ESE's works engine tuner

[wobbly]

1-2-4-5-3 minimizes the rocking couple, in theory.
As used by Audi, VW and Volvo.
Myself and a mad mate built a 5cylinder H1 Kawasaki with this and it felt fine, long before Millyard.

[Jan Van Hamme]

Hi, when designing a cylinder 3D printing project, I'm unsure of the minimum recommended distance between the A transfer and the main exhaust port.
Is 5.57mm sufficient for a full FOS transfer concept with all the associated scavenging angles?

I'm also considering rounding the piston according to the recommended dimensions on FOS OneDrive.
I’m using a Wössner 8302D200 piston for a YZ125 2005-2021 for this project.
If I apply the radius, will the remaining 1.56mm still be thick enough?

Regards, Jan

[Viking]

I'm not a Viking but I am pretty sure he's using 670 Rotax cylinders that look a lot like this (pictures from ebay ads I found on the interweb).

The experts can opine if those are lift shafts, to me they are not the MOST squared off lift shaft transfers I've ever seen....but they don't look much like a teacup.



Unexpected happening. I found a cut Rotax 670 cylinder in my office.
A-transfer duct and B-transfer duct almost similar.
Exhaust duct length 60mm and diameter 45mm at flange interface.

[Wos]

Hi, when designing a cylinder 3D printing project, I'm unsure of the minimum recommended distance between the A transfer and the main exhaust port.
Is 5.57mm sufficient for a full FOS transfer concept with all the associated scavenging

angles?




I'm also considering rounding the piston according to the recommended dimensions on FOS OneDrive.
I’m using a Wössner 8302D200 piston for a YZ125 2005-2021 for this project.
If I apply the radius, will the remaining 1.56mm still be thick enough?

Regards, Jan

If you do it from scratch, why dont you take a domed, single ring piston?

Cant remember any advatage of the flat ones...

Then positioning ring gap in the middle of c port...you are more free doing minimum bridges between b and c ports...

Have a look at oler yamaha yz pistons
Or on suzuki rm 125...we use wössner too..

Exhaust t port?...the bridge is a weak point...not as sturdy as triple port layoutļ

Just my two cents ��

Wolfgang

[Jan Van Hamme]

If you do it from scratch, why dont you take a domed, single ring piston?

Cant remember any advatage of the flat ones...

Then positioning ring gap in the middle of c port...you are more free doing minimum bridges between b and c ports...

Have a look at oler yamaha yz pistons
Or on suzuki rm 125...we use wössner too..

Exhaust t port?...the bridge is a weak point...not as sturdy as triple port layoutļ

Just my two cents ��

Wolfgang

Hi Wolfgang, thanks for your reply.

It's an RD125LC. I've chosen to limit my rpm to 10,000 rpm.
If I cut out the bottom of the skirt (like with the old YZ125H), there's not much support left against piston tilt.
I'm thinking of making my own windows (two or three).
That way, I'll have some surface area left over to provide support against tilting.
That's why I opted for two piston rings, for the engine speed and a bit more resistance to rattle.

It's a VHM connecting rod (110 instead of 105).
I haven't found any 56mm pistons with two rings, a dome, a 15mm pin diameter offset by 1mm, and a lower compression height that I can shorten or drill holes in (cylinder intake reed valve).
Wössner did have them. That's why I was forced to use the flat piston.
The plan is to install a torroid insert.

On this piston, the ring gap of both piston rings is in the center of the C port. One is directly in the center, the other a millimeter off center.

A single exhaust port (70% and safe roof) is sufficient for blowdown and low timing for the intended power and rpm.
Therefore, I would opt for a T-port or triple exhaust port.

I'm not sure if the distance between the exhaust and the A-port is large enough to prevent shortcutting.

Vriendelijke groeten,
Jan

[Wos]

Hi Wolfgang, thanks for your reply.

It's an RD125LC. I've chosen to limit my rpm to 10,000 rpm.
If I cut out the bottom of the skirt (like with the old YZ125H), there's not much support left against piston tilt.
I'm thinking of making my own windows (two or three).
That way, I'll have some surface area left over to provide support against tilting.
That's why I opted for two piston rings, for the engine speed and a bit more resistance to rattle.

It's a VHM connecting rod (110 instead of 105).
I haven't found any 56mm pistons with two rings, a dome, a 15mm pin diameter offset by 1mm, and a lower compression height that I can shorten or drill holes in (cylinder intake reed valve).
Wössner did have them. That's why I was forced to use the flat piston.
The plan is to install a torroid insert.

On this piston, the ring gap of both piston rings is in the center of the C port. One is directly in the center, the other a millimeter off center.

A single exhaust port (70% and safe roof) is sufficient for blowdown and low timing for the intended power and rpm.
Therefore, I would opt for a T-port or triple exhaust port.

I'm not sure if the distance between the exhaust and the A-port is large enough to prevent shortcutting.

Vriendelijke groeten,
Jan

Ok jan ;)

I stuck with bore of 54.5 for a 125cc

But we run a 125 with adaptet reed valve to cilinder that has down skirt a cutout...and 2 Windows to, with only one ring...absolutely no problem...the wössner is stiff enough...35 h no ploblem


...doing a printed cilinder...wow :) ...dont you think about changing bore and stroke to square?
...every kind of pistons avaiable...and next to best bore stroke ratio...

Some Pages earlier frits gave a rule of thumb, about minimum space between ports...

Formula was bore x 0,044

If this rule is applyable to bridge between Ex and A port...you should be save ;)



Keep us informed about...especially printing your dream cilinder! ;) ;)

Wolfgang

[diesel pig]

Ok jan ;)

Keep us informed about...especially printing your dream cilinder! ;) ;)

Wolfgang

I would like to second that. Please keep us informed about your project. Metal printing is very interesting!

[Jan Van Hamme]

Ok jan ;)

I stuck with bore of 54.5 for a 125cc

But we run a 125 with adaptet reed valve to cilinder that has down skirt a cutout...and 2 Windows to, with only one ring...absolutely no problem...the wössner is stiff enough...35 h no ploblem


...doing a printed cilinder...wow :) ...dont you think about changing bore and stroke to square?
...every kind of pistons avaiable...and next to best bore stroke ratio...

Some Pages earlier frits gave a rule of thumb, about minimum space between ports...

Formula was bore x 0,044

If this rule is applyable to bridge between Ex and A port...you should be save ;)



Keep us informed about...especially printing your dream cilinder! ;) ;)

Wolfgang

You're absolutely right. I'd read in Frits' columns and OneDrive that oversquare engines aren't good for two-stroke engines (though they are for four-stroke engines).

So I looked into making a crankshaft with a 54,5 stroke instead of a 50-stroke, which, as you rightly point out, would also allow a wide range of pistons to be used.

The original crankshaft webs are 87,8mm in diameter. The crankcase has a 89.8mm diameter.
I'd have to mill out the crankcase to make room for the increased stroke.
This would put me too close to the holes used to hold the crankshaft halves together. There wouldn't be enough "meat" left there after the milling.
So, there went my hope of making a crankshaft myself to square up the engine.

I'd read on other forums that the auxiliary exhaust ports on the RSA only came very close to the A transfers over a very short distance.
They wrote that it was very critical to make that close-in zone longer. It was also pointed out that the distance between the main exhaust port and the A transfers needed to be much greater.
I looked at photos of an RSA cylinder, and they do indeed stay far away from the main port. How far?
As you rightly mentioned, I also noticed that Frits explained that formula a few pages back.
Because of those earlier photos and the larger distance at the RSA than the formula, I started wondering... would 5.57mm be enough?

By creating a 3D-printed cylinder, I'm trying to combine everything I've read over the years by Jan Thiel, Frits Overmars, Wayne Wright and try to apply it by and with Engmod2T from Neels Van Niekerk to the possibilities and limitations of an RD125LC.
As a hobbyist, I'm sure there will still be many obstacles in my project.

Working on my motorcycle like this makes me realize how incredibly impressive the knowledge and experience these people possess, what they've developed and achieved.
As I once wrote, their combined experience could fill an entire galaxy.
I haven't yet reached the level of the first ridge on their shoe soles (and for some, even their sandals). Nor do I have the ambition to do so.
I'm glad they, and people like you and others, are helping me through this digital means.

Groeten Jan

[bad'rule]

Re: Wos,
Have you checked on DT125E piston

Sent from my RMX1911 using Tapatalk

[Jan Van Hamme]

Re: Wos,
Have you checked on DT125E piston

Sent from my RMX1911 using Tapatalk

A DT125 has a 16mm piston pin diameter.

My VHM connecting rod has a small-end bore for a 19x15 needle bearing.

19x16 doesn't exist. I briefly considered filling the space with loose needles or using adapter bushings, but I opted for a commonly available silver-caged needle bearing measuring 19x15x19,5.

Groeten Jan

[Wos]

125 lc is without ypvs system?

All parts for are still available...:drool: ��

Yz 125 1983 had powervalve too...

https://mxlocker.com/product/1983-yamaha-yz125-oem-cylinder-24x-11311-00-00-565-mm-bore-y-ITDol

[Jan Van Hamme]

125 lc is without ypvs system?

All parts for are still available...:drool: ��

Yz 125 1983 had powervalve too...

https://mxlocker.com/product/1983-yamaha-yz125-oem-cylinder-24x-11311-00-00-565-mm-bore-y-ITDol

It's an RD125LC-10W. They don't have a power valve.

Because of the higher power I'm aiming for, I wanted a stronger, yet lightweight connecting rod.
I ended up with a VHM connecting rod. So the standard piston parts from a DT or RD won't fit.
The footprint of a YZ125 cylinder doesn't fit on my crankcase.
I also want the cylinder to look like the original on the outside.

I've already bought the VHM connecting rod, three Wössner pistons, and needle bearings.
Thanks for the input, but my main concern is the distance to avoid an exhaust shortcut.

[Wos]

Chance to adapt the ypvs to your print 😉

[wobbly]

JVH, as your engine will be developing a low bmep, the pipe diffuser will be nowhere near SOTA, and thus will not be generating a huge depression around BDC.
Honestly I dont think you need to be worrying about short circuiting, as long as the A port front wall is radially pointing sufficiently back toward the boost port.

[Jan Van Hamme]

Honestly I dont think you need to be worrying about short circuiting, as long as the A port front wall is radially pointing sufficiently back toward the boost port.

That's the answer I needed to clear up my doubts and concerns and move forward with my Solidworks design.
This is the exhaust I'll be using. It's not the same as the one I uploaded in my Pack file to the Engmod2Tgroup.
Thanks again

[wobbly]

JVH, there is alot of residual Blowdown pressure, shown by the bump at TPO - this will be reversing flow down the transfers.
I assume this is a function of the single Exhaust port and conservative timing to help front side.

[JanBros]

a question about carb's. I have 4 engines for my MX-mopets, and now I've bought a whole lot of used incomplete Dell Orto PHVA and PHBN carb's very cheaply- over 20 of them, enough to make spare carb's so I have for each engine at least 2 identical carb's so I can quickly swap them when we are having carb troubles during races.

Since I had to put everything together myself, I had to figure out all the settings myself, and the ones I've selected are working fine, except one thing gives me some troubles : when closing the throttle after full open and the engine needs to come back to idle, they keep idling at arround 2700rpm , allthough after starting and warming up they idle fine at arround 1600. stop the engine and restart immediatly and they idle fine again. I've tried idle jet's from 30 to 40, throttle slide cuts from 10 to 50, different needles, but on some carb's the problem stays . but they work fine when the mopeds are racing.

anyone have an idea of what exactly is the cause of this and how to fix it ?

[wobbly]

A carb " hanging up " above idle after reving is always one of four things.
First is the idle circuit is too lean, where is the idle air screw set ? It should idle and instantly transition best between 1 1/4 and 1 3/4 of a turn - outside this range the pilot needs changing.
Second is the throttle cable has insufficient free play - I like at least a couple of mm of movement on the cable end inside the adjuster screw.
Next is that when reving it, the fuel level is dropping due to the float valve being too small, thus leaning out the fuel ratio. Once the bowl fills again at idle with no load, it returns to a normal A/F.
Lastly is the possibility that once the engine is warm, it has a case leak thru a gasket or seal.

[JanBros]

A carb " hanging up " above idle after reving is always one of four things.
First is the idle circuit is too lean, where is the idle air screw set ?
depends on the idle jet : small ones almost full in, big ones full out. the 30 was too small, the 40 way too big.


Second is the throttle cable has insufficient free play - I like at least a couple of mm of movement on the cable end inside the adjuster screw.
I'll check
Next is that when reving it, the fuel level is dropping due to the float valve being too small, thus leaning out the fuel ratio. Once the bowl fills again at idle with no load, it returns to a normal A/F.
I'll check the fuel flow, but I'm just over 9BHP with the 70's (at +/- 8500), so they are not exactly in need of gallon's of fuel.
Lastly is the possibility that once the engine is warm, it has a case leak thru a gasket or seal.
I don't thinck this is the problem, as it's on more than 1 engine, even on engines that have raced a couple of 4-6h races without any problem's.

It should idle and instantly transition best between 1 1/4 and 1 3/4 of a turn - outside this range the pilot needs changing.
it responses to the air screw, but it might be (so not sure) that the problem is I do not find settings that allow the slide to go down enough and somehow the needlejet is also influencing the idle mixture. could the problem be the mixture tubes ? as I have many different ones and selected the ones that were most common (so swapping them out) so I could have carb's with everything exactly the same for each engine. mostly I'm using the 209GN mixture tubes.
https://sbd.etailercdn.de/media/pimg/l/-/thumbs/290292_2583276.jpg

[wobbly]

My instant response is that is a 4 stoke emulsion tube.
With hardly any exception ( a couple of RD Yamaha's ) NO 2T has air corrector holes in the tube - they use a shroud in the bore.
So now we are off on a whole new tangent, especially as you have the issue of the needle/tube combination affecting idle - a major pointer, that should not happen right there.

[JanBros]

yet these carb's are common on 2strokes. I've found a website that sell's replacement dellorto's for all kinds of bikes where all the jet's , needles and tubes numbers are referenced, and they all use these types of tubes. On 1 engine 1 use PHBG's and they also use that type of tubes and on that one everything works just fine.
example's :
Carburateur DELL ORTO PHVA Ø17.5US Honda/ Kymco Scooters 50 2T E2 - Carburateurs - EasyParts.nl - De grootste in onderdelen en accessoires voor scooter en brommer (https://www.easyparts.nl/Carburateur-DELLORTO-PHVA-%C3%9817.5US-Honda-Kymco-Scooters-50-2T-E2-p16281211)
Carburateur Dell Orto PHVA Ø17.5ED Malaguti Ciak 100 2T 1999-2001 - Carburateurs - EasyParts.nl - De grootste in onderdelen en accessoires voor scooter en brommer (https://www.easyparts.nl/Carburateur-DellOrto-PHVA-%C3%9817.5ED-Malaguti-Ciak-100-2T-1999-2001-p33842063)

I've tried many combinations of the settings on that site but problem stays. I make my own throttle slides (because I hate the original's where you have to put the cable through a hole instead of just hanging it in through the groove that prevents the slide to turn), but it does the same with original slides.

[Jan Van Hamme]

JVH, there is alot of residual Blowdown pressure, shown by the bump at TPO - this will be reversing flow down the transfers.
I assume this is a function of the single Exhaust port and conservative timing to help front side.

Wobbly, I tried using higher timings today. I can't get rid of that bump at TPO.
I see the same bump in all the graphs on page 2716.
Is there a way to eliminate something like that? I have no idea how to do that.

[wobbly]

JVH, you cannot delete the Transfer bump, unless you have an excessive amount of Blowdown STA.
And having some excess Blowdown pressure at TPO is vital to how transfer stagger actually works.

In your case I was commenting on it due to having relatively low superposition, plus a limited wave peak amplitude before EPO.
In this context the residual Blowdown pressure is quite high, when seen in light of that low pressure ratio amplitude before EPO.
Maybe this is due in part to the fact you are using a huge duct exit diameter, with no steeply tapered slip joint transition up into the header - that pulls down the high pressure ratio at EPO much quicker.


JanBros - using that series of emulsion tubes I have never seen in a 2T before, but having said that I have never worked on the tiny diameter Dellorto's
for scooter type things.
Even the 30mm Dellorto used in KZ racing uses the normal 2T tubes with no holes at all.
Its odd in that in the " Dellorto Motorcycle Carburetor Tuning Guide " they show the two different air corrector systems,
The 2T version has the shroud inside the bore, and an air corrector drilling from the bell mouth that exits into a short well around the needle entry.
Then the 4T version has the corrector air entering around the outside of the emulsion tube, where the size / number and height of the corrector holes changes the fuel curve from part to full throttle.
And I have seen another Dellorto guide showing the two tube types - saying the ones with holes are specifically for 4T

The so called STIC conversion for Keihin carbs uses this principle, and the advertising blurb says it atomizes the fuel droplets better, some swear by it - others swear at it.
With a huge range of tubes having differing corrector hole patterns, dialing in the best response must be a nightmare.

[Vannik]

Wobbly, I tried using higher timings today. I can't get rid of that bump at TPO.
I see the same bump in all the graphs on page 2716.
Is there a way to eliminate something like that? I have no idea how to do that.

Jan, inspect the severity of the bump with both Mach Index (which usually show a large return flow) and with Mass Flow. Usually the Mach Index makes one panic and then the Mass Flow makes you realize that it is nothing to worry about as the physical mass reverse flowing is very small. Bottom line, do not look at the pressure trace in isolation.

[Jan Van Hamme]

Jan, inspect the severity of the bump with both Mach Index (which usually show a large return flow) and with Mass Flow. Usually the Mach Index makes one panic and then the Mass Flow makes you realize that it is nothing to worry about as the physical mass reverse flowing is very small. Bottom line, do not look at the pressure trace in isolation.

Hi Neels,
Do I understand and interpret you correctly that the A-Transfer Mass Flow Rate of -0.86 in that small time span is only a small amount (a small curve area below the zero line) and therefore has little impact compared to +81 ?

If these graphs don't reveal any problems, I'll start building the cylinder and engine.
Currently, my 123cc engine is producing in simulation 36 hp at 10,000 rpm with a flat torque curve.
That's a BMEP of 13.08.
Getting there as a hobbyist is more than enough for me.
I don't have the knowledge yet to improve it further.

[Vannik]

Hi Neels,
Do I understand and interpret you correctly that the A-Transfer Mass Flow Rate of -0.86 in that small time span is only a small amount (a small curve area below the zero line) and therefore has little impact compared to +81 ?

Yes, you understand correctly. I wanted you to see there is more than just pressure traces and also one needs to look at a bigger picture.

[Jan Van Hamme]

Yes, you understand correctly. I wanted you to see there is more than just pressure traces and also one needs to look at a bigger picture.


Recognizing, knowing and estimating which bump is bad and which is negligible in the graphs is the next learning curve for me.

[koenich]

While we are on the topic of carbs...I have a very strange issue with my 50cc Bidalot: if you need to roll off throttle earlier than usual (e.g. slower rider in front of you before a corner) once you go back on throttle the engine stutters around, doesn't pick up revs and feels like it has loaded up with fuel. after few meters it'll clear and ride as usual.

Other than that it's working perfectly fine, any ideas what could help?

[wobbly]

Koenich, as I have been thru the exact opposite of your problem, with a couple of customers who had fitted Sudco 35mm Keihin carbs to LC/YPVS racebikes, the fix becomes quickly obvious.
They, because of ignoring my insistence they use EGT to tune the bikes, found that when backing off slightly into a fast corner, the thing seized immediately.
So, as they had received their ace tuners badge in a box of wheatbix, they decided that the main was too lean.
Result, another seizure.
Do that 3 times, then ring the guy who built the engine.
The correct answer would have been instantly obvious on the EGT trace, if they had bothered to fit a data logger - too expensive apparently , even compared to 6 pistons and cylinders.
Your fix is the dead opposite of what they needed.
In your case when backing off, more mass airflow is reduced, than is the total fuel flow - thus the needle tip diameter is too small.
Increase your tip diameter, and this will reduce the fuel curve sufficiently in line with the drop in mass airflow and that will push the A/F mixture closer toward stochiometric.
Be mindful that the needle tube/ tip diameter annulus area also affects the WOT fuel flow, thus a larger main would be good initial insurance as well.

[flyonly]

Koenich, as I have been thru the exact opposite of your problem, with a couple of customers who had fitted Sudco 35mm Keihin carbs to LC/YPVS racebikes, the fix becomes quickly obvious.
They, because of ignoring my insistence they use EGT to tune the bikes, found that when backing off slightly into a fast corner, the thing seized immediately.
So, as they had received their ace tuners badge in a box of wheatbix, they decided that the main was too lean.
Result, another seizure.
Do that 3 times, then ring the guy who built the engine.
The correct answer would have been instantly obvious on the EGT trace, if they had bothered to fit a data logger - too expensive apparently , even compared to 6 pistons and cylinders.
Your fix is the dead opposite of what they needed.
In your case when backing off, more mass airflow is reduced, than is the total fuel flow - thus the needle tip diameter is too small.
Increase your tip diameter, and this will reduce the fuel curve sufficiently in line with the drop in mass airflow and that will push the A/F mixture closer toward stochiometric.
Be mindful that the needle tube/ tip diameter annulus area also affects the WOT fuel flow, thus a larger main would be good initial insurance as well.

What logger wobbly?


Sent from my iPhone using Tapatalk

[wobbly]

Having used many, my quick answer is a Mychron - 2T, this has been used by Karters forever.
You need the 2T as it allows water temp as well as EGT.
With GPS it draws a track map showing GPS speed, rpm, water and EGT, if you want 2X EGT you need an expansion box.
Its only limitation is the the data record rate is set at 10 HZ , so as Ricky has found we cant log suspension travel as the rate of change is too quick.
We are building a stand alone logger at 100Hz to get this vital information.

[F5 Dave]

I had trouble comprehending that until i reread it.
Just be sure what you mean by backing off verses backing off a little. On a small carb in a 50 small track possibly, does that mean closing the throttle almost completely?

Wobbly is saying winding off a bit which is still constrained by delta of annulus to needle- at that point.
So the question to be sure of is -name your position of needle correctly.

Bikes with too small pilot and large needle base diameter like to sieze on closed.

But on a side note. Beware of the tiny carb that doesn't flow enough petrol into the float to keep it brimmed. Funny shit happens then. Gets exposed on longer tracks or an All gears run on the dyno with tall gearing, any drop in hight gears means you have a fuel flow issue. Played that game too often.

[Storbeck]

For what it's worth I have a two or three generations outdated aim evo 4 that can log at 1000 Hz. I would imagine the newer models are even better.

[koenich]

Thanks for that! Actually have a Mychron incl. EGT - need to look into that, maybe I can find a run where it happened.

Completely closing throttle earlier than normal, however carb is not so tiny at 30 mm and no issue on all gear runs on a dyno which fits very well to our acceleration times on track.

Re suspension - I'm using my Mychron 5S with an Expansion module and even with Aliexpress linear potentiometers works pretty good. Sample rate is 25 Hz, the only thing you need is a math channel which converts mV to actual position since you can't add a custom sensor

356583.

[Wos]

"

Completely closing throttle earlier than normal, however carb is not so tiny at 30 mm and no issue on all gear runs on a dyno which fits very well to our acceleration times on track. "

My guess for koenichs problem

Idle jet to big/ rich

and/or

cutaway to small/ rich

This may dropp pipe temperatures maybe so deep, that pipe is out of resonance !?

Next depending issue could be, that rpm s are dropping to such a low level, where ignition advance is high and this is resultig in another lower egt :( ...trapped in double issues!???

Wobbly ? He uses a pwk type carb... without tps...only 2d ignition curve

are these other possible reasons for phenomenon??

Thanks for advice, opinion and help ! :)

[wobbly]

The Mychron 5 needs an Expansion Box to run suspension position sensors , and according to its manual this has a set sample rate of 10Hz.
How do you get 25Hz, but apparently even this will not detect chatter as its way too fast a rate of change.
Aim has a software update that allows a Fourier Transform into the first derivative of velocity, but according to their own information we need up to 500Hz to see
high speed rate of change correctly.
https://www.datamc.org/data-acquisition/suspension-data-analysis/histograms-and-suspension-velocity-analysis/

Re the jetting issue - it was not obvious at all to me that following a slower bike you would " back all the way off ", but anyway, surely the idle and transition jetting has been tuned
such that there is no issues at idle or on initial acceleration.
Im guessing that you have tuned the main, on the dyno, or on the track to suit the bowl fuel level height after a period of WOT.
In the circumstance you describe, maybe the bowl level is dropping at WOT, and when you back off, as no fuel is being used - the bowl refills back to its nominal height and then when
cracking open the gas again the fuel curve is way rich.
This means the float valve is too small - Easy to check by adding a small breather fitting into the bowl nut and running a tube up the side of the carb.

I had that exact issue using Lectron HV40 carbs with clear bowls on a TZ400. On the dyno when hitting WOT you could see the level drop all of 20mm by the end of a dyno run.
The carbs had 3mm valves, fitting the so called high flow 3.5mm versions with side squirt holes, the issue went away instantly.

[F5 Dave]

An age ago on a mikuki i tried bigger valve etc to try solve a problem where upright you could just make it to the end of straight at Ruapuna B but would die as soon as you opened the throttle after the corner.
I ended up soldering an extension on the bottom of the button style jet in frustration. That fixed the symptoms kinda.
But the real reason turned out to be that the cross carb drilling was the actual bottleneck.

Once that was drilled out (and plug the brass ball again) normal jets could be run.

And that wasn't the last time I encountered that.

[koenich]

True - it's only 10 Hz and yes you need the expansion to add analog inputs, for the basic setup (and if you're not really good with interpreting the data) it's plenty capable in my opinion and was my "budget" solution compared to the likes of a MXM or others with high resolution. To get the velocities I added a math channel with the first derivate of position and it easily went up to 400 mm/s - which either way is too much acc to the information I could gather.

Guessed right - all circuits have been tuned, main been done on the dyno. it rides perfectly rolling on the throttle out of corners, main seems to be spot on as long as I'm on my pace. As its a 50cc obviously WOT is used quite a bit so your theory makes sense and thats also what I feel - that it's uber rich if I'm not pinning it till braking point but rather coasting. I'll check that - thanks :)

[wobbly]

As I understand it now, even if we see a full stroke dive under brakes at 400mm/s in 1/10th of a second, then there will be only two data points, the start position velocity, and the end position.
With chatter there could easily be 4 or more cycles, up and down in that time frame, with no intermediate data points to show this.
Thus only one peak velocity point will be displayed, instead of what is actually happening - the front wheel going spastically up and down at a high frequency above the sample rate.
In the digital world the Nyquist–Shannon sampling theorem, states that to accurately capture a signal, the sample rate must be more than twice the highest frequency present, thus I can absolutely believe
that to display high frequency cyclic position changes that 200Hz could be regarded as a minimum.
Doing the sampling and data logging is easy with a cheap stand alone processor board - but then integrating that into the Mychron with a CAN line is beyond me.

[koenich]

Well explained, found the same answer while trying to understand the limitations of my setup in the last days.

Besides the MXm there is also the option to use a Solo 2 DL with an AiM Analog to Can Converter which has a sampling rate of 200 Hz.

[Storbeck]

As I understand it now, even if we see a full stroke dive under brakes at 400mm/s in 1/10th of a second, then there will be only two data points, the start position velocity, and the end position.
With chatter there could easily be 4 or more cycles, up and down in that time frame, with no intermediate data points to show this.
Thus only one peak velocity point will be displayed, instead of what is actually happening - the front wheel going spastically up and down at a high frequency above the sample rate.
In the digital world the Nyquist–Shannon sampling theorem, states that to accurately capture a signal, the sample rate must be more than twice the highest frequency present, thus I can absolutely believe
that to display high frequency cyclic position changes that 200Hz could be regarded as a minimum.
Doing the sampling and data logging is easy with a cheap stand alone processor board - but then integrating that into the Mychron with a CAN line is beyond me.


Apologies if everyone is already well aware of it but rather than starting with a dash/display and adding an expansion, one can start with an evo4s and add a display and have much more capable data logging, 5 channels at 1000hz plus you can still use the expansion through CAN to get more if needed , for sort of around the same cost (a bit more but not huge increase), and still be in the aim ecosystem of software if one is already familiar/comfortable with it.

https://discoveryparts.com/products/aim-gs-dash-and-evo-4s-data-logger-dash-display-w-gps?variant=43645960782043&gad_source=1&gad_campaignid=21067563027&gbraid=0AAAAApOP0ApvZUYReIuv4xUf4aYthrIHQ&gclid=CjwKCAjwq9rFBhAIEiwAGVAZP8jpNSxC4EFKAIOpMnPx hHyRIgUf2uJMDT1zP-I6qnjNbKfk2yiQqBoCQlQQAvD_BwE

For the budget conscious the now outdated "evo 4" (note the lack of an "S") are out there pretty cheap used as people are upgrading. It uses the previous generation software, but still gets you 1000Hz. My opinion these things are an unbeatable bargain if one wants to get into datalogging on a budget. I don't recall but I think the gps updates more slowly on the old evo4 which could be a problem if track mapping is really important to you.

https://www.ebay.com/itm/127304812034?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=127304812034&targetid=2512152189032&device=c&mktype=pla&googleloc=9019701&poi=&campaignid=21214286338&mkgroupid=161030074701&rlsatarget=aud-1314496317547:pla-2512152189032&abcId=9407521&merchantid=6296724&gad_source=1&gad_campaignid=21214286338&gbraid=0AAAAAD_QDh_APNYBeXFFgQCoWsRAx3LSA&gclid=CjwKCAjwq9rFBhAIEiwAGVAZP94s-glnrqiIt8CMc_WTTYopY9q3yjBaRZzf7OPdoBIaCttIR5K40ho CZSAQAvD_BwE

[wobbly]

Several racebikes I look after already have the Mychron 5 2T with expansion to run 2X EGT - so I am looking for the most cost effective way of getting suspension data into
that package.

[Peter1962]

I was looking on the freetech50 website, and found it surprising that the first 5 competitors in the 2024 championship were all on membrane bikes, most derbi with Bidalot cilinders. I would have thought that the rotary inlet engines would be dominating, but allas...
And another surprise : the championship leader is on a prototype with two carburetors ! Last time I saw that was in the late 1970's with the french Moto BUT-HO made by Eric Offenstadt.

https://freetech50.com/

[wobbly]

Jan has said that if he were to do it again the RSA would have a rotary valve on each side - maybe the reed in the same configuration has an advantage when you cant simply
add a 14 speed gearbox to offset the loss of front side power of the Rotary Valve.
The two small / short reed petals would inherently suit the revs needed to get high piston speeds, and thus bmep out of the 50cc cylinder.

EDIT - sorry I just read that having a billet machined case with 8 speeds is already running.

[Peter1962]

Jan has said that if he were to do it again the RSA would have a rotary valve on each side - maybe the reed in the same configuration has an advantage when you cant simply
add a 14 speed gearbox to offset the loss of front side power of the Rotary Valve.
The two small / short reed petals would inherently suit the revs needed to get high piston speeds, and thus bmep out of the 50cc cylinder.

EDIT - sorry I just read that having a billet machined case with 8 speeds is already running.

Indeed, Jan spoke about that on pitlane.biz and also here at kiwibiker if I remember correctly. The 2 rotary valve 50 cc has been done by yamaha in 1961-63 I think. Wasn't even water cooled.

I did not follow the freetech championship for the last couple of years, but was surprised that the rotary valve is no longer the winning technology.

Now imagine a 50cc based on a Rimar billet crankcase, 8 speed gearbox, rotary valve equiped with Neil's sliding gibs, a Lectron or SmartCarb carburator equiped with a TPS and electronic Powerjet, a temp sensor in the exhaust for tuning.

Wouldn't that not be -theoreticaly- a better base than a derbi with reed valve ?

[wobbly]

IMHO, a single front rotary valve with gibs, plus the cylinder backwards for a straight pipe, PWM - PJ , deto feedback ignition , Servo PV on all 3 ports would only need 6 speeds, due
to a huge power spread, and would easily destroy even the twin reed engine that is currently SOTA in the class.
Using a Honda RS gearbox that had a huge range of options available would fix the issue I have seen of the 50"s dropping out of the power in some slow corners, or doing a block pass.

Here is a 500 twin using this layout, being drawn now.
With twin Rotary Valves across the front driven by the balance shaft to allow 90* firing in parallel cylinders, like the 250GP KTM.

EDIT - I just saw a video of the last round and No34, a Kreidler with side Rotary Valve was easily the fastest in a straight line, but got blitzed in the twisty bits.

[F5 Dave]

On a kart track reed engines have (or can have if you jet them) beautiful throttle response. Just the change from my 1/2 piston/reed RG to the full reed Derbi was evident in at least 2 corners and probably more where creating a stable platform helped grip.

I had a Borrowed fast for the day KE100/RG400 barrel for a while. I could ride it fairly effectively but it was borderline dangerous coming on power if you were near full lean.

I thought they ran on full size tracks?

[Flettner]

That's exactly what the sliding disc valve cover gibs are for.

[Jan Van Hamme]

I would like to second that. Please keep us informed about your project. Metal printing is very interesting!

Hi, I've made it this far with the transfer ports and exhaust.
The C-port and inlet port are the next step.

Does anyone have any comments, tips, or suggestions for improvements to the duct shape, B-hook, or other suggestions?
Footprint of the crankcase original Yamaha RD125LC-10W to all scavenging angles FOS concept.

Regards
Jan

[Frits Overmars]

Hi, I've made it this far with the transfer ports and exhaust.
The C-port and inlet port are the next step.
Does anyone have any comments, tips, or suggestions for improvements to the duct shape, B-hook, or other suggestions?
Footprint of the crankcase original Yamaha RD125LC-10W to all scavenging angles FOS concept.Jan, with the exhaust duct shape in your drawings you are leaving a lot of blowdown flow on the table. The pictures below may show what I mean.
Never mind the center bridge and the auxiliary exhaust ports in my pics (although it would be good if you could accommodate these).
356623356622
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356621&d=1615039443&thumb=1 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356621&d=1757669391)https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356620&d=1615039443&thumb=1 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356620&d=1757669290)

[Jan Van Hamme]

[QUOTE=Frits Overmars;1131239985]Jan, with the exhaust duct shape in your drawings you are leaving a lot of blowdown flow on the table. The pictures below may show what I mean.
Never mind the center bridge and the auxiliary exhaust ports in my pics (although it would be good if you could accommodate these).

Beste Frits, bedankt voor de aanbeveling.
Ik had die 2 tekeningen al zien staan in uw tips en tricks op onedrive.
Ik dacht, verkeerd dus, dat dit enkel bedoeld was voor uitlaatpoorten met een brugje.

Wat dat brugje betreft...de zuiger die ik ga gebruiken is een Wössner voor een YZ125. Die heeft 2 gaatjes van 1mm in de zuigerwand om de uitlaatbrug te koelen.
Omdat ik gelezen heb van Jan Thiel dat ALLE centrale brugjes op termijn breken, wou ik liever geen uitlaatbrug tekenen.
Als men die gaatjes aan beide zijden afschuint (soevereint) kunnen ze blijvend opgevuld worden met JB Weld extreme heat zei iemand mij waarvan ik het blindelings geloof.
Daarom dacht ik de gewone enkele uitlaatpoort te gebruiken.

Toch een brugje in de uitlaat maken zou dit opvullen elimineren maar hoe breed en hoe diep maak je zo een brugje in de uitlaat/poort zodat het zo lang mogelijk standhoudt voor het breekt of scheurt?
Brugje ook wat terugslijpen maar hoever en welke vorm?
.…Die vlakke YZ125 zuiger heeft een schuin vlak van 12° aan de rand. Ik zou dit kunnen wegdraaien naar dome. Maar dan heb ik maar maximum een tangentiële hoek van 4°.
De bodems van de A en B poorten ook 4° (voor dome) of 12° maken dan? Dome zal wel het beste zijn maar is 4° dan niet weinig?

Ik zit momenteel al voorbij de BMEP 13,5. Voor jou is dat peanuts maar voor mij en mijn standaard RD125LC versnellingsbakje en motorconstructie is meer blowdown en transferoppervakte en dus vermogen misschien gegarandeerd breuk?
Ik weet dat niet en kan dat niet echt inschatten.
Meer blowdown door extra auxiliaire uitlaatpoorten (bredere totale uitlaatpoort)… gaat dat geen frontpower en of powerbandbreedte kosten?
Er staan me ongetwijfeld nog enkele slapeloze nachten te wachten om uw goede raad in mijn hoofd te verwerken en te proberen analyseren.

Hartelijk bedankt voor uw vorige en verdere antwoorden en uw tijd.
Groeten Jan



Dear Frits, thanks for the recommendation.
I had already seen those two drawings in your tips and tricks on OneDrive.
I thought, wrongly, that this was only meant for exhaust ports with a bridge.

Regarding that bridge... the piston I'm going to use is a Wössner for a YZ125. It has two 1mm holes in the piston wall to cool the exhaust bridge.
Because I've read from Jan Thiel that ALL central bridges break eventually, I preferred not to draw an exhaust bridge.
If those holes are beveled on both sides, they can be permanently filled with JB Weld Extreme Heat, someone told me, and I blindly believe it.
That's why I thought about using the standard single exhaust port.

Making a bridge in the exhaust would eliminate this filling, but how wide and deep do you make such a bridge in the exhaust/port so that it lasts as long as possible before it breaks or tears?
Grind the bridge back a bit, but how far and what shape?
...That flat YZ125 piston has a 12° slant on the edge. I could turn it down to a dome. But then I'd only have a maximum tangential angle of 4°.
Should the bottoms of the A and B ports also be 4° (for the dome) or 12°? A dome would probably be best, but isn't 4° a small amount?

I'm currently already past the BMEP 13.5. That's peanuts for you, but for me and my standard RD125LC gearbox and engine design, more blowdown and transfer surface area, and therefore power, perhaps guaranteed to break?
I don't know and can't really estimate.
More blowdown due to additional auxiliary exhaust ports (wider total exhaust port)... won't that cost front-end power and/or power bandwidth?

I'm sure I'll have a few more sleepless nights ahead of me as I process and analyze your valuable advice.

Thank you so much for your previous and subsequent replies and your time.
Regards, Jan

[Frits Overmars]

I would definitely not make a central bridge in the exhaust. But judging by your drawings, there are no cylinder studs in the way, so you could make auxiliary exhaust ports.
These will give you so much blowdown angle.area that the exhaust timing does not need to be excessively high, which is good for bottom power.
I am familiar with the flat Yamaha pistons with a 12° slant. I would not modify them (but I would prefer to use a different piston brand).
The axial angles of the transfer ducts should be equal to their roof angles, about 25° for the A-ports and about 12° for the B-ports, but only where they transition into the cylinder bore, so while the port roofs have a certain flat part, make the lengths of the flat part of the bottoms zero. This also helps in making the inner radii of the transfer ducts as large as possible.

A BMEP of 13,5 is impressive. I never held an RD125LC cylinder in my hands, but I am somewhat familiar with the RD350LC and my biggest concern would be the cooling. I felt that there was water everywhere, except where it was needed...

[Jan Van Hamme]

I would definitely not make a central bridge in the exhaust. But judging by your drawings, there are no cylinder studs in the way, so you could make auxiliary exhaust ports.
These will give you so much blowdown angle.area that the exhaust timing does not need to be excessively high, which is good for bottom power.
I am familiar with the flat Yamaha pistons with a 12° slant. I would not modify them (but I would prefer to use a different piston brand).
The axial angles of the transfer ducts should be equal to their roof angles, about 25° for the A-ports and about 12° for the B-ports, but only where they transition into the cylinder bore, so while the port roofs have a certain flat part, make the lengths of the flat part of the bottoms zero. This also helps in making the inner radii of the transfer ducts as large as possible.

A BMEP of 13,5 is impressive. I never held an RD125LC cylinder in my hands, but I am somewhat familiar with the RD350LC and my biggest concern would be the cooling. I felt that there was water everywhere, except where it was needed...

These are the dimensions as I drew them. So at the A port it should also be 22° at the bottom.
For cooling, I wonder if it would be useful to draw cooling fins internally in the cooling channels of the printed cylinder.

[Frits Overmars]

For cooling, I wonder if it would be useful to draw cooling fins internally in the cooling channels of the printed cylinder.The transfer ducts look okay to me. The problem with the cooling is getting circulation around (and under!) the exhaust duct.

[Storbeck]

THis is not so much a suggestion but a question for the more knowledgeable folks on here.

Wouldn't it be better if the walls of the transfer ports are kept parallel as much as possible, except for the hooks on the b ports?

I understand the reality of fitting things into the existing crankcase may prevent this to some extent and it's hard to picture in 3d so maybe that's what JVH is already doing within the constraints he has ?

356630356631

[wobbly]

My two cents worth.
Change the water path completely with all the cold water entering above the boost port - or better if the case can be modified, each side of the boost from below.
Then cut access slots between the bore and the inner transfer wall - as per the RSA and KR3.
This way all the cold water cools the transfer ducts first , then moves forward around to both the top and bottom of the Exhaust duct.
Make the head cover such that no water can flow up around the insert except thru slots or two holes above the Exhaust duct , into the head, across the chamber and out above the boost port.
If the engine/head is angled forward at all, then a small air bleed is needed directly below the exit spigot into the cylinder, the high point where an air lock can occur.

EDIT, Jan's comment about T port mechanical issues only apply to the " all out " versions used in Honda GP Kit cylinders that usually have a dead flat timing edge to gain the maximum Blowdown area.
In your case this nowhere near what is required, with a curved timing edge the, vast majority of the load on the center bridge is reduced considerably, and a huge number of MX bikes with T ports have absolutely no
issues at all.

And yes I agree, air does not like to transit around a duct turn in two planes concurrently, Storbecks sketch is pointing in the right direction, literally.

[Jan Van Hamme]

My two cents worth.
Change the water path completely with all the cold water entering above the boost port - or better if the case can be modified, each side of the boost from below.
Then cut access slots between the bore and the inner transfer wall - as per the RSA and KR3.
This way all the cold water cools the transfer ducts first , then moves forward around to both the top and bottom of the Exhaust duct.
Make the head cover such that no water can flow up around the insert except thru slots or two holes above the Exhaust duct , into the head, across the chamber and out above the boost port.
If the engine/head is angled forward at all, then a small air bleed is needed directly below the exit spigot into the cylinder, the high point where an air lock can occur.

EDIT, Jan's comment about T port mechanical issues only apply to the " all out " versions used in Honda GP Kit cylinders that usually have a dead flat timing edge to gain the maximum Blowdown area.
In your case this nowhere near what is required, with a curved timing edge the, vast majority of the load on the center bridge is reduced considerably, and a huge number of MX bikes with T ports have absolutely no
issues at all.

And yes I agree, air does not like to transit around a duct turn in two planes concurrently, Storbecks sketch is pointing in the right direction, literally.

Wobbly, I'm going to look into creating the water flow path as you suggest.
The original water path enters from the rear side and then flows over the top (only the top) of the transfer ports to the front.
Then over only the top of the exhaust port.
Because of the cylinder head gasket, it can only go through two small holes upward.
Then around the combustion chamber to the rear and then through an opening to the radiator. See drawing.


I don't want to modify the original crankcase, but I will try to fully implement your proposed water path in the 3D-printed cylinder.
Could I close the cylinder at the top with printed aluminum and leave 2 openings in it to provide water passage to the cylinder head?
Then I can use O ring grooves in the cylinder instead of that seal.


The reason the transfer duct is rotated this way is because the crankcase's starting position is fixed, and the final FOS outlet positions in the cylinder wall deviate significantly from it radially.


If I understand you correctly, in my application (with a 75% top radius), I should be able to create a central bridge that will hold up.
Any suggestions for the width and depth of the bridge, and the top and bottom radii of that central bridge?
How far should I grind back radially in depth, and what profile shape should be removed?
I'll then re-simulate everything in Engmod2T with a T port and once with a triple port.
Drawing that triple port in solidworks seems like a real challenge.

[wobbly]

If you are achieving balanced STA numbers with the single port, then I dont understand why you even need a T port at all.
Of course I agree with Frits that a 3 port is superior and then the Exhaust timings can be dropped, with equal Blowdown, thus pumping up the front side - very helpful with no PV.
Have a look at a TM KZ cylinder, the whole outer surface of the cylinder bore above the transfers ,up to the deck has ribs in the cooling water - dramatically increases heat transfer ability.
You can easily do a head cover/insert that prevents any water from exiting the cylinder upwards, except for two holes above the Exhaust duct, then use O rings and no gasket.

[Jan Van Hamme]

If you are achieving balanced STA numbers with the single port, then I dont understand why you even need a T port at all.
Of course I agree with Frits that a 3 port is superior and then the Exhaust timings can be dropped, with equal Blowdown, thus pumping up the front side - very helpful with no PV.
Have a look at a TM KZ cylinder, the whole outer surface of the cylinder bore above the transfers ,up to the deck has a ribs in the cooling water - dramatically increases heat transfer ability.
You can easily do a head cover/insert that prevents any water from exiting the cylinder upwards, except for two holes above the Exhaust duct, then use O rings and no gasket.

Okay, thanks to Frits' and your advice, I'm abandoning the idea of ​​a T-port.
I'm now going to try and regain that lost front/bottom power with a 3 port and lower exhaust timing.
So, I'm putting the drawing activities on hold and going back to Engmod2T.

No idea at all how many degrees of difference there should be between main and aux ports.

I'll also try those cooling ribs like in your KZ cylinder when I'm back in the design phase.

[wobbly]

The RSA had around 4* timing split ie around 2mm, a TM KZ has 2.3*, around 1.1mm on a 54.5 stroke..
So its down to how much Blowdown you need with the main port geometry optimized first.
The RSA had a PV and a high main port up near 200*, the KZ has no PV and a main port timing near to what you have at 196*, so simply juggle the port timings and widths to gain
the effect you want in EngMod.

The 3 port geometry isnt hard - use the same construction as the main port.
Insert a plane at an angle in the bore, construct the 3 port chordal geometry on that and transfer it to the bore surface as loft driving sketch number one.
The other sketch can be a round shape, if you are going to have " ears " at the exit face.
Then construct 4 guide curves for the corners, these can be 3D splines with constraining dimensions on each spline end/start point.
Sometimes you can enter construction planes angled horizontally to put the 4 corner guide curves onto.
I always do one side and mirror it across.

[Wos]

Little Off topic fellows

Yesterday the 8 H endurance 50cc race in liedolsheim/ germany took place.
We faught hard:devil2:...we faught well :)

And the winner is our KOENICH from this Forum with his Team König Racing
:first:

Congratulations!! :clap:Well done!:2thumbsup

And many Thanks for lend us the bigger idle jet:cool:

Viele Grüße

Wolfgang

[Jan Van Hamme]

Little Off topic fellows

Yesterday the 8 H endurance 50cc race in liedolsheim/ germany took place.
We faught hard:devil2:...we faught well :)

And the winner is our KOENICH from this Forum with his Team König Racing
:first:

Congratulations!! :clap:Well done!:2thumbsup

And many Thanks for lend us the bigger idle jet:cool:

Viele Grüße

Wolfgang

Hi Wos,
8-hour race, congratulations to Racing Team König and your team.
I'll be happy if my engine holds up under normal use.
Let alone 8 hours of racing.
Vele groeten,
Jan

[Jan Van Hamme]

The RSA had around 4* timing split ie around 2mm, a TM KZ has 2.3*, around 1.1mm on a 54.5 stroke..
So its down to how much Blowdown you need with the main port geometry optimized first.
The RSA had a PV and a high main port up near 200*, the KZ has no PV and a main port timing near to what you have at 196*, so simply juggle the port timings and widths to gain
the effect you want in EngMod.

The 3 port geometry isnt hard - use the same construction as the main port.
Insert a plane at an angle in the bore, construct the 3 port chordal geometry on that and transfer it to the bore surface as loft driving sketch number one.
The other sketch can be a round shape, if you are going to have " ears " at the exit face.
Then construct 4 guide curves for the corners, these can be 3D splines with constraining dimensions on each spline end/start point.
Sometimes you can enter construction planes angled horizontally to put the 4 corner guide curves onto.
I always do one side and mirror it across.

Thanks Wobbly,
In my case, this is the difference between a single-port exhaust and a three-port exhaust.
I'm going for the 185° version with a three-port exhaust.
Back to solidworks now.

[Jan Van Hamme]

Jan, with the exhaust duct shape in your drawings you are leaving a lot of blowdown flow on the table. The pictures below may show what I mean.
Never mind the center bridge and the auxiliary exhaust ports in my pics (although it would be good if you could accommodate these).
356623356622
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356621&d=1615039443&thumb=1 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356621&d=1757669391)https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356620&d=1615039443&thumb=1 (https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356620&d=1757669290)

Thanks Frits

Bedankt Frits, het scheelt een slok op een borrel .
Sorry maar ik krijg zo een uitdrukking niet goed vertaald.

[wobbly]

JVH, just something to try - when the main port duration is 190* to 192* with the pipe length adjusted to suit, I have found more overall power
due to a naturally very wide band of superposition prior to EPO.
This may also allow more timing split with the Aux ports, so their differing ( longer ) duct length has less effect on the wave amplitude generated by the main port into the diffuser.
But this may not show up as a huge difference in EngMod as there is no mechanism in the code to define the Aux ports duct length, only an assumption on my part - dangerous.

[Vannik]

JVH, just something to try - when the main port duration is 190* to 192* with the pipe length adjusted to suit, I have found more overall power due to a naturally very wide band of superposition prior to EPO.

This is the difference between a resonating pipe and a tuned pipe:

1. A tuned pipe is a pipe where the pressure pulse reflected from the reverse cone arrives in time to push over scavenged fresh charge back into the cylinder;

2. A resonating pipe is a tuned pipe that builds stronger pulses by combining the new pulse with the residual pulse from the previous cycle to build pulses and suction pulses of substantially higher amplitudes.

[Jan Van Hamme]

This is the difference between a resonating pipe and a tuned pipe:

1. A tuned pipe is a pipe where the pressure pulse reflected from the reverse cone arrives in time to push over scavenged fresh charge back into the cylinder;

2. A resonating pipe is a tuned pipe that builds stronger pulses by combining the new pulse with the residual pulse from the previous cycle to build pulses and suction pulses of substantially higher amplitudes.

Months ago, I read somewhere on a forum, perhaps here or on Facebook, that an exhaust only starts working properly at timings of 190°. I have no idea why.
With this in mind, I tried first 185°. It produces a better power curve than the single exhaust port. So I thought, yes, 185° will be fine.
With your explanation Neels, I now understand what I read about 190°. A pipe will probably only starts resonating at 190°.

I'll definitely try that in Engmod.

Just a question for information. I learned in Mechanics that when designing machines, engines, bridges, etc., you have to pay attention to the natural frequencies of the structure.
When the load or operating conditions generate a frequency close to or at the natural frequency of the structure, this leads to total failure.
For example, as everyone knows, a platoon of soldiers shouldn't walk across a bridge in rhythm, or the bridge could resonate and bend further and further until it breaks.
This applies to solid matter, but apparently a gas can also resonate? A resonating exhaust.
Apparently, those resonating gases don't cause fracture.

I once read from Frits that the waves in a 2-stroke exhaust are not the same as the sound waves in a trumpet, for example.
Difficult material for me to dig deeper into.

In any case, I'm going to try a 190° version in Engmod and then come back here.

[Wos]

"No idea at all how many degrees of difference there should be between main and aux ports"

JVH... why go to a limit with the bridges on a triple exhaust when you have much chances to gain enougth blowdown. ..?
Stay on the save side and gain long reliability!? Thats nice to have :)



If i remember coreectly once frits told us 5 degree for every bridge between every port in a cilinder ...

Such a nice thing like a printed cilinder...them i would change case transfers too
Maybe, if case is sturdy...only a big one per side!? So you are more free with directions of cilinder transfer !? ;) good thing ...

Grüße Wolfgang

[Jan Van Hamme]

"No idea at all how many degrees of difference there should be between main and aux ports"

JVH... why go to a limit with the bridges on a triple exhaust when you have much chances to gain enougth blowdown. ..?
Stay on the save side and gain long reliability!? Thats nice to have :)



If i remember coreectly once frits told us 5 degree for every bridge between every port in a cilinder ...

Such a nice thing like a printed cilinder...them i would change case transfers too
Maybe, if case is sturdy...only a big one per side!? So you are more free with directions of cilinder transfer !? ;) good thing ...

Grüße Wolfgang

I think you misunderstood my question. I meant the difference in height between the main and auxiliary levels. Not the degrees that represent the width of the bridges.
Wobbly already pointed me in the right direction and answered.
Thanks anyway.

Groeten Jan

[Frits Overmars]

I once read from Frits that the waves in a 2-stroke exhaust are not the same as the sound waves in a trumpet, for example.The waves are essentially the same. Waves moving through a gas are local compressions of the gas where the molecules are closer together.
Compare it to circular waves on the water surface when you throw a stone into a pond. You see that the wave tops move outwards from the point where the stone hit the water, even though the water itself does not move, which you can see by looking at what is floating on the water.

The difference between exhaust pulses and a trumpet sound is not in the nature of the waves, but in the way you can describe their behavior.
For the trumpet sound you can use acoustic rules. And I deliberately write acoustic RULES and not acoustic LAWS because they are not laws. Those rules are derived from gas dynamics laws, simplified with a lot of assumptions that are acceptable as long as the sound pressure does not exceed a certain limit.
The wave pressures in a two-stroke exhaust exceed that limit by a factor of over a thousand. So forget about acoustics when you are dealing with waves in exhaust systems.

Now you may remember where you read it Jan :msn-wink:.

[Jan Van Hamme]

JVH, just something to try - when the main port duration is 190* to 192* with the pipe length adjusted to suit, I have found more overall power
due to a naturally very wide band of superposition prior to EPO.
This may also allow more timing split with the Aux ports, so their differing ( longer ) duct length has less effect on the wave amplitude generated by the main port into the diffuser.
But this may not show up as a huge difference in EngMod as there is no mechanism in the code to define the Aux ports duct length, only an assumption on my part - dangerous.

Main exhaust timing adjusted to 190°, main to aux = 3,8° instead of 2,3°.
Transfers and blowdown fully balanced. Pipe tuned lenght to 10k exactly.

Result: bmep rises from 13,58 @ 185° to 13,93 @ 190°.
1hp more but...lost a lot of front and mid power.

[Jan Van Hamme]

Compare it to circular waves on the water surface when you throw a stone into a pond.

That's a nice visually understandable comparison



Now you may remember where you read it Jan :msn-wink:.

Indeed. You can't imagine all the things I've read from you.
But remembering it all...that's no longer possible at 55.

[koba]

Here is a short report on the racing at Liedolsheim.
It's not too detailed, basically due to laziness and a lack of ability to make things interesting in written form.

I decided to take a look at this race after asking a very helpful person on here for info on different race options.
I was surprised to see a countdown with a small number on it, so off we go!

The race has been run since 1994, on a 1KM Kart track.
There are 3 classes, badly summarised here:


*Open 50cc
*Restricted 50cc (Aircooled, other stuff)
*125cc 4T "Stock"


There is the usual practice, qualifying etc. We turned up at just the right time, as the bikes were being rolled out to the dummy grid.
This was really cool, it was oddly familiar for me; basically buckets.
The classes are a little different but almost all of the bikes would have worked for NZ bucket racing. Likewise, NZ 50's and some 4T 125's would have fit here.

Le Mans start, always fun! This time uneventful, other than the slight jump with people running at the raising, rather than the drop of the flag.

Then, lots and lots of exciting racing.
There were about 6 teams showing really good early pace.
The fastest were really impressive but after the time wore on, and on, and on, it started becoming clear that there were two main contenders.
#29 and #91.
Other bikes were faster in a straight line and for short runs but these two really both had a lot of things working right.
The rider changes and refuling were done well, all riders were fast, they cut through traffic very well (and cleanly).

8 hours.
8 hours is a fucking long time.
That is 8 1-hour shifts on the bike, the teams have a maximum of 3 people.
I've done a 1 hour shift on a 50 before and it wrecked me pretty badly, It's another level (Respect!) to then go and do it twice more.

So, this kind of racing, the nerds can crunch some numbers on pace, time laps left etc.
It was amazing to see it was still a competitive race until the end!

Then there were beers, music and things.

Bloody good time, I met some cool people there.

Something that was really good was the lack of crashes, there were a few, I got a good eyeful of a decent highside- that was, picked, up, taped up, back out!

moto5.de has more info.

So, if you are reading this and are able to take a look next year; it is well worth it.

[wobbly]

JVH, so the next question to ask is have you tried to use my 1.5 X duct length - 75% area ideas, now you have converted to a 3 port.
You will be making your own pipe, so the cylinder does not need to be " stock appearing ".
This will pump up the peak and overev considerably, allowing a much longer pipe to assist the front side.

[F5 Dave]

Hey Mal thank for the report.
Full size tracks are so much easier than karts . You've done Battle of Buckets vs 2hr. But yeah 8hr I wouldn't be much chop even when I was fit.

[Jan Van Hamme]

JVH, so the next question to ask is have you tried to use my 1.5 X duct length - 75% area ideas.

No, I used the same 50mm exhaust duct length as with a single port.
I've saved your PDF about duct design V3.0 somewhere and will check what lengths and diameters it prescribes.
So far, I've always pressed the calc button in engmod and used that exhaust exit diameter.

[Wos]

JVH, so the next question to ask is have you tried to use my 1.5 X duct length - 75% area ideas, now you have converted to a 3 port.
You will be making your own pipe, so the cylinder does not need to be " stock appearing ".
This will pump up the peak and overev considerably, allowing a much longer pipe to assist the front side.

These were my immediately thaughts too...a pipe that peaks at 9000 maybe...and you get back frontside...and maybe 190 degree is to very early to pipes proper resonance job ...maybe that depends on curvature of upper side ex you use too...

Is engmod today able to do a propper ignition curve itself that suits to given circumstances?
What does it look like engmod is calculating with?
Is it a flat line ignition?




Further i miss a clear resojnance dip?...as seen usually seen in a dyno graph?

No crtics to you! Maybe its just the way engmod works...


Thanks to the involved specialists!! ;)

Grüße Wolfgang

[Frank S.]

Here is a short report on the racing at Liedolsheim.
Then, lots and lots of exciting racing.
There were about 6 teams showing really good early pace.
The fastest were really impressive but after the time wore on, and on, and on, it started becoming clear that there were two main contenders.
#29 and #91.

moto5.de has more info.

So, if you are reading this and are able to take a look next year; it is well worth it.

Hi koba,
it was a pleasure to meet you and your family.

Btw #29 has won the race. He is known as koenich.
Well done Daniel😁

[wobbly]

JVH, the 50mm duct is WAY too short - and yes Neels has put the 75% area guide in the code, and that is the result you get when pressing the duct exit radio button
when having input a 3 port.

[koenich]

Great you enjoyed it and nice to meet you :drinknsin

Thanks for the flowers gents!

[yatasaki]

Here is a short report on the racing at Liedolsheim.
It's not too detailed, basically due to laziness and a lack of ability to make things interesting in written form.

I decided to take a look at this race after asking a very helpful person on here for info on different race options.
I was surprised to see a countdown with a small number on it, so off we go!

The race has been run since 1994, on a 1KM Kart track.
There are 3 classes, badly summarised here:


*Open 50cc
*Restricted 50cc (Aircooled, other stuff)
*125cc 4T "Stock"


There is the usual practice, qualifying etc. We turned up at just the right time, as the bikes were being rolled out to the dummy grid.
This was really cool, it was oddly familiar for me; basically buckets.
The classes are a little different but almost all of the bikes would have worked for NZ bucket racing. Likewise, NZ 50's and some 4T 125's would have fit here.

Le Mans start, always fun! This time uneventful, other than the slight jump with people running at the raising, rather than the drop of the flag.

Then, lots and lots of exciting racing.
There were about 6 teams showing really good early pace.
The fastest were really impressive but after the time wore on, and on, and on, it started becoming clear that there were two main contenders.
#29 and #91.
Other bikes were faster in a straight line and for short runs but these two really both had a lot of things working right.
The rider changes and refuling were done well, all riders were fast, they cut through traffic very well (and cleanly).

8 hours.
8 hours is a fucking long time.
That is 8 1-hour shifts on the bike, the teams have a maximum of 3 people.
I've done a 1 hour shift on a 50 before and it wrecked me pretty badly, It's another level (Respect!) to then go and do it twice more.

So, this kind of racing, the nerds can crunch some numbers on pace, time laps left etc.
It was amazing to see it was still a competitive race until the end!

Then there were beers, music and things.

Bloody good time, I met some cool people there.

Something that was really good was the lack of crashes, there were a few, I got a good eyeful of a decent highside- that was, picked, up, taped up, back out!

moto5.de has more info.

So, if you are reading this and are able to take a look next year; it is well worth it.
You should try MEC 24 hours in Kula, Serbia ..
We were holding 3rd place ten minutes before end ....than bracket of dellorto sha broke..
Ended fifth😔
How much performance you have to give for reliability 😎

[Gradella23]

Great you enjoyed it and nice to meet you :drinknsin

Thanks for the flowers gents!

congrats for your win Koenich!
may i ask which engine are you using? do you have some pics and some dyno curves?

I also won a 50cc championship this sunday in Italy, using my own components. I'd love to compare with other european competitors in the coming years.
We always race in short and slow circuits so I've been forced to privilege relatively low rpm usage, having peak power at 12700 with a nice overrev and some hp earlier in the power range, but I'm happy for the torque figures we see, 11,4 Nm at 12400 at the wheel is a good result after just 2 races and a couple of dyno runs.
Some pics of my cylinder here:

[Jan Van Hamme]

JVH, the 50mm duct is WAY too short - and yes Neels has put the 75% area guide in the code, and that is the result you get when pressing the duct exit radio button
when having input a 3 port.


Regarding your recommendations for the 3-port, I've now come up with 84 mm for the port and 28 mm for the transition piece.
I tried a bit today with the 3-port 190° version, but I can't get it quite right.

[Muciek]

Onboard vid from last Freetech 50 race in Poznan Poland. driver #51 Sebastian Jonker


https://www.youtube.com/watch?v=Kr6ttRmrhiQ

And results.

[Peter1962]

Onboard vid from last Freetech 50 race in Poznan Poland. driver #51 Sebastian Jonker


https://www.youtube.com/watch?v=Kr6ttRmrhiQ

And results.

:clap:

That is some beautiful racing ! And a very nice racing circuit. Long sweeping corners, very impressive.

[DSE]

The waves are essentially the same. Waves moving through a gas are local compressions of the gas where the molecules are closer together.
Compare it to circular waves on the water surface when you throw a stone into a pond. You see that the wave tops move outwards from the point where the stone hit the water, even though the water itself does not move, which you can see by looking at what is floating on the water.

The difference between exhaust pulses and a trumpet sound is not in the nature of the waves, but in the way you can describe their behavior.
For the trumpet sound you can use acoustic rules. And I deliberately write acoustic RULES and not acoustic LAWS because they are not laws. Those rules are derived from gas dynamics laws, simplified with a lot of assumptions that are acceptable as long as the sound pressure does not exceed a certain limit.
The wave pressures in a two-stroke exhaust exceed that limit by a factor of over a thousand. So forget about acoustics when you are dealing with waves in exhaust systems.

Now you may remember where you read it Jan :msn-wink:.

I would like to welcome Mr. Frits Overmars and ask a question....
I have been reading your posts on the French forum and here for a long time with interest, I wanted to know your opinion.
Mr. Frits Overmars, do you think there is a need to cool the jumper in the exhaust duct?
I made 4 exhaust duct options in the models, and somehow such a question arose by itself.
I'm still designing the cylinder blank for the kart motor.
It will be an engine without a gearbox. Please excuse me for possible errors in automatic translation into English.

[DSE]

These are 2 variants of the 3-channel exhaust channel.

[DSE]

The second option is a 3-channel exhaust window.

[DSE]

And this is the exhaust duct with a jumper

[wobbly]

DSE - forget the T port - its well proven the 3 port is superior and more reliable.
With the 3 port design, your bridges between the main and Auxiliary ports are too long - in a 54 bore I have tested every conceivable length and shape.
15mm from the port to the center of a hollow 1/2 moon entry shape is best, not a straight edge parallel to the bore or perpendicular to the duct centerline.

The port roof should be down at 25* - not the centerline.
The roof should then have a convex radius centered over the side port entries.
The floor should exit perpendicular to the bore , then radius down as a ski jump, so the main port area reduces , exactly where the side port entries are increasing the CSA.
Past the convex roof and floor radi, the duct should be kept dead straight, no radiused shapes that do nothing but increase the volume and area.

Why is the floor of the boost port way below BDC - this promotes severe tumbling turbulence off the piston edge - with no inner wall to the duct.
Also having the Auxiliary ports at the same timing as the main, destroys power everywhere, due to the big difference in the wave fronts path lengths to the header entry.

[DSE]

DSE - forget the T port - its well proven the 3 port is superior and more reliable.
With the 3 port design, your bridges between the main and Auxiliary ports are too long - in a 54 bore I have tested every conceivable length and shape.
15mm from the port to the center of a hollow 1/2 moon entry shape is best, not a straight edge parallel to the bore or perpendicular to the duct centerline.

The port roof should be down at 25* - not the centerline.
The roof should then have a convex radius centered over the side port entries.
The floor should exit perpendicular to the bore , then radius down as a ski jump, so the main port area reduces , exactly where the side port entries are increasing the CSA.
Past the convex roof and floor radi, the duct should be kept dead straight, no radiused shapes that do nothing but increase the volume and area.

Why is the floor of the boost port way below BDC - this promotes severe tumbling turbulence off the piston edge - with no inner wall to the duct.
Also having the Auxiliary ports at the same timing as the main, destroys power everywhere, due to the big difference in the wave fronts path lengths to the header entry.

Still, sometimes Google Translate turns the text into a secret script, sometimes you have to filter what it composes when translating written material. :yes:
I'll write to you later. Thank you.

[Frits Overmars]

Mr. Frits Overmars, do you think there is a need to cool the jumper in the exhaust duct?DSE, I assume that your 'jumper' is what Wobbly calls his 'ski jump', the hump at the bottom of the exhaust duct. And yes, if there is such a hump, cooling it will be good.

Wobbly already commented on your exhaust drawings, so I will concentrate on your transfers. Contrary to what you have drawn, the A-ports should have larger axial angles than the B-ports. You may want to take a look at the 'leaning tower of Pisa' story below for both the axial and radial angles.

I also noticed that the inner radii in your transfer ducts, indicated here with Ri, can be made be way larger than they are now; see the constant-radius inner radius in the A-duct drawing below.
356682356683 356684

[DSE]

DSE - forget the T port - its well proven the 3 port is superior and more reliable.
With the 3 port design, your bridges between the main and Auxiliary ports are too long - in a 54 bore I have tested every conceivable length and shape.
15mm from the port to the center of a hollow 1/2 moon entry shape is best, not a straight edge parallel to the bore or perpendicular to the duct centerline.

The port roof should be down at 25* - not the centerline.
The roof should then have a convex radius centered over the side port entries.
The floor should exit perpendicular to the bore , then radius down as a ski jump, so the main port area reduces , exactly where the side port entries are increasing the CSA.
Past the convex roof and floor radi, the duct should be kept dead straight, no radiused shapes that do nothing but increase the volume and area.

Why is the floor of the boost port way below BDC - this promotes severe tumbling turbulence off the piston edge - with no inner wall to the duct.
Also having the Auxiliary ports at the same timing as the main, destroys power everywhere, due to the big difference in the wave fronts path lengths to the header entry.

Here's the thing, in 2010 I managed to find thermal paints, the so-called thermal markers. The paint set included about 20 cells. Each cell with paint had a certain temperature threshold, above which it changed color. The principle is this: you apply paint, cover with a protective varnish, dry and the thermal marker is ready for use.
I, for my karting engines, have the opportunity to produce pistons manufactured using the following technology: - isothermal stamping. I design, and my friends and colleagues stamp and process according to my documentation. I really wanted to understand the thermal stress of pistons during operation. When I got these paints, I just applied markers from inside the piston and rolled off the motor on the motor test bench.
I rolled the engine on a stand without a window in the piston.
And he conducted tests with a window in the piston.
The difference in the thermal stress of the piston bottom was almost 45 degrees Celsius. For an aluminum alloy, as materials scientists say, it is practically a gift.
Having formed a purge through the piston, we partially cool it. If my memory serves me correctly, this solution was applied by MZ in the last century.
I use it too.
Having observed what is happening under the piston while working on the stand, it is simply clear that the upper head of the connecting rod is always smeared and the temperature limits do not climb high.
The photos are below. (I don't know how well Google translated it)
356685356686356687356688356689356690

[DSE]

On the cylinder it looks like this.
I make the cylinders myself, or rather, I order them according to my drawings.

[wobbly]

DSE, here is a quick sketch of my meaning.
I have tested the low boost port floor, with and without a hole in the piston.
With this system, the EGT is always lower ( due to more lost charge out the Exhaust, from the boost port ) and leaning it down does not gain back the power.
In the KZ engines we have been as high as 685*C EGT running C12 in the USA and have never had issues with the piston crown overheating.
We always have timing edge deto, well before the piston dome is in trouble , and that is with 50+ sprocket Hp.

[DSE]

DSE, I assume that your 'jumper' is what Wobbly calls his 'ski jump', the hump at the bottom of the exhaust duct. And yes, is there is such a hump, cooling it will be good.

Wobbly already commented on your exhaust drawings, so I will concentrate on your transfers. Contrary to what you have drawn, the A-ports should have larger axial angles than the B-ports. You may want to take a look at the 'leaning tower of Pisa' story below for both the axial and radial angles.

I also noticed that the inner radii in your transfer ducts, indicated with Ri, can be made be way larger than they are now; see the constant-radius inner radius in the A-duct drawing below.
356682356683 356684

Mr. Overmars, I apologize to you for the incorrectly worded question.
I did not convey the essence in detail, I wanted to ask you about the cooling of the jumper in the exhaust duct of the cylinder.
In the photo of the 3D model of the cylinder, I made the appropriate sections to make this cooling channel visible. In fact, it won't be possible to get such a channel in the cylinder casting, so I thought about making it by drilling.
This is a cylinder of a go-kart engine, with a volume of 193 cubic centimeters.
This is just an example, since he is one of....the ones I did.
The models of the gas distribution channels that I listed above are the engine that I want to make, with a cylinder displacement of 250.
The stroke of the piston is 65 mm, the cylinder diameter is 69.5 mm.
I read about the Leaning Tower of Pisa carefully. Conclusions will follow.
I've taken into account your comments on the geometry of the channels, and I'll redo the 3D models over the weekend.

[DSE]

DSE, here is a quick sketch of my meaning.
I have tested the low boost port floor, with and without a hole in the piston.
With this system, the EGT is always lower ( due to more lost charge out the Exhaust, from the boost port ) and leaning it down does not gain back the power.
In the KZ engines we have been as high as 685*C EGT running C12 in the USA and have never had issues with the piston crown overheating.
We always have timing edge deto, well before the piston dome is in trouble , and that is with 50+ sprocket Hp.

Thank you, I read it carefully. There is something to think about.

[DSE]

DSE, here is a quick sketch of my meaning.
I have tested the low boost port floor, with and without a hole in the piston.
With this system, the EGT is always lower ( due to more lost charge out the Exhaust, from the boost port ) and leaning it down does not gain back the power.
In the KZ engines we have been as high as 685*C EGT running C12 in the USA and have never had issues with the piston crown overheating.
We always have timing edge deto, well before the piston dome is in trouble , and that is with 50+ sprocket Hp.

How do you track it?

[wobbly]

DSE, we have the best power EGT and the RAD from the test on the dyno.
Its easy to track the EGT, up to the point with one jet leaner , the temp does not increase.
That is the deto limit.

[DSE]

I use thermocouples, type K. The ones I made myself, the cases.

[wobbly]

Exposed tip ? , 3X bore from piston face ? tip on centerline of the header ?

[Frits Overmars]

I did not convey the essence in detail, I wanted to ask you about the cooling of the jumper in the exhaust duct of the cylinder.
In the photo of the 3D model of the cylinder, I made the appropriate sections to make this cooling channel visible. In fact, it won't be possible to get such a channel in the cylinder casting, so I thought about making it by drilling.DSE, from your above post I gather that by ‘jumper’ you don't mean Wobbly's ‘ski jump’, but the center bridge in a T-shaped exhaust port. As Wobbly already pointed out, such a center bridge is not desirable. But if it is there anyway, it is certainly a good idea to cool it internally. Casting an internal cooling channel is indeed impossible (unless your name is Neil Hintz), but drilling is quite feasible.
Honda did this in their last NSR250 factory cylinders. I would love to show you the photos I have (and don't ask how I got them) but unfortunately me and my archive are currently not in the same country.

[DSE]

Exposed tip ? , 3X bore from piston face ? tip on centerline of the header ?

Actually, here is a thermocouple with a "hot junction".
Then I give it to the laboratory for verification.
Some spikes of up to 600 degrees Celsius are accurate. There is an error of 700 and 800, by 2 degrees.
Then I put it in a shrink tube, warm it up, and mount the plug.
I'm dressing the case.
Done.
Some buildings, however, are about 15 years old, maybe more ... it doesn't matter in principle.
The tip of the thermocouple sticks out in the large window, and purging takes place through the round hole.
I put it in the center of the collector section, 120 mm from the sleeve mirror.
That's about it.
(p.s. - . I really didn't quite understand about the 3 holes...maybe I missed something. I almost forgot, these thermocouples are for working on the stand) )

[wobbly]

The distance from the piston face to the position of the EGT probe in the header, should be three times the bore diameter ( square bore/stroke ).
That is a very strange method of shrouding the thermocouple tip, why is that even necessary?
The best EGT probes I have been using for over 10 years are Stingers from Exhaust Gas Technologies in USA - they have a 3 year guarantee, and are only around $70 USD .
I have bought literally hundreds of them for race customers, and never had a failure - the junction is completely exposed to get the fastest response time for data logging
on the dyno or at the track.

[koenich]

may i ask which engine are you using? do you have some pics and some dyno curves?

We always race in short and slow circuits so I've been forced to privilege relatively low rpm usage, having peak power at 12700 with a nice overrev and some hp earlier in the power range, but I'm happy for the torque figures we see, 11,4 Nm at 12400 at the wheel is a good result after just 2 races and a couple of dyno runs.
Derbi EBS with Bidalot cylinder - 19 HP and 10 Nm with peak HP around 13.500 1/min (at the wheel on a conservative Dynojet).

Well done with your cylinder - looks amazing, especially with the low revs! However, why not rev further to be able to gear shorter? If you gear for similar vmax your wheel force will increase...?

[DSE]

DSE, from your above post I gather that by ‘jumper’ you don't mean Wobbly's ‘ski jump’, but the center bridge in a T-shaped exhaust port. As Wobbly already pointed out, such a center bridge is not desirable. But if it is there anyway, it is certainly a good idea to cool it internally. Casting an internal cooling channel is indeed impossible (unless your name is Neil Hintz), but drilling is quite feasible.
Honda did this in their last NSR250 factory cylinders. I would love to show you the photos I have (and don't ask how I got them) but unfortunately me and my archive are currently not in the same country.

Mr. Frits, please take a look at these channel cross-section sketches.
Is it possible to consider such an interpretation of the cross sections of the purge channel profiles?

With the graduation channel, I'll probably work with the sketches before starting to build 3D models, and of course I'll show the result.
It probably wouldn't be a bad idea to attach a profile of the piston bottom, I didn't think about it right away.
I'm laying the piston with a sphere with a radius of 360 mm and a compression height of 30.5 mm.

I stopped at a connecting rod with an inter-center distance of 129 mm. At least this size seemed to me more optimal in terms of calculating lateral forces.... Well, what will happen with gas exchange and filling, it will probably have to be evaluated only in bench tests.
The engine is still being drawn and is in the stage of sketches and layouts.

[Frank S.]

Hi DSE,
just a small remark, Mr Overmars prefers to be called Frits😁
Keep on designing your personal 2T Engine and keep us informed🤗

Regards

[DSE]

Hi DSE,
just a small remark, Mr Overmars prefers to be called Frits😁
Keep on designing your personal 2T Engine and keep us informed🤗

Regards

It's clear. thank you.

[Gradella23]

Derbi EBS with Bidalot cylinder - 19 HP and 10 Nm with peak HP around 13.500 1/min (at the wheel on a conservative Dynojet).

Well done with your cylinder - looks amazing, especially with the low revs! However, why not rev further to be able to gear shorter? If you gear for similar vmax your wheel force will increase...?

we weren't able to find the right match with the original cagiva gear spacing, so we always lacked the right timing in super slow corners.. this low revs config helped us covering this problem.
anyway we'll develop some more during the off season to gain something revving higher.

in the coming weeks i'll have a pair of derbi (but euro3) cylinders to begin playing with. I want to finally develop a credible alternative to the very good bidalot kit.

[Frits Overmars]

Mr. Frits, please take a look at these channel cross-section sketches.
Is it possible to consider such an interpretation of the cross sections of the purge channel profiles?
With the graduation channel, I'll probably work with the sketches before starting to build 3D models, and of course I'll show the result.
It probably wouldn't be a bad idea to attach a profile of the piston bottom, I didn't think about it right away.
I'm laying the piston with a sphere with a radius of 360 mm and a compression height of 30.5 mm.
I stopped at a connecting rod with an inter-center distance of 129 mm. At least this size seemed to me more optimal in terms of calculating lateral forces.... Well, what will happen with gas exchange and filling, it will probably have to be evaluated only in bench tests.
The engine is still being drawn and is in the stage of sketches and layouts.Thank you DSE. Yes, I prefer to be called just Frits, without the 'Mr' or even the 'Dr' that Germans seem to be so fond of.
And of course everybody is free to use the nickname he or she prefers on the internet, be you would make me happy if I could call you by your first name too.

Your posts raised a number of questions. And I guessed wrong with your 'jumper' so now I will simply ask instead of guess: what is a graduation channel?

Your engine has a 69,5 mm bore and a 65 mm stroke so it's definitely short-stroke which as you may know, is unfavorable for the specific angle.areas in a two-stroke engine.
Your 129 mm con rod length is less than twice the stroke. If I were free to design an engine, I'd use a rod/stroke ratio of 2,2 , so noticeably longer than you are planning to use.

You wrote that you studied the 'tower of Pisa' concept but it does not show in your drawings. Your axial transfer angles are steeper than the proposed values in my concept,
which is meant for a square bore/stroke engine. For your short-stroke engine those angles should be even smaller.

The most import radial transfer angle is the leading direction angle of the A-transfer port. Why make it 40° instead of 30° if you still enjoy the freedom of the designing stage?
356727 356728

[koenich]

Let me know once they are available ;)

[DSE]

Thank you DSE. Yes, I prefer to be called just Frits, without the 'Mr' or even the 'Dr' that Germans seem to be so fond of.
And of course everybody is free to use the nickname he or she prefers on the internet, be you would make me happy if I could call you by your first name too.


The most import radial transfer angle is the leading direction angle of the A-transfer port. Why make it 40° instead of 30° if you still enjoy the freedom of the designing stage?
356727 356728

I understand you.
Of course, I'm not German, but where I was born and raised, at an early age, respect for people older than you is embedded in education, and even more so for those from whom you study.

I do not know the correct equivalent in English, as I could in general. If I offended you, please excuse me.
My name is Slava, among colleagues and friends.

Now, regarding the radial angle of the purge channel, I will have to clarify.
I assumed that for an engine with a cylinder volume of 250 cubic centimeters, I would be able to use a backup crankcase from the 193 cc engine, which I had designed and manufactured earlier. And on it, the attachment points of the cylinder are very close. And it is difficult to deploy the purge channel. Now it becomes clear that I will have to design and manufacture a new engine crankcase. .
Here he is, 193 engine.

[DSE]

Your engine has a 69,5 mm bore and a 65 mm stroke so it's definitely short-stroke which as you may know, is unfavorable for the specific angle.areas in a two-stroke engine.
Your 129 mm con rod length is less than twice the stroke. If I were free to design an engine, I'd use a rod/stroke ratio of 2,2 , so noticeably longer than you are planning to use.



I also understood the axial angles, I'll also redo them and show them. There is, however, a slight problem in this, in my opinion, when processing the sleeve, but I think that a 5-axis machine can handle it.
I also realized from the connecting rod that I would have to postpone the workpieces and "draw" a new connecting rod.
On the 193 engine, by the way, I have a connecting rod with a ratio of 2.15.
I've been wanting to make a connecting rod like this for a long time, but somehow I can't get my hands on it. Now you'll definitely have to do it with a 2.2 ratio.
(p.s. - again, he writes nonsense, the ratio of the length of the connecting rod to the stroke of the piston, Google interprets in its own way..)

[DSE]

Your posts raised a number of questions. And I guessed wrong with your 'jumper' so now I will simply ask instead of guess: what is a graduation channel?



I'll be watching more closely what Google translates.:rolleyes:

[koba]

we weren't able to find the right match with the original cagiva gear spacing, so we always lacked the right timing in super slow corners.. this low revs config helped us covering this problem.
anyway we'll develop some more during the off season to gain something revving higher.

in the coming weeks i'll have a pair of derbi (but euro3) cylinders to begin playing with. I want to finally develop a credible alternative to the very good bidalot kit.

I cover this problem with clutch abuse.

(Not close to the same power level).

[Gradella23]

I cover this problem with clutch abuse.

(Not close to the same power level).

it helps!
unfortunately we were racing with an almost 90kg street production bike Cagiva Prima, against some handmade and/or proper racing bikes with magnesium rims, great suspension, and weighing 65kg so having some more power down low was even more valuable

[Frits Overmars]

I assumed that for an engine with a cylinder volume of 250 cubic centimeters, I would be able to use a backup crankcase from the 193 cc engine, which I had designed and manufactured earlier. And on it, the attachment points of the cylinder are very close. And it is difficult to deploy the purge channel. Now it becomes clear that I will have to design and manufacture a new engine crankcase. Here he is, 193 engine.
I also understood the axial angles, I'll also redo them and show them. There is, however, a slight problem in this, in my opinion, when processing the sleeve, but I think that a 5-axis machine can handle it.
I also realized from the connecting rod that I would have to postpone the workpieces and "draw" a new connecting rod.
On the 193 engine, by the way, I have a connecting rod with a ratio of 2.15.
I've been wanting to make a connecting rod like this for a long time, but somehow I can't get my hands on it. Now you'll definitely have to do it with a 2.2 ratio.
(p.s. - again, he writes nonsense, the ratio of the length of the connecting rod to the stroke of the piston, Google interprets in its own way..)
Thank you, Slava. I see that your “freedom of the design stage” is not unlimited, as I had assumed until now.
A connecting rod/stroke ratio of 2.15 is acceptable. But a 250cc single with a cylinder sleeve and an exhaust centre bridge is asking for thermal problems.
Your pictures have made me curious. How do you use an engine without a gearbox on a kart? Does it get an automatic clutch or a CVT transmission?
I find the spark plug caps interesting. Where did you find them?
As for Google Translator, I don't use it anymore. The translator from Deepl.com is much, much better.

[porttiming124]

Hello, I'm looking for a 67.5mm cast piston with an 18mm pin.
I'm from Canada and I can't find anything good here or in the United States. Do you know of any brands in your country? Thanks.

[DSE]

Thank you, Slava. I see that your “freedom of the design stage” is not unlimited, as I had assumed until now.
A connecting rod/stroke ratio of 2.15 is acceptable. But a 250cc single with a cylinder sleeve and an exhaust centre bridge is asking for thermal problems.
Your pictures have made me curious. How do you use an engine without a gearbox on a kart? Does it get an automatic clutch or a CVT transmission?
I find the spark plug caps interesting. Where did you find them?
As for Google Translator, I don't use it anymore. The translator from Deepl.com is much, much better.

I bought these ignition coils when my friend was making a programmable system. This is from Suzuki's outboard motor. Coil tips: - fluoro-rubber. I use a centrifugal clutch (pictured below), but this decision is not final.

I found one here: - ..https://aliexpress.ru/item/1005008600186848.html?spm=a2g2w.detail.rcmdprod.6. 7317228aLM8QFT&mixer_rcmd_bucket_id=UnknownMixerAbId&pdp_trigger_item_id=0_1005005642857582&ru_algo_pv_id=3c44c1-61b690-bbae6c-759904-1758654000&scenario=aerSimilarItemPdpRcmd&sku_id=12000045899905149&traffic_source=recommendation&type_rcmd=core

[DSE]

I'm looking at such a model, I would probably try it.
I'm falling asleep now, and I'm going on a business trip tomorrow.

I'll answer any questions in a couple of days.

https://www.bmikarts.com/Bully-34-Turbo-Jackshaft-Clutch-10200-RPM_p_20809.html

Regards

[dtenney]

Frits, Wobs or others: Is it important to have the rotary valve drive balanced to offset the imbalance of the rotary valve itself? We are thinking there may be additional power to be gained with a balanced disc.

[Frits Overmars]

Frits, Wobs or others: Is it important to have the rotary valve drive balanced to offset the imbalance of the rotary valve itself?
We are thinking there may be additional power to be gained with a balanced disc.In theory yes, without a doubt. But I have no idea how much extra power it would yield; never measured it.

[wobbly]

I have seen a couple of engines with the center boss of the valve weighted on one side.
But most dont seem to worry about it.
The force is a constant circular out of balance vector, not a cyclic one.
Bearings be they ball or roller dont mind constant radial forces, within their load rating of course - cyclic ones where the elements have wildly varying loads is what creates issues.

[Wos]

I bought these ignition coils when my friend was making a programmable system. This is from Suzuki's outboard motor. Coil tips: - fluoro-rubber. I use a centrifugal clutch (pictured below), but this decision is not final.



I found one here: - ..https://aliexpress.ru/item/1005008600186848.html?spm=a2g2w.detail.rcmdprod.6. 7317228aLM8QFT&mixer_rcmd_bucket_id=UnknownMixerAbId&pdp_trigger_item_id=0_1005005642857582&ru_algo_pv_id=3c44c1-61b690-bbae6c-759904-1758654000&scenario=aerSimilarItemPdpRcmd&sku_id=12000045899905149&traffic_source=recommendation&type_rcmd=core


fluorine rubber ( fkm in germany also known as viton) has nothing to do with special marine use. Its a rubber with one of the best oil and heat resistance and is used in all ngk rubber spark plug caps and in many sealing rings too... ;)

[ApolloMotoMoto]

Curious if anyone here has any experience with 3d printing functional intake parts, reed valve boxes, reed valve bodies, carburetor mounting flanges, etc.

Bonus points for experience with ethanol/methanol fuels using 3d printed intake parts.

For a few reasons I am attempting to come up with a working solution for 3d printed reed boxes for my application.

3-4 different carbon type filaments have been used in standard FDM style printers, and so far have failed pretty miserably.

Following a thread from a few different manufacturers that are actually selling retail 3d printed intake parts, I have my latest round of test parts back, printed out of Nylon PA11 and Nylon PA12 (expirimenting between the two) printed on an HP MJF machine, the important distinction being that its not a filament deposition technology, but instead a "powder bed fusion" technology.

Pictured below.

The darker "flange" that bolts to the cylinder is Nylon PA11, the lighter reed box that bolts to the flange is Nylon PA12.

Will post back with the results from testing these samples.

[Gradella23]

Curious if anyone here has any experience with 3d printing functional intake parts, reed valve boxes, reed valve bodies, carburetor mounting flanges, etc.

Bonus points for experience with ethanol/methanol fuels using 3d printed intake parts.

For a few reasons I am attempting to come up with a working solution for 3d printed reed boxes for my application.

3-4 different carbon type filaments have been used in standard FDM style printers, and so far have failed pretty miserably.

Following a thread from a few different manufacturers that are actually selling retail 3d printed intake parts, I have my latest round of test parts back, printed out of Nylon PA11 and Nylon PA12 (expirimenting between the two) printed on an HP MJF machine, the important distinction being that its not a filament deposition technology, but instead a "powder bed fusion" technology.

Pictured below.

The darker "flange" that bolts to the cylinder is Nylon PA11, the lighter reed box that bolts to the flange is Nylon PA12.

Will post back with the results from testing these samples.

I regularly use MJF PA12 reed cages on my engines with no issues. The material is super strong and you can even make threads on it

[quallman1234]

Curious if anyone here has any experience with 3d printing functional intake parts, reed valve boxes, reed valve bodies, carburetor mounting flanges, etc.

Bonus points for experience with ethanol/methanol fuels using 3d printed intake parts.

For a few reasons I am attempting to come up with a working solution for 3d printed reed boxes for my application.

3-4 different carbon type filaments have been used in standard FDM style printers, and so far have failed pretty miserably.

Following a thread from a few different manufacturers that are actually selling retail 3d printed intake parts, I have my latest round of test parts back, printed out of Nylon PA11 and Nylon PA12 (expirimenting between the two) printed on an HP MJF machine, the important distinction being that its not a filament deposition technology, but instead a "powder bed fusion" technology.

Pictured below.

The darker "flange" that bolts to the cylinder is Nylon PA11, the lighter reed box that bolts to the flange is Nylon PA12.

Will post back with the results from testing these samples.


Hey ya,

I've just printed an airbox for our TST100 project. It took a bit of playing around but i have sucessfully printed PA6-CF and PPA-CF to a decent level on a consumer FDM printer (Creatliy K1 Max). I even had the lid off.
Its actually pretty easy. Theres just one trick. Buy a filament dryer and dry the living shit out of it for a few days at the max temp (or around 80c if it goes that high). And print directly from the dryer after that.
Another trick is that supports are quite hard to get off. Tree supports are a bit easier.
I printed on a smooth bed with lots of glue stick.
I just used pretty generic profiles in Orca for it, and it printed all good.

Side note heres a little TST100 update : https://www.youtube.com/shorts/OlqkOsqxdw0


This filament is the eSun PA-CF. But had similar results with other brands.
356749356750356751

[F5 Dave]

Cool update, pipes look good.

[TZ350]

356752

Speedpros's 40 RWHP twin cylinder turbocharged FXR125. A cut down 4 cylinder FXR250.

Maybe we should relax the F4 rules to allow turbo/supercharging up to 125cc four strokes and 100cc two strokes. Just a thought.

[F5 Dave]

K'n hell! So yeah drop it down to 100cc, but then just turn up the boost and be back there.
Really turbos have proven again and again they make silly power in racing classes.

[speedpro]

Regarding 3D printing. I've been looking seriously at 3D printing a few bits. I'm tending towards nylon with carbon but that's as far as I've got with filament selection. Drying is critical, and not just with "special" filaments. I've been drying filaments in the printer on the print plate set to 50-60°C and then storing the reels in plastic buckets with tight fitting lids and with trays of "damprid" inside. Last I checked with the little humidity gauge I bought it was sitting at 26%. The other thought I've had is that the orientation of the part on the print plate should be considered. I normally go for minimum support with other mundane things, but I think there will be benefits with having filament orientation running the length of parts. Velocity stacks might benefit from being printed on their side with the filament running their length. Having said that I've only ever printed stacks on end. I've got a Bambu Labs P1S which is a very nice printer.

[speedpro]

356752

Speedpros's 40 RWHP twin cylinder turbocharged FXR125. A cut down 4 cylinder FXR250.

Maybe we should relax the F4 rules to allow turbo/supercharging up to 125cc four strokes and 100cc two strokes. Just a thought.

FZR250. Imagine a 80hp turbo 250.

[ApolloMotoMoto]

Regarding 3D printing. I've been looking seriously at 3D printing a few bits. I'm tending towards nylon with carbon but that's as far as I've got with filament selection. Drying is critical, and not just with "special" filaments. I've been drying filaments in the printer on the print plate set to 50-60°C and then storing the reels in plastic buckets with tight fitting lids and with trays of "damprid" inside. Last I checked with the little humidity gauge I bought it was sitting at 26%. The other thought I've had is that the orientation of the part on the print plate should be considered. I normally go for minimum support with other mundane things, but I think there will be benefits with having filament orientation running the length of parts. Velocity stacks might benefit from being printed on their side with the filament running their length. Having said that I've only ever printed stacks on end. I've got a Bambu Labs P1S which is a very nice printer.

That is the 'magic' of "powder bed fusion" 3d printing technologies, the powder bed provides support, for one, so no need for any tree's in any case;

But waaaaay more importantly, the nature of how the grains are fused together, you have full isometric load distrubtion through the part REGARDLESS of print orientation.

There is no "plane of cleavage" along the slicer plane like with FDM style 3d printing.

Yes, you can "account" for the fact that you have a "weak plane", but this adds a lot of complexity to the design review process, and may not necessarily be intuitive to find the best solution in all cases.

Powder bed fusion 3d printing does NOT have a plane of cleavage, it has a truly isometric load distribution.

All my failed FDM 3d prints failed along the "slicer" plane.

[quallman1234]

Regarding 3D printing. I've been looking seriously at 3D printing a few bits. I'm tending towards nylon with carbon but that's as far as I've got with filament selection. Drying is critical, and not just with "special" filaments. I've been drying filaments in the printer on the print plate set to 50-60°C and then storing the reels in plastic buckets with tight fitting lids and with trays of "damprid" inside. Last I checked with the little humidity gauge I bought it was sitting at 26%. The other thought I've had is that the orientation of the part on the print plate should be considered. I normally go for minimum support with other mundane things, but I think there will be benefits with having filament orientation running the length of parts. Velocity stacks might benefit from being printed on their side with the filament running their length. Having said that I've only ever printed stacks on end. I've got a Bambu Labs P1S which is a very nice printer.

Can confirm its about drying any filament. even pla it helps

[diesel pig]

FZR250. Imagine a 80hp turbo 250.

In a book I read a while ago that is what Honda wanted to do in the GP250 class in the early 1980's but those in charge said a turbo is basically a exhaust driven supercharger and supercharging is not allow in GP racing. It's a good thing they ever worked out what a well designed expansion chamber do on a two stroke.

[husaberg]

In a book I read a while ago that is what Honda wanted to do in the GP250 class in the early 1980's but those in charge said a turbo is basically a exhaust driven supercharger and supercharging is not allow in GP racing. It's a good thing they ever worked out what a well designed expansion chamber do on a two stroke.

From memory the oval piston 250 turbo was run a few times wth Fredy. I have feeling it was a v twim.
Pretty sure hrc also turbo'd a Vt250. and ran in in a race series.
google
https://enoanderson.com/2015/11/11/honda-nr250-turbo-vt250ftc-duet-dahsyat-anti-regulasi/
https://enoanderson.com/2015/11/11/honda-nr250-turbo-vt250ftc-duet-dahsyat-anti-regulasi/2/
Plus a pick of thehonda rear disc 125 twin i had never seen before t(he pic not the bike)
https://magazine.cycleworld.com/article/1984/11/1/beyond-pit-road

[TZ350]

.
50cc ... 30HP 2Stroke Stuffing.

<iframe width="560" height="315" src="https://www.youtube.com/embed/y9QiGfB7Jfs?si=5TCQJ7oA26YRfyUz" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen=""></iframe>


I might be the only one, but I would really love to have the unrestricted fuel rule back for F4 & F5, like it used to be.

[diesel pig]

I think having to refill fuel tank's with gas mask's on would get old fast.

[F5 Dave]

.
50cc ... 30HP 2Stroke Stuffing.

<iframe width="560" height="315" src="https://www.youtube.com/embed/y9QiGfB7Jfs?si=5TCQJ7oA26YRfyUz" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen=""></iframe>


I might be the only one, but I would really love to have the unrestricted fuel rule back for F4 & F5, like it used to be.
When was it like that? Circa 1988 it was 95 pump gas max and then it went Av gas when our changeover to unleaded went sideways with sketchy quality. . For a while it said no additives which technically meant 2 stroke oil.

[TZ350]

When was it like that? Circa 1988 it was 95 pump gas max and then it went Av gas when our changeover to unleaded went sideways with sketchy quality. . For a while it said no additives which technically meant 2 stroke oil.

Yes, certainly not in my time. I have heard Flettner lament the loss of methanol. Maybe I have just heard rumors and imagined it was totally open fuel in the beginning. Anyway I would just love to be able to apply a bit of chemistry to my bucket racing.

[F5 Dave]

Meths was a formula 3,2 etc thing.
Never buckets in my knowledge.

Mike?

[husaberg]

Yes, certainly not in my time. I have heard Fletlander lament the loss of methanol. Maybe I have just heard rumors and imagined it was totally open fuel in the beginning. Anyway I would just love to be able to apply a bit of chemistry to my bucket racing.
Alcohol fuel was only allowed as was supercharging turbo etc with 100cc Four strokes. These were the days of 130cc four strokes and 104cc two stroke, ie pre 125cc ac 24mm carbs.
I have one of the old rule books ACU from the 90's.
i dug out a book it was pre 92-93
MNZ was called NZACU then

[speedpro]

I do remember experimenting with methanol in my AC50 bucket racer when I was in the Air Force. Probably because I had it lying around for my other bike. Never raced the bucket with it. I think in the air force days that nobody cared. With the state of tune back then it wasn't needed so as far as I recall there was nobody using it. I hardly knew Neil back then so he might have been. A bit of Methanol for the FZR would be nice although even on petrol it's still tuned reasonably cautiously so currently not required.

[DSE]

fluorine rubber ( fkm in germany also known as viton) has nothing to do with special marine use. Its a rubber with one of the best oil and heat resistance and is used in all ngk rubber spark plug caps and in many sealing rings too... ;)

Thank you for declaring the brochure, as I understood from the first sentence of your post.
But I couldn't quite understand the meaning of the second sentence.
Probably because of a problem with Google translation.…
Well, let's get back to the ignition coils that were discussed.
I have not puzzled over why the manufacturer used this material, which we are discussing, on the spark plug caps. I just needed an ignition coil with two terminals and certain electrical potential characteristics. And I bought it.
From my own practical experience, I can say that I have used this type of elastomer to protect steel parts during coating, in particular chrome plating. Galvanic electrolytes could not destroy the protective covers made of fluoro-rubber for a whole year. There were about thirty chrome plating cycles....
Why is seawater scarier to use than electrolytes?

The composition of Viton may vary depending on the manufacturer and the specific product, but in general, it includes the following components.

....let's turn to the reference books:

Fluorinated rubber, which provides high chemical and thermal stability. This material contains fluorine and other chemical groups that give it certain characteristics.
Seals, fillers, and modifiers that can affect the mechanical and chemical characteristics of the material.
Stabilizers and antioxidants, the main task of which is to prevent degradation of the material under the influence of heat and the environment.
Various additives can be introduced to improve the processing, mechanical properties and other characteristics of Viton.
It is important to note that the specific compositions of Viton may vary from manufacturer to manufacturer and for different products within the same brand.
Viton (FKM) is a group of fluorinated elastomers with different chemical structures, and its operating temperature may vary depending on the specific type of Viton.

Viton (FKM) material has several features that make it popular and valuable in various industrial fields, some of them:

Chemical resistance – the material can withstand aggressive chemical environments, including oils, solvents, acids, alkalis and other chemically active substances.;
Thermal stability – Viton is capable of operating in a wide range of temperatures, both low and high. This allows it to be used in conditions where preservation of sealing and insulating properties at elevated temperatures is required.;
Mechanical strength – the material is resistant to bending, stretching and tearing. This makes it suitable for applications where it is under mechanical stress.;
Oil and fuel resistance is what makes it valuable in the automotive and aviation industries.;
Elasticity – Viton can retain its sealing properties even under compression, bending or stretching;
Radiation resistance – the material is useful for use in the nuclear and aerospace industries;
Insulating properties – Due to its chemical resistance and elasticity, Viton is also used in insulation and sealing products such as gaskets and rubber seals.
Can you name a really strong argument against using this material in spark plug tips???

[Flettner]

Yes, alcohol was allowed in 100cc fourstroke, as was supercharging, in fact fuel for such was open. Vinduro rules allow supercharged fourstroke, fuel open, but unfortunately recently have outlawed EFI.
Buggers, I can't win.

[Wos]

Thank you for declaring the brochure, as I understood from the first sentence of your post.
But I couldn't quite understand the meaning of the second sentence.
Probably because of a problem with Google translation.…
Well, let's get back to the ignition coils that were discussed.
I have not puzzled over why the manufacturer used this material, which we are discussing, on the spark plug caps. I just needed an ignition coil with two terminals and certain electrical potential characteristics. And I bought it.
From my own practical experience, I can say that I have used this type of elastomer to protect steel parts during coating, in particular chrome plating. Galvanic electrolytes could not destroy the protective covers made of fluoro-rubber for a whole year. There were about thirty chrome plating cycles....
Why is seawater scarier to use than electrolytes?

The composition of Viton may vary depending on the manufacturer and the specific product, but in general, it includes the following components.

....let's turn to the reference books:

Fluorinated rubber, which provides high chemical and thermal stability. This material contains fluorine and other chemical groups that give it certain characteristics.
Seals, fillers, and modifiers that can affect the mechanical and chemical characteristics of the material.
Stabilizers and antioxidants, the main task of which is to prevent degradation of the material under the influence of heat and the environment.
Various additives can be introduced to improve the processing, mechanical properties and other characteristics of Viton.
It is important to note that the specific compositions of Viton may vary from manufacturer to manufacturer and for different products within the same brand.
Viton (FKM) is a group of fluorinated elastomers with different chemical structures, and its operating temperature may vary depending on the specific type of Viton.

Viton (FKM) material has several features that make it popular and valuable in various industrial fields, some of them:

Chemical resistance – the material can withstand aggressive chemical environments, including oils, solvents, acids, alkalis and other chemically active substances.;
Thermal stability – Viton is capable of operating in a wide range of temperatures, both low and high. This allows it to be used in conditions where preservation of sealing and insulating properties at elevated temperatures is required.;
Mechanical strength – the material is resistant to bending, stretching and tearing. This makes it suitable for applications where it is under mechanical stress.;
Oil and fuel resistance is what makes it valuable in the automotive and aviation industries.;
Elasticity – Viton can retain its sealing properties even under compression, bending or stretching;
Radiation resistance – the material is useful for use in the nuclear and aerospace industries;
Insulating properties – Due to its chemical resistance and elasticity, Viton is also used in insulation and sealing products such as gaskets and rubber seals.
Can you name a really strong argument against using this material in spark plug tips???


Indeed we missunderstood us !

FKM is one of the best Materials for the use in spark plug caps in general, no matter if marine, offroad or street.

Thats the reason why NGK uses it in every Rubber cap :niceone:

[speedpro]

Yes, alcohol was allowed in 100cc fourstroke, as was supercharging, in fact fuel for such was open. Vinduro rules allow supercharged fourstroke, fuel open, but unfortunately recently have outlawed EFI.
Buggers, I can't win.

Methanol is really tolerant of running rich. I know it hurts thinking about it but a carb wouldn't be all that bad with methanol. Add an ECU to handle everything else. Pretty much what I'm doing with my McIntosh. I'm using the original Zenith carb, with JATO mods, and the intake manifold, because that's the rule, and putting my Link ECU on to run everything else. The ECU will be in charge of boost control and ignition and monitor all the usual.

[Storbeck]

Yes, alcohol was allowed in 100cc fourstroke, as was supercharging, in fact fuel for such was open. Vinduro rules allow supercharged fourstroke, fuel open, but unfortunately recently have outlawed EFI.
Buggers, I can't win.

Is efi outlawed, or is it that you must run a carb? Maybe you can run a carb then also supplement it with an injector?

[Flettner]

Is efi outlawed, or is it that you must run a carb? Maybe you can run a carb then also supplement it with an injector?

It does specifically outlawed EFI, but if I wanted to I could just ignore the rule and enter in the Vinduro trail bike class, no points, just participate. But I not that old just yet. 😁

[Flettner]

Im tempted to do a tandem twin, disc valve, twin exhaust port per cylinder, water cooled, powervalve .... you know, the works. Wouldn't that be fun in Vinduro. 125cc.
34 flat slide too big for a 63cc ? ( over bore allowance).

[husaberg]

Im tempted to do a tandem twin, disc valve, twin exhaust port per cylinder, water cooled, powervalve .... you know, the works. Wouldn't that be fun in Vinduro. 125cc.
34 flat slide too big for a 63cc ? ( over bore allowance).
Honda did a disc valve behind the cylinder twin 125 in about 1984-86
Frits i think has posted pics of it.
2x 24mm i think would be ample giving good drivability.

Had a ribi frontend
https://www.motorcyclespecs.co.za/model/Honda/honda_RC125M.htm
Although looking at this pic it might be cylinder Reed

https://scontent.fchc2-1.fna.fbcdn.net/v/t39.30808-6/473621498_18482228488002306_6933280163139729539_n. jpg?_nc_cat=111&ccb=1-7&_nc_sid=127cfc&_nc_ohc=L-BIsf_SFaYQ7kNvwHP6zSX&_nc_oc=AdmZ-w4B49iCK4rOqHf2vqCpyQ5ITiaCkB794R9sVbwbY_39R0N8tm7-WkupW729SnuBySeqw-PyAUq9Iq7-4VY9&_nc_zt=23&_nc_ht=scontent.fchc2-1.fna&_nc_gid=bRYbjMeSDBlNUnJV-PyaIQ&oh=00_AfeZtEhZSoIwI1ljZPYesxxdhf2k51rpVtsiRUdKLRA4 Tg&oe=68E93A86
They definitely did a behind the cylinder disc at the same time maybe on a single?

This was the honda behind the cylinde disc of the same period Frits posted.
it looks more 250 due to the clutch cable on the left like a 350/500CR also that twin has a left foot kick. Right side drive.
https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=251916&d=1322918391

Gillera did a twin 125 maybe a few years before?

[Sketchy_Racer]

We fired up the TST100 with its 3D printed crankcases the other night. Pretty happy with how it went considering.

First learning with the injection, my primary injector was way too large and I lost control of fueling low down, it'd either lean bog or flood. Easy fix though. At the moment it's running a typical alpha-n map, but once the new injectors turn up, we'll swap over to the custom software.

https://www.youtube.com/watch?v=0LkzgFYekEk

[Flettner]

Rob, what would be a suitable rod and piston combination for a 63cc disc valve engine?

[Storbeck]

Im tempted to do a tandem twin, disc valve, twin exhaust port per cylinder, water cooled, powervalve .... you know, the works. Wouldn't that be fun in Vinduro. 125cc.
34 flat slide too big for a 63cc ? ( over bore allowance).

Practical or not, a 125 twin would be kinda cool.

There might be interesting things you could do with electronic controls on a carb. Maybe controlling float bowl pressure somehow or pwm controls on jets, that sort of thing. I play with watercraft that use diaphragm controlled carbs always thought it could be interesting to control fuel pressure in the diaphragm with a computer controlled bleed of stone sort. No idea if it would actually work in any useful way

[Flettner]

Practical or not, a 125 twin would be kinda cool.

There might be interesting things you could do with electronic controls on a carb. Maybe controlling float bowl pressure somehow or pwm controls on jets, that sort of thing. I play with watercraft that use diaphragm controlled carbs always thought it could be interesting to control fuel pressure in the diaphragm with a computer controlled bleed of stone sort. No idea if it would actually work in any useful way

34mm carburetors, only because I have a couple. I'll look for something smaller.
If its a disc valve engine I could hide all EFI stuff behind the 'carb ' cover. Not the first time I've done this. Pre 75 VMX, there was no actual rule so to avoid upsetting anyone I hid my EFI system all behind my Kawasaki 350 intake cover, and never plugged the laptop top in at an event. But with Vinduro it's an actual written rule., no EFI.
I can live with carburetors.
I don't know enough about diaphragm carburetors.

[Gradella23]

Rob, what would be a suitable rod and piston combination for a 63cc disc valve engine?

When i was thinking about designing a cylinder and crank kit for the italjet formula 125 twin, i was eying the kawasaki kx60 vertex piston, 43mm bore with one ring.
and a 85 or 90 mm conrod

[husaberg]

Frits Overmars makes a cameo appearance in this video

Lexus lfa exhaust. for those with short attention spans about 16.50

https://youtu.be/crEeOEs4ZP0
https://www.youtube.com/watch?v=crEeOEs4ZP0

[F5 Dave]

We fired up the TST100 with its 3D printed crankcases the other night. Pretty happy with how it went considering.

First learning with the injection, my primary injector was way too large and I lost control of fueling low down, it'd either lean bog or flood. Easy fix though. At the moment it's running a typical alpha-n map, but once the new injectors turn up, we'll swap over to the custom software.

https://www.youtube.com/watch?v=0LkzgFYekEk
Sounds fantastic Glen. Look forward to seeing it on track.

[Frits Overmars]

Frits Overmars makes a cameo appearance in this video. Lexus lfa exhaust. For those with short attention spans about 16.50World fame after all :2thumbsup
https://www.youtube.com/watch?v=crEeOEs4ZP0#t=16m47s

[Flettner]

When i was thinking about designing a cylinder and crank kit for the italjet formula 125 twin, i was eying the kawasaki kx60 vertex piston, 43mm bore with one ring.
and a 85 or 90 mm conrod

I actually have a KX65 cylinder here somewhere, I must dig it out.

[husaberg]

I actually have a KX65 cylinder here somewhere, I must dig it out.
Pretty sure i have one here too. Sing out if you want it..

[Flettner]

Pretty sure i have one here too. Sing out if you want it..

Thankyou.
I'll likely cast my own but I might take a look at the transfer arrangement.

[husaberg]

Thankyou.
I'll likely cast my own but I might take a look at the transfer arrangement.
they aren't that good tbh, flat roofed things.
if you were going to copy anything i would copy the ktm65 2009 on.
The ktm 50 was designed as a 65 and shrunk down.

this is what they look like

356795356796356797356794
this one is only $149nzd a few hunded kms away
i wonder why lol.

https://pronorthparts.co.nz/65-sx-2009-2025-cylinder-barrel-ktm-46230138000-278/

this is their piston
356793
For the rod in 12mm gudgeon you can go up to 98mm with a ts90/100. They have those weird Suzuki 19mm crankpins,
but Honda on the mbx80 nrs50 are 91mm to suit the 12mm se pin. 18mm big end pin
Yamaha pw80 is 12mm pin and 20mm bigend 94mm
Derbi senda is a 90mm on in 16mm be pin

[Flettner]

Where could we use this little beauty
https://youtube.com/shorts/id6LxB2RN7E?si=eFXDlYC34mK6zF5V

[husaberg]

Where could we use this little beauty
https://youtube.com/shorts/id6LxB2RN7E?si=eFXDlYC34mK6zF5V

https://www.youtube.com/watch?v=WZgAPV5M5Es

[ApolloMotoMoto]

Where could we use this little beauty
https://youtube.com/shorts/id6LxB2RN7E?si=eFXDlYC34mK6zF5V


Dynamic tailpipe restrictor nozzle.

Larger diameter at low rpm, closing down as RPM's rise to extend the effective resonant range of the pipe, similar in concept to a powervalve on the exhaust port.

[Peter1962]

Dynamic tailpipe restrictor nozzle.

Larger diameter at low rpm, closing down as RPM's rise to extend the effective resonant range of the pipe, similar in concept to a powervalve on the exhaust port.

Frits Overmars allready designed that, with a solution that is mechanicaly more easy to operate. (linear motion for the restrictor in the tailpipe)

[Peter1962]

Where could we use this little beauty
https://youtube.com/shorts/id6LxB2RN7E?si=eFXDlYC34mK6zF5V

This idea could well evolve into a Mark II version of your 'double sliding gibs' on the rotary valve ! :niceone:

[ApolloMotoMoto]

Frits Overmars allready designed that, with a solution that is mechanicaly more easy to operate. (linear motion for the restrictor in the tailpipe)

Correct ;)

[Flettner]

Frits Overmars allready designed that, with a solution that is mechanicaly more easy to operate. (linear motion for the restrictor in the tailpipe)

Not at all what I had in mind.

[JdG]

I know there has been a lot of talk about hydro formed exhaust, especially about the cons.

But I think this video is worth to watch.

https://youtu.be/nRP-MMZlzJQ?si=MG6j_xDxIMwnnb-k


Verzonden vanaf mijn iPhone met Tapatalk

[husaberg]

https://www.lonely.geek.nz/kiwi-tv/images/stories/meta/branding/test_patterns/technical_issues/tv_kiwi_technical_problem_broom.jpg

[Peljhan]

I know there has been a lot of talk about hydro formed exhaust, especially about the cons.

But I think this video is worth to watch.

Very good fabricating skills.
I made about 50 different hydroformed exhaust for mopeds, but my procedure was a bit different.
I cut the shape, weld the edge with TIG without rolling the edge, pump the exhaust with strong pressure washer and if the seam poped, weld it back together. Than I welded all the seams around with TIG again so it was smooth. Pressurized the exhaust with air and heated wrinkles with acetilene-oxy torch and a bit of hammering. Than cut and rotate where needed.
My way avoids so much hammering he demonstrated.

I think the 5-7% reduction adjustment in diameter he makes on template is same as welding the seam directly without rolling as welding "eats" a bit of metal. I also figured out how much tighter the radius gets after forming and I think the coefficient was around 0,81. If you want 100° bend, you shoud make it 81° on template.

I started building exhaust from cones later as I made them for racing mostly. Hydroformed were quite ok for stock mopeds. I never did comparison hydroformed and coned on dyno, but that would be my wish someday to compare the performance.

[ApolloMotoMoto]

Not at all what I had in mind.

Well then, what DID you have in mind? ;)

[wobbly]

After winning the Superkart World Title with Hines at Zipkart I went and started work at JL Exhausts.
There I spent months learning how to do hydroformed pipes for the Rotax 256, as the front one was effectively a 180* bend straight off the manifold.
The biggest advancement was pumping up the pattern between two steel platens in a big press, that were slowly adjusted apart
This stopped the mid section from fully blowing up first, with the header forming last.

But even using a split clamp on the mid section, it was impossible to stop the diffuser end, and the rear cone start, from forming a smooth gradually changing angle.
Nothing like the correct design angles of cones.
This meant that no matter what techniques and no matter how nice the pipes looked, it was impossible to get within 2 Hp ( in just over 40 Hp ) of a fully welded section pipe on the dyno.
Eventually we gave up, and had a CNC machined press tool made for the header and initial diffuser U bend, just using cones for the rest of the pipe.
This was way less work and made identical Hp.
Interesting that KTM used exactly this setup on their 250GP parallel twin.
And Honda used split dies for years until Titanium became popular to reduce weight.

[Flettner]

Well then, what DID you have in mind? ;)

I want a sliding pipe but do not have the room to fit one (or two as the case may be) ,
Ideally I'd like to shorten up the pipes, and it might be nice to sharpen up the reverse cone angle at the same time.

[Flettner]

After winning the Superkart World Title with Hines at Zipkart I went and started work at JL Exhausts.
There I spent months learning how to do hydroformed pipes for the Rotax 256, as the front one was effectively a 180* bend straight off the manifold.
The biggest advancement was pumping up the pattern between two steel platens in a big press, that were slowly adjusted apart
This stopped the mid section from fully blowing up first, with the header forming last.

But even using a split clamp on the mid section, it was impossible to stop the diffuser end, and the rear cone start, from forming a smooth gradually changing angle.
Nothing like the correct design angles of cones.
This meant that no matter what techniques and no matter how nice the pipes looked, it was impossible to get within 2 Hp ( in just over 40 Hp ) of a fully welded section pipe on the dyno.
Eventually we gave up, and had a CNC machined press tool made for the header and initial diffuser U bend, just using cones for the rest of the pipe.
This was way less work and made identical Hp.
Interesting that KTM used exactly this setup on their 250GP parallel twin.
And Honda used split dies for years until Titanium became popular to reduce weight.

I use press dies to get my pipes as identical as possible, being two pipes into one cylinder. Makes life much easier.

[husaberg]

I want a sliding pipe but do not have the room to fit one (or two as the case may be) ,
Ideally I'd like to shorten up the pipes, and it might be nice to sharpen up the reverse cone angle at the same time.

It didnt work on a road race bike ie Doohans NSR500 but water injection or actually cooling the header with a sleeve might work in an enduro situation.
This is how I believe the NSR actually worked.

356814356815

The other option is the Atac valve, which in a rooundabout way also make the pipe longer.
356816356817

[Flettner]

It didnt work on a road race bike ie Doohans NSR500 but water injection or actually cooling the header with a sleeve might work in an enduro situation.

Just because Honda couldn't do it, doesn't mean it can't be done.
Their requirements are different to mine.

[husaberg]

Just because Honda couldn't do it, doesn't mean it can't be done.
Their requirements are different to mine.
After all, I was told twin pipes wouldn't work together, they do, but a powervalve and water cooling is nessasary it seems.

I am still trying to add photos . But on second thoughts, atac is simipler and KISS.

I think it's not the case of honda not being able to do it, more a case of Doohan not needing it or wanting it.
One of Frits first posts was a hydraulic or maybe phnematic adjustable header.
okay its cable but KISS
356818356819

[Flettner]

I am still trying to add photos . But on second thoughts, atac is simipler and KISS.

I think it's not the case of honda not being able to do it, more a case of Doohan not needing it or wanting it.
One of Frits first posts was a hydraulic or maybe phnematic adjustable header.
okay its cable but KISS
356818356819

It's not like I've got room on an off road bike to move the pipe.

I'll report back when I have a working (tested) example.

[Flettner]

I am still trying to add photos . But on second thoughts, atac is simipler and KISS.

I think it's not the case of honda not being able to do it, more a case of Doohan not needing it or wanting it.
One of Frits first posts was a hydraulic or maybe phnematic adjustable header.
okay its cable but KISS
356818356819

It's not like I've got room on an off road bike to move the pipe.

I'll report back when I have a working (tested) example. You don't know how simple my system is, yet.

I see the pictures, hardly off road friendly ��

[Frits Overmars]

I want a sliding pipe but do not have the room to fit one (or two as the case may be) ,
Ideally I'd like to shorten up the pipes, and it might be nice to sharpen up the reverse cone angle at the same time.

It didnt work on a road race bike ie Doohans NSR500 but water injection or actually cooling the header with a sleeve might work in an enduro situation....The other option is the Atac valve, which in a roundabout way also make the pipe longer.To the best of my knowledge Honda never used sliding pipes. Accommodating those to their 500-4 would have been a nightmare anyway.
They did use ATAC (to avoid Yamaha's power valve patent) but ATAC was not so much a detour as an additional volume to lower the Helmholtz frequency of the exhaust system.
It disappeared when Honda introduced their sliding power valve that apparently was sufficiently different from Yamaha's rotating drum valve patent.
I think it's not the case of honda not being able to do it, more a case of Doohan not needing it or wanting it.Water injection did work, both on Doohans Honda 500-4 and, years earlier, on the Aprilia RSW250 where it added 10 hp at 10.000 rpm.
But the rider (Reggiani) managed to keep the revs always above 11.000 rpm, so the water system was abandoned in the interest of KISS and weight.
It also appeared that the water effect took some time to wear off. After the injection stopped, the pipe was too slow in getting up to the higher temperature needed for the higher revs. That did not help rider confidence and lap times.
But if you can accommodate a sliding pipe, it will outperform any power valve, power jet etc. by far.
Here is a story about it that I wrote some time ago.
---------------------------------------------------------------------------
There are several options in lengthening an exhaust pipe. You can move the end cone, or you can lengthen the header, like a trombone.
The gas pressure generates a force that is proportional to the cross section area of the moving part and proportional to the pressure difference at either side of that area. For a moving end cone this force can be up to 6 times larger than for a sliding header. That is one reason to go for the trombone system rather than the moving cone system.

The second reason: sealing. The circumferential gap that has to be sealed, is three times shorter for the trombone system. That means three times less leakage and three times less friction.

The third reason: say you wish to lengthen the total length of the pipe by 10 %. If you do it by moving the end cone, you will also enlarge the pipe volume by a little over 10 %.
But in a good pipe configuration the header length is about 1/3 of total pipe length, so in the trombone system, lengthening the pipe by 10 % will be done by lengthening the header by about 30 %. That gives a far greater variation in the pipe's Helmholtz frequency than a 10 % volume change.

It is true that the length percentages of all pipe components should be in a rather fixed relation to each other. Varying the lengths of all components by the same percentage would be the theoretical optimum, but that is not feasible.
Lengthening the belly will disturb the optimum relations, as will lengthening the header. So the pipe in its lengthened version will not be the optimum for the low resonance rpm dictated by the length. But it will be a hell of a lot better than using an exhaust power valve that spoils the 180° effective exhaust timing, necessary for true resonance.
And a pipe shortened beyond its optimum may not show the optimum length relations between its components either, but it will be a lot more effective in overrev than artificially raising the exhaust gas temperature by retarding the ignition, or by weakening the mixture strength through closing a power jet, which has the disadvantage that not all inhaled air is used for combustion.

Video courtesy of Rimar Motors:
http://www.youtube.com/watch?v=0odVzSgufjk&feature=youtu.be

[lohring]

We used water injection on our 26 & 35cc RC boat engines to get the torque needed to accelerate up to the speed traps. Since there's an unlimited water supply it worked really well with a simple on off servo operated valve. Attached is an acceleration graph that shows the plateau reached with the water on and the increased rpm with it off. We have dyno results that show the same thing. Also attached is a picture of the injection into the pipe.

Lohring Miller

356822 356823

[Flettner]

We used water injection on our 26 & 35cc RC boat engines to get the torque needed to accelerate up to the speed traps. Since there's an unlimited water supply it worked really well with a simple on off servo operated valve. Attached is an acceleration graph that shows the plateau reached with the water on and the increased rpm with it off. We have dyno results that show the same thing. Also attached is a picture of the injection into the pipe.

Lohring Miller

356822 356823

Yes, for me, water supply is an insurmountable issue for an off road bike, with events being one and a half to two hours none stop.

[Flettner]

My pipes are a compromise, one I like at the moment for the mid and low range power, top end is great but shorter pipes with steeper cones would be better, for top end.

[F5 Dave]

What if it's rainy season? Some sort of creek crossing scoop mechanism?:msn-wink:

[katinas]

My pipes are a compromise, one I like at the moment for the mid and low range power, top end is great but shorter pipes with steeper cones would be better, for top end.

One of Honda's solutions, but of course not the same as sliding header.

[Peljhan]

The second reason: sealing. The circumferential gap that has to be sealed, is three times shorter for the trombone system. That means three times less leakage and three times less friction.

Video courtesy of Rimar Motors:
http://www.youtube.com/watch?v=0odVzSgufjk&feature=youtu.be

Frits, you forgot about downside of sealing on the header compared to sealing on the belly, the temperature! Header heats up three times more than belly.
Do you know how sealing was done on this rimar engine trobone pipe? I am thinking about some kind of piston rings in combination with fiberglass rope?

[wobbly]

I tested the ATAC system on the BSL500. With a volume close to the cylinder displacement ( bigger or smaller wasnt better ) and a very short tube right at the header start with a solenoid operated
butterfly valve in line with the flow, it made 28% more power below the pipe.
It used a solenoid as the valve had to snapped open at a specific rpm, ramping open or closed lost power big time.

The only time it was useful was in testing a Pukekohe, where if the bike was geared to pull over 300Km/H we did not have a low enough 1st gear to get off the hairpin - a scenario not seen at any GP track.

[Flettner]

I tested the ATAC system on the BSL500. With a volume close to the cylinder displacement ( bigger or smaller wasnt better ) and a very short tube right at the header start with a solenoid operated
butterfly valve in line with the flow, it made 28% more power below the pipe.
It used a solenoid as the valve had to snapped open at a specific rpm, ramping open or closed lost power big time.

The only time it was useful was in testing a Pukekohe, where if the bike was geared to pull over 300Km/H we did not have a low enough 1st gear to get off the hairpin - a scenario not seen at any GP track.

In vinduro I have to get out of the 'hairpin' every second corner.

[Flettner]

What's the deal with two angle reverse cones? Why are they used?

[wobbly]

Two , or even better three angle, rear cones are used to manipulate the power curve by changing the amplitude and duration of the return plugging wave fronts shape.
If you start with a single rear cone , this can be changed to a progressively increasing angle three cones, starting very shallow, and ending in a steeper angle than before.
This gives more power everywhere - and the amount of overev generated is set by the length/angle of the final steeper cone.

If you have a PV that closes a T port, or all the ports in a 3 port, you can divide the rear length into three equal cones, starting steep, and getting progressively shallower.
This geometry looses front side, but the PV eliminates that issue, and this setup gives a huge increase in upper front side and peak, but the shallow last cone allows plenty of overev.
Dead perfect for road racing, or in an end use such as 500cc oval dirt track mini sprint cars, where they use one gear and rev it to the moon.
In that case I used semi steps ( 1/2 moon, top and bottom ) on the manifold face to pump up the bottom end, and the rear cone to generate the peak and overev needed.

A very powerful tool to tailor the power curve to the end use.
In your case Flett, an ATAC would give you more bottom end than you could wave a stick at - and easy to operate with a solenoid connected to any rpm switched supply.

[Storbeck]

I tested the ATAC system on the BSL500. With a volume close to the cylinder displacement ( bigger or smaller wasnt better ) and a very short tube right at the header start with a solenoid operated
butterfly valve in line with the flow, it made 28% more power below the pipe.
It used a solenoid as the valve had to snapped open at a specific rpm, ramping open or closed lost power big time.

The only time it was useful was in testing a Pukekohe, where if the bike was geared to pull over 300Km/H we did not have a low enough 1st gear to get off the hairpin - a scenario not seen at any GP track.


I fear I'm about to ask a stupid question, but here we go anyway.

Is there any use adding one of these to a 2 into 1 pipe? I'm thinking the leg of the manifold going to the other cylinder pretty much acts as an atac at all times, so adding an additional chamber may be pointless.

But, I'm playing around with watercraft that use parallel twins and 2 into one pipes. I recently built a motor with relatively high ports and not surprisingly it is great mid to top, but very weak down low to the point that it's hard to get an impeller that works.

As a watercraft the obvious thing to try is water injection but it has the same issue of the pipe not heating fast enough when it gets up in the rpms so top end power suffers, which makes it all kind of pointless, could just build a motor with lower ports.

But if there is any benefit available from something like an atac volume I think I could fabricate it relatively cheap/easily. Exhaust valves would help too but that's not so easy.

We use 2 into one pipes like the one pictured, I was thinking stick the atac volume as indicated in the picture. The extra volume in the manifold is still less than a cylinder worth of displacement, I haven't measured but I'd estimate about half.

[Flettner]

Two , or even better three angle, rear cones are used to manipulate the power curve by changing the amplitude and duration of the return plugging wave fronts shape.
If you start with a single rear cone , this can be changed to a progressively increasing angle three cones, starting very shallow, and ending in a steeper angle than before.
This gives more power everywhere - and the amount of overev generated is set by the length/angle of the final steeper cone.

If you have a PV that closes a T port, or all the ports in a 3 port, you can divide the rear length into three equal cones, starting steep, and getting progressively shallower.
This geometry looses front side, but the PV eliminates that issue, and this setup gives a huge increase in upper front side and peak, but the shallow last cone allows plenty of overev.
Dead perfect for road racing, or in an end use such as 500cc oval dirt track mini sprint cars, where they use one gear and rev it to the moon.
In that case I used semi steps ( 1/2 moon, top and bottom ) on the manifold face to pump up the bottom end, and the rear cone to generate the peak and overev needed.

A very powerful tool to tailor the power curve to the end use.
In your case Flett, an ATAC would give you more bottom end than you could wave a stick at - and easy to operate with a solenoid connected to any rpm switched supply.

I already have a full powervalve system, closing both ports.

[wobbly]

Flett, the ATAC power increase I quoted of 28% was with a servo operated full PV system as well.

[husaberg]

It's not like I've got room on an off road bike to move the pipe.

I'll report back when I have a working (tested) example. You don't know how simple my system is, yet.

I see the pictures, hardly off road friendly ��

the way i see it you dont need a lot of room as its gets shorter :)
chuck a fork gator over it still way less complicated tnan camchains valve etc.

but seriously, cagiva on the v93 ran a pV and atac system together in parallel (well series)

[Frits Overmars]

One of Honda's solutions, but of course not the same as sliding header.Tried and tested by my German buddy Björn Enke.
356827356828356829

[Frits Overmars]

Frits, you forgot about downside of sealing on the header compared to sealing on the belly, the temperature! Header heats up three times more than belly.
Do you know how sealing was done on this rimar engine trombone pipe? I am thinking about some kind of piston rings in combination with fiberglass rope?No I did not forget and yes I know how Richard sealed the sliding header but I do not feel at liberty to divulge his solution here: that's up to him.


I fear I'm about to ask a stupid question, but here we go anyway.
Is there any use adding one of these to a 2 into 1 pipe? I'm thinking the leg of the manifold going to the other cylinder pretty much acts as an atac at all times, so adding an additional chamber may be pointless.Not a stupid question at all, and you even nailed the main problem: one leg of the Y-pipe functions as an ATAC volume to the other leg of the Y-pipe at all times.
That atac-volume of a Y-pipe will kill power when a real ATAC knows when it's time to close.

[Storbeck]

No I did not forget and yes I know how Richard sealed the sliding header but I do not feel at liberty to divulge his solution here: that's up to him.

Not a stupid question at all, and you even nailed the main problem: one leg of the Y-pipe functions as an ATAC volume to the other leg of the Y-pipe at all times.
That atac-volume of a Y-pipe will kill power when a real ATAC knows when it's time to close.


The big question though is if there might be any benefit to an additional atac volume that does turn off.

[lohring]

Sliding pipes are common on racing outboards. See https://www.facebook.com/watch/?v=389274510418137 They are a sliding fit without seals. A friend made a sliding pipe with seals that was coupled to the boat's rudder. It lengthened in the turns as the rpm got pulled down. I built a pipe with a manually adjustable baffle cone. It depended on fit for a seal. Pipes are creating shock waves that don't depend on a good seal. Our pipes develop around 100 inches of water or 3 to 4 psi at the large diameter. We water cool the pipe to header connection to save the o rings. Again, we have lots of cold water.

Lohring Miller

356830356831356832

[wobbly]

As the 2:1 Y pipe scenario works best with what would be considered " radical " 200* Exhaust duration ( with all the downsides of that ), the thought occurred to me that if you are happy
to go to all the trouble of adding a " third leg " ATAC, then why not arrange a flap valve inside the Y that alternately shuts of the leg to the opposing cylinders in turn.
Sure it has to operate at the crank rpm ( that is relatively low in this case ), but with some lateral thought it may be possible.
EDIT - after a coffee I thought of a pair of inline drum valves driven with a tooth belt off the crank.

The other " cheat " available is to cut the piston skirts slightly short, such that the port, and thus the crankcase, is open to the Y when each piston is at TDC.
This plays absolute havoc with the fueling, but pumpers can be made to work with it, and it increases power everywhere.
Been there, done that, won the " Stock " Jetski Title.

[katinas]

Thank you Frits for the photos, the result is clearly visible in the graph.

[Storbeck]

As the 2:1 Y pipe scenario works best with what would be considered " radical " 200* Exhaust duration ( with all the downsides of that ), the thought occurred to me that if you are happy
to go to all the trouble of adding a " third leg " ATAC, then why not arrange a flap valve inside the Y that alternately shuts of the leg to the opposing cylinders in turn.
Sure it has to operate at the crank rpm ( that is relatively low in this case ), but with some lateral thought it may be possible.
EDIT - after a coffee I thought of a pair of inline drum valves driven with a tooth belt off the crank.

The other " cheat " available is to cut the piston skirts slightly short, such that the port, and thus the crankcase, is open to the Y when each piston is at TDC.
This plays absolute havoc with the fueling, but pumpers can be made to work with it, and it increases power everywhere.
Been there, done that, won the " Stock " Jetski Title.

Does the short skirt trick work without the super high duration? Currently at 195 and having trouble getting an impeller flat enough to work well so a little hesitant to go further.

Looks like I'm better off to put the effort into figuring out the pump then bump up to 200 degrees of I want to get frisky.

The rotary valve thing is cool but a bit more than I'm willing to take on at this point

[Flettner]

As the 2:1 Y pipe scenario works best with what would be considered " radical " 200* Exhaust duration ( with all the downsides of that ), the thought occurred to me that if you are happy
to go to all the trouble of adding a " third leg " ATAC, then why not arrange a flap valve inside the Y that alternately shuts of the leg to the opposing cylinders in turn.
Sure it has to operate at the crank rpm ( that is relatively low in this case ), but with some lateral thought it may be possible.
EDIT - after a coffee I thought of a pair of inline drum valves driven with a tooth belt off the crank.

The other " cheat " available is to cut the piston skirts slightly short, such that the port, and thus the crankcase, is open to the Y when each piston is at TDC.
This plays absolute havoc with the fueling, but pumpers can be made to work with it, and it increases power everywhere.
Been there, done that, won the " Stock " Jetski Title.

What was the BSL reverse cone angle?

[wobbly]

The BSL500 pipes, the later Titanium sets were similar rear cones to the RSA125 Tubo 102.
The pipes were longer and fatter but the rear angles were much the same.
EDIT - those angles only work for very fat pipes used in a road race situation.

[katinas]

[QUOTE= cagiva on the v93 ran a pV and atac system together in parallel (well series)[/QUOTE]

Suzuki, Yamaha, Roberts KR3 also used dual exhaust control.
From 1995 on rgv250 and 500 screw on chamber type with separate control of pv and atac.
Yamaha may have used from 1999 an integrated chamber into the cylinder that opens and closes like one unit with drum type powervalve. Since 2001 only Biaggi spec cylinders, with double exhaust ports, had a removable type atac chamber . 2002 all latest YZR 500 equipped with engines similar to Biaggi's 2001 type.
Latest TZ 250 5KE4 cylinders made with cast in camber type like on Olivier Jacque's YZR 250 2000 .
Roberts KR3 cylinders also with a removable chamber but operates like one unit with pv.

[husaberg]

Suzuki, Yamaha, Roberts KR3 also used dual exhaust control.
From 1995 on rgv250 and 500 screw on chamber type with separate control of pv and atac.
Yamaha may have used from 1999 an integrated chamber into the cylinder that opens and closes like one unit with drum type powervalve. Since 2001 only Biaggi spec cylinders, with double exhaust ports, had a removable type atac chamber . 2002 all latest YZR 500 equipped with engines similar to Biaggi's 2001 type.
Latest TZ 250 5KE4 cylinders made with cast in camber type like on Olivier Jacque's YZR 250 2000 .
Roberts KR3 cylinders also with a removable chamber but operates like one unit with pv.

Cool KR3 photos i had never seen those pics.
the 1989 Cagiva had the atac and rotary PV but there were a lot of cross pollination with Cagiva and Yam.:)
the Last Cagiva tested extending headers with Chandler in practice with a hydraulic pump by tag and extended 20mm. (100 bar)

[Flettner]

So collectively we are saying a reverse cone that shortens the pipe and steepens that same cone at the same time, with no extra complication than say a ATAC system, is worthless?

[Peter1962]

Would it be possible to add an ATAC chamber, to an existing modern 250cc two stroke MX or enduro engine that is equiped with an electronic powervalve ? (thinking of the 250 and 300 cc KTM models from 2023 and up) If so, the added torque in the lower RPM's could make it a formidable weapon against the fourstroke armada.

[Frits Overmars]

So collectively we are saying a reverse cone that shortens the pipe and steepens that same cone at the same time, with no extra complication than say a ATAC system, is worthless?No.
Ever wondered why ATAC-pioneer Honda abandoned ATAC as soon as they developed a way to circumvent Yamaha's rotating powervalve patent (which in turn lead Yamaha to copy Honda's sliding powervalve)?
Shortening a pipe may be more cumbersome but it is also much more effective. But it should be done with a sliding header instead of a sliding reverse cone, as I tried to explain here earlier.
Having said this, I enjoy your out-of-the-box thinking and I would like to know how you plan to steepen a cone.
Mind you, reverse cones can be too steep. Then they will generate shock waves instead of decent stuffing pulses.

[lohring]

Our experiments with the sliding baffle (reverse) cone showed that moving the diffuser section didn't matter much if you hold the tuned length (reverse cone position moved to maintain the same tuned length) constant. Moving the reverse cone definitely effected the power; mainly by changing the tuned length. It also made the power band width worse. The designed position of the cones gave the best result. In all other experiments on experimental tuned pipes, we change the tuned length by moving the whole pipe along the header.

Lohring Miller

[Peter1962]

No.
Ever wondered why ATAC-pioneer Honda abandoned ATAC as soon as they developed a way to circumvent Yamaha's rotating powervalve patent (which in turn lead Yamaha to copy Honda's sliding powervalve)?
Shortening a pipe may be more cumbersome but it is also much more effective. But it should be done with a sliding header instead of a sliding reverse cone, as I tried to explain here earlier.
Having said this, I enjoy your out-of-the-box thinking and I would like to know how you plan to steepen a cone.
Mind you, reverse cones can be too steep. Then they will generate shock waves instead of decent stuffing pulses.

Frits, do you know why Thijs Hessels who had a working prototype of a sliding header system, did not go further with this development ? Were there technical difficulties, like for example sealing issues ?

[Flettner]

No.
Ever wondered why ATAC-pioneer Honda abandoned ATAC as soon as they developed a way to circumvent Yamaha's rotating powervalve patent (which in turn lead Yamaha to copy Honda's sliding powervalve)?
Shortening a pipe may be more cumbersome but it is also much more effective. But it should be done with a sliding header instead of a sliding reverse cone, as I tried to explain here earlier.
Having said this, I enjoy your out-of-the-box thinking and I would like to know how you plan to steepen a cone.
Mind you, reverse cones can be too steep. Then they will generate shock waves instead of decent stuffing pulses.

How steep is too steep?
I considering going from 18 (what I'm running now) to 24 degrees max.

[Frits Overmars]

Our experiments with the sliding baffle (reverse) cone showed that moving the diffuser section didn't matter much if you hold the tuned length (reverse cone position moved to maintain the same tuned length) constant. Moving the reverse cone definitely effected the power; mainly by changing the tuned length. It also made the power band width worse. The designed position of the cones gave the best result. In all other experiments on experimental tuned pipes, we change the tuned length by moving the whole pipe along the header. Lohring Miller
Right Lohring, moving the whole pipe along the header is precisely what I recommend.


Frits, do you know why Thijs Hessels who had a working prototype of a sliding header system, did not go further with this development ? Were there technical difficulties, like for example sealing issues ?I don't know Peter, but knowing the quality of Thijs' work I suspect that there were no technical difficulties. Maybe the market just was not ready for it.


How steep is too steep? I considering going from 18 (what I'm running now) to 24 degrees max.Neil, using degrees is not the best way to express the steepness of exhaust cones. It's better, and more universally applicable, to express a cone length as a percentage of the total tuned length. For example I used 25% in the first versions of my exhaust concept, but I found that 26% works better, even for road racing. So you might consider those 26% as the minimum percentage for your vinduro-vehicle. If you are willing to use the below concept, you may just want to reduce the maximum diameters D3 and D4 in order to keep your legs from getting cooked, while using all other dimensions as suggested in the concept.
By the way, the easiest way to calculate the pipes for your twin-exhaust bike is to just calculate one pipe for an engine with the same exhaust timing but with half the cylinder capacity.

[wobbly]

How steep is too steep - depends entirely upon the belly diameter and the end use.
In your case Neil, your pipe will not be fat, and as you are needing wide range power then changing from 18* to 24* will kill all the bottom end dramatically.
There is never a free lunch, and even using a two or three angle rear in your application, everything you gain in front side and top, is taken away from the bottom.
Then there is the issue of overev.
Again, your pipe will be " long " and the shallow rear cone combined with that length easily allows a wide flat band of power, running into overev without shutting off hard at all.

[Flettner]

How steep is too steep - depends entirely upon the belly diameter and the end use.
In your case Neil, your pipe will not be fat, and as you are needing wide range power then changing from 18* to 24* will kill all the bottom end dramatically.
There is never a free lunch, and even using a two or three angle rear in your application, everything you gain in front side and top, is taken away from the bottom.
Then there is the issue of overev.
Again, your pipe will be " long " and the shallow rear cone combined with that length easily allows a wide flat band of power, running into overev without shutting off hard at all.

It's 18 at the moment and has excellent bottom / mid range (with the powervalve in operation) but does go a little flat around 11, 000. I want more but don't want to fuck up what I already have.
My pipes mid section are equivalent to 114mm dia.
My next cylinder (54×54) will have 90mm (×2) mid section. This is the engine I'll run my pipe 'warping' system on. Haha, perhaps I'll call it Warp Drive.
It will also be a disc valve engine with my 'sliding gib' arrangement. Because of rules, it will have to stay carburetored unfortunately.

[F5 Dave]

Is that related to the steamer collapsing thingy you posted a picture of Neil?

[F5 Dave]

Could the powerjet of the very lean carb be an injector? ;)

[wobbly]

Two 90mm pipes on a 125 = 127mm single pipe.
That certainly isnt fat, but is a little bigger than most 125 MX pipes, so could probably deal with a steeper 24* rear cone, especially with a PV and the Gibbs in action.
Again, this approach would need a shorter overall TL as well, or it will make more upper and peak power, then fall flat off a cliff before 11000.

[Flettner]

Could the powerjet of the very lean carb be an injector? ;)
Muddy waters.

[Flettner]

Is that related to the steamer collapsing thingy you posted a picture of Neil?

It's what gave me the idea, while out 'antique' shopping with the good wife.
Even she can't understand why I wanted it. Sort of similar but simpler.
In fact I have several approaches to try.

[katinas]

Cool KR3 photos i had never seen those pics.
the 1989 Cagiva had the atac and rotary PV but there were a lot of cross pollination with Cagiva and Yam.:)
the Last Cagiva tested extending headers with Chandler in practice with a hydraulic pump by tag and extended 20mm. (100 bar)

From my experience, changing the header by 20 mm corresponds to about 1000 rpm.( in range over 10000 rpm). I checked the notes from my previous tests with 125cc, shortened header 11mm plus 500 rpm and 18mm plus 1000 rpm.
About KR3, did the first type engine (with 2 lower cylinders) really have a combined crankcase chamber for cylinders 2 and 3? It is clearly visible that the two cylinders on the left are closer to each other than the cylinder on the right. The engine should have been narrower than later type, maybe without bearing between two big end pins, what could have caused some crank deformations. I've never seen this first type engine photo with open crankcase, just latest one.

[Wos]

Think with two pipes instead of one the heat loss would be much bigger and for good overrev we need rising temperatur for faster Action/ speed of sound!?

One step forward could be to try to isolate/ wrap the two pipes?
Another solution maybe to reduce the restrictors a little more than calculated in FOS Formula?

Experts what do you think?? ;)

Thanks Wolfgang

[Frits Overmars]

Another solution maybe to reduce the restrictors a little more than calculated in FOS Formula? Experts what do you think?I think you might want to try that solution for yourself before passing it on to others, Wolfgang :D

[husaberg]

From my experience, changing the header by 20 mm corresponds to about 1000 rpm.( in range over 10000 rpm). I checked the notes from my previous tests with 125cc, shortened header 11mm plus 500 rpm and 18mm plus 1000 rpm.
About KR3, did the first type engine (with 2 lower cylinders) really have a combined crankcase chamber for cylinders 2 and 3? It is clearly visible that the two cylinders on the left are closer to each other than the cylinder on the right. The engine should have been narrower than later type, maybe without bearing between two big end pins, what could have caused some crank deformations. I've never seen this first type engine photo with open crankcase, just latest one.

These are all the photos i have
https://www.kiwibiker.co.nz/forums/album.php?albumid=5025
In that other other of yours Kenny looks like Vlad Putin.https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356872&stc=1&thumb=1&d=1760951934

[Storbeck]

https://www.youtube.com/watch?v=8bMb5J3gC6s&list=PLmxTBAJjAAmU8b-IzoSIW9A4DHjnfXl1N&index=91

Around 38:20 into the video.

A bit off topic but some who have been following this thread for a while may find it amusing, Kevin's way of communicating his opinion of Witteveen "...he's enjoying his retirement now..."

[wobbly]

Yea, funny that Witteveen, dubbed " the great leader " by those who knew ( despised ) him was psychotic about chassis stiffness, when at the same time Mike Sinclair and the other Kiwi
guys at Team Yamaha, and later KR , were cutting holes with large battery drills and saws in the factory alloy beams to increase longitudinal chassis twist.

The first KR3 design was a complete disaster.
Yes it did have a common crankcase ( a la Swiss Auto ) for two cylinders, with a pair of pistons hitting TDC together, via a slight offset in the crank pins due to the odd V angle.
But its downfall was spastic vibration, due to no balance shaft - needing everything to be made stronger ( heavier ) to prevent fatigue failures.
When they were warming one up in the Philip Island pits, I was discussing balance with Askland and he let me hold the throttle for a few seconds- it felt like my hand was burning.

Later when we had the BSL first time warming up, KR strode over, gave me a wink and grabbed the throttle.
His immediate reaction in front of over 100 people including his whole team, he yelled, why cant you fuckers design a proper sewing machine like this fucking thing.
Any width advantage from the narrow crank, was hugely offset by crazy cost of exotic materials, so it would last a race, and the impossibility of stopping carb froth with out clever weird arse
pump around carbs with no floats.

The balance design for the BSL, I got Simon Longdil ( later of Prototipo fame ) to write the code for his PhD thesis to analyze every possible combination of 3 cylinder angle, firing order and balance shaft layout
to minimize rotational inertia and vibration.
Best by far, was a 120*V, cylinders 1 and 3 facing down, with 1 and 2 firing together, that also had the 1:1 drive gears between them to drive the balance shaft and clutch primary drive.
This gave perfect 1st order balance, zero rocking couple, and a constant 2nd order balance vector rotating around the mains.

[katinas]

Ohh, thank you Husa, thank you Wobb.
I just found the beginning of the answer from Husa KR3 photo album, without the continuation (marked in red), but Wobb completed the story.
Yes, nearly impossible to equalize cylinders filling with common crankcase for upper and lower cylinders, especially with different exhaust pipes positions, bends and temperatures.

Thanks

[Flettner]

By the way, the easiest way to calculate the pipes for your twin-exhaust bike is to just calculate one pipe for an engine with the same exhaust timing but with half the cylinder capacity.[/QUOTE]

That's exactly what I do.

[Wos]

I think you might want to try that solution for yourself before passing it on to others, Wolfgang :D

Tanks for your warning Frits!:niceone:

I am aware of the risk of overheating and verry careful when i try to find save restrictor diameter...in every case had to deal with i stayed little above the calculated value cause we do not have the optimum of cooling system like rsa

should have told that ;)

Thanks again ! ��

Grüße Wolfgang

[Storbeck]

Back to basics question:

Resistor plug, resistor plug cap.

ALL kinds of opinions on the internet but very little explanation why.

Do they do the same thing, so using both is redundant (and maybe counter productive)?

Do they do something different, so it is best to use both, or is there a situation where it is better to use one or the other or both?

Is there a downside to either or both, especially if you are dealing with an oem/old/weak ignition (when you might not care about the rf interference effects of the non resistor plug/cap).

Hopefully this isn't an annoying "what oil" or "look at my plug" question, I see very little actual info out there mostly I see people repeating what they've heard with no understanding and there are people on this thread who might have deeper understanding.

[fpayart]

These are all the photos i have
https://www.kiwibiker.co.nz/forums/album.php?albumid=5025
In that other other of yours Kenny looks like Vlad Putin.https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=356872&stc=1&thumb=1&d=1760951934

Thank you for this wonderful album.

Francis.

[wobbly]

Storbeck, the use of a resistor plug and cap is mandatory for any modern digital ignition to reduce the RF EMI from the AC high voltage present between the coil and the plug body.
The resistance and capacitance forms an RF filter that stops the ECU from false input spikes on the power lines - seeing it as trigger information.
This effect is also reduced by selecting " falling edge" triggering for the input , as the interference resembles a rising spike of voltage.

The same issue faces the ECU in dyno readings.
My SportDevices I/O box goes completely spastic when reading the rpm trigger off the coil wire without a resistor plug and cap.
Exactly the same effect can be had by using a spiral wound shielded coil wire ( Magnacore is the best ) and a resistor plug - I have tried this on a racebike where I needed a very low plug cap height.

In KZ kart racing we use the shorty version of the R7376 race plug, partly as it makes way better power than say a B10 EGV, and secondly it gives extra elbow room with the very short body and cap combo.
Using a data driven track dyno simulation ( NT Project ) the fine wire Iridium/Platinum plug and cap gives very slightly better power over a " normal " plug and non resistor
plug cap combo , when tested in the real world.
The PVL analogue ignition probably looses some spark energy with the added series resistance on the secondary, but this is more than made up for by the plugs superior in cylinder geometry.

Thus in summary, even with an old style analogue source coil type ignition, the superior fine wire rare earth race plug with 5K resistance will make more power, more so with a non resistor cap - as that is not needed with
those ignitions.

[ApolloMotoMoto]

Storbeck, the use of a resistor plug and cap is mandatory for any modern digital ignition to reduce the RF EMI from the AC high voltage present between the coil and the plug body.
The resistance and capacitance forms an RF filter that stops the ECU from false input spikes on the power lines - seeing it as trigger information.
This effect is also reduced by selecting " falling edge" triggering for the input , as the interference resembles a rising spike of voltage.

The same issue faces the ECU in dyno readings.
My SportDevices I/O box goes completely spastic when reading the rpm trigger off the coil wire without a resistor plug and cap.
Exactly the same effect can be had by using a spiral wound shielded coil wire ( Magnacore is the best ) and a resistor plug - I have tried this on a racebike where I needed a very low plug cap height.

In KZ kart racing we use the shorty version of the R7376 race plug, partly as it makes way better power than say a B10 EGV, and secondly it gives extra elbow room with the very short body and cap combo.
Using a data driven track dyno simulation ( NT Project ) the fine wire Iridium/Platinum plug and cap gives very slightly better power over a " normal " plug and non resistor
plug cap combo , when tested in the real world.
The PVL analogue ignition probably looses some spark energy with the added series resistance on the secondary, but this is more than made up for by the plugs superior in cylinder geometry.

Thus in summary, even with an old style analogue source coil type ignition, the superior fine wire rare earth race plug with 5K resistance will make more power, more so with a non resistor cap - as that is not needed with
those ignitions.

I can 100% attest to this power increase with the double fine-wire (fine wire ground strand and fine wire electrode) NGK racing plugs. I use an analog ignition with solid core wires and non-resistor plug cap, and there is a noticeable increase in engine performance and general "smoothness" in acceleration response when switching from a "standard" fine wire irridium (NON resistor) plug to the $40 double-fine wire race plug (WITH internal 5k resistor).


Like Wayne says, the extra unnecessary resistance (in the case of my analog ignition) in the $40 race plugs is definintely robbing a bit of spark energy compared to the non resistor plug, but the advantages the double-fine wire plug brings in the chamber MORE than makes up for this ignition energy loss.

I notice the difference most at the very top end of over-rev.

[F5 Dave]

Just for giggles here's a couple of pics I took a year or so back. Funny what makes its way to NZ.

I did wonder about the mk1 idea for the carbs (not pictured, maybe) with the no float idea presumably with a pressure regulator to try make for consistent fuel supply.

[wobbly]

The MK1 carbs used a pump around system, where fuel enters the bowl up to the level of a weir, where it is the pumped out of the weir back to the tank.
Thus the fuel level remains constant without using a float and needle valve, but even this system is subject to fuel frothing, and thus wildly varying mixture control thru the main jet.
The only solution is a correctly balanced engine.

[husaberg]

The MK1 carbs used a pump around system, where fuel enters the bowl up to the level of a weir, where it is the pumped out of the weir back to the tank.
Thus the fuel level remains constant without using a float and needle valve, but even this system is subject to fuel frothing, and thus wildly varying mixture control thru the main jet.
The only solution is a correctly balanced engine.


If they were not pole mounted floats the fuel supply might have been a bit hit an miss under hard braking.

[husaberg]

Thank you for this wonderful album.

Francis.
You are too kind Francis.
Thank you for the beautiful engines. They are like modern sculptures.

there are about 9 pages of albums including a few of yours. pls Lots from Frits. plus a lot from Flettner
https://www.kiwibiker.co.nz/forums/album.php?u=28036

[F5 Dave]

If they were not pole mounted floats the fuel supply might have been a bit hit an miss under hard braking.

No it shoild compensate for that better by adding or removing. Sounfs like it could have been a real advancement if the engine was smooth perhaps?

Ended up i read, with Honda gifting them some Keihins and adapting Dellorto floats. Could have read that in Cycle world but who knows?

[husaberg]

No it shoild compensate for that better by adding or removing. Sounfs like it could have been a real advancement if the engine was smooth perhaps?

Ended up i read, with Honda gifting them some Keihins and adapting Dellorto floats. Could have read that in Cycle world but who knows?

No idea but i have recall tales Honda (or more likely i assume Jeremy Burgess) once anonymously gifted bank of works Honda nsr Keihin carbs in to help Patton. I think that was mentioned in a TDC?

[Frits Overmars]

I have recall tales Honda (or more likely i assume Jeremy Burgess) once anonymously gifted bank of works Honda nsr Keihin carbs in to help Patton. I think that was mentioned in a TDC?I don't know about Paton; I understood that Honda gave a Keihin set to keep Cagiva in the game. As did Yamaha: they gave Cagiva a complete Yamaha TZR500 bike on loan for a month. I happen to have the works drawings (don't ask how or why, in Italy anything is possible :msn-wink:).

[wobbly]

The carbs on the BSL were SPJ Keihins from a post 1998 unleaded fuel RS125 Honda. with integrated TPS and solenoid PJ.
But as they were facing backwards the float arm angle and pivot position forced the bowls to flood under brakes.
The solution was I CAD up some new CNC bowls with the floats on slider poles and used the plastic float /needle arm assembly off TMX Mikuni's - worked perfectly.
Easy work on an engine with no discernable vibration at all.

[Maxdelta]

Is removing the center bridge in the intake port of a piston port cylinder advisable to gain port area? Is there a % of bore rule of thumb for a single intake port? Any help would be appreciated.

[wobbly]

Dont even think about taking the bridge out.
You can lift the port roof up to just below the ring at BDC, and widen the top considerably, ensuring the piston skirt does not become unsupported.
The piston thrust on the bore is the highest as the piston drops over the port to BDC - a TZ250G would kill its pistons in about 100Km due to the port being too wide with no bridge.
If the cylinder was turned around as we did for Superkarts, the pistons lasted for over 500Km with no wear.

[husaberg]

No idea but i have recall tales Honda (or more likely i assume Jeremy Burgess) once anonymously gifted bank of works Honda nsr Keihin carbs in to help Patton. I think that was mentioned in a TDC?


I don't know about Paton; I understood that Honda gave a Keihin set to keep Cagiva in the game. As did Yamaha: they gave Cagiva a complete Yamaha TZR500 bike on loan for a month. I happen to have the works drawings (don't ask how or why, in Italy anything is possible :msn-wink:).

In regards to at least the carb story it was actually the then head of HRC and it was three sets of carbs to Paton I also never knew it had a 1993 Cagiva frame though.

pg 97 i gave up trying to attach it after 20 attempts


https://magazine.cycleworld.com/article/2007/10/1/the-tt-centenary

paton is a family business based near Milan, Italy. As a manufacturer, it scored points in GPs as early as 1966 and competed from 1975, allegedly without interruption, until 2001. That was when the new four-stroke rule and the associated expense forced them to concentrate on a brand-new classic racer (an oxymoron, I know, but they make spec vintage racers from scratch). Linsdell and his son Ollie normally race air-cooled, four-stroke 500cc Paton Twins, but Steve wanted one of the strokers that lined up on the same grid, albeit at the rear, as Valentino Rossi, Max Biaggi and Loris Capirossi back in 2000.Amazingly, everyone agreed, and the bike that turned up behind the TT Grandstand is the PG500RC, the most wonderful GP mongrel. The frame and swingarm are modified 1993 Cagiva C593, as raced by John Kocinski, Doug Chandler and Mat Mladin. It is the only two-stroke Paton that doesn’t have a Paton frame.


The engine is Paton, built with a keen


recycler’s ingenuity. It is a 70-degree V-Four, with a big-bang firing order. The cases are sandcast magnesium. Barrels are Swissauto while the bores house Honda RS125 pistons that have had their crowns turned off in a lathe. Ignition and ECU are by Walbro.


Roberto Pattoni, the son of one of the company founders and chief mechanic for the TT effort, tells a story about when Paton was competing in GPs. At the time, the then-boss of HRC, Youichi Oguma, was interviewed and said, “Everyone should have a passion like Paton. I would


like to help them if I could.” Paton didn’t need a second invitation and said, “If you’d like to help us, you could sell us some of those top-secret magnesiumbodied Keihin carburetors your NSR runs so well on.” In 1993, those carbs cost $25,000 for a set of four. “They cost that much because they didn’t want anyone to buy them,” says Pattoni. A week later, a box arrived from Japan with three sets of carbs, free of charge. One bank of four is on this bike.

[Maxdelta]

Thanks Wobbly. I asked about a "rule of thumb" for single port intakes because i do know there are some that run the single port without a bridge. An example is Yamaha SRX440 snowmobile cylinder. It has a single port. See pic


356884

[TZ350]

.
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

[F5 Dave]

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.

[wobbly]

Max, even in that pic you can see that the inlet is a way narrower chordal width than the Exhaust.
As I said this is due to the rod angularity pushing the skirt into the bore as the piston approached IPC.
Having a bridge helps this immensely, allowing the two ports to be much wider at the top.