in the
combustion chamber can be up to 2300 ° C. But due to the expansion on the downstroke, this cools the exhaust
largely again before the outlet opens.
And this Expansion can vary. It starts namely, when the combustion is just completed and the cylinder pressure
is maximum, and it lasts until Eo. The sooner after TDC the combustion is finished, the greater is the subsequent
expansion and the cooler the exhaust gas when it flows into the exhaust pipe.
When combustion is completed depends on two factors: the ignition timing and the combustion speed.
The latter in turn depends on the quantity (much or little fresh gas), the quality (clean fresh gas or much mixing
with exhaust gas), the mixing ratio air / gasoline (rich, lean or just right), and from the turbulence that is caused
by the pinch edge.
If you really want to have hot exhaust gas, so set the ignition timing to late so that the combustion starts late, use
a small main jet because lean mixture burns slower and therefore longer, and install a handful of head gaskets so
that the there is very low compression.
You may have already experienced the reverse: pre-ignition, rich mixture and high compression prevent the
engine fmor revving.
But you should not play with all the above factors. For power and a healthy engine too it is important that the
combustion takes place as quickly as possible. So really, one uses a compact combustion chamber and squeezes
the mixture effectively.
To influence the exhaust gas temperature, this leaves us with ignition timing. Now we are at the heart of the
matter: at low speeds either the exhaust is too short or the speed of sound too high. Variable exhaust pipe lengths
require too much effort, so we want to reduce the exhaust gas temperature and thus the speed of sound.
We achieve this with advanced ignition timing.
And for high speeds, the exhaust is actually too long, so we compensate for that with late ignition timing.
Intersections
Any engine that is even close to healthy can withstand 16 ° of ignition advance. With this fixed value we do a
baseline test and thereby comes out a performance curve.
Then we set the ignition to 12 ° and measure again. When we compare that to the 16 ° power curve , the 16 de-
gree is best is up to 10,000 rpm, and the 12 ° in turn is better after 10,000 rpm.
At 10,000 rpm, both curves intersect; so they have the same performance at that point.
You could say: at 10,000 rpm 16 ° is just as early as the 12 ° is too late. 14 ° could be the optimal value for 10,000
rpm.
Then we set the ignition to 14 ° fix and make again a power curve. For example, this 14 ° curve crosses the 16 °
curve at 8000 rpm and the 12 ° curve at 11000 rpm.
Then we can conclude that 15 ° is optimal at 8000 rpm, 14 ° at 10,000 rpm, and 13 ° at 11000 rpm.
To dispose
At the top RPM you can experiment without worries. After the peak power speed there is very little detonation
risk, and it makes no sense anyway to give it a lot of ignition advance. On the other hand, you have to be care-
ful about the peak torque RPM; there, too much ignition timing can be expensive.
Even further down, where the engine has little torque, and thus poor cylinder filling, the danger is smaller again.
Below the torque peak, even GP engines can easily handle 30 ° ignition advance, and that works even up to 8000
rpm. But someone who tries a 30 ° flat advance for a complete power curve up to the maximum RPM, can actu-
ally avoid the effort and just dispose of the engine immediately. With so much ignition advance, you can only
test this where the engine has poor cylinder filling. So stop before the torque rises steeply.
From then on to the peak power speed you have to be very careful and After each partial measurement, spark
plug and piston must be checked for signs of detonation. A warning: do not look at four-stroke advance val-
ues; they operate with much more ignition timing. Formula 1 engines eg : With their huge bore and ultra short
stroke, have a combustion chamber like a pancake. There is little squish area, because valves are everywhere.
The things are therefore even at full throttle operating with more than 50 ° ignition advance because otherwise
the flame does not reach all corners in time.
GP-curve For example, I show the full-throttle ignition curve of a 125cc GP engine at 12750 rpm maximum
torque and at 13000 rpm has its peak performance:
Dynamic
The whole ignition story is a temperature game. It only serves to lower the exhaust gas temperature to optimize
for each situation.
It is important that the circumstances at the test bench are exactly the same as on the race track. The accelera-
tion time, ie the time in which the exhaust is heated, must be practical. That’s why you can only determine these
ignition curves on a dynamic test bench; in a static power measurement, the exhaust is much too hot.
Incidentally, this also applies to the design of exhaust systems: Pipes developed on a static test bench are far too
long. Then you turn the engine up on the track you either have to retard the timing (costs performance) or too
meager (cost piston, Cylinder and possibly driver).
Another advantage of a dynamic test bench: because the engine only measures about ten seconds during a mea-
surement instead of five minutes, in this case it can also survive a bit too much ignition advance, which at one
static measurement would end in tears.
Incidentally, even with an optimal exhaust and a matching ignition curve of the engine will not over-rev un-
restricted, because the time cross sections (blowdown time-area, I am guessing- RN) get too small at overrev.
Because of the insufficient blowdown time-area after peak, the cylinder pressure is still above the case pressure
and exhaust gas will back-flow into the transfer ducts.
When the cylinder scavenging finally starts, you will first be flushed with exhaust gas. (because exhaust gas has
been pushed down into the transfers) Next comes partially-contaminated charge up from the transfers and final-
ly clean purge gas enters the cylinder. That’s why overrev performance drops so steeply .
Balance and residual energy
Dips in the power curve, I already explained: the resonances are no longer fit for speed and disturb the scaveng-
ing instead of promoting it.
Fortunately, with low cylinder filling, the combustion temperature and thus also the exhaust gas temperature are
low, so that the speed of sound drops. At the next working stroke, there is somewhat less scavenging and a little
more filling. This is how a balance is established.
That works too without ignition adjustment. Automatic ignition advance is still a positive effect. With more ad-
vance, the expansion due to burning before Eö is greater. This reduces not only the exhaust gas temperature but
also the residual energy that is available for exhaust resonance.
At very low speeds then come the resonances totally in the wrong moment, but at least they are not so strong and
have less effect.
Last note
Finally, a practical note: if you are dealing with an unknown engine, you should always first start with a much
larger main jet than ideal, and then reduce until the mixture is right. The danger lies in installing a slightly
larger main jet, especially if the engine was originally too much was lean. Much too lean means: totally no per-
formance and therefore no heat development. But if you give this very lean engine a slightly larger jet, it becomes
only just a little too lean; then the power comes, and thus the heat, which can then be terminal. By the way, here
too the difference between dynamic and static testing can decide how to measure life or death for the engine
https://www.zweitaktforum.de/wbb/attachment/32332-frits-overmars-adapted-to-english-making-an-advance-curve-pdf/


Pretty sure Frits did a post in the Pitlane thread were where said something along the lines of ...... so ending the myth of low crankcase volume. i can't find it
Does that sound like you Frits? Or was it Wob saying ending a fairy tale about crankcase compression here?

[Frits Overmars]

Boy, I wrote quite a lot over the years, didn't I?
I've got a slight headache now, feeling a bit dizzy after reading that last long text. What does it say there? What should it have said? What did this more or less English text look like in the German in which I originally wrote this piece for some friends?
As it happens I'm in Germany again, getting snowed in, so I'll have plenty time to read and drink coffee (or Glühwein).

To answer your last question: both Wobbly and yours truly have been trying for decades to eradicate the persistent misconceptions about the desirability of small crankcase volumes and high crankcase compression ratios. What we still encounter on the internet every day can make you want to cry.

[Wos]

As usual, I'm seeking advice.
My water-cooled Honda 50, with a 26mm carb, has EO 192, the ex port extended to twice the bore and water-cooled, with the Wobbly reduction to 90% at the flange. The CR is 14.0:1, running on 98 pump fuel with Motul 800 at 30:1.

I designed and built a pipe using a planned peak power RPM of 13000, using guessed EGT of 470⁰C. This gave SoS of 546m/s, and Lt = 672mm.

After much racing with this pipe, a dyno session showed the peak power RPM to be at 11800.
Of course, with a single ex port, blowdown is compromised, but there is reasonable over-rev (see graph), so I don't think the low RPM is due to that.

Calculating back, with known Lt and peak Power RPM, the actual average SoS is only 496m/s, suggesting an average EGT of only 340⁰C.

If I now make a new pipe, using this EGT and SoS, and still aiming for 13000RPM peak, Lt will be 610mm.

But maybe the higher peak power RPM would produce a higher EGT, so the pipe would then be too short.

So should I compromise somewhere between the two values of Lt for the new pipe?

357691



Maybe your ex timing / blowdown area is a little to low for 13000



Typical for advanced 50 cc with peak power at about 13000 are 195 - 197 degree and there is a need for boost ports.

Earlier ex opening is rising egt too

[Flettner]

54 x 54 twin port cylinder underway. Rear disc valve this one, this is for Vinduro so is 125cc.
This same setup ( bottom end) with a smaller cylinder could well be my next Bucket engine, after what, thirty odd years.

[husaberg]

Boy, I wrote quite a lot over the years, didn't I?
I've got a slight headache now, feeling a bit dizzy after reading that last long text. What does it say there? What should it have said? What did this more or less English text look like in the German in which I originally wrote this piece for some friends?
As it happens I'm in Germany again, getting snowed in, so I'll have plenty time to read and drink coffee (or Glühwein).

To answer your last question: both Wobbly and yours truly have been trying for decades to eradicate the persistent misconceptions about the desirability of small crankcase volumes and high crankcase compression ratios. What we still encounter on the internet every day can make you want to cry.
You have wrote far more and we are greatfull for everpart thats just little what a quick search turned up.
That last translated part i had never seen before? I never had a chance to read it. My own german is limited to what was in comics.
looks like it was indeed translated from something your wrote in 2009 translated using google and posted by RN? 2019?

Ignition curves
Copyright © 2009 Frits Overmars - (translated via google translate and some manual editing RN Jan-2019Ignition curves

here is another verson
looks closer to english
https://opensimspark.org/_media/fos-ignition-curves-eng.pdf


hint for kb users

when looking back at reposts
Where the arrow is after the poster name of you click there it takes you to the original post when posts are quoted it looks requoted bits.

[F5 Dave]

54 x 54 twin port cylinder underway. Rear disc valve this one, this is for Vinduro so is 125cc.
This same setup ( bottom end) with a smaller cylinder could well be my next Bucket engine, after what, thirty odd years.

Wooden Powervalve technology. Sustainable. I like it.