ESE's works engine tuner

[peewee]

Peewee, I like the look of that Japanese handpiece.
.

i think i mentioned the head is japan but the handle was from a unknown maker. turns out i guess cc makes the handle. well the handle didnt even last 30min and the bearings and shaft inside were flopping around like mad so its on its way back to cc. my other 90 handpiece from germany has been going strong for a couple years now and zero problems. ill let you know how this turns out as im not real happy. im basically on the other side of the country from cc so ill be out of commision for about 2weeks while this gets sorted out. ya i can use my bigger 90 but that small headed one worked alot better in these small cylinders.

[seattle smitty]

You're in the States? I had good luck with everything CC Specialty sent me, but that was all in the Seventies . . . .

Detonation and pre-ignition: I once disassembled two dead Datsun L16 engines, each of which had one holed piston. I kept those two pistons for decades as show-and-tells because one was a perfect textbook example of detonation (sharp-edged, broken hole in the crown) and the other was a perfect textbook example of pre-ignition (hole with melted edges, other melting at piston edge and ring lands). Sort of amazing to get these at one time. When I moved last year, I gave them to the local high school auto shop teacher.

[TZ350]

306944 Pumper 306943 EFI

EFI still detos like crazy especially on over run.


I thought the problem was "auto" ignition caused by the mixture in the transfer ducts being heated by a burst of hot exhaust gas overcoming the weak pressure in the case/duct momentarily before it finally makes it's way into the cylinder where it is polluted by burnt hot gases before being compressed at which point it autoignites.


Detonation was not a problem with the carb and 3D ignition map until well past 12K rpm.

But .. Yes Auto ignition and I think you are right about the EFI creating a weak mixture in the transfers so I intend putting in some effort to get the timing of the injection squirt to coincide properly with the transfer port open time.

When I shut the EFI beast off at 9-11.5K rpm the deto sounds like a swarm of very angry bees.


Auto ignition - yes, weak mixture - no.

The problem as I understand it is that because the throttle is closed there is hardly any crankcase compression. As the transfers crack open, even though there was not a lot happening on the previous power stroke and not much exhaust to be spent, because of the minimal crankcase pressure there is an amount of exhaust blown down the transfers. This mixes with the fresh charge. Eventually this mix of old & new makes it's way into the cylinder where it doesn't do a particularly good job of scavenging the cylinder, is trapped as the ports close and then compressed. This mixture of combustion products from the previous cycle and fresh mixture is prone to auto-ignition.

Hi Speedpro, I agree with everything you say but "weak mixture - no", well not in this case because this engine runs well with a carb but not with transfer port injection EFI so the problem must be with the EFI or at least with the way I am trying to use it.

Remember with a carb all inducted air has fuel mixed with it but with EFI this is not necessarily true. The problem with EFI and transfer port injection is that as the rpm gets up, a lot of air can get through the port but there is not necessarily enough time to inject sufficient fuel into the air stream.

I think that its becoming obvious that with transfer port injection, matching the timing of the injection cycle to the transfer port open period is vital.

306956

The way I see it.

If the injection cycle starts to early a bulk amount of fuel simply loops around with the initial scavenge air and is lost out the exhaust port. Also if the injection cycle ends to early there will be a lean fuel patch. So correctly timing the injection end point is vital.

If the injection cycle is longer than the transfer port air flow period then some of the necessary bulk fuel for the correct air/fuel ratio is left waiting in the transfer duct and is lost on the next cycle along with the initial burst of scavenging air that purges the cylinder.

Adding more fuel (bigger map number) won't do any good because that just lengthens the injection cycle and more fuel is wasted. With a bigger map number no more fuel gets trapped in the cylinder than before as fuel injected before and after the transfer port opens/closes is simply left in the transfer duct waiting to be blown out the exhaust port along with the initial scavenge air. Bigger injectors are slower injectors so longer injection cycle there too.

With transfer port injection it looks like timing is critical and the length of the injection cycle has to match the period that there is bulk outward air flow in the transfer duct and I guess this will be significantly shorter than the transfer open period.

[SwePatrick]

306944 Pumper

With a pumper carb this engine reliably made 28hp at 12,250 rpm, with EFI, 24hp at 11,500rpm is the best so far and the EFI is short about 1,000 rpm.


Hi,
A little question, Have you considered loss of 'inertia' in the fresh mixture entering crankcase as a factor of loss of power?
Now with 'dry' flow your inertia is way lower and doesn´t fill the crankcase as a carburated engine does.

Rgds

[F5 Dave]

With a set amount of energy it must take a little to suck and drag along that extra weight of fuel from a traditional carb, so the gain in inertia has to be paid for. But an interesting idea and a bit off normal thought process.

[husaberg]

The roof axial angle should be about 20° down; the floor could use a bit more downward angle, but that would land you in the A-transfers, so you'll have to becareful there.
The radial position angle of the RSA's aux. exhaust ducts is quite radical; past mid-cylinder. But the radial direction angle is less severe.
The drawing below shows that the flanks of the aux ducts start with 20° less than the radial position angle, irrespective of the radial position angle that you may choose. And don't overdo it or you might get massive short-circuiting from the A-ports to the exhausts, even when using RSA-type closed-end piston pins.

Frits this is the bit I was meaning, just at the start of the Aux port, the pics don't clearly show it (the flat roofed area)so well, hence the kids felt used to highlight it. (Right side second Pic)
Is this an error of interpretation in the DEA version I have?

[peewee]

The roof axial angle should be about 20° down; the floor could use a bit more downward angle, but that would land you in the A-transfers, so you'll have to becareful there.
The radial position angle of the RSA's aux. exhaust ducts is quite radical; past mid-cylinder. But the radial direction angle is less severe.
The drawing below shows that the flanks of the aux ducts start with 20° less than the radial position angle, irrespective of the radial position angle that you may choose. And don't overdo it or you might get massive short-circuiting from the A-ports to the exhausts, even when using RSA-type closed-end piston pins.

cant see the pic for some reason. maybe its just my computer. ill try my phone and see if i can see it

anyways the cylinder i been working on is a cheapie i picked up from ebay for $50 to practice on. seeing how thick material is in certain areas. where i have to weld. how big i can make the boyesens. how bad the transfer tunells are etc etc. so when i port my good cylinders ill know what to expect and maybe make less mistakes

if the aux is tear drop shape and protrude slightly into the wristpin path dont you think the benefit of a wider exh area outweighs the drawback of possible linking bewteen the exh and A transfer ? it doesnt seem like the linking would be that harmful if the aux upper/outer corner is only hanging into the wristpin by 1 or 2mm but maybe im wrong.

[TZ350]

306969

Making progress, touching 12,000 rpm and nearly 25hp 3 to go.

306970306971

At 12,000 rpm the transfer is open for 1.8ms and looking at the Ecotrons run data the injectors at 12,000 rpm are open for 1.9ms so we are pretty stuffed for much more progress.

Maybe I think its time to change tack and start thinking about Injection into the inlet.

Transfer injection on an engine that revs to 8-9k would work very well (Flettner has done it on a big Kawasaki single) and with careful timing you could get some fuel efficiency's but the much reduced time available at 12k rpm to get things done. Lack of time makes it hard to do on my little 125.

[SwePatrick]

With a set amount of energy it must take a little to suck and drag along that extra weight of fuel from a traditional carb, so the gain in inertia has to be paid for. But an interesting idea and a bit off normal thought process.

But maybe gains are a bit higher, therefor more gain of power at high rpm´s.
Next, when comparing to fourstroke engines, highrevving models of those do have the injector way back in the inletrunner, sometimes actually above the velocitystack.

This to gain 'time' for atomizing the fuel before entering the cylinder.
AND,, what i mentioned earlier higher inertia of gasflow.

A little clip to visualize a bit:
https://www.youtube.com/watch?v=y2iBbwocYZw

Rgds

[wobbly]

If the main Ex is at 72% and 200* then you have no choice but to add Blowdown STA by widening the top of the Aux.
In this case the positive Blowdown power tradeoff is a desireable one against a small amount of port linking power loss.

[speedpro]

A little clip to visualize a bit:
https://www.youtube.com/watch?v=y2iBbwocYZw

Rgds

The thing I am interested in with this video is that you can see fuel running down the surface of the intake. The Ecotrons system actually has a value you can change that allows for the fuel dropping out of suspension and also the reverse depending on whether the throttle is being opened or closed. Obviously if fuel drops out the mixture will be lean for the duration of the event, and vice versa. By allowing for it the fuelling can be made more precise as throttle position changes. Sort of like an accelerator pump.

I feel for Rob with the lack of time for the injection to happen. Even on my 4T the injectors are getting close to 100% duty cycle, and I have 720degrees of crank rotation. I've actually installed bigger injectors because of it and I think it still leans out right at the top, 16,000rpm. I've had the engine over 18K so have unused rpm available. However the motors originally made max power at somewhat lower rpm so I'm not stressing.

[Frits Overmars]

Frits this is the bit I was meaning, just at the start of the Aux port, the pics don't clearly show it (the flat roofed area)so well, hence the kids felt used to highlight it. (Right side second Pic). Is this an error of interpretation in the DEA version I have?I can't see any contradiction between my description and your pictures, husa.

[husaberg]

I can't see any contradiction between my description and your pictures, husa.
the pics don't likely don't show it to clearly? I will post one with it marked better.
The original question was.

it appears the floors angle down immediatly from the bore edge. the roof however looks to be flat for a few mm into the duct and then angle downward. ?

[Frits Overmars]

At 12,000 rpm the transfer is open for 1.8ms and looking at the Ecotrons run data the injectors at 12,000 rpm are open for 1.9ms.'Open' does not cover it in your case, TeeZee. You'll need to match the mass flow, which is zero and slowly rising in the case of the opening transfers, versus zero and much quicker rising in the case of the injectors. And I'm afraid you can't do much about either of those.


Maybe I think its time to change tack and start thinking about Injection into the inlet.With the experience you must have gathered by now it will be a piece of cake to get indirect injection working. But the real job is not to find the power you got with a carburettor; the real job is making that power controllable. What you really want is a linear relationship between throttle position and rear wheel torque. And yes, that means looking at the transmission too. That is why Honda is using a 'torqductor' between the secundary gear shaft and the pinion on their MotoGP works bikes (the client bikes don't have them).

[Frits Overmars]

the pics don't show it to clearly? I will post one with it marked better. The original question was: "it appears the floors angle down immediatly from the bore edge. the roof however looks to be flat for a few mm into the duct and then angle downward."Yes, now I see what you mean. The flow can't turn at a sharp 90° angle there, so there will be turbulence at the port roof.

[husaberg]

Yes, now I see what you mean. The flow can't turn at a sharp 90° angle there, so there will be turbulence at the port roof.

I have suspicions we are talking two different subjects.
So I will try to explain better.

What I am suggesting is, the cylinder I have here, has a flat top roof (ie that is approx. 90 degree angle to the cylinder walls for a few mm of its length) then follows the same approx. 30 degree angle of the main ex port.
The floor of the aux ports however appears to follow the same angle downwards as the main ex post for its entire length.





At 12,000 rpm the transfer is open for 1.8ms and looking at the Ecotrons run data the injectors at 12,000 rpm are open for 1.9ms so we are pretty stuffed for much more progress.

Maybe I think its time to change tack and start thinking about Injection into the inlet.

Transfer injection on an engine that revs to 8-9k would work very well (Flettner has done it) and with careful timing you could get some fuel efficiency's but the much reduced time available at 12k rpm to get thing done just makes it to just to hard on my little 125.
Rob You don't have additional time for injection to meet the demands at high revs, but you do still have the option to apply MORE PRESSURE.
It would be a shame to give up on it now to go to Throttle body injection.

[teriks]

husaberg, that looks like something Id be tempted to do on a production cylinder.
-Should see much less variation in height of the timing edge after machining than if the cast port had an angled roof.
Ah well, only speculation...

EDIT: Fixed speling... doh..

[TZ350]

Hi, A little question, Have you considered loss of 'inertia' in the fresh mixture entering crankcase as a factor of loss of power? Now with 'dry' flow your inertia is way lower and doesn´t fill the crankcase as a carburated engine does. Rgds

Good idea and I thought about it for a while but in this case I am pretty sure the missing 1000 rpm is due to time considerations, there is just not enough time for the injector to do its business. There are still one or two small tricks left. Might try them tonight but its getting pretty desperate.

I have increased the injection pressure from 3bar to 4.5. I will also look at endpoint timing carefully and change the injector minimum off time for the No2 injectors so that the No1 injector will have to start working again earlier at higher rpm. The way the injectors work is :- No1 then N02 then No2 + No1 to make up any shortfall in time ava to No2 at higher rpm.

[F5 Dave]

So hybrid system with an added inlet injector for high rpm? The Willis cocktail?

[FastFred]

The Willis cocktail?
:laugh: TeeZee has not started talking about fuel yet, but a little bird has told me, that now fuel additives aren't banned anymore he is looking at adding a little water to 91 oct for combustion control and detonation suppression.

Water in Petrol everyone knows water and petrol don't mix .... :killingme ..... or do they .... :scratch:

[TZ350]

Water in Petrol everyone knows water and petrol don't mix .... :killingme ..... or do they .... :scratch:

Everyone knows Diesel and water don't mix either. Ok, I am not sure about Petrol and water but the US IRS offers a Tax refund to operators who use Diesel with water added to it so it may be possible to add a little water to petrol too for combustion control and anti detonation.

http://www.irs.gov/publications/p510/ch02.html
Diesel-Water Fuel Emulsion http://www.irs.gov/publications/p510/ch02.html#en_US_2013_publink1000116965

[richban]

Not many 2 strokes entered for boxing day at the cemetery (http://cemeterycircuit.co.nz/) circuit but this will be on the streets making the right noises. Should be fun.

306990

[F5 Dave]

It'll feel strange to be cheering you on:msn-wink:, but now you're on the good side -Go Rich.:first:

[TZ350]

.

Yes ... Go Rich.

We look forward to hearing how it went.

[wobbly]

Tested water injection when working at ZipKarts on Hines champ winning Rotax Superkart 250s.
We put a powerjet on the old magnesium Dellorto 38s and used an rpm switch to turn on water injection around peak power.
We mucked about for ages trying idiot ignition advance, and compression as the Pommie rules were 91 pump gas way back then.
No matter how much com or advance I tried I couldnt blow it up, it didnt make more power though either.
But it didnt run that long, and a big end locked up, the rod broke off near the small end and sawed the case and a cylinder in 1/2.
Oh dear, must have been running too long on the dyno.
But no, put on another new engine, ran it in, did some baseline runs, then back into abusing the shit out of it.
BANG, another rod went west.
Looking at the big end bearing we found the oil was mixing with the water spray and turning into non lubricating white muck - end of test, my shout
of warm beer and pork scratchings for lunch at the local.

[Drew]

Tested water injection when working at ZipKarts on Hines champ winning Rotax Superkart 250s.
We put a powerjet on the old magnesium Dellorto 38s and used an rpm switch to turn on water injection around peak power.
We mucked about for ages trying idiot ignition advance, and compression as the Pommie rules were 91 pump gas way back then.
No matter how much com or advance I tried I couldnt blow it up, it didnt make more power though either.
But it didnt run that long, and a big end locked up, the rod broke off near the small end and sawed the case and a cylinder in 1/2.
Oh dear, must have been running too long on the dyno.
But no, put on another new engine, ran it in, did some baseline runs, then back into abusing the shit out of it.
BANG, another rod went west.
Looking at the big end bearing we found the oil was mixing with the water spray and turning into non lubricating white muck - end of test, my shout
of warm beer and pork scratchings for lunch at the local. But direct injected to the combustion chamber 10 degrees before ignition, would that achieve the desired effect?

[peewee]

If the main Ex is at 72% and 200* then you have no choice but to add Blowdown STA by widening the top of the Aux.
In this case the positive Blowdown power tradeoff is a desireable one against a small amount of port linking power loss.

200 ? at 190 with the large aux the STA lines up well with A at 128 and B/C at 130, (B is widened as far as it can go). seems like at 200 there would be a large mismatch of the STA unless the transfers were sky high or am i missing something here ?

[Larry Wiechman]

TZ, do the rules allow methanol? If so, you might cure deto, aid cooling and maybe find a little more power.

[F5 Dave]

We're on pump av at best

[Drew]

What was the concensus as to water injection all those pages ago? Water injection is water cooling, and not allowed for a 125?

[TZ350]

What was the consensus as to water injection all those pages ago? Water injection is water cooling, and not allowed for a 125?

It was water injection into the intake that the RRC thought would constitute water cooling. Water injection into the exhaust was not discussed and is probably a technically different thing as its purpose is to change the resonant time of the pipe.

[TZ350]

307007

The horse is having a rest .... yer right!

307006

26 hp and repeatable, but so fiddly to get and still detos like mad, however much fuel I throw at it. All the extra fuel does is make more exhaust smoke.

307008

Green line is where we were at the beginning of the week, changed the end point, increased the logical injector size, increased/decreased the Alphan N map but with transfer port injection its just not going to equal the carb. I think there really is just not enough time, 1.8ms for the injection cycle through the transfers at 12krpm.

Ok time to change over to injecting down the inlet tract.

[Larry Wiechman]

http://i881.photobucket.com/albums/ac11/LJW197/BRC3_zpsa7dd4eb4.jpg (http://s881.photobucket.com/user/LJW197/media/BRC3_zpsa7dd4eb4.jpg.html)http://i881.photobucket.com/albums/ac11/LJW197/BRC4_zps805e3c43.jpg (http://s881.photobucket.com/user/LJW197/media/BRC4_zps805e3c43.jpg.html)http://i881.photobucket.com/albums/ac11/LJW197/BRC2_zpsafa8cf00.jpg (http://s881.photobucket.com/user/LJW197/media/BRC2_zpsafa8cf00.jpg.html)http://i881.photobucket.com/albums/ac11/LJW197/BRC1_zps57544757.jpg (http://s881.photobucket.com/user/LJW197/media/BRC1_zps57544757.jpg.html)

[dark art]

26 hp and repeatable, but so fiddly to get and still detos like mad, however much fuel I throw at it. All the extra fuel does is make more exhaust smoke.

307008

Green line is where we were at the beginning of the week, changed the end point, increased the logical injector size, increased/decreased the Alphan N map but with transfer port injection its just not going to equal the carb. I think there really is just not enough time, 1.8ms for the injection cycle through the transfers at 12krpm.

Ok time to change over to injecting down the inlet tract.

What about trying to lower max rpm range without loosing power? Will it be too hard on the air cooled engine? Or just loosing power?

[TZ350]

What about trying to lower max rpm range

That is a good thought but the carb graph is the performance baseline, to progress I need to better it in rpm and torque throughout the original rpm range.

[41juergen]

Thanks' to everybody to be welcome!
@TZ: I really enjoy all your open discussions and the idea with EFI. Would be nice to see how far you can get in a racing application!

@ Frits: bedank u well, my dutch is getting a bit rusty now... :rolleyes: Unfortunately my wife has only 3 brothers, so may be not very interesting for you. But as we both were born in a small city named Wesel close to Arnhem she joined several times when we visited the different race tracks in the Netherlands (she also might now what Tarzanbocht is :drool: ). And as she works in the accountant department of a big company, her calculation to buy the simu software was driven by costs savings.

About the roll over, yes agree will just play with some more blow down to see what can be reached.

@Wob: thanks for lighten me up a bit more. I had in mind that something like TL=850 mm should work fine for most of the RZ and Banshee applications. So tried the 930mm and I was getting better. Will try 950mm to see what the outcome is. I also changed the comb eff to 0,86 but only got less max. power but still the detos in the lower range. So there must be another mismatch there. Yam1 for the scavenging model is ok?

[TZ350]

307020

Thanks Larry, Pico Injectors, Billet Carb/Throttle body, looks great.

Do you have to time the injection cycle to coincide with any particular part of the induction cycle?

With two injectors the same, I guess you run one for low speed then both together for when the engine is making power?

I have some Pico Injectors but thought they were a bit slow, but I guess not if they are working for you.

[TZ350]

Page 1070 links list to go here.:Police:



Everyone talks about the axial angle on A,B and C but never any mention of the axial for the roof and floor of the aux. got any suggestions ? tried to look at the rsa but couldn't really tell much from the odd angle photos i've seen
The roof axial angle should be about 20° down; the floor could use a bit more downward angle, but that would land you in the A-transfers, so you'll have to be careful there.
The radial position angle of the RSA's aux. exhaust ducts is quite radical; past mid-cylinder. But the radial direction angle is less severe.

307075

The drawing hows that the flanks of the aux ducts start with 20° less than the radial position angle, irrespective of the radial position angle that you may choose. And don't overdo it or you might get massive short-circuiting from the A-ports to the exhausts, even when using RSA-type closed-end piston pins.


Riley Will of BRC is already achieving good results with EFI and so is Roland Holzner of Modena engines in Italy. The experimental 24/7 engine does not seem to care about the obligatory 30 mm inlet restriction.

Frits has posted some pictures of a working 24/7 setup.


A few of us have these systems now. I thought it might be useful to have a separate thread to swap information. I'm just starting with mine on a 4 stroke twin that will eventually be turbo or supercharged, Rob has his 2 stroke single with triple injectors coming along, and Sketchy with his supercharged Honda clone.

Link to the start of Speedpros Ecotrons EFI thread.

<iframe width="560" height="315" src="//www.youtube.com/embed/ifSEql1X4R0" frameborder="0" allowfullscreen=""></iframe>

EFI Kawasaki BigHorn running transfer port injection and E85. Runs to 8,000 rpm

Some more Youtube clips of transfer port injected 2T's
http://youtu.be/eleqBGvOM4M
http://youtu.be/hOGZ5llowoU
http://youtu.be/1YG9ko8-Nwk
http://youtu.be/UEQli7nuak4
GerbilGronk is worth a Youtube search.

I have been working on a EFI transfer port injection system of my own but trying to take the concept to 12,500rpm.


306944 Pumper

With a pumper carb this engine reliably made 28hp at 12,250 rpm, with EFI, 24hp at 11,500rpm is the best so far and the EFI is short about 1,000 rpm.

306943 EFI



I think that its becoming obvious that with transfer port injection, matching the timing of the injection cycle to the transfer port open period is vital.

I am finding transfer port injection above 9,000rpm is very difficult and need to find another way to get to 12,500+rpm.

Below is an example of 15,000 rpm Inlet Port Injection.


Husa put me onto this post in PitLane http://translate.google.co.nz/translate?hl=en&sl=fr&u=http://www.pit-lane.biz/t839p15-technique-2-tempset-l-injection&prev=search

It talks about split injection where a injector fires every second revolution, it may be the way forward. Husa reminded me that he had suggested it to me before ...

Gentlemen,

2 years ago I did an Indirect EFI project on a 125cc Disk Valve Kart Racing Engine. I used a Vortex FC engine which produced 49HP carbureted. With our EFI, it made 55HP!!! The engine was very easy to start and the tuning was very simple. Here is how I did it:

Rather than attach sensors to figure out the everything for me, I went with information that was known to me. I have been tuning Del'Lorto carbs for years and have used their needle charts along with various softwares that calculate Comparative MainJet Sizes at 10% throttle increments. I used this information to calculate an initial map for the injectors. I did a test on the carbureted version at each throttle position to note the EGT that was giving the correct performance. Once running with the EFI i tried to tune it to achieve the same EGT numbers as the carbureted version.

In total I ran for 3 hours on the dyno and ended up with 10% more power everywhere!

The only sensors I used were Throttle Position, Engine RPM, Crank Angle, and Water Temp for initial start up enrichment.

How did I get an injector to fire every cycle at 15000 rpm?????? I didnt! What I did is used a Janvey 41mm butterfly throttle body with 2 injectors on the engine side of the butterfly. That way when the throttle is closed, fuel still feeds the engine to lubricate it like a Pilot Jet would do. To get 15000 RPM, I had each injector firing at alternating engine revolutions. Thereby the injectors were seeing 7500 pulse at 15000rpm of engine speed. I tricked them into thinking this was a 2 cylinder 4 cycle engine firing in Tandem.

In total I spent $1600.00 in componentry to validate my "Simple EFI" idea! I will be doing more tests this winter and will be track testing in the spring. We are workind on the miimum battery requirements and packaging.

I used 2.5 Bar of pressure and will be testing more. I chose a disk valve engine for the symmetrical inlet timing. I used a valve the opened at 137 degrees BTDC and closed at 87 degrees ATDC. I started firing the injector 10 degrees earlier on the opening and stopped the injector 10 degrees after the valve closed.

Upon engine disassembly it was noted that the lubrication seemed to be better dispersed thru-out the engine (only an observation). The engine would start at less than 800 rpm of crank speed and would instantly accept full throttle load from 1200 rpm and up!

The only hurdle I see to over come is the packaging.

I am confident that my way of giving the ECU the MAP rather than having the ECU calculate the map is why I was successful. We have tuned by EGT for years and continue to see the relevance when using EFI in correlation to EGT. The increase power came by better fuel atomization. It stands to reason due to the limited time "Tuning" the system that even more power gains are to be realized with more work and data collection/analysis.

I am posting this information so more people will try this simple method and post their results here. I hope you all find the success that I did.


307073
Larrys post has a few pictures of the BRC fuel injected BRC throttle bodies. More of BRC can be seen here:- http://brceng.com/brc-motorsports/

Video clip of a Inlet Port injected 15,000rpm 2T in action on the dyno.


Here are BRC EFI 125 engine videos


https://www.youtube.com/watch?v=8AWlJN4QMws


And photos of power curve and inlet

306947306948

[TZ350]

307036

Ok, rearranged the injectors, injector one is still in the rear of the cylinder and injector two is firing down the carb. With the injection cycle timed to end at inlet closing.

307035

Red line is both injectors in the rear of the cylinder. Blue line is with the second injector in the inlet tract. The lines diverge at the point the inlet injector takes over.

Pretty crap, but par for the course. Been here before so I expect we will sort it out in time.

Followed a link Husa sent me:- https://www.facebook.com/brcracingcanada to where BRC Racing talks about its EFI system.

""Our EFI project has been successful. In 2015 we will be track testing. At the moment we have achieved Dyno tests that match our very best using the Del'Lorto 42mm carbs.""

Its impressive and pretty interesting that they talk about the EFI matching their Carb setups, its interesting because I was expecting there may have been some improvements with EFI,

Its interesting because it goes to show that carbs can be pretty good.

[TZ350]

.
Money Shot

307037

I had the injection cycle timed to end at inlet port closing but looking at the picture all that does is bounce fuel of the rotary valve. I will experiment with ending the injection cycle earlier.

[Martin1981]

Merry Christmas to all Kiwibikers and of course to all others poking around in this Thread!:drinknsin

[Frits Overmars]

Followed a link Husa sent me:- https://www.facebook.com/brcracingcanada to where BRC Racing talks about its EFI system. "Our EFI project has been successful. In 2015 we will be track testing. At the moment we have achieved Dyno tests that match our very best using the Del'Lorto 42mm carbs."
Its impressive and pretty interesting that they talk about the EFI matching their Carb setups, its interesting because I was expecting there may have been some improvements with EFI, Its interesting because it goes to show that carbs can be pretty good. The main advantage of EFI on a kart is that the motorcycle carbs everyone is using were never designed to handle acceleration in four directions. It's the one factor that gives more trouble on kart engines than all other factors put together.
Riley Will of BRC is already achieving good results with EFI and so is Roland Holzner of Modena engines in Italy. But injection has yet to be homologated on 125 cc karts, which could be a special problem for Modena. Their heat-insulating inlet insert was already more advanced than the ultraconservative FIA-CIK officials would have liked to see and you can imagine how they feel about Modena's experimental 24/7 engine which does not seem to care about their obligatory 30 mm inlet restriction.

[Haufen]

.
Money Shot

307037

I had the injection cycle timed to end at inlet port closing but looking at the picture all that does is bounce fuel of the rotary valve. I will experiment with ending the injection cycle earlier.

Maybe I missed something, but why don't you inject directly into the crankcase, between the crank webs?

[Peter1962]

The main advantage of EFI on a kart is that the motorcycle carbs everyone is using were never designed to handle acceleration in four directions. It's the one factor that gives more trouble on kart engines than all other factors put together.
Riley Will of BRC is already achieving good results with EFI and so is Roland Holzner of Modena engines in Italy. But injection has yet to be homologated on 125 cc karts, which could be a special problem for Modena. Their heat-insulating inlet insert was already more advanced than the ultraconservative FIA-CIK officials would have liked to see and you can imagine how they feel about Modena's experimental 24/7 engine which does not seem to care about their obligatory 30 mm inlet restriction.

Frits, is het gelukt met de 24/7 ? Did it work out with the 24/7 timing ? Congratulations ! I hope we will soon see more details on this.

[TZ350]

Maybe I missed something, but why don't you inject directly into the crankcase, between the crank webs?

I had thought about that and it would lubricate the bigend nicely but its was mechanically easier to start with transfer injection, also I wanted to squirt the fuel directly onto the underside of the piston crown for cooling.

When I started this EFI project I knew nothing about EFI, probably not much has changed, but I have developed a bit of a feel for how many ms it takes for a crank to move so many degrees at 12,000 rpm.

Looks like I have spent a lot of time going down a blind ally but you get a bit of that on projects .... :laugh:

[TZ350]

.

Husa put me onto this post in PitLane http://translate.google.co.nz/translate?hl=en&sl=fr&u=http://www.pit-lane.biz/t839p15-technique-2-tempset-l-injection&prev=search

It talks about split injection where a injector fires every second revolution, it may be the way forward. Husa reminded me that he had suggested it to me before ...

Gentlemen,

2 years ago I did an Indirect EFI project on a 125cc Disk Valve Kart Racing Engine. I used a Vortex FC engine which produced 49HP carbureted. With our EFI, it made 55HP!!! The engine was very easy to start and the tuning was very simple. Here is how I did it:

Rather than attach sensors to figure out the everything for me, I went with information that was known to me. I have been tuning Del'Lorto carbs for years and have used their needle charts along with various softwares that calculate Comparative MainJet Sizes at 10% throttle increments. I used this information to calculate an initial map for the injectors. I did a test on the carbureted version at each throttle position to note the EGT that was giving the correct performance. Once running with the EFI i tried to tune it to achieve the same EGT numbers as the carbureted version.

In total I ran for 3 hours on the dyno and ended up with 10% more power everywhere!

The only sensors I used were Throttle Position, Engine RPM, Crank Angle, and Water Temp for initial start up enrichment.

How did I get an injector to fire every cycle at 15000 rpm?????? I didnt! What I did is used a Janvey 41mm butterfly throttle body with 2 injectors on the engine side of the butterfly. That way when the throttle is closed, fuel still feeds the engine to lubricate it like a Pilot Jet would do. To get 15000 RPM, I had each injector firing at alternating engine revolutions. Thereby the injectors were seeing 7500 pulse at 15000rpm of engine speed. I tricked them into thinking this was a 2 cylinder 4 cycle engine firing in Tandem.

In total I spent $1600.00 in componentry to validate my "Simple EFI" idea! I will be doing more tests this winter and will be track testing in the spring. We are workind on the miimum battery requirements and packaging.

I used 2.5 Bar of pressure and will be testing more. I chose a disk valve engine for the symetrical inlet timing. I used a valve the opened at 137 degrees BTDC and closed at 87 degrees ATDC. I started firing the injector 10 degrees earlier on the opening and stopped the injector 10 degrees after the valve closed.

Upon engine disassembly it was noted that the lubraction seemed to be better dispersed thru-out the engine (only an observation). The engine would start at less than 800 rpm of crank speed and would instantly accept full throttle load from 1200 rpm and up!

The only hurdle I see to over come is the packaging.

I am confident that my way of giving the ECU the MAP rather than having the ECU calculate the map is why I was successful. We have tuned by EGT for years and continue to see the relevance when using EFI in correlation to EGT. The increase power came by better fuel atomization. It stands to reason due to the limited time "Tuning" the system that even more power gains are to be realized with more work and data collection/analysis.

I am posting this information so more people will try this simple method and post their results here. I hope you all find the success that I did.

http://translate.google.co.nz/translate?hl=en&sl=fr&u=http://www.pit-lane.biz/t839p15-technique-2-tempset-l-injection&prev=search

[husaberg]

.

Husa put me onto this post in PitLane http://translate.google.co.nz/translate?hl=en&sl=fr&u=http://www.pit-lane.biz/t839p15-technique-2-tempset-l-injection&prev=search

It talks about split injection where a injector fires every second revolution, it may be the way forward. Husa reminded me that he had suggested it to me before ...



I stole it from Cagiva though.


Anything well just about anything can be made to work given enough time, money and more importantly determination.

I remember the Cagiva system involved huge pressures.
The biggest potential advantages i see with fuel injection are economy and emissions drive-ability but maybe, i am short sighted about this.

The one thing i did pick up from a few pages back was the split system with each set of injectors handling half the revolutions. So two injectors on each cylinder running each fueling alternate revolutions. Which should solve a few of the problems with doing it in the past.

You could also maybe alter the characteristics under overrun even possibly dial in some engine braking.
Maybe include a four stroke switch for slippery conditions and learner racers.

2011 Return of the two stroke. Possibly premature.
http://www.youtube.com/watch?v=goNP9pLHhyU&lc=rwsGLtvui8s1Pt4dgQ7L18qW3Iqbnn2MaWTHlcr08SQ&context=C3714f15ADOEgsToPDskL7BjBrQhia1uTNqMht_TCF


You knew it to Rob ya just didn't remember.........

Sensible, and works for a 4T but the problem I face with my 2T is that an injector small enough for starting and clean running at low rpm is to small when the engine gets on the pipe so you have to have two different sized injectors and swap between them for high and low speed running.

I think my real problem is in finding injectors dynamic enough to handle what would be 28,000 rpm in 4T terms.

It might be that I will have to run two injectors in parallel firing on alternate cycles.
I might have to patent the foul stroke switch idea though, might even make a crap noise function app

This is what I believe Frits was referring to, a couple of pages back with the Honda and making effort to make it un-twitchy


BRC (make Rotax 256 copy kart engines) Riley Will (who contributed to the pitlane.biz RSA thread) spoke the most sense there
The 2002 500cc bikes used 35-36mm carbs with electronic solenoid type power jets.

KTM used a hybrid system where they used an injector to augment the fueling requirements. It was used in their 250cc program, but I'm not 100% sure if they used it in the 125cc bike as well. Probably, but I cannot be certain.

Aprilia was guilty of throwing out what they perfected (carburation)and introducing a totally new concept loaded with technology EFI system. It was an intelligent system that made all the theoretical calculations at light speed..... It was a perfect system....... Too perfect! For years 2 stroke engine development was being done using less than perfect carburetor. This includes rider knowledge, tire construction, and suspension..... The end result was that the riders and machinery (tires) couldn't cope with the instantaneous increase in torque when the throttle was opened while at maximum lean angles.

When I discussed how I was going to do my EFI, their main electronics engineer started clapping..... What I wanted to do (and later did) was to upload a fuel distribution curve similar to a Del'Lorto needle/tube (needle jet) combination and did not let the computer adjust it. I used a TPS, H2O sensor, Air temp sensor, and Hall Sensor for crank angle/rpm. This way I was using what I knew, but getting the benefit of 3 bar of fuel pressure and injector atomization. I had total control and could add fuel to make the fuel curve "imperfect" if need be. I used 2 injectors mounted on the engine side of the throttle valve and I alternated their firing so that I could rev upto 15000 rpm. That way each injector was mislead into thinking it was feeding a 7500 rpm max 4 stroke cylinder. In total I invested $1600 into the total system and had it running pulling load on the dyno in 3 hours
Riley later says he timed the injector to squirt 10deg before inlet open and finish 10deg after inlet close

[Frits Overmars]

Frits, is het gelukt met de 24/7 ? Did it work out with the 24/7 timing ? Congratulations ! I hope we will soon see more details on this.It works. It works to such an extent that I am not at liberty to divulge anything about the power curve (for fear that the FIA-CIK tech people might outlaw it even before it hits the track).

[teriks]

It works. It works to such an extent that I am not at liberty to divulge anything about the power curve (for fear that the FIA-CIK tech people might outlaw it even before it hits the track). Now that is some really fun reading, congratulations Frits!

[wobbly]

Yam 1 is OK if you keep the old fashioned and inefficient axial angles on the transfers.
Way better to do some welding on the B ports and flatten them to around 10*.
And epoxy the A port roof to get 25 - 28*.
Then Yam 12 is the correct scavenging model - also hugely more efficient scavenging pattern, especially if the B port rear wall is progressively
ground back and a proper radiused hook put on the duct exit.

Having the transfers up at 130 is as wild as any RZ Banshee motor should go,having these with a 190 Ex is just not remotely right at all, no matter what
the end use is of a 5 port reasonably modern layout ( RZ perfect example ) so yes something is not right.

A 950 pipe will go out to near 12,000 if every other component is set up to be doing this, including Ex timing up at 196 - 200.
Most important of course is the ignition curve,a stock Banshee or RZ ignition is useless for this, as is the PV curve.
And getting the Ex duct nozzle dimensions correct gives a huge boost in power with the 3 port, as well as allowing a much better pipe design to be used.

Off to open pressys and drink far too much and become obnoxious - cant wait.

[F5 Dave]

Bluur. Eaten too much. Had a quick kip. Kids playing with hot wheels track. Still sober enough for wielding rifflers (wouldn't trust myself with grinder) might have a quick fettle of transfers till next guests arrive. And pack for going to see cmtry cct racing at Wanganui tomorrow.

[TZ350]

307087

Started making myself a twin injector manifold for the Inlet.

Quiet start to the day, Mass, casual lunch, watched the Queens Xmas speech on telly and the film "Red Dog", worked on the bike in the evening, grand kids tomorrow, perfect Christmas. http://www.dailymail.co.uk/news/article-2886775/Queen-wraps-early-Christmas-service.html

[peewee]

hi frits it seems your familiar with modena 125cc version. it says max power is 15000rpm :shit:. that seems like quit an accomplishment. but what i dont understand is the port arrangment, mostly the transfers. exh opens at 195*, presumably for the main and the flanking ports probly a couple degrees later im guessing. A 130.5*, B 126.5*, C 128.5*. the transfers seem unconventionally staggered compared to what im used to reading about. can you give some thoughts on the theory behind this approach ?

i almost forgot something else. why only a 106mm rod ?

[Frits Overmars]

hi frits it seems your familiar with modena 125cc version. it says max power is 15000rpm :shit:. that seems like quit an accomplishment. but what i dont understand is the port arrangment, mostly the transfers. exh opens at 195*, presumably for the main and the flanking ports probly a couple degrees later im guessing. A 130.5*, B 126.5*, C 128.5*. the transfers seem unconventionally staggered compared to what im used to reading about. can you give some thoughts on the theory behind this approach ? i almost forgot something else. why only a 106mm rod ?I don't know where you read it, Peewee, but maximum power is produced much earlier than 15000 rpm, so you'd better not believe everything you see in writing.
Other than that I am not going to comment on anything related to Modena for the above-mentioned reason; I can't afford to be quoted at the moment.

[peewee]

yes maybe i got some bad information. but thats what it says on their site. read for yourself :bleh:. click on engine information http://www.modena-engines.it/eng/index.php

[jasonu]

yes maybe i got some bad information. but thats what it says on their site. read for yourself :bleh:. click on engine information http://www.modena-engines.it/eng/index.php

It says max RPM is 15000. It quotes a max power figure of 44cv (what ever a cv is) but not at what RPM it is made.

[peewee]

my bad. i didnt read it correctly. still it lists a strange stagger pattern on the transfers. although the drawing doesnt seem to match as the C appears to be same height as B. im sure frits will clarify it when the time is right

[husaberg]

yes maybe i got some bad information. but thats what it says on their site. read for yourself :bleh:. click on engine information http://www.modena-engines.it/eng/index.php


my bad. i didnt read it correctly. still it lists a strange stagger pattern on the transfers. although the drawing doesnt seem to match as the C appears to be same height as B. im sure frits will clarify it when the time is right
so you'd better not believe everything you see in writing.
I am not going to comment on anything related to Modena for the above-mentioned reason; I can't afford to be quoted at the moment.

[Flettner]

so you'd better not believe everything you see in writing.
I am not going to comment on anything related to Modena for the above-mentioned reason; I can't afford to be quoted at the moment.

Yes, this is getting exciting.

[wobbly]

Everyone that works within such small niche technical markets like race engine manufacturing always has to sign a NDA.
Ive been doing this for years and if you dont abide by the agreement terms, you dont get the work - simple.

[twotempi]

44cv

CV = chevaux - horsepower

Citroen 2CV ( Deux Chevaux ) = 2 horse power but having driven one I doubt it was that much !! :laugh::laugh:

[peewee]

hey wob i figured the case ratio to be 1.43 on this yam. im not sure yet if ill dive in and do any welding to correct the transfers, keeping that in mind do you see any harm if i lifted the cylinders a few mm or would it do better leaving the case volume small ?

[Frits Overmars]

so you'd better not believe everything you see in writing.
I am not going to comment on anything related to Modena for the above-mentioned reason; I can't afford to be quoted at the moment.
Yes, this is getting exciting.My own impression: it sounds rather pompous :p. But like Wob says: you gotta do it this way or not at all.

[Martin1981]

Hello,

can someone please tell me the compression height of the aprilia rsa piston? i heard of 24mm but i do not know if this is right. are there 54mm pistons available with even less com height?

i have another question regarding carb area and its relation to the cylinder intakeport area. should the intakeport have the same area as the carb (i think so) or should it be bigger or smaller for some reason? thanks

[Drew]

Hey TZ. Is there a chance that the ball valve you're using with the bike injected, is screwing with the air flow at part throttle and causing the detonation?

I see the two sharp edges creating a wicked flow disruption when I picture the valve partially open, and I recall Malcolm (koba) once showing me a simulation of air going through different shaped carbs and trying to explain the pros and cons of each scenario.

[wobbly]

1.43 case com is insanely small and will not help power production in any way, shape,or form.
You will need to do everything you can to get some volume in there, heading for 1.33.
Barrel spacers ( long rods will help here as well ), reed spacers, cut the case for crank clearance etc etc

[Flettner]

Hey TZ. Is there a chance that the ball valve you're using with the bike injected, is screwing with the air flow at part throttle and causing the detonation?

I see the two sharp edges creating a wicked flow disruption when I picture the valve partially open, and I recall Malcolm (koba) once showing me a simulation of air going through different shaped carbs and trying to explain the pros and cons of each scenario.

If the ball vale was a problem, it would have shown up on the Kawasaki F9 ( same valve ). Could it be any worse than the back side of a carb?

[Drew]

If the ball vale was a problem, it would have shown up on the Kawasaki F9 ( same valve ). Could it be any worse than the back side of a carb?
Only gets disturbed once with a carb, on the bottom of slide. Not on the leading edge and then the trailing edge.

[wobbly]

A slide with corners front and rear, 1/2 way down, has a big round hole in front of it - and a big round cavity on the other.
Sounds like a huge 2X flow disruption to me.

[Flettner]

Only gets disturbed once with a carb, on the bottom of slide. Not on the leading edge and then the trailing edge.

Have a close look at how the ball works.

[husaberg]

likely overstated a bit, artistic licence.but...
307132

[TZ350]

Only gets disturbed once with a carb, on the bottom of slide. Not on the leading edge and then the trailing edge.

307133307134

True there is a sharp trailing edge at part throttle but at wide open WOT there is an unobstructed and smooth tract. The Kawasaki F9 made 45 rwhp with this style of throttle.

<iframe width="560" height="315" src="http://www.youtube.com/embed/ifSEql1X4R0" frameborder="0" allowfullscreen=""></iframe>

[TZ350]

Hey TZ. Is there a chance that the ball valve you're using with the bike injected, is screwing with the air flow at part throttle and causing the detonation?

True as well as the EFI the throttle is different too, hadn't considered that, but the runs are done at WOT and I get patches of deto and deto at 11 to 12K+rpm and heaps of deto on over run with a closed throttle.

307137 307135 307136

The Blue line is my best with transfer port injection the Green line is where I have got to today with the twin injectors aimed down the inlet throat. It was the same map as the transfer port injection, and better than yesterdays single injector effort. But not as good as the transfer port injection and no where near as good as my best with a carb. Today I just fiddled with the injection endpoint then a bit of map tweeking.

Anyway today was not a total bust, as I got to have lunch with Kel at a neat little cafe in Ellerslie.

[peewee]

1.43 case com is insanely small and will not help power production in any way, shape,or form.
You will need to do everything you can to get some volume in there, heading for 1.33.
Barrel spacers ( long rods will help here as well ), reed spacers, cut the case for crank clearance etc etc


disregard the 1.43. originally i had 1.34 with all standard oem parts measured with oil. engmod was saying 1.43 but the only thing that i can think of that changed was a oem reed block to the vf4 which would decrease volume alittle but not much i wouldnt think. ill have to do some digging and find out why the numbers aint matching up. maybe its not that important because i know how much oil i poured in, i can just base any further parameter changes off the original oil number.

do you think 1.324 is to much volume ? if anything the performance might gain nothing but lose nothing either

[husaberg]

I have never noticed this cylinder Nor do I know what variant it is, Anyone?306581


I think this is a DEA cylinder


Right. In fact it's two DEA cylinders; the left and center pictures show a 2013 cylinder; the right pic shows a 2014 cylinder from the DEA superkart tandemtwin with RSA-based cylinders. The notches in the bore surface are supposed to retain some oil for the benefit of the exhaust bridges.


They look a bit more than just notches...Do they go through to the transfer ducts ? When i saw them in the pic I wondered if they matched holes in the piston skirt at BDC for a little under piston cooling/mixture moving through but assumed not for reasons you'd already mentioned.


No Grumph, notches don't. This picture shows under what angle and how deep the cutter went in.306604.


Thank you Frits - much better angle to see how deep the notches are. I suppose the question is - did they work ? If they weren't used on the later engines, the assumption is, it wasn't worth doing....


That picture was from a 2013 DEA cylinder because it showed the notches best. But the 2014 cylinder has them too, so they can't be all bad.
Andrea degli Esposti (DEA) is a free thinker who does more than just copy Aprilia stuff. Here he is with his home-built pulsating flow bench.


I was watching the gnani making a GP bike Video and I was pretty surprised to see this.
307172

https://www.youtube.com/watch?v=I-2rJtnkYq4

Also I don't speak Italian ...Anyone what the heck is this all about?
https://www.youtube.com/watch?v=kyC3vbdzZ_A

[breezy]

Stay away from this dentist stuff, unless you can get it for free. Doing one 125 cc cylinder once took me five dentist sets. When the cylinder was ready, all five sets were binnable. The bevel gears and bearings are just not up to the job.
If you can afford it, look for a hand tool with a swiveling head. I can't find a picture so I will try to describe it: there is a 30° kink at the business end of the handgrip. The right-angled head can swivel around the kinked axis, so the angle between the handgrip and the cutter can vary from anything between 60° and 120°.

It won't be any different from what we are used to, Breezy. On the flow bench the central scavenging column created by the six incoming transfer streams has proven to be very stable; even if I blocked one of the transfer ducts completely, that column remained intact, albeit off-centre. And the exhaust characteristics depend on the gas dynamics in the pipe. The gas will be the same, the pipe proportions will be the same, so the pipe behaviour and the engine characteristics will be the same.

Here:
http://www.pit-lane.biz/t117p318-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked
http://www.pit-lane.biz/t117p333-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked
(it took me over an hour to find those links; I think I should cut back on my forum activities. Which one should I drop first? :p)

Like any other pipe resonance-dependent two-stroke.

Sure, also like on any other pipe resonance-dependent two-stroke: programmable ignition, power jet, power valves, trombone pipe.
But since I am under the impression that you can build anything you can think of: how about shrouds in the transfer roofs? If you lower them, you will lower the transfer timing, so wrongly-timed exhaust pulses will have less chance of shoving fresh cylinder charge back into the transfer ducts. Moreover, lowering the transfer timing while leaving the exhaust ports alone will increase the blowdown angle.area. That will put an end to the dreaded part-throttle detonation that plagued all Aprilia racing engines.
Taking this thought a little further, you could even use the movable transfer ceiling instead of a throttle.

I am, and I wonder why you would think so. Like I mentioned above, the engine character will be no different from what we're all used to at the moment.
Having said this, I am all in favour of CVTs.

frits, would this barrels scavenging sytem be defined as " reverse flow"?

[wobbly]

As I have said before I have never seen a power increase when going bigger than 1.3 ratio with a reed.
But it seems that the worse the transfer ducts are - the better the engine performs with a slightly tighter case.
So around 1.32 will be fine

[peewee]

im about to join the aux tunell into the main tunell. is there any general rules for how far the divider should extend into the main tunell ?

[F5 Dave]

More metal mass in that area has to help I'd think to pull heat away to the rest of the cooler barrel.

[peewee]

i checked a unporterd 250 cylinder and the divider was 20mm long. cant imagine i need to be any more than that, maybe even less but it should be a good place to start i guess

[wobbly]

Less metal mass in the divider = less heat input = less expansion distortion into the bore.
But way more important issue is to get the exit area ratio correct, and now the duct needs to be oval with the Aux ports outer wall
extending right thru the pipe spigot to the header.
This will need welding top and bottom as the duct exit is too big to start with.

[peewee]

now i know why hardly nobody bothers putting extra ports in the stock cylinders. its alot of damn work :eek5:. got the hole punched through but still along ways to go

hey it seemed like you posted the duct exit should be 90% of the total exh area at the bore for a mono port if i recall correct. is it supposed to be like 95% if im using 3 exh ports ?

[TZ350]

now i know why hardly nobody bothers putting extra ports in the stock cylinders. its alot of damn work :eek5:. got the hole punched through but still along ways to go

hey it seemed like you posted the duct exit should be 90% of the total exh area at the bore for a mono port if i recall correct. is it supposed to be like 95% if im using 3 exh ports ?

Yes, Triple Ex is a lot of hard work. And I think from memory, the smallest point of the duct area as it transitions from oval to round is supposed to be 75% of the total area of all the exhaust ports combined for a 3 ex port setup.

[wobbly]

The area ratio TeeZee has answered but here is the basic idea.
The exit area should be related to the Blowdown STA,as rightly pointed out by Frits, but i just havnt got that far yet.
3 port engines can generate alot more blowdown as well as total Ex STA when compared to a single port setup, and from general observation
the exit areas of these can , and usually do end up as 100% of the main port effective area - ignoring the Aux area.
This makes perfect sense when the general rule for the single port is best exit area is at 90% ie less blowdown, less BMEP, less exit area.

[peewee]

ok i just converted the duct exit diameter to area mm sqaured. its 77.3% of the total area of all 3 ports. sounds like im not far off from where i need to be

duct exit diamter 34.8mm = 951.149mm sqaured area

total area for all three ports 1229.5mm sqaured
951.149/1229.5 = .7736= 77.4%

remember the exh is only at 190 right now which wobbly said is to small so ill have to sort that out but if i raise the exh higher then i will probly be close to the 75% without needing to do much to the exit

[husaberg]

Here some pics (attached)if that helps, its no RSA of course. They I believe had a CNC finished Duct.

follow the path in this
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=306934&d=1419235154

[peewee]

i wont go to all the trouble of cutting off the spigot exit and making a new removable manifold. ill probly just extend the aux tunells pretty far down the main tunell like wobbly drew in the pic

[peewee]

sure wish i had a machine like this. hell even a simple drill press would probly do fine with a fixture to hold the cylinder. would save alot of time. machine could do the majority of the work making the rough hole then do the fine details with hand grinder

[Muciek]

ok i just converted the duct exit diameter to area mm sqaured. its 77.3% of the total area of all 3 ports. sounds like im not far off from where i need to be

duct exit diamter 34.8mm = 951.149mm sqaured area

total area for all three ports 1229.5mm sqaured
951.149/1229.5 = .7736= 77.4%

remember the exh is only at 190 right now which wobbly said is to small so ill have to sort that out but if i raise the exh higher then i will probly be close to the 75% without needing to do much to the exit


Did You used exit angle of port in calculations ?? Here's what Woobly wrote when I was asking about this (exh port dimensions)


In the port STA calculations the programs use the chordal width and the piston movement over the port height.
If the floor and roof of the duct are parallel exiting the bore then the area is simply Width X Height but if they are angled
then the height in reality is X the cosine of the angle.

[peewee]

i just used the area values from engmod. i assume thats the correct way ? it said total area of all 3 ports was 1229.5mm sqaure. roof and floor angle is around 15* . im not sure how to figure area with cosine involved

heres a cosine calculator but i dont know what number values to use http://www.calculatorsoup.com/calculators/geometry-plane/triangle-law-of-cosines.php

[Muciek]

Cosine of 15 degrees is 0,965925826....
1229.5 * cos15* = 1187,60. I don't have engmod so I can't tell You is that 1229 vaue already with cosine or without it.

[husaberg]

sure wish i had a machine like this. hell even a simple drill press would probly do fine with a fixture to hold the cylinder. would save alot of time. machine could do the majority of the work making the rough hole then do the fine details with hand grinder

http://www.harborfreight.com/5-in-rugged-cast-iron-drill-press-milling-vise-69159.html
307206
i'm going to have a go with something similar to the top one, to mill a pattern in a drill press as I don't have access to a mill.
http://www.amazon.com/Wilton-11754-4-Inch-Cradle-Style/dp/B009E0EBFM
307207

[jasonu]

http://www.harborfreight.com/5-in-rugged-cast-iron-drill-press-milling-vise-69159.html
307206
i'm going to have a go with something similar to the top one, to mill a pattern in a drill press as I don't have access to a mill.
http://www.amazon.com/Wilton-11754-4-Inch-Cradle-Style/dp/B009E0EBFM
307207

Harbor Freight Tools sells cheap stuff mostly made in China. Some of it is good for one offs or home handy man applications but not for serious money making ventures.

[husaberg]

Harbor Freight Tools sells cheap stuff mostly made in China. Some of it is good for one offs or home handy man applications but not for serious money making ventures.

No Worries tis for wooden pattern for me...........I just can justify dropping mondo money on a decent mill, the rest i can do with a router, im not expecting it to do much else,I know Ya gets what ya pay for.
I used Harbour Freight as an example for pewee because I guessed he was in the Land of the free and home of Knave, same as you.
the NZ eq of Harbour freight is http://www.topmaq.co.nz/item/view/100mm-Cast-Iron-Cross-Slide-Vice?sku=MEVI1900

Still Chinese but they have this also.
http://www.trademe.co.nz/business-farming-industry/industrial/manufacturing-metalwork/vices/auction-829460087.htm
307478
Compound Sliding Table 450x168mm
Features:
- Working area 450x168mm.
- X-axis travel: 210mm.
- Y-axis travel: 140mm.
- Dimensions (LWH): 580x390x80mm
- Has slotted foot for secure mounting

[Flettner]

Like any other pipe resonance-dependent two-stroke.

Sure, also like on any other pipe resonance-dependent two-stroke: programmable ignition, power jet, power valves, trombone pipe.
But since I am under the impression that you can build anything you can think of: how about shrouds in the transfer roofs? If you lower them, you will lower the transfer timing, so wrongly-timed exhaust pulses will have less chance of shoving fresh cylinder charge back into the transfer ducts. Moreover, lowering the transfer timing while leaving the exhaust ports alone will increase the blowdown angle.area. That will put an end to the dreaded part-throttle detonation that plagued all Aprilia racing engines.
Taking this thought a little further, you could even use the movable transfer ceiling instead of a throttle.

.

That's actually quite hard to do, there is not much room as the exhaust ports are almost right there! BUT I have a plan, as you could imagine. The CNC will come in very handy, are you sure you don't mind me bastardising your FOS system?
How much are we allowd to angle the transfers up? To give room for the exhausts to angle down over them.

[TZ350]

307219307220307221

Well tonight's effort was a total bust, the two injectors send out such a cloud that it wets out on the bellmouth and dribbles down into the plenum which totally negates the reason for having injectors in the first place. Ie to stop fuel pooling in the plenum.

I can see the advantage of having the injectors behind the throttle slide like they have on the BRC engine. Gave up for the night after the EFI filled the crankcase with raw fuel.

Neels sent me some very informative links.

http://www.sandia.gov/ecn/gaso<wbr>lineSprayCombustion.php (http://www.sandia.gov/ecn/gasolineSprayCombustion.php)

http://www.cmt.upv.es/ECN.aspx

Neels also suggested I take a closer look at what happens at an injector, things like the "liquid length" and atomization and finally evaporation. Also the effect of impinging on a wall at what stage of the plume development.

[Frits Overmars]

how about shrouds in the transfer roofs? If you lower them, you will lower the transfer timing, so wrongly-timed exhaust pulses will have less chance of shoving fresh cylinder charge back into the transfer ducts. Moreover, lowering the transfer timing while leaving the exhaust ports alone will increase the blowdown angle.area....you could even use the movable transfer ceiling instead of a throttle.

That's actually quite hard to do, there is not much room as the exhaust ports are almost right there! BUT I have a plan, as you could imagine. The CNC will come in very handy, are you sure you don't mind me bastardising your FOS system? How much are we allowed to angle the transfers up? To give room for the exhausts to angle down over them.You can bastardize all you like, Neil. I have the transfers angled up 25°; any less would make the exhaust floor too thin locally; any steeper would not only limit the transfers' cross-sectional area, but also 'ease' the collision of the converging transfer streams to such an extent that too much of their initial flow velocity would survive, resulting in a central scavenging column with so much velocity that too much of the fresh charge would loop via the cylinder head into the exhaust ducts.
It also depends on the envisaged piston speed. A high flow velocity of the central scavenging column suits a high-revving engine. If you want to keep the revs moderate, you ought to reduce the axial transfer angle.

[AndreasL]

i just used the area values from engmod. i assume thats the correct way ? it said total area of all 3 ports was 1229.5mm sqaure. roof and floor angle is around 15* . im not sure how to figure area with cosine involved

heres a cosine calculator but i dont know what number values to use http://www.calculatorsoup.com/calculators/geometry-plane/triangle-law-of-cosines.php

The EngMod numbers should be good to use as is. That's how I have used it anyway…
I think EngMod is set to a 95% value per default if letting the program do the calc for you. I'm sure the more experienced users can give us the correct answer.

[wobbly]

Yes, all the area/effective diameter numbers in EngMod are already calculated with the duct down angle taken into account.
Make the angle greater and you will see the area and then the STA drop proportionally.
The duct to effective window area ratio, is shown automatically in the display panel, so getting 90% or 75% numbers are easy to do.

[Flettner]

You can bastardize all you like, Neil. I have the transfers angled up 25°; any less would make the exhaust floor too thin locally; any steeper would not only limit the transfers' cross-sectional area, but also 'ease' the collision of the converging transfer streams to such an extent that too much of their initial flow velocity would survive, resulting in a central scavenging column with so much velocity that too much of the fresh charge would loop via the cylinder head into the exhaust ducts.
It also depends on the envisaged piston speed. A high flow velocity of the central scavenging column suits a high-revving engine. If you want to keep the revs moderate, you ought to reduce the axial transfer angle.

Thank you Frits, set at 25 then. Angle will reduce as the transfers and revs lower. As Freddie said, "I want it all".

[peewee]

Yes, all the area/effective diameter numbers in EngMod are already calculated with the duct down angle taken into account.
Make the angle greater and you will see the area and then the STA drop proportionally.
The duct to effective window area ratio, is shown automatically in the display panel, so getting 90% or 75% numbers are easy to do.

cool i just noticed it shows the passage to window area ratio. i never noticed that before. guess i didnt pay attention. so it seems the downward angle is already figured in and no manual calculations are needed

[TZ350]

.

Ok so I have starting to work it out.

307244

It was a bit hard but finally ... Success .....

I have been struggling with detto and running out of injection time trying to squirt in enough fuel to stop it.

In the end, the issue was all about the piston, which was (only just) tapping the head, not a big problem and I was to lazy to fix it, well tonight I did and the deto has disappeared.

307242

I shifted the injectors back to the transfer ports and now with a bit of decent squish clearance the Beast rev's to 12,500rpm plus with injection time to spare.

307245

So transfer port injection is a realistic option.

Initially I thought 9,000rpm was going to be the limit for transfer port injection but the Beast is now running to well past 12,000 rpm with the original transfer port injection setup.

307243

The injectors swap over at about 7k rpm and the two main injectors still have some injection time left at 12,800 rpm and so it looks like it could go to 13 easy enough.

Ok so now that it works, its time to tune it properly and see if we can better the old carb setup.

[Farmaken]

That is some cool news TZ, best bring it to T-nui so we can have a play....

[TZ350]

That is some cool news TZ, best bring it to T-nui so we can have a play....

The Beast is probably not ready for that but I will see if I can take Chambers wire wheel FZR/GP125.

[breezy]

Thank you Frits, set at 25 then. Angle will reduce as the transfers and revs lower. As Freddie said, "I want it all".

how about a crecy sleeve set up to completly close the exhaust ports... make Sir Harry Ricardo happy..

[Frits Overmars]

I have been struggling with deto and running out of injection time trying to squirt in enough fuel to stop it.
In the end, the issue was all about the piston, which was (only just) tapping the head, not a big problem and I was to lazy to fix it, well tonight I did and the deto has disappeared.The piston to head tapping that caused the vibration frequency that fooled your deto sentor into thinking there was deto has disappeared.
You're not the first person something like this has happened to, TeeZee. Once upon a time Volvo went Touring car racing with their 850 Turbo.
But whatever they tried (less ignition advance, more fuel, even water injection) the engine would detonate at 8.500 rpm. Or so they thought.
It turned out that the bouncing of the closing inlet valves at 8.500 rpm generated exactly the frequency that the deto sensor was trained to recognize as deto.

[Frits Overmars]

Thank you Frits, set at 25 then. Angle will reduce as the transfers and revs lower. As Freddie said, "I want it all".You got me curiouser and curiouser. Are you thinking sliding or hinged transfer roofs? Me, I've even considered reducing the piston stroke while the engine was running, raising the BDC position while maintaining the TDC position, so the transfers would only partly open (I'd probably had too much to drink).
I hope you will come up with something much, much simpler.

[seattle smitty]

Maybe a sleeve valve arrangement, not the usual kind, but the sleeve moving up and down (very short travel, just changing port timing) with throttle position or rpm-related control (or in a boat, your slider-pipe control) . . . . It would violate the KISS principle, however.

(Frits, I'm hoping you will say something about my 24/7 notions on the French site, please.) EDIT: Damn, I just looked, and somehow that post got almost completely deleted!! Nevermind, sorry.

[seattle smitty]

Okay, since the French cut me short (for once I don't think I did it, because it was all up for a while), here's the gist of my 24/7 speculation:


It draws from Frits' 24/7 intake concept, with which i'll assume you all are familiar; he uses a reedblock in which the reeds swing out of the way once the engine rpm has risen past the point at which the pipe comes in. It also relates to a recent remark by Frits that he had experimented with bypassing the crankcase, and mounting a pair of carbs over a pair of transfers; he said that the engine ran okay but failed due to insufficient lubrication at the bearings. Finally, it relates to Wobbly's story of a water injection experiment in which the bearings didn't like being lubricated partly with emulsified water.

My first notion for a 24/7 system was to use two carbs. The first carb, which would get the engine up to "pipe-speed" would be valved in one of the usual ways (piston-port, rotary valve, or reed valve), while the second, valveless carb would feed directly to the crankcase when it opened. I suggested this on Pit-Lane a while back; Frits or others said that the idea had already been proposed.

My current suggestion, yet to receive much feedback (possibly because it got deleted???), is to locate the second (24/7) carb on the side of the cylinder opposite the exhaust, directly above the lower portion of the boost-port. I would re-direct the bottom of the boost port to connect directly and smoothly with this second carburetor, and plug off its previous connection to the crankcase. The boost port would only "draw" when this second carb is open, which is only when the engine is on the pipe (obviously part of the success of a 24/7 scheme using two carbs depends on good sealing of the second carb when it is not in use).

Now rather than having a modern-style skinny boost-port, one could try an older-style wide boost-port, as used to be seen in some lower-power 2-strokes, Or, you could have dual boost-ports. Or, you could make your direct connection to the B transfer ports. Or to the "finger-ports" that we used to grind into old-fashioned 3-port cylinders (I have several such engines, mostly Konigs). Or any combination of these. You could end up having only the "A" pair of transfers connected to the crankcase, rather like very old loop-scavenged 2-strokes, and none of the other ports would come into play until the engine got up to "pipe-speed."

Plainly, such a development program would call for having a good supply of spare pistons!! But at least as a concept (until you tell me that it's unworkable or pointless for some reason) it would seem to me that at least it would solve both the problem Frits had with lack of lube to the bearings (and there must be a reason he tried that layout), and the problem Wobbly had with water in the bearings. The crankcase is always getting lubricating oil from the primary carburetor. If desired, water injection could go in to the secondary carb, which has no direct connection to the crankcase.

I'd be very interested in your reactions. I have boxes of obsolete engine parts I can play with and screw up, LOL.

FWIW, I just bought a machine shop (well, that's over-stated, but it feels like it). Where previously I have owned a number of small lathes, currently a 13X36", and have had a small Taiwanese knee mill, soon I'll have set up a heavy 16X40" lathe and a 2J head Bridgeport with all attachments, oh the glory!!

--Smitty

[Frits Overmars]

Maybe a sleeve valve arrangement, not the usual kind, but the sleeve moving up and down (very short travel, just changing port timing) with throttle position or rpm-related control (or in a boat, your slider-pipe control) . . . . It would violate the KISS principle, however.I would like to vary the transfer port height so much that it can be used instead of an inlet throttle; that would mean closing the transfer ports almost completely.
Using a sleeve would mean varying the exhaust timing as well. I'm not sure I want that. Using a sleeve also means creating a thermal barrier between the piston and the surrounding cylinder material. And I'm quite sure I don't want that. So I would KISS the sleeve goodbye (although I remain curious about Flettners sleeve creation).

[TZ350]

The piston to head tapping that caused the vibration frequency that fooled your deto sensor into thinking there was deto has disappeared.

Fooled the deto sensor and me, Yes ... totally.

Towards the end, I was starting to wonder why the motor hadn't expired after hours of rattling away on the dyno.

[seattle smitty]

[QUOTE=Frits Overmars;1130810900].
Using a sleeve would mean varying the exhaust timing as well. (quote)

Why? This doesn't have to be a sleeve like an older 2-stroke had, an iron sleeve whose finished I.D. forms the cylinder bore. It can made as a ring, sitting in a wide slot just barely below the exhaust ports. Depending on the intake port shapes and spacing, you could have this ring-sleeve rotate rather than move up and down, to reduce the port area, even the port opening height (sorry I can't make a sketch).

Such a ring would not interfere at all with most of the heat transfer path, from TDC down to just below the bottom of the exhaust ports. Below that, yes it's a barrier. And the ring itself would get hot and transfer heat into the intake charge. I can imagine some possible partial remedies, but maybe they would not overcome the problem. I do think that current water jacketing design in conventional 2-stroke cylinders has room for improvement, if more cooling is wanted. You remember what the big "goldfish bowl" water jacket of the Harley/Aermachi RR250 looked like . . . suppose it had been cast with cooling fins INSIDE the water jacket, greatly increasing heat dissipation over the exhaust port . . . if that's what you need (I'm an outboard guy, and our cooling requirements are more easily dealt with). One thing about that engine as it was, was that the cylinder head had what in effect was a big single cooling fin around its out edge, hanging far into the enormous water jacket. IF you want a lot of cooling in your cylinder head, that's a way to get it.

(As usual, conceptualizing is easy and fun; executing is hard, LOL.)

[Yow Ling]

You got me curiouser and curiouser. Are you thinking sliding or hinged transfer roofs? Me, I've even considered reducing the piston stroke while the engine was running, raising the BDC position while maintaining the TDC position, so the transfers would only partly open (I'd probably had too much to drink).
I hope you will come up with something much, much simpler.

How would you change the stroke when its running ? The second part I can follow maybe using a junk headand moving the cylinder up or down

[husaberg]

307279
How would you change the stroke when its running ? The second part I can follow maybe using a junk headand moving the cylinder up or down


<iframe width="420" height="315" src="//www.youtube.com/embed/zPEbv3DlGh0" frameborder="0" allowfullscreen></iframe>

290165

Crecy Engine .

........................
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=290165

For variable transfer height this in configured in reverse.
http://img215.imageshack.us/img215/9854/raveyes1.gif

307269307270
or even a Yamaha spool valve.

later
http://forums.autosport.com/topic/74960-new-engine/page-

[Frits Overmars]

How would you change the stroke when its running ?Like in the pictures below (there are multiple solutions). But I dropped the idea almost as soon as I got it: too complicated and certainly not suitable for high revs.

[seattle smitty]

No, NOT like that. Your deal does NOT need a sleeve that moves at engine speed. It only moves as fast as your engine climbs its power curve, or comes back down. Outboard racers don't pull their trombone pipes in and out twelve thousand times a minute! Maybe on a bike or shifter kart you want your port-timing to change in every gear, as the engine climbs (or descends) the power curve, so you can't change the port-timing manually, as outboarders do their pipes, but still this is NOTHING like trying make another mechanical movement at engine speed, at every stroke. You don't run the guillotine-valve in your exhaust port in and out at twelve thousand times a minute. A port-timing valve (for that matter, like a variable-timing rotary valve) only has to respond as fast as that guillotine-valve in the exhaust. Okay, my notion involves doing this with a partial "sleeve," but it is NOT like a cylinder sleeve or the sleeves in an ancient sleeve-valve engine.

[136kg136ps]

With the roof angle changing,the area changing it seems the volume will necessarily change as well?

Given the small clearance to the exhaust ducts,I'd keep the actuation and directional control method simple to stay compact.

A hinged piece(shaped to fit up into the transfer port roof as close to the bore as possible),hinged at the outside radius where there is more meat in the cylinder.Moving with a simple rod actuating it. A rod which runs perpendicular to the bore inside the cylinder and being actuated from outside the cylinder via rocker arms(or some other mechanism) in turn connected to each other to ensure they are coordinated in motion.

My experience is gas turbines which have variable vanes (many) situated around the turbine whose ends protrude into the turbine gas flow but are controlled from the outside.They are situated radially and act rotationally but the principle is similar.

This gives us sealing the hinged piece within the duct and actuator within the cylinder as one problem.I can't see any others yet.Other than a few pounds of extra mass.

[speedpro]

I envisage something like a "comma"(,) shaped piece lying horizontal forming the roof of the transfer port. It would pivot on a shaft through the part that would normally be the top part of a written comma. In the position with the comma fully raised it would form a smoothly contoured transfer duct outer wall and port top/roof. Pivoted to a lower position obviously the roof slope would decrease as would the proximity to the cylinder wall. Most likely neither change would be an issue when it happens which would be at "part open" or closed throttle. I don't see it being too difficult to do which makes me wonder why nobody has done it yet.

[ken seeber]

Couple of things that can be observed from the FOS layout. I did a rough sketch of the ports based on a 54 stroke, 120 rod crs, 190 ex duration and 130 transfer duration .
1. As the floor of all the exh ports are, say 2.5, above the top of the transfers (compared to a conventional RSA style layout where central exh floor is approx. @ BDC), it can be seen that the piston needs to only be around 41 long. Taking advantage of this, the transfer passage entry “roof” can be raised to correspond with the piston @ BDC. This then allows the “floor” of the entry to be raised. What this means is there is a much greater mixture flow higher up the piston, exposing the piston to more cooling plus more lubrication for the pin bearing. The bulk mixture flow at the max flow rate instance, say @ BDC, would be improved because one is not drawing from the more shielded inside of a longer piston. The piston would also be much lighter due to not having the long conventional skirts.
2. If the exh outlets were fore and aft (ie square to the crank axis), this would mean that the piston pin bore might not uncover an exh port, eliminating any exh to transfer port short circuiting.
3. Given that we have tons of transfer port area, I thought it would be reasonable to consider having the floor of the transfer ports a few mm above BDC. For a 2 mm step, this would give a 50 deg duration of no interference to the transfer flow by the piston edge. With the piston relatively lower to the transfer port floor, it also means that, with a well-designed coolant passage inside the “cup handle”, the ring would be closer to the coolant passage. Additionally, because of the symmetry of all the transfer passages, this coolant passage would be simple to implement.
I’d envisage a vertical reed block between the crank webs. While I do recognize a reed is not as good as a disc valve, perhaps with the Frits 24/7 feature, this disadvantage is no longer relevant.
Personally I’m keen on the DAS (Direct Atmosphere System), but can see that it would be hard to implement, say in CIK and seemingly all karting controlling bodies where the opportunity for technical advancement is about zero. Gotta say the freedom that was there in 125 GP racing, was a wonderful thing.
I’d imagine Frits is aware of all these things, but it is interesting all the same.
What also is abundantly clear is that there is stuff all room between the floor of the exhaust and the roof of the transfers, particularly when they overlap as can be seen in a top down elevation. So, when considering throttling (or controlling the mixture flow rate) via lowering the roof of the transfers there is precious little real estate to incorporate valves etc. There are other methods of course. Still, I have the feeling that right now there are lots of dudes on the case at present, so let’s wait and see.
Anyways, better get into the New Year’s eve party thing.
307313307314

[breezy]

Couple of things that can be observed from the FOS layout. I did a rough sketch of the ports based on a 54 stroke, 120 rod crs, 190 ex duration and 130 transfer duration .
1. As the floor of all the exh ports are, say 2.5, above the top of the transfers (compared to a conventional RSA style layout where central exh floor is approx. @ BDC), it can be seen that the piston needs to only be around 41 long. Taking advantage of this, the transfer passage entry “roof” can be raised to correspond with the piston @ BDC. This then allows the “floor” of the entry to be raised. What this means is there is a much greater mixture flow higher up the piston, exposing the piston to more cooling plus more lubrication for the pin bearing. The bulk mixture flow at the max flow rate instance, say @ BDC, would be improved because one is not drawing from the more shielded inside of a longer piston. The piston would also be much lighter due to not having the long conventional skirts.
2. If the exh outlets were fore and aft (ie square to the crank axis), this would mean that the piston pin bore might not uncover an exh port, eliminating any exh to transfer port short circuiting.
3. Given that we have tons of transfer port area, I thought it would be reasonable to consider having the floor of the transfer ports a few mm above BDC. For a 2 mm step, this would give a 50 deg duration of no interference to the transfer flow by the piston edge. With the piston relatively lower to the transfer port floor, it also means that, with a well-designed coolant passage inside the “cup handle”, the ring would be closer to the coolant passage. Additionally, because of the symmetry of all the transfer passages, this coolant passage would be simple to implement.
I’d envisage a vertical reed block between the crank webs. While I do recognize a reed is not as good as a disc valve, perhaps with the Frits 24/7 feature, this disadvantage is no longer relevant.
Personally I’m keen on the DAS (Direct Atmosphere System), but can see that it would be hard to implement, say in CIK and seemingly all karting controlling bodies where the opportunity for technical advancement is about zero. Gotta say the freedom that was there in 125 GP racing, was a wonderful thing.
I’d imagine Frits is aware of all these things, but it is interesting all the same.
What also is abundantly clear is that there is stuff all room between the floor of the exhaust and the roof of the transfers, particularly when they overlap as can be seen in a top down elevation. So, when considering throttling (or controlling the mixture flow rate) via lowering the roof of the transfers there is precious little real estate to incorporate valves etc. There are other methods of course. Still, I have the feeling that right now there are lots of dudes on the case at present, so let’s wait and see.
Anyways, better get into the New Year’s eve party thing.
307313307314

Do we know what bore or stroke Frits had in mimd? thoughs little areo engines which run at really high sort of ticking over speeds( sure ive read 14000 rpm whilst not under load on the ground) could be looked at and scaled up perhaps. No wonder cvt would be very helpfull at thoughs kind of rpm values (P. L. A..N. when you can only raise the rpm to produce more power) A sleeve, recessed around the cylinder sleeve, which moves up and down when required around the cylinder sleeve to fully expose the transfers and vary the exhaust ports hieght was what came to mind. The sleeve could be made of a steel alloy material and raised and lowerd by magnetism.

[136kg136ps]

Speedpro,exactly:clap:.The comma shape describes what I was thinking perfectly.It would seem the side that forms the port wall would have to conform in shape to the port.I do worry about turbulence at the edge as well as caused by a rapid change in volume and shape.

Since it's not in a high temp environment ,mounting could be pretty simple.One could even retrofit a conventional existing cylinder to test out various mounting methods.Just make the comma,grind out a recess in the transfer port roof,figure a way to have it rotate around a pin and then on to actuation.

[seattle smitty]

Six transfer ports. So six push-pull rods opening and closing your "comma-valves"? And how do you actuate them, what sort of linkage to six pushrods all around the cylinder? It could be worked out, but seems more complex than my notion of a sliding or twisting sleeve.

With my ring-sleeve, if you make it move up and down, you only need two pushrods, one on either side, ganged together outside the cylinder, OR if you make rotate sideways to change port area/timing, you have a rack-and-pinion on the bottom edge, so just one rod, with a bellcrank outside the cylinder, OR, move it with a little cam. The movements are short. At least they are slow (relative to engine speed).

And although your comma-valves are not "in" a high temp environment, they are very close to one, could pick up a lot of heat, could transfer that heat to the intake charge. This is also a problem for my sleeve scheme.

Happy New Year, y'all!!!

[136kg136ps]

smitty,I agree your method would likely have fewer parts and failure points.

I believe in the moveable roof scenario there would be better directional control and there would likely be less than 10 parts per transfer port all very simple shapes other than the piece that fits into the transfer port.A powervalve style motor could be run off the ignition to vary the position with a variety of inputs TPS,MAP,EGT etc...After seeing how convoluted some PV actuation systems are I am surprised no one has tried a variable transfer port with success.

Imagine the rocker arms arranged with the actuated arm shorter than the arm connected to the motor so that each arm could be connected to another.They would be rocking around the circumference not up and down axially.

Sealing the actuating rod would be simplest if there was no penetration of a water cavity but even if so,it's low pressure water at a moderate temp.

There would be no or little thermal issues.

Compared to a http://www.geaviation.com/marine/engines/military/lm2500/
our 2 strokes are the epitome of simple,even the oval bore H@n&a foul strokes with 8 valves would be.

You can see on the link above where the variable stator vanes are and get an idea of how simple actuating multiple parts are.After safety wiring all those parts together as well as every cannon plug,fuel,air and hydraulic line I got to know them far to intimately.

[seattle smitty]

[QUOTE=136kg136ps;1130811327] . . . and there would likely be less than 10 parts per transfer port
There would be no or little thermal issues. (end quote)

That's 60 parts. Looking at a photo of one of Frits' prototypes, it's not easy to envision how you would lay out all of your linkage. (but not easy to package my sleeve, either).

Why do you see no thermal issues? Each of your six valves will rotate up against the back of an exhaust port floor, leaving no room for any water jacketing. (Again, this is an issue with my idea, though possibly addressable by various means, maybe including ceramic coating the exhaust port floors, although that has a drawback or two.)

[136kg136ps]

Without the moveable part that metal would be in direct contact with that same exhaust floor.With the moveable part,the part is in direct contact with a pin,there would be a small air gap around the part allowing it to move freely so it should be actually be cooler than originally.Albeit the big end would be closer to the exhaust,the heat would be conducted less efficiently to the comma via air and a pin it rotates on than if it were 1 contiguous piece of metal.I assume it would of course be cooled by the transfer stream as well.

In the diagrams Frits has provided there is no water passage I can see near the bore between the exhaust floor and transfer roof.The comma shape as speedpro suggested in fact tapers as it approaches the bore due to the lack of metal there for much of anything.I may be wrong but I did look first to see if it impinged on any water passages.

As far as parts counts,KTM,H0n$@ and Suzuki had similar amounts for their PV systems.One could go the route of spring loading the comma piece lowering the count but giving up precise control.

Thanks for taking the time to help hash this out,I only wish I had the ability to spend the $ and time knocking together a model to test.

[seattle smitty]

[QUOTE=136kg136ps;1130811344] In the diagrams Frits has provided there is no water passage I can see near the bore between the exhaust floor and transfer roof.The comma shape as speedpro suggested in fact tapers as it approaches the bore due to the lack of metal there for much of anything.I may be wrong but I did look first to see if it impinged on any water passages. (end quote)

No, I didn't see one either, just saying that without flowing coolant there, that localized area is likely to be a rather hot stretch of aluminum. Yes, the intake flow will cool your valves or mine (good), but conversely our valves will be heating the intake flow (bad).

As for incorporating a spring, with either of our schemes at least a small spring might at least be wanted to take lash out of the linkage (since we want control of the port timing to be as crisp as possible). If we have a spring for taking up slack, maybe we should consider incorporating it to go on and perform part of the opening/closing operation.

This is fun (I have kept walking back to the computer today, to see the comments on this)!! Still, I hope Frits will comment in detail, even if it's to tell me my ideas have some obvious killer-flaw I should have seen.

[136kg136ps]

http://www.google.co.ug/patents/WO1992003645A1?cl=en
http://www.mavintech.com/resume.html

Only mentions I found of variable height patents,though they have been discussed,even early on in this thread.

I am the same way,watch every new idea get confirmed or denied by Frits,Jan or Wobbly and in the process learn more.A long way from the late 70s and early 80s grinding away unknowing of TA or flow characteristics on RDs or putting whatever TZ parts we could get on them.

[Flettner]

What are we after, timing changes yes but also nozzleing down the port to increase flow speed into the cylinder at lower transfer gas volumes. If we don't change the transfer open / shut timing but maintain high gas flow with this " nozzleing" will that alone help?
I have several proposals but probably want to think about them a little more.
Although for simple nozzeling I would move the transfer floors ( the complete inside curve shape of the transfer port) up and down ( x6 ) as a single machined piece, like a six spline looking from underneath the cylinder, the center of this machined part would form part of the cylinder (x6 slots). The transfers would become open slots with the foor curve shape being moved up and down, full open to full closed. But this will NOT change transfer open and shut timing.
I have thought about using silicon ports and adding pressure ( oil?) behind to change the shape, I think too inconsistant.

[136kg136ps]

That patent mentions using a liquid to deform some type of material to change the shape of the ports.Maybe a bladder of sorts.Can't see that being as accurate as a solid part moving.

[peewee]

If the main Ex is at 72% .

unmodified i measured it to be 68.5% or so if i recall. ive since went to 70% with flat roof and 8mm top corners. if i went to 72% do you see any problem staying flat on the top with the 8mm corners ? the huge cc engines im used to working with would make me a bit nervous doing that but maybe the small cylinders will do fine

perhaps i would be better off using a slight roof arc and smaller top corners such as 6mm ? ?

[lodgernz]

A small question: Why does the FOS cylinder have to have individual transfer passages?
Since the ports are all close together, surely there can't be much flow impedance by simply having a large transfer "gallery" surrounding the cylinder and feeding all the ports? Obviously there would be some CSA issues at the crankcase entry points, and maybe this would mandate a pair of such galleries rather than a single one.
If this is logical and workable, would such a system make some of your ideas for movable transfer roofs and/or floors more achievable?

[wobbly]

The reason each transfer port needs its own dedicated duct length is again pointing back to what I said before about creating coherent
shaped streams entering the cylinder.
What you are proposing goes back to old Mac chainsaw based engines, where they had exactly as you describe, a large pocket on each side of the bore
with several port "holes " simply bored in from outside the cylinder, and the outer face filled with a pressed in plug.
The scavenging regime of these engines was super basic and super ineffectual.
To prevent chronic short circuiting, the only way to achieve a band of coherent columns that hold their shape and direction vector, and then coalesce into a single rising loop stream, is to have
sufficient, shaped, duct length below the port from the case.

Re the 72% chordal Ex width.
In pistons of the RZ size this is the practical limit, and must be combined with a roof radius and corner rads to prevent ring snagging.
This sort of shape and size goes back to the TD and later the TZ350, so search out how the Ex port was done by Yamaha in the previous century - nothing has changed.

[lodgernz]

The reason each transfer port needs its own dedicated duct length is again pointing back to what I said before about creating coherent
shaped streams entering the cylinder.
What you are proposing goes back to old Mac chainsaw based engines, where they had exactly as you describe, a large pocket on each side of the bore
with several port "holes " simply bored in from outside the cylinder, and the outer face filled with a pressed in plug.
The scavenging regime of these engines was super basic and super ineffectual.
To prevent chronic short circuiting, the only way to achieve a band of coherent columns that hold their shape and direction vector, and then coalesce into a single rising loop stream, is to have sufficient, shaped, duct length below the port from the case.

Fair enough. I thought FOS system might be different in that all the transfers aim radially to the centre and axially up at the same angle so transfer passage wall inner and outer would be the main control factors.
Perhaps a gallery would be feasible if each port separator had a short wall back into the gallery to direct the flow radially at the port window. Getting too complicated really.

[TZ350]

307334

Alpha-N maps need to be smooth without any peaks or severe troughs between cell steps.

Ecotrons has a function where you can export a map to an Excel spread sheet and use the charting function to help smooth the map data.

307335 307336

Raw data and the chart showing how rough the data is and the engine ran just as roughly.

307337 307333

Smoothed data and chart.

No Idea if I have done this right, will get to find out tomorrow, hopefully .... :D

[seattle smitty]

What you are proposing goes back to old Mac chainsaw based engines, where they had exactly as you describe, a large pocket on each side of the bore
with several port "holes " simply bored in from outside the cylinder, and the outer face filled with a pressed in plug.

Lots of engines were made like that, back then. The incoming charge streams were made "coherent" by running into a big deflector atop the piston, LOL. Not a pretty system, at least for high performance, but we hopped them up and raced them and had a real good time. Plus, the open megaphones were easy to make, and produced a wonderful shriek (that some of the neighbors hated; eff them!!), well, good as long as your ignition was working properly, otherwise the sound could be highly embarrassing!!



I finally got a chance to flop down on a recliner chair, close my eyes, and try to "see" how the hell my notion of how best to do variable intake timing in a Frits-motor (FOS) could be BUILT. Of course, it would entail a cylinder-bock made in at least two sections, to be held together with studs, O-rings, etc.. So far, I can't figure out how to do it without having a pressed-in iron cylinder sleeve. Frits has said that this is sub-optimal for bikes and karts (although IMHO it is not a deal-killer for an outboard). I tried to envision a way to move the whole upper wall of the transfers up and down, to change volume along with timing and keep the contours of the long-turn and short-turn un-altered, . . . at least up to about the final 4-5mm (cyl. sleeve thickness) before the port window. Big problem. I'm starting to agree with the other fellows that their "comma-valves" are a better idea than mine. But those still would be a real challenge to actually construct (for one thing, how would you keep them from bouncing at some resonant frequency?).

Personally, the whole idea of variable intake timing in a Frits-motor interests me less than how one might apply one of his other cool ideas, the 24/7 intake, both to a conventional cylinder and to this FOS cylinder.

I keep clinging to the hope that the brainy guys here will give me some reaction to my notions about running the boost port and probably the B transfers of a conventional cylinder directly from a 24/7 carb (Page 1074, post #16109, hint , hint). To do this on a Frits-motor gets more involved (but again, not so bad on an outboard motor as a bike motor). The Frits-motor has two of its six transfers directly under an exhaust port and pipe, so I'd leave those to be fed from the "primary" carburetor that feeds the engine through the crankcase full-time. The other four transfers could possibly be treated as adjacent pairs, each pair being connected at their bottom ends directly to a 24/7 carburetor (remember this system only opens when the engine comes on the pipe). But what a lot of STUFF! Three carbs and two pipes per cylinder, and all the controls for them!! Maybe an old deflector engine wasn't such a bad thing!!

[seattle smitty]

Oops. Admin, please delete this (and tell me how to delete an entire post).

[TZ350]

Oops. Admin, please delete this (and tell me how to delete an entire post).

To completely remove a post.

307340

Click "Delete"

307341

Then click "Delete Message"

Then click "Delete Post"

[breezy]

how about a crecy sleeve set up to completly close the exhaust ports... make Sir Harry Ricardo happy..

"Lower operating temperatures of all power-connected engine parts, cylinder and pistons, Harry Ricardo showed that as long as the clearance between sleeve and cylinder is adequately settled, and the lubricating oil film is thin enough, sleeves are 'transparent to heat'."

[seattle smitty]

Lower operating temperatures of all power-connected engine parts, cylinder and pistons, Harry Ricardo showed that as long as the clearance between sleeve and cylinder is adequately settled, and the lubricating oil film is thin enough, sleeves are 'transparent to heat'.

Well THAT's new to me!!! I thought any discontinuous interface was a barrier to heat transfer to a greater or lesser degree, even if it was, say, an aluminum sleeve in an aluminum casting. What is "adequately settled"?? Do you know where I might find this in Sir Harry?

Frits has described the problem as one of the iron sleeve and aluminum block each moving around when hot; small gaps appear, which are then filled with exhaust soot, a poor thermal conductor. Obviously this doesn't affect what Sir Harry said, since, as I take it, the sleeve would no longer be "adequately settled." But I still wonder at his statement, which is at varience to what I've read (but I'm full of bum information, unfortunately).


TeeZee, I saw no "Delete" box at all. (I have endless problems with this laptop, this steaming pile of dog-doo, possibly because its running Win 8.1. A local kid, computer whiz, says he's going to help me convert to some form of Puppy Linux; I hope that helps me).

[136kg136ps]

smitty,turbines use something similar to heim joints to remove lash and ensure all parts move in unison.

I had taken a look at variable valve timing and compression in foul strokes to see if there was anything useful in that respect.I think we are better served with variable exhaust timing, volume and or length along with 3D PJ,PV and timing curves as our esteemed resident professionals have described. Adding in the variable transfers is the next logical and attainable step.Go Team ESE.

[husaberg]

TeeZee, I saw no "Delete" box at all. (I have endless problems with this laptop, this steaming pile of dog-doo, possibly because its running Win 8.1. A local kid, computer whiz, says he's going to help me convert to some form of Puppy Linux; I hope that helps me).

Edit post then press advanced. You should have enough posts by now for this function to be enabled.

[breezy]

"Lower operating temperatures of all power-connected engine parts, cylinder and pistons, Harry Ricardo showed that as long as the clearance between sleeve and cylinder is adequately settled, and the lubricating oil film is thin enough, sleeves are 'transparent to heat'."

this is a quote i came across from hours of surfing Harry Richardo information..., if i can find the source again, i will post.

[wobbly]

I built a Mac 101 sometime last century with 4 carbs.
Two were on the "bottom" of the crankcase feeding thru pyramid reeds, and one on each side feeding thru plate reeds into
the transfer cavity's.
Who knows if it needed that much intake area, and yes it was real easy to "port" the cylinder by simply removing the transfer cover plugs
and squaring up the round drilled holes with small files.
This was also the time I made my first pipe for a 2T engine, having discovered everything known to man about racing twostrokes in the little red book.
I could never get it to run properly though, it would be fine outside the powerband and crap inside, or visa versa.
Then I discovered the Vevey rear cone concept, added a progressive linkage so each pair of carbs opened independently, and it finally won an open title.
Would love to find that thing, just to remind me how dumb I was.
Also prompts me to remind you guys that in here, the vast majority of people have big trouble getting a conventional 2T anywhere near its real potential.
But we are now discussing all manner of weird arse ways of making what is really a simple system, way more complicated ?

[Flettner]

I built a Mac 101 sometime last century with 4 carbs.
Two were on the "bottom" of the crankcase feeding thru pyramid reeds, and one on each side feeding thru plate reeds into
the transfer cavity's.
Who knows if it needed that much intake area, and yes it was real easy to "port" the cylinder by simply removing the transfer cover plugs
and squaring up the round drilled holes with small files.
This was also the time I made my first pipe for a 2T engine, having discovered everything known to man about racing twostrokes in the little red book.
I could never get it to run properly though, it would be fine outside the powerband and crap inside, or visa versa.
Then I discovered the Vevey rear cone concept, added a progressive linkage so each pair of carbs opened independently, and it finally won an open title.
Would love to find that thing, just to remind me how dumb I was.
Also prompts me to remind you guys that in here, the vast majority of people have big trouble getting a conventional 2T anywhere near its real potential.
But we are now discussing all manner of weird arse ways of making what is really a simple system, way more complicated ?

You are absolutly right Wayne but isn't interesting anyway? I like looking into engines just like you described above.

[breezy]

this is a quote i came across from hours of surfing Harry Richardo information..., if i can find the source again, i will post.

T S M uniflow ... noticed this web site via google,,, wonder if its up and running?

[Flettner]

No, have a look at the bucket foundry posts there you will see the cases for the sleeve engine as of yesterday. I'm hoping by the end of today to have them ready to cast. These same cases will also have the FOS / variants fitted and run as well. It has provision for a balance shaft. Flettner = Uniflow, same person.

[seattle smitty]

[QUOTE=wobbly;1130811832] . . . Also prompts me to remind you guys that in here, the vast majority of people have big trouble getting a conventional 2T anywhere near its real potential . . . (QUOTE]

Who? ME???? And why do you think I'd want to be reminded, Wobbly?LOL. Throwing water on our fun, that's cold, man!! Has your Christmas spirit departed already?LOL

An old-timer who has hung four carbs on a McCulloch (and some of us used to grind bridges between ports entirely out, rather than squaring them) ought to have some empathy for our weird speculations, LOL. Come on, Wobbly, pg. 1074, #16109. Tell me it's stupid, whatever, I want to hear whatever you think of it.

Yeah, getting the timing right, getting the carburetion spot-on, getting everything lock-wired, and getting a perfect start and beating the pack to the first turn . . . that actually would pay off better than having the craziest engine in the pits, but 2-stroke guys aren't just racers, we're gear-heads, wild-eyed maniacs with rotary files. It's often an incurable condition.

I'm 21 hours and 10 minutes into the new year and haven't screwed anything up yet!!!

[peewee]

hey wob im sure some how theres a way to determine the correct size of carb for any specific engine but i dont have any idea how to figure it out. on engmod STA page it lists a recomended size of carb. do you see any reason i shouldnt use ( or atleast start with) the carb size it recomends ? also what happens when the carb is to big for the engine ?

[F5 Dave]

C`mon Smitty you come across as a bit aggressive and we actually like having Wob on here. Don't piss on him.

[breezy]

T S M uniflow ... noticed this web site via google,,, wonder if its up and running?

ok...., when i read on about the efi bike it started to sound familiar. ... best of luck . you managed the efi so i recon youll be sucessfull with this.( just flicked through the posts... where was i when this was going on, cant believe ive missed so much)

[Frits Overmars]

This doesn't have to be a sleeve whose finished I.D. forms the cylinder bore. It can made as a ring, sitting in a wide slot just barely below the exhaust ports... You could have this ring-sleeve rotate rather than move up and down, to reduce the port area...(sorry I can't make a sketch).Preventing spent gases from entering the transfers is the main purpose. That will only work if the blowdown phase is lengthened, so the transfers must be lowered. Smitty, I am trying to picture your proposal in my mind, but I have a hard time doing that without a drawing.


A hinged piece(shaped to fit up into the transfer port roof as close to the bore as possible),hinged at the outside radius where there is more meat in the cylinder.
I envisage something like a "comma" shaped piece lying horizontal forming the roof of the transfer port. It would pivot on a shaft through the part that would normally be the top part of a written comma. In the position with the comma fully raised it would form a smoothly contoured transfer duct outer wall and port top/roof. Pivoted to a lower position obviously the roof slope would decrease as would the proximity to the cylinder wall.I'll get back to this further on.


One could even retrofit a conventional existing cylinder to test out various mounting methods.Just make the comma, grind out a recess in the transfer port roof, figure a way to have it rotate around a pin and then on to actuation.This may actually do some good to the power characteristics of a conventional engine. Maybe even a lot of good.


What also is abundantly clear is that there is stuff all room between the floor of the exhaust and the roof of the transfers... Still, I have the feeling that right now there are lots of dudes on the case at present.I enjoy that same feeling. I love brainstorming with you guys!


With my ring-sleeve, if you make it move up and down, you only need two pushrods, one on either side, ganged together outside the cylinder.
And although your comma-valves are not "in" a high temp environment, they are very close to one, could pick up a lot of heat, could transfer that heat to the intake charge.
Without the moveable part that metal would be in direct contact with that same exhaust floor....so it should be actually be cooler than originally.That's right. The temperature of the original transfer roofs would be like that of the A-transfer roofs in a conventional cylinder with auxiliary exhausts.
Keeping the roofs cooler will improve cylinder filling and deto resistance.


have a look at the bucket foundry posts there you will see the cases for the sleeve engine as of yesterday. I'm hoping by the end of today to have them ready to cast. These same cases will also have the FOS / variants fitted and run as well. It has provision for a balance shaft. Flettner = Uniflow, same person.Some person! I wish you would live around the corner instead of around the world. Could you give us a link to those posts Neil? It would save me some time.
It may amuse you guys to know that I've spent more time on this forum than on all other forums put together over the whole year (2015, that is :p ).
While 'm on the subject: best wishes, everybody!



The comma shape can definitely be made. But for my purpose, preventing spent gases from entering the transfer ducts, and functioning as throttles, I see a problem. Because my transfer ducts are tapered towards the cylinder bore, the commas must be tapered too. But because of their swinging motion this means that in certain comma positions gaps will arise between the side walls of the commas and the side walls of the transfer ducts. There will also be gaps between the inward tips of the commas and the cylinder bore. Spent gases entering the volume above the lowered commas can still enter the transfer ducts via these gaps.

What I'm thinking about right now, is something along the lines of the sketch below. On the left you see the current situation; on the right I've added curved yellow 'fingers', bolted to a red ring that can slide up and down. It's all still far from perfect; the red ring gets in the way of the inlet flow, although maybe it can be shortened at the inlet side, and I haven't given its guidance much thought yet either.

[seattle smitty]

C`mon Smitty you come across as a bit aggressive and we actually like having Wob on here. Don't piss on him.

No, no, I was pulling his leg, Dave!! Wobbly, you knew that, right?? Dave, nobody values Wobbly's generosity here more than I do, or needs it more. I'll go back to that post and put in some LOLs and smiley faces (the emoticons weren't working yesterday, for me). Maybe my tone there didn't translate from Merkin to Kiwi.

[husaberg]

Some person! I wish you would live around the corner instead of around the world. Could you give us a link to those posts Neil? It would save me some time.
It may amuse you guys to know that I've spent more time on this forum than on all other forums put together over the whole year (2015, that is :p ).
While 'm on the subject: best wishes, everybody!

.


Sleeve valve crank case patterns. Bit of a half assed way to build them but too bad this is how it's going to be. Note the cavity to house the balance shaft. Gearbox is YZ250.
Not Neil but this is the thread.
http://www.kiwibiker.co.nz/forums/showthread.php/162399-The-Bucket-Foundry/page48?p=1130811501#post1130811501

[peewee]

can any engmod experts give me some advice. on the subsystem screen where it says edit engine, edit exh port, edit transfer port, edit inlet port etc etc, when i try to click on edit exh type and data a box pops up that says 'this exhaust system is meant for a 0 cylinder engine', when i click OK it makes me stay on the subsystem screen and wont let me go the the exh pipe screen. i was going to contact neels about it but figured i would ask here first in case its a simple problem. ive used engmod for other engines and never had this problem.

also when i click exit program to close the whole program another box pops up that says 'error in exhaust sytem file'. ive never even gone to the exhaust file yet on this particular engine. i put in all the general engine data and all the exh port, transfer and inlet port data. i was just now getting around to putting in the exh pipe data but it wont let me get there because the box keeps poping up

[Flettner]

http://twostrokemotocross.com/forum/general-two-stroke-talk/yz-250-efi/

http://twostrokemotocross.com/forum/general-two-stroke-talk/efi-bighorn/msg52196/#msg52196

So that's how it's done? Do these links work?

[wobbly]

Ive never seen a pop up that says you have a 0 cylinder engine - must be a bug ( is it the latest download ).
The code wont allow you to have 0 in the number of cylinders field, so it cant have been saved like that.
Pack it up and send to Neels.

Re selecting carb size - when you have a seriously developed engine the areas of the Ex, Trans, Intake/Carb all converge.
This then makes it easier to decide where to go first with mods to get the STA correct.
Here is a 50cc bucket thats pretty hard out - notice that the areas all are close to each other, and the actual SmartCarb will have a 25mm venturi.
If you go too big on the carb size, it will be a bitch to get transition tuning right, and any sign of mid power under the pipe will disappear -with no real advantage up top.
Look at the KZ2 engines where we are getting 48Hp at the sprocket from a 125 with a 30mm carb.

I havnt had time to really look at your idea Smitty, had a wedding to get done and a heap of work to finish - will take a serious poke around soon.

[husaberg]

http://twostrokemotocross.com/forum/general-two-stroke-talk/yz-250-efi/

http://twostrokemotocross.com/forum/general-two-stroke-talk/efi-bighorn/msg52196/#msg52196

So that's how it's done? Do these links work?

Yes..............
Depending on the set up you have on the forum just copy the address of where you want to link and past it in, or use the button that looks like the globe with a cassette tape under it.
Posting an image or video direct from the web is pretty much the same, except you use the button 3 and 4 to the right of it, if you hover your curser over the buttons they tell you what each is for.
You may have to press the go advanced button near the submit button bottom right if all the 3 rows of icons are not visible.
I have attached the how to do attachments photo display. plus the last three are how to do a link. the photos are done the same way but the icon that you use is as I mentioned the one that looks like a palm tree on a background.

Most of Neils pics should be accessible here.
http://www.kiwibiker.co.nz/forums/album.php?albumid=4864

[TZ350]

307425

Making progress towards the magic 28, at least now I know this EFI thing is going to work. Just a lot of careful step by step adjustment of the maps is required. I expect time and patience will see it running very nicely.

307424

Blue is where I was when I thought we were not going to be able to squirt enough fuel to get past 11,500 rpm and I also thought it had a terminal deto problem. Deto turned out to be the piston hitting the head. The Red line is where I am now without any sign of real deto anywhere, even in severe over rev. And if I can get the Blue line back with a bit of adjustment, it should be a good little runner.

If anyone is interested, the specs are:- 250 deg Inlet duration, 128 deg Transfers and 200 Exhaust at 72%.

[mr bucketracer]

307425

Making progress towards the magic 28, at least now I know this EFI thing is going to work. Just a lot of careful step by step adjustment of the maps is required. I expect time and patience will see it running very nicely.

307424

Blue is where I was when I thought we were not going to be able to squirt enough fuel to get past 11,500 rpm and I also thought it had a terminal deto problem. Deto turned out to be the piston hitting the head. The Red line is where I am now without any sign of real deto anywhere, even in severe over rev. And if I can get the Blue line back with a bit of adjustment, it should be a good little runner.

If anyone is interested, the specs are:- 250 deg Inlet duration, 128 deg Transfers and 200 Exhaust at 72%.looking good rob , why has it lost the mid range to gain more topend ?, even though on the track it don't matter

[TZ350]

looking good rob , why has it lost the mid range to gain more topend ?

Lifting the barrel 0.5mm (one extra base gasket) to give it some squish clearance. Seen it before with these engines going from ex opening at 81 atdc to 80 makes quite a difference on the dyno. 80 must be on the steep downward side of the resonance curve for the pipe, so I am starting to lose that long flat torque curve. With some fine tuning I hope to get most of the Blue line back.

[speedpro]

.5mm? How hard was that piston tapping the head?

[mr bucketracer]

Lifting the barrel 0.5mm to give it some squish clearance. Seen it before with these engines going from ex opening at 81 atdc to 80 makes quite a difference on the dyno. 80 must be on the steep downward side of the resonance curve for the pipe. With some fine tuning I hope to get most of the Blue line back.same as my brothers rs125 , thought you may of just machined the head to get the squish , but we put a extra gasket under the rs .made 1.5 more hp but lost the midrange , maybe need to get it back as he did feel it on the track in the uper gears as i recall now , but all good seeing what dose what:niceone:

[Martin1981]

wobbly, strange thing to me with that carb size issue.

48 sprocket hp from a 125 single cylinder engine with only a 30mm carb. that leads me to think that all those 125 mx bikes with their 38 mm carbs are totally wrong. with only about i guess 35 sprocket hp the 38mm carbs are way too big, aren`t they? so why did the factorys do that if you dont need a big carb like this and can have even more low and mid power with a smaller carb? the 35 hp mx bikes should be happy with a 28mm carb easilie!?

but on the other hand several other engines are running such big carb sizes. 50ccm engines with 32mm carbs are not a joke for example. Frits can confirm.

maybe there is a difference between rotary disc valve engines and reed valve engines. can one say that a reeder needs a much smaller carb than the rotary?

happy new year to all!

[peewee]

ill send it off to neels and have him take a look. it lets me go into every subsection except the exh pipe. on the general engine section ive got it saved as 2cylinder so i dont know what the problem could be. 36mm seems right or atleast a good starting point for 190cc per hole so ill probly try the engmod recomendation.

i think maybe why the mx 125 engines use 38mm carb is because they also have a PV to drop the exh roof ? or maybe theyre not concearned much with midrange power

wob you said earlier 190exh didnt sound right. i think i found the problem. i had the front of A transfer slanted forward like many modern cylinders which was reducing the area of the window which made the 190exh STA seem correct. ive since made A full rectangle and that let me raise the exh up to 194 and widen it to 72% and everything matches up fine again. i think this will be a good place to start from anyways. later i can raise it further if need be. grinding it too high right off the bat is probly not a good idea because then how do i lower it again :laugh:

[136kg136ps]

Frits,you mention your FOS transfer ducts taper towards the bore.
Is this to increase velocity in the transfer streams to cope with the higher RPMs made possible with all that transfer and exhaust area?

[F5 Dave]

Carbs are weird shit. On my old 50 I had a 24,26,28 mikuni all flat slide. After faffimg about with jets I was hoping to get a kart track and a long track setup.
28 gave me the best range and peak.
24 almost matched the peak but worse range.
26 worse everywhere

How are you getting on with the SCs Wob? Dirt bike guys have very varied results and pissing around with tapers on needles and concern about wear. Handled one a month or so back. They're pretty heavy.

[TZ350]

.5mm? How hard was that piston tapping the head?

Not sure, could easily turn it over by hand and using solder, measured about 0.6mm over the pin bosses. I wondered at the time about how much the solder would compress the the piston assembly or cock it to one side which would exaggerate the measurement.

Contact must have been only at high rpm, the det sensor would flashed Red at anywhere from 8K to 11k plus depending on fuel and it flashed big time on over rev. There was a clear but very light impression of the squish band on the piston crown.

So dynamically I guess it now has a little less than 0.5mm clearance during over rev.

[F5 Dave]

So there was witness in one area? Best to measure in 4 corners, or you can even take head off and plastercine the solder front to back to answer your question of rock which on a small bore with tight clearances would be less

[speedpro]

So dynamically I guess it now has a little less than 0.5mm clearance during over rev.

And a bit more than that under power, which I would have thought would have been about .4 too much? Will be screwing with the squish velocity, compression, and efficiency. When I set the last motor up which was around 15:1, even .1mm made a huge difference to the compression. The maths is pretty simple.

[TZ350]

So dynamically I guess it now has a little less than 0.5mm clearance during over rev.And a bit more than that under power, which I would have thought would have been about .4 too much? Will be screwing with the squish velocity, compression, and efficiency.

Yes you are right, but it was the easy thing to do, maybe not the right thing to do if your looking for the ultimate setup but this is a donkey motor being used to see if the Ecotrons EFI kit is a workable possibility for a 2T at 13,000rpm and it looks like it is. The real target is the air cooled RGV125.

307480 307481

[wobbly]

Re the 50cc carb deal - yes there are plenty of very hotrod 50 racers using 30mm carbs in Europe.
As far as I am aware they are mostly using Lectrons, the HV version of these has a nice radiused venturi behind the slide and the standard dimensions
of this is 4mm smaller than the exit diameter.
Thus a 30 is actually a 26 venturi at the slide.
This correlates real well with the port areas of those engines that run up past 14,000.
I will be doing the same with the 50 engine in the sim I posted - the SmartCarb is a 30 to match the reed inlet, but the egg shaped venturi is a 25.
The SmartCarbs do work real well, its just that they dont have the well developed range of flat sided needles like Lectron do.
So you do have to datalog the engine and adjust the needle by moving it up/down and rubbing it on a sand stone and measuring with a digital.
I asked them right at the beginning to incorporate a jet adjustable powerjet to fine tune, especially on a twin, but they know everything and ignored me.

[husaberg]

wobbly, strange thing to me with that carb size issue.

48 sprocket hp from a 125 single cylinder engine with only a 30mm carb. that leads me to think that all those 125 mx bikes with their 38 mm carbs are totally wrong. with only about i guess 35 sprocket hp the 38mm carbs are way too big, aren`t they? so why did the factorys do that if you dont need a big carb like this and can have even more low and mid power with a smaller carb? the 35 hp mx bikes should be happy with a 28mm carb easilie!?

but on the other hand several other engines are running such big carb sizes. 50ccm engines with 32mm carbs are not a joke for example. Frits can confirm.

maybe there is a difference between rotary disc valve engines and reed valve engines. can one say that a reeder needs a much smaller carb than the rotary?

happy new year to all!

http://www3.telus.net/MyScoot/Carbmm.JPG

[Martin1981]

Yes Husa, that diagramm looks familar. it is in a dellorto manual i have.

but...... it recommends about a 40mm carb for 40hp. remember wobblys 48 hp kz2 engine with a 30mm carb....

and remember all the mx bikes with their 38mm carbs. and i guess they are nowhere near 48hp.

i am really confused that this was not tested to dead. when i have a lets say 35hp mx engine that will be happy with a lets say 28mm carb and will have an even better low and mid range pull with a smaller carb, why should i use a 38mm? i can not imagine that the factorys are stupid or way behind in development.

on the other hand, the 30mm carb of the 48hp kart engine is meant to be a restriction by the rulemakers. so without that restriction what carb size would one use to achieve max power with the kz2 engine?

i am asking so much because i think that calculating the right carbsize should be possible for guys like frits and wob for example and one of the easier things on a two stroke. if there is anything easy on a two stroke at all, apart of its simple mechanical structure.

from my logical thinking (if it is logical...) i would say that the carb area can not be bigger than the total area of all transfer ports. it even can be way smaller because the tranferports are not completely open all the time. the carb is when on full throttle.

[wobbly]

The 125 KZ2 engines are rule limited by the carb size, the straight line ignition, and no powervalve.
They have to pull hard out of the slowest hairpin corners at around 9000 rpm,and the best configurations make peak Hp at around 13000
and will spin to 15,000 with the drop off slope shallow enough to enable not having to change gear between close corners.
In this case the small carb only really just gets the job done down at 9000 with no advance and no powervalve.
Thus they are a special scenario, with huge development time put in by hundreds of us trying to get the best jet settings/port timings/pipe lengths
etc to operate with the highest peak, and widest powerband within the CIK rule limits.

125 MX engines all have digital ignitions with a proper advance curve, and all have powervalves.
Thus ripping out of dirt corners is made easy with the big 38mm carb matched to the ports for good top end and overev - any more mid from a small carb would simply light up the tyre and loose traction.
The 125 GP engines up over 50 Hp at the sprocket also have digital ignitions and powervalves, so they can utilise 41mm+ carbs to get max peak and overev to 14500.

[husaberg]

Yes Husa, that diagramm looks familar. it is in a dellorto manual i have.

but...... it recommends about a 40mm carb for 40hp. remember wobblys 48 hp kz2 engine with a 30mm carb....

and remember all the mx bikes with their 38mm carbs. and i guess they are nowhere near 48hp.

i am really confused that this was not tested to dead. when i have a lets say 35hp mx engine that will be happy with a lets say 28mm carb and will have an even better low and mid range pull with a smaller carb, why should i use a 38mm? i can not imagine that the factorys are stupid or way behind in development.

on the other hand, the 30mm carb of the 48hp kart engine is meant to be a restriction by the rulemakers. so without that restriction what carb size would one use to achieve max power with the kz2 engine?

i am asking so much because i think that calculating the right carbsize should be possible for guys like frits and wob for example and one of the easier things on a two stroke. if there is anything easy on a two stroke at all, apart of its simple mechanical structure.

from my logical thinking (if it is logical...) i would say that the carb area can not be bigger than the total area of all transfer ports. it even can be way smaller because the tranferports are not completely open all the time. the carb is when on full throttle.
I haven't read your answer but the original question was about the size the size of the carb, while the MX and GP bikes have huge ones compared to your kart the size depends on the rules, the gearbox ratios and the availability of a clutch
A single gear kart runs small carbs to enable them to work with a single gear, An mx bike has 6 ratio and a clutch, as well as the ability to use both in tandem and break traction at will.
Manufacturers spend huge amounts of time getting the big carbs on mx bikes to work over a wide rev range and to carburate cleanly. Maybe have a look through Camerons section on carbs in the sportbike performance handbook.
As do Kart people with restricted carb rules and single speed gearboxs. As always compromises are made and clever dodges are employed to work within a set of rules.
If you want to see whats the real best way to make the most hp look at the 250 superkarts, the carb sizes for the ultimate power answer is there.

[lodgernz]

My rule of thumb for determining appropriate carb size is very simplified, based on the unsubstantiated assumption that the flow speed through a carb should not exceed 30m/s. The flow volume rate in cc/min might be engine cc * RPM. Divide that by the CSA of the carb throat in cm3 and you have the flow speed in cm/min. Reduce that to m/s and you have a possible flow speed.

In reverse, carb throat diam D = SQRT(cc*peak RPM/(450*pi)) mm.
So a 50 at 12000 RPM needs at least 20.6mm throat, and a 91cc motor needs at least 27.8mm.

All this is approximate and subject to argument because the amount ingested by the engine will be dependent not only on its swept volume, but also on its reed/RV efficiency, scavenging efficiency and the effectiveness of the exhaust system and, I'm sure, a number of other factors I haven't considered.

It's just a starting point. Use it if you like.

[ken seeber]

FOS transfer port lowering/restriction thoughts
Possibly living in dreamworld, I thought it’d be neat to incorporate removable covers for the transfer passages. Given the liberty of doing some shitty pencil sketches that don’t have any semblance to accurate scaling, I have come up with the following:
A. General idea of covers. Probably possible for the front and rear passages, but could be a real task for those partially under the exhausts.
B. By using covers, this opens up the scope to be able to realistically manufacture and incorporate a range of valve types. This one is using the roller shutter principle where the valve is a thin spring steel strip (think tape measure) that follows the contour if the side slots
C. Thinking about covers, one would expect that the temps would not be too high that one could not use 3D ABS filament printed covers. However, if they were metal, eg cast aluminium, one might as well incorporate some finning
D. This got me thinking about regular rear exh facing cylinders, KZs being a case in point. I am sure that at any time, the external surfaces of the transfer passages (which are usually exposed in their contoured shape) are running much hotter than ambient. Given this, any form of additional air cooled finning must be beneficial. Note this is not like putting fins on the outside of a water jacket
E. The swing style valve could be incorporated by putting its spindle axis at the cover/cylinder interface. Actually I think this style of valve is not bad as it does provide an insulating layer for those passages under the exhaust passage.
F. Guillotine valve, with the top edge aimed at a level suitable for an appropriate step change in port height. Cover not really necessary for this.
G. Straddling valve
H. Sliding cylinder. In this case the head insert and crankcase are rigidly connected and the cylinder (inc exhaust & cooling) slide up and down. For a 54 stroke 120 rod engine at 190 exhaust and 130 transfers, if the cyl was dropped by 4 mm, these timings would become 173 and 108 respectively. Have no idea if this is enough. Certainly would be a monstrosity from the outside. The cylinder should be independent from any major axial forces.
Pretty much all these completely disobey the KISS principles with no consideration to any linkages & actuation mechanism etc. D is possibly the simplest.
However, there are many questions re what transfer duration reduction would be necessary and would partially blocking/restricting the passage somewhere upstream be also beneficial?
There you go. Back to work tomorrow.

[TZ350]

307490307491307492307493

These are someone elses pictures of a RGV250 cylinder and port maps but I have a couple of these cylinders with three piece valves that I am building a motor with. Plenty of transfer STA straight off and the Exhaust can be modified to have the STA of a RS125's but better, as it will have a progressive power valve setup too.

307489 307494

I want the EFI for this air cooled RGV125 setup. I am hoping for high 30's with the RGV cylinder, larger rotary valve, 34mm Ball Valve inlet and 3L plenum chamber. The straight cut gear is out of a Chinese clone Honda monkey bike engine. It has the same C/C distance as my GP primary drive.

[seattle smitty]

Ken, what's "dreamworld" about that? Does a person have to apologise for thinking out of the box? But I guess I do that, too.

For starters, the idea of putting the "long-turn" or "roof" or whatever term we are using to describe the outside curve of the transfers into a removable cover has been done, and not just on Wobbly's old crossflow kart motors (back a page or two) but on a few loop-scavenged designs, one being the Anzani (back a bunch of pages). As long as block stiffness is maintained, and you can seal the covers, why not? And on the Anzani, the transfer covers weren't serving your purpose of installing timing-valves.

As to your valves (and your sketches are clear enough), I still wonder if the first one would flutter when passing through some harmonic range. The others are interesting, too. Yes, not simple; yes, a problem to actuate; and yes, maybe only doable on four of the six transfers.

I was trying to envision how a carrier with all the intake ports and passages could be done. Seems like a real can of worms, but there are better minds than mine. When Frits was speculating on this, he said he didn't want the exhaust timing tied to the intake timing; he just wanted to change the latter.

[peewee]

FOS transfer port lowering/restriction thoughts

E. The swing style valve could be incorporated by putting its spindle axis at the cover/cylinder interface. Actually I think this style of valve is not bad as it does provide an insulating layer for those passages under the exhaust passage.
F.


i had a idea like the swing valve with spindle, then maybe a electric motor to turn the spindle but im not sure what kind of cdi box would send the message to the electric motor, or how would you program it. what got me thinking about it was the ktm exh valve which just swings up and down on a spindle. even some of the hondas are simple swing valves as well. i didnt put much thought into it so i really didnt get as far as how to install the valves but a removable cover like you have would probly work

[Flettner]

FOS transfer port lowering/restriction thoughts
Possibly living in dreamworld, I thought it’d be neat to incorporate removable covers for the transfer passages. Given the liberty of doing some shitty pencil sketches that don’t have any semblance to accurate scaling, I have come up with the following:
A. General idea of covers. Probably possible for the front and rear passages, but could be a real task for those partially under the exhausts.
B. By using covers, this opens up the scope to be able to realistically manufacture and incorporate a range of valve types. This one is using the roller shutter principle where the valve is a thin spring steel strip (think tape measure) that follows the contour if the side slots
C. Thinking about covers, one would expect that the temps would not be too high that one could not use 3D ABS filament printed covers. However, if they were metal, eg cast aluminium, one might as well incorporate some finning
D. This got me thinking about regular rear exh facing cylinders, KZs being a case in point. I am sure that at any time, the external surfaces of the transfer passages (which are usually exposed in their contoured shape) are running much hotter than ambient. Given this, any form of additional air cooled finning must be beneficial. Note this is not like putting fins on the outside of a water jacket
E. The swing style valve could be incorporated by putting its spindle axis at the cover/cylinder interface. Actually I think this style of valve is not bad as it does provide an insulating layer for those passages under the exhaust passage.
F. Guillotine valve, with the top edge aimed at a level suitable for an appropriate step change in port height. Cover not really necessary for this.
G. Straddling valve
H. Sliding cylinder. In this case the head insert and crankcase are rigidly connected and the cylinder (inc exhaust & cooling) slide up and down. For a 54 stroke 120 rod engine at 190 exhaust and 130 transfers, if the cyl was dropped by 4 mm, these timings would become 173 and 108 respectively. Have no idea if this is enough. Certainly would be a monstrosity from the outside. The cylinder should be independent from any major axial forces.
Pretty much all these completely disobey the KISS principles with no consideration to any linkages & actuation mechanism etc. D is possibly the simplest.
However, there are many questions re what transfer duration reduction would be necessary and would partially blocking/restricting the passage somewhere upstream be also beneficial?
There you go. Back to work tomorrow.

Ken, yes D is what I had in mind but the floors of the transfers would be fixed so that as the cylinder came down the transfers nozzled untill eventully there is no transfer passages at all or a combination of both movements. But the exhaust! Well thats another can to open

[Yow Ling]

307490307491307492307493

These are someone elses pictures of a RGV250 cylinder and port maps but I have a couple of these cylinders with three piece valves that I am building a motor with. Plenty of transfer STA straight off and the Exhaust can be modified to have the STA of a RS125's but better, as it will have a progressive power valve setup too.

307489 307494

I want the EFI for this air cooled RGV125 setup. I am hoping for high 30's with the RGV cylinder, larger rotary valve, 34mm Ball Valve inlet and 3L plenum chamber. The straight cut gear is out of a Chinese clone Honda monkey bike engine. It has the same C/C distance as my GP primary drive.

For a true "carburetion equivelent" of 24mm surley you would need to take into account that the carburettor does not supply a constant flow of air or air fuel mixture . if say the valve timing was 180 degrees then the restrictor feeding the plenum should be 180/360 x 24mm aprox 17mm, this would allow the throttlebody to flow a similar amount of air as a 24mm carburettor set up.

[lodgernz]

For a true "carburetion equivelent" of 24mm surley you would need to take into account that the carburettor does not supply a constant flow of air or air fuel mixture . if say the valve timing was 180 degrees then the restrictor feeding the plenum should be 180/360 x 24mm aprox 17mm, this would allow the throttlebody to flow a similar amount of air as a 24mm carburettor set up.

Then surely the same must apply to a normal carb arrangement.
Since the carb does not flow all the time perhaps 17mm should be the standard for 125 air cooled?

[Yow Ling]

Then surely the same must apply to a normal carb arrangement.
Since the carb does not flow all the time perhaps 17mm should be the standard for 125 air cooled?

no it would only apply to the plenum arrangment as the plenum refills continuously from the 24mm restrictor and then feeds intermittently into the engine via the 38mm throttle valve fited to the disk valve in this case, in a standard carburetted engine the feed is intermittent through a 24mm carb

[Grumph]

For a true "carburetion equivelent" of 24mm surley you would need to take into account that the carburettor does not supply a constant flow of air or air fuel mixture . if say the valve timing was 180 degrees then the restrictor feeding the plenum should be 180/360 x 24mm aprox 17mm, this would allow the throttlebody to flow a similar amount of air as a 24mm carburettor set up.

that ship's sailed mike - too many precedents in motorsport where a plenum intake has been taken as the inlet limiting factor...If it works and he comes within your reach, you could always try a protest. good luck.

[TZ350]

For a true "carburetion equivalent" of 24mm surely you would need to take into account that the carburettor does not supply a constant flow of air or air fuel mixture . if say the valve timing was 180 degrees then the restrictor feeding the plenum should be 180/360 x 24mm aprox 17mm, this would allow the throttlebody to flow a similar amount of air as a 24mm carburettor set up.

Makes sense, fortunately its not the way the rules are written or the rest of the racing world handles it.

307545

The Bucket rules require that 125 2T engine is air cooled and sucks its air through a 24mm carb or equivalent.

Now the 24mm flatslide Keihin with its slide acting as the choke looks pretty much like an equivalent to a 24mm carb to me.

307546

No throttle body in the plenum, just a big 24/7 hole, (might need to think about protesting the 24/7 concept too).

307547

Injectors are in the back of the cylinder.

Plenums ... 24/7 .... EFI .... Copper heat sinks and Studying the Science of 2T tuning, surely all this cleverness can't be in the spirit of Bucket racing.... :laugh:

[TZ350]

Page 180 links list to go here ....

[TZ350]

307542

27.6hp - getting close with EFI to the best ever achieved with a carb on this cylinder.

307543

Blue line is where we started, Red line is where we are now. The big issue is getting back on the gas and running to rich below 8,000 rpm. Anyway its coming right bit by bit.

[husaberg]

307542

27.6hp - getting close with EFI to the best ever achieved with a carb on this cylinder.

307543

Blue line is where we started, Red line is where we are now. The big issue is getting back on the gas and running to rich below 8,000 rpm. Anyway its coming right bit by bit.

Neat, so the smoothing spreadsheet worked?
Is the Ecotrons capable to stop it injecting to much fuel when the throttle is closed......?

[TZ350]

Is the Ecotrons capable to stop it injecting to much fuel when the throttle is closed......?

Yes, fully map-able ... and it seems the little injectors Ecotrons supplies are good for at least 13,000 rpm in a 2T.

[Muciek]

Maybe it's time to use ATAC now to get rid of that torque dip at around 7000?


KTM FRR cylinder pictures off Pitlane ( http://www.pit-lane.biz/t118p20-gp125-caracteristiques-ktm-frr )

http://imgur.com/a/JNQy1/all . Someone with higher rank could upload them to KB I can do only 6 per post. :(

[breezy]

Preventing spent gases from entering the transfers is the main purpose. That will only work if the blowdown phase is lengthened, so the transfers must be lowered. Smitty, I am trying to picture your proposal in my mind, but I have a hard time doing that without a drawing.

I'll get back to this further on.

This may actually do some good to the power characteristics of a conventional engine. Maybe even a lot of good.

I enjoy that same feeling. I love brainstorming with you guys!

That's right. The temperature of the original transfer roofs would be like that of the A-transfer roofs in a conventional cylinder with auxiliary exhausts.
Keeping the roofs cooler will improve cylinder filling and deto resistance.

Some person! I wish you would live around the corner instead of around the world. Could you give us a link to those posts Neil? It would save me some time.
It may amuse you guys to know that I've spent more time on this forum than on all other forums put together over the whole year (2015, that is :p ).
While 'm on the subject: best wishes, everybody!



The comma shape can definitely be made. But for my purpose, preventing spent gases from entering the transfer ducts, and functioning as throttles, I see a problem. Because my transfer ducts are tapered towards the cylinder bore, the commas must be tapered too. But because of their swinging motion this means that in certain comma positions gaps will arise between the side walls of the commas and the side walls of the transfer ducts. There will also be gaps between the inward tips of the commas and the cylinder bore. Spent gases entering the volume above the lowered commas can still enter the transfer ducts via these gaps.

What I'm thinking about right now, is something along the lines of the sketch below. On the left you see the current situation; on the right I've added curved yellow 'fingers', bolted to a red ring that can slide up and down. It's all still far from perfect; the red ring gets in the way of the inlet flow, although maybe it can be shortened at the inlet side, and I haven't given its guidance much thought yet either.

How about the area above the finger, would that not fill with spent gases?

[Frits Overmars]

Frits, you mention your FOS transfer ducts taper towards the bore. Is this to increase velocity in the transfer streams to cope with the higher RPMs made possible with all that transfer and exhaust area?No, it's to counter the inertia of the mixture columns in the transfer ducts. The local flow velocity anywhere in a duct is inversely proportional to the local cross flow area. Larger areas require lower flow speeds; only the mixture in the final, narrow part of the duct has to be accelerated to the entry flow velocity. This keeps the pressure loss in the ducts down, to the benefit of mass transfer.


My rule of thumb for determining appropriate carb size is very simplified, based on the unsubstantiated assumption that the flow speed through a carb should not exceed 30m/s.
The flow volume rate in cc/min might be engine cc * RPM. Divide that by the CSA of the carb throat in cm3 and you have the flow speed in cm/min. Reduce that to m/s and you have a possible flow speed. In reverse, carb throat diam D = SQRT(cc*peak RPM/(450*pi)) mm30 m/s seems rather conservative; it may stem from your unmentioned assumption that the carb flows constantly instead of only during opening hours.
Apart from that, we seem to use the same rule of thumb. Mine is: D = SQRT(cc * rpm of max power / 900)


FOS transfer port lowering/restriction thoughts:
A. General idea of covers. Probably possible for the front and rear passages, but could be a real task for those partially under the exhausts.Yes, especially as the transfer ducts under the exhausts are surrounded by coolant. I've prepared a ZIP-file that will clarify the complete cylinder layout, but there's still no option to attach anything but pictures here, so I'll mail it to Mental Trousers and ask him to make it available to y'all.


B. By using covers, this opens up the scope to be able to realistically manufacture and incorporate a range of valve types. This one is using the roller shutter principle where the valve is a thin spring steel strip (think tape measure) that follows the contour if the side slots.Shutters and guillotine valves can be either fully retracted or fully down, almost touching the piston. But in all intermediate positions there will be leakage between valve and piston. And contrary to exhaust power valves where the main object is to weaken wrongly-timed exhaust return pulses, my transfer valves not only need to separate blowdown gas and fresh mixture. They also need to control the transfer flow from nearly zero to unrestricted because I want to use them as throttles.


D. This got me thinking about regular rear exh facing cylinders, KZs being a case in point. I am sure that at any time, the external surfaces of the transfer passages (which are usually exposed in their contoured shape) are running much hotter than ambient.Right.


Given this, any form of additional air cooled finning must be beneficial. Note this is not like putting fins on the outside of a water jacket.Right, but putting a water jacket where you wish to put those fins, will be even more effective.


E. The swing style valve could be incorporated by putting its spindle axis at the cover/cylinder interface. Actually I think this style of valve is not bad as it does provide an insulating layer for those passages under the exhaust passage.Right again.


would partially blocking/restricting the passage somewhere upstream be also beneficial?For engine power control: yes (that's what we've got now, much further upstream). For detonation control: no.


... the floors of the transfers would be fixed so that as the cylinder came down the transfers nozzled untill eventully there is no transfer passages at all or a combination of both movements. But the exhaust! Well thats another can to openMoving the cylinder would be about as far-fetched as my idea of varying the stroke while the engine is doing a piston speed of 30 m/s, so I'm not the only one thinking way out of the box.
My sketch from yesterday with those 'fingers' attached to an up-and-down sliding ring looked nice when I drew it. Small detail: the ring will cut all six ribs that hold the sleeve in place. So now I am inclined to the 'comma' approach. It has the added benefit of reducing the axial scavenging angle when less power is required. That's good for reducing the transfer column loop velocity and it's good for piston cooling.


How about the area above the finger, would that not fill with spent gases?Yes. But thas gas won't be able to penetrate any deeper into the transfer ducts.
Incidentally, that's another advantage of the commas: the volume above lowered commas will be much smaller than above lowered fingers.

[Yow Ling]

Makes sense, fortunately its not the way the rules are written or the rest of the racing world handles it.

307545

The Bucket rules require that 125 2T engine is air cooled and sucks its air through a 24mm carb or equivalent.

Now the 24mm flatslide Keihin with its slide acting as the choke looks pretty much like an equivalent to a 24mm carb to me.

307546

No throttle body in the plenum, just a big 24/7 hole, (might need to think about protesting the 24/7 concept too).

307547

Injectors are in the back of the cylinder.

Plenums ... 24/7 .... EFI .... Copper heat sinks and Studying the Science of 2T tuning, surely all this cleverness can't be in the spirit of Bucket racing.... :laugh:

I have no problem with that configuration, it is quite a different system with the ball valve removed

[F5 Dave]

So Rob, now you're close the million dollar question is; have you been able to stop the det where the previous carb couldn't?

Erm that was on over-rev right? I've just had a terrible thought involving clearances at high revs if it was close before?

KTM barrel has that hole below ex. Is that where they situated the closed throttle injector? I thought it was in the bottom end area.

[136kg136ps]

Thanks for the reply Frits,it will be interesting to see how many new "rules"are going to be found when you get some FOS cylinders into circulation.Both regulatory and design.

[TZ350]

So Rob, now you're close the million dollar question is; have you been able to stop the det where the previous carb couldn't?

Past peak power, Yes ..... it looks like it.

[crbbt]

Hi,

My name is Chris. I race 125gp bikes in Australia (was hoping to do NZSBK this year but I haven't saved up enough money) I've been lurking for awhile and really appreciate the information that has shared!

I would like to share my idea for variable transfer port timing.

here is my rough sketch:
307567

Ok, the shaded part is sleeve which would move up an down. this would also vary the exhaust open/close timing.

The few issues I can see with it:
When the sleeve is moved down. The inside wall of the transfer port would end up below the piston crown.
Also when the sleeve is moved down. This creates a cavity above the where the transfer were and the water jacket. So Im guessing only a single port exhaust could be used.
OR
If a triple port exhaust was used, this could double as a resonant chamber. Which would create other issues.

I'm slowly making a 3d model to 3d print. The cheapest and quickest way (for me) would be to adapt it to my Honda. I doubt I would get that far as life has other priorities.

Thanks for your time!

[F5 Dave]

Hi Chris thanks for joining the party.
Sketch looks good as a 2D section, but unless I'm missing something (usually the case) on a round bore what works for ring support and bore parallelity (a new word) integrity?

[crbbt]

parallelity - concentric? The cylinder head would basically look a "T" and the top of the sleeve locate and have to seal around that.

the cylinder look like similar to an open deck engine block.
http://members.rennlist.com/vilhuer/HPIM5059.jpg
mounted upside down

I'll knock up a quick Cad model as pricture are better - hold your breath

*edit*

307571

Here we go. hopefully that's better

[peewee]

i think kens idea of swing valve is pretty good. seems like frits agrees also :clap:

[husaberg]

Maybe it's time to use ATAC now to get rid of that torque dip at around 7000?


KTM FRR cylinder pictures off Pitlane ( http://www.pit-lane.biz/t118p20-gp125-caracteristiques-ktm-frr )

http://imgur.com/a/JNQy1/all . Someone with higher rank could upload them to KB I can do only 6 per post. :(

They appear to be very Honda like in layout......307587 307589307593 307590307591307592
Then again I understand so were Bartol Yamaha cylinders............

[TZ350]

Maybe it's time to use ATAC now to get rid of that torque dip at around 7000?

Yes it would be a good idea.

[husaberg]

Yes it would be a good idea.

Maybe it's time to use ATAC now to get rid of that torque dip at around 7000?


:(

:2thumbsup

Where is lozza

[Frits Overmars]

When the sleeve is moved down. The inside wall of the transfer port would end up below the piston crown.Hi Chris, glad to have you thinking along.
Having the transfer floors flush with the piston crown in BDC is very important for power. But one of the purposes of lowering the transfers is to reduce the power,
so temporarily dropping the transfer floors below BDC is not a problem at all.

There are two reasons for wanting to lower the transfers:

1: Normally the blowdown time.area is such that the cylinder pressure has dropped below the transfer pressure by the time the transfers open. But if the revs are very high, or if the transfer pressure is low because of a partially closed throttle, spent gases will enter the transfers, heat up the fresh mixture and so provoke detonation. Lowering the transfers while leaving the exhaust timing alone will increase the blowdown TA and solve the problem.

2: At revs below the power band the exhaust return pulse arrives back at the cylinder when the transfers are still open. This pulse then pushes the cylinder contents back into the crankcase. That's the cause of the torque hole at 2/3 of maximum torque rpm.
Lower transfers close earlier, so the exhaust return pulse has less opportunity to cause havoc.

In the latter case lower transfers will give more power. This in turn will influence the necessary throttle position. Hence my idea to get rid of the inlet throttling altogether and control the engine power via the transfer height. Not direclty, but via ride-by-wire, because both the engine rpm and the required power have an influence on the optimum transfer timing, so a little help from some electronics may be welcome. My ideal would be a linear relation between throttle and torque.

[F5 Dave]

Ahh from your sketch I'd though you intended to move the top section to close the transfers. See I told you I'd get the wrong idea.

[speedpro]

I'll knock up a quick Cad model as pricture are better - hold your breath

*edit*

307571

Here we go. hopefully that's better

You said something about a concern that your moving sleeve with the transfer ports would end up lowering the exhaust port at the same time the transfers were lowered. If the sleeve was manufactured using CNC machining it could be made say 1mm thick in the exhaust port area. The exhaust port in the sleeve could be made tall enough so that it never protruded into the exhaust passage and therefore never altered the port timing or area. The only drawback would be a slot in the exhaust port roof where the sleeve has risen when on the power and the transfers need to be fully open in the raised position. Being only 1mm as proposed it might not be critical. The trick will be machining the 1mm semicircular slot.

Actually I may have got your drawing wrong. I was thinking the surface the piston runs on is stationary and there was a moveable sleeve which had the transfer ports in which was raised and lowered. A further 2nd thought is the moveable sleeve does not require an exhaust port, or perhaps extending up to the base of the exhaust duct when fully raised, and therefore would not effect exhaust port height or T/A at all.

[senso]

And can you keep the sleeve free to move after it as warmed up?
Or how to maintain a good thermal path to the water jacket?

[Frits Overmars]

I've been doing some sketching based on the comma idea. I can be done, but I haven't yet figured out where to put the actuator linkages. These would get in the way of the coolant passages that don't show up on the sketches, so I'm not done thinking yet.
The lowered yellow comma reduces the transfer timing from 130° to 60°. That is an 80% reduction in area and a 91% reduction in angle.area, which should be good for idling at about 2000 rpm.
The second picture shows how the lowered yellow comma fits nicely between the transfer duct sidewalls and the piston.
The blue comma on the left disappears into the transfer roof when it's completely up, but it will show some leakage at intermediate positions. I think I can live with that.

[Haufen]

There is a lot of area on top of the fingers for the blowdown pressure to act on. Do you think these would withstand a misfire or several?

[Frits Overmars]

There is a lot of area on top of the fingers for the blowdown pressure to act on. Do you think these would withstand a misfire or several?In my sketches the fingers may appear thin, but remember that they are curved in two planes, so they are quite stiff.
The actuators may be spring-loaded so that any unforeseen pressure peaks can push the fingers either up into their recesses, or all the way down, where they can rest on the transfer floors.
Think of it: a misfire in the cylinder, for example because of a faulty ignition, may push the fingers down, so the misfiring will never reach the crankcase.

[Flettner]

Is it just me, am I the only one who can't see the pictures you post Frits.

[mr bucketracer]

Is it just me, am I the only one who can't see the pictures you post Frits.right click and go to open link

[F5 Dave]

Just you Neil.

[F5 Dave]

How about an expanding wax trapped in cavities actuating the commas like a thermostat?

As the engine heats up the performance gets better.

I haven't thought past the first corner, but I'm a big picture type of guy, the rider can surely work out the details.

[Flettner]

right click and go to open link

Thank you, somtimes I just wish I knew how to use a computer properly.

[F5 Dave]

Move to a tablet. I'm still wondering which finger to use to right click:msn-wink:

[Haufen]

In my sketches the fingers may appear thin, but remember that they are curved in two planes, so they are quite stiff.
The actuators may be spring-loaded so that any unforeseen pressure peaks can push the fingers either up into their resesses, or all the way down, where they can rest on the transfer floors.
Think of it: a misfiring in the cylinder, for example because of a faulty ignition, may push the fingers down, so the misfiring will never reach the crankcase.

A friend and I once tried to use that principle to upgrade an old cylinder with an exhaust power valve. Unfortunately, it did not work out. Even the severely reinforced second version was destroyed within minutes. Of course, it took piston no2 and cylinder no2 with it. Fortunately, these cylinders were no special one off high BMEP racing parts but rather cheap and common. As the pressure in our application was about 4 to 5 times that of yours, I think there is a good chance for your fingers to work and last. But as your cylinder is a rare one off, a FEM simulation might be beneficial to get an idea about the safe side and the danger side.

[Lucas M]

Hello Guys (and maybe girls?),

At first, I want to say thank you for this epic thread. I spend the last few weeks reading this topic (short nights :laugh: )
After reading this, there are not really big questions in my mind anymore. So I want to take the chance to show you some stuff out of my two stroke world. I´m 22 and I spend most of my free time with two stroke engines and racing. Here in Germany I take part in a 50ccm racing class. There are some restrictions like original main frame, air cooled and inlet port piston controlled.

At the moment I got 14 rwhp. Not too bad, but I think I know where I can gain maybe 1hp more. Datas are 26,5mm carburetor, bore 38mm stroke 44mm(like original for this engine), no programmable ignition timing, port timings for inlet 170°, transfer all 130° and main exhaust 190°.

There are just 2 questions left. Did someone already a test with filling the exhaust duct floor with a measurable result? This may be a good benefit for my engine. The one made by TZ350 was a little bit confusing?!
If you have a closer look in my diagram, you will see the small hump at the end of powerband. I took an already existing well working exhaust pipe from a scooter and lengthen the first part about 50mm, otherwise it would be too short. Unfortunately I think this wasn’t a good idea, where the small hump in the circle came from. What do you think guys? If I find the time, I will build a new pipe where I will lengthen all parts about the same amount and not only one part.

The other question is especially for Frits. Some earlier you wrote that you are also in a German speaking forum. Is this an open forum and I may can join to read some more stuff? Or did you wrote the most stuff already here?

Greetings, Lucas.

[mr bucketracer]

hi Lucas , thats a nice looking bike you have there , looks like it would go well to ..i like that seat

[136kg136ps]

I can't see any simple solution from the crankcase direction either.

Even with hydraulic or pneumatic direct actuation there would be lines to run not mention temp issues.Casting lines into the cylinder would be a real PITA too.How hard to seal the water jacket penetrations with bushing or grommet type seal,or are they unreachable?I don't imagine the actuator rod being over a mm or 2...more complicated I know.

[TZ350]

Did someone already a test with filling the exhaust duct floor with a measurable result? This may be a good benefit for my engine. The one made by TZ350 was a little bit confusing?!

Hi Lucas, your bike looks great, very professional.

The work on the exhaust port floor and the motor I tried it on was just all thrown together and in the end it proved to be not very suitable for proper long term testing.

But my impression from the initial results of the exhaust port floor experiment is good. And that it is a very beneficial thing to do. I will certainly be looking to use the concept in my future motors, I think there is power to be had there.

[senso]

I have the idea(or misconception) that directly bolting the carburettor to the cylinder will cause fuel frothing(foaming) in the fuel bowl that will tend to wreck havoc with the jetting, but its just a very random and fuzzy idea.

[wobbly]

Lucas - here are some guides that will let you see where to start.
The pipe lengths should be around 32% from piston to header end, and 66% from piston to diffuser end.
Having 50mm added to the header will for sure make the lengths all wrong.
The cylinder duct exit should be 75% of the total effective Ex port area, and the header start should be 100%, with an oval duct ( plus ears )
to promote Aux blowdown flow - with a smooth transition in the spigot from oval to round.
The rear wall of the Aux Ex is way too shallow, the exit radial angle should be to bore centre, with a pocket turn into the duct.
There is going to be a blowdown mismatch in the STA numbers at 190/130 , can you widen the B port without getting into the ring pins.
Also I can see that the B port is angled up sharply, this needs the roof ground flatter to say 10*, then epoxy the A port roof to 25*.
With no powervalve you should have the A port highest, then staggered down to B and C like a Honda RS.
Can you fit a programmable.
Having a 50cc make peak at 11500 means the pipe and ports are not matched, to use the rev potential of the little engines stroke.

[136kg136ps]

Lucas,starting at the beginning of this thread helped me to see how all the pieces come together,starting around page 250 Wobbly starts giving very detailed guides to inlet,port,timing and exhaust parameters.When Frits joined the party it became even more in depth and as people have joined in this has become the best 2 stroke build thread anywhere.I tried to cut and paste our esteemed teachers words only and it just doesn't give enough context.I would suggest starting early on and see if your questions have been addressed already not just by Frits and Wobbly but all the others who post their results using this new information.We are getting a free education.

Getting a direct answer is not nearly as good as understanding why that answer is correct.Welcome.

[Grumph]

At some point someone should sort and edit this thread into subsections - eg, Aprilia RSA, TZee's work, direct questions and answers from Wob..Where did I go wrong,Theoretical speculation...Just some of the sections it could use.
There would be a demand for it either in hard copy or on disc i'm sure. The search function is too limiting to leave it as is, even with Tzee's very useful 10 page summaries.

As has alredy been said, it's an education in current state of the art 2 stroke tuning....

[F5 Dave]

I'm just surprised you can get 14hp at just 11500, that's an achievement in itself.

[peewee]

could any of you experienced alloy welders offer some advice and let me know if its a good idea . what im thinking here is get a piece of solid round bar (copper, brass or something else ?) and basically use it as a plug so i can weld over the top of it and make the aux tunell . then pull the plug out and finish grinding the fine details of the tunell. i havent a clue about welding but i have 3 junk cylinders to practice on. was thinking to use a spool gun ( 4043 wire ??) since that might be easiest welding method for a novice. i meen how hard can it be to blob some weld on there :laugh:. . aint like it has to look real good.

i have some alloy pipe on the way. i can cut in half horizontally for the outer bubble of the aux tunell and weld it in place

[Flettner]

could any of you experienced alloy welders offer some advice and let me know if its a good idea . what im thinking here is get a piece of solid round bar (copper, brass or something else ?) and basically use it as a plug so i can weld over the top of it and make the aux tunell . then pull the plug out and finish grinding the fine details of the tunell. i havent a clue about welding but i have 3 junk cylinders to practice on. was thinking to use a spool gun ( 4043 wire ??) since that might be easiest welding method for a novice. i meen how hard can it be to blob some weld on there :laugh:. . aint like it has to look real good.

i have some alloy pipe on the way. i can cut in half horizontally for the outer bubble of the aux tunell and weld it in place

Out of interest in the past I've used CO2 core sand ( for casting ) to stuff up inside a trasfer port that did not cast properly ( a short ), set the sand, scrape it down to the depth required then weld over it. The result is a bit like casting alloy over the sand anyway, finish is the same as a casting would be. After welding the sand will be broken out of the port like normal.
May be of some use?

[wobbly]

Spool welding alloy is a real art in itself, alot harder than tig - I have been playing with using alloy repair stick welding to get inside Ex ducts.
So far it seems to work real well as the sticks are only 3mm diameter.
By holding the work at an angle so the flux runs away from the pool you can build up very easily but it needs
alot of heat and moving quickly to keep the weld free of porosity.
Having said that it is easy to grind the built up area, and if there is a hole, its just as easy to zap a blob over the top of it.

Re the 50cc power - Turning 14 RWHP into crank add 12% = 16 @ 11500.
BMEP = 12.4 Bar
To use the 50cc short stroke but still keep good powerband width, move the same BMEP up to 13500 and you get 18.7 crank Hp.
Nothing hard about doing that if all the STA numbers and components add up with some synergy.

[peewee]

I have been playing with using alloy repair stick welding to get inside Ex ducts.
So far it seems to work real well as the sticks are only 3mm diameter.
.


is that the stuff you use with mapp gas or propane torch, similar to a soldering or brazing methods ? pretty sure thats how millenium welds up exh tunells, atleast thats what it looked like on the ones i seen. http://durafix.com/

flettner i sent a pm so we dont cluster the forum with chitchat about sand :laugh:

[Grumph]

could any of you experienced alloy welders offer some advice and let me know if its a good idea . what im thinking here is get a piece of solid round bar (copper, brass or something else ?) and basically use it as a plug so i can weld over the top of it and make the aux tunell . then pull the plug out and finish grinding the fine details of the tunell. i havent a clue about welding but i have 3 junk cylinders to practice on. was thinking to use a spool gun ( 4043 wire ??) since that might be easiest welding method for a novice. i meen how hard can it be to blob some weld on there :laugh:. . aint like it has to look real good.

i have some alloy pipe on the way. i can cut in half horizontally for the outer bubble of the aux tunell and weld it in place

I have a friend who is an exceptional TIG welder who I've watched build up a broken threaded boss by inserting an ordinary steel bolt of the right size and building the boss up again around it. No helicoil or tapping needed...
For your purpose, withdrawing your shape pattern means that flettner's core sand may well be easier.

[peewee]

at my work we weld against carbon blocks and copper plates. this is with some kind of steel MIG wire for rail tracks. ive never heard of welding over or against sand. how does it work ?

is core sand just silica sand mixed with clay ?

[wobbly]

The rods are just normal coated stick welding type for easy repairs in the field like alloy boats etc.
Sold in NZ by Weldwell.
They should be available anywhere.

[TZ350]

307710

The EFI is touching 28, but its still very reluctant to come back on the throttle after rolling off.

It will be a pig to ride so I guess I will take my laptop to Tammers and the weekend for me will be all about starting off the back of the grid and adjusting the EFI map to try and get the Beast track ride-able.

I am looking forward to it as I might have more luck getting it right by riding it than trying to tune its low to mid range on the dyno. Anyway the weekend away camping with every one else will be fun and the local RSA does a real great Saturday night dinner ..... Yum ... :p

[Frits Overmars]

Frits... you wrote that you are also in a German speaking forum. Is this an open forum and I maybe can join to read some more stuff?That German forum might be just the thing for you, Lucas, because it mainly concentrates on your machine brand: Simson.
It's not an open forum, but what you can do is this: the power graph you posted shows a phone number. Dial it and ask for LuKas (:D).
He is one of the forum administrators. If you can convince him that you will be an asset to the forum, he may let you in.

One more thing: on 31 January the annual Tunerbattle takes place in Zwickau. It's a test bench competition for Simson tuners. Lukas can tell you all about it.
And one day before, on friday 30 January, many members of this german forum will meet in Zwickau and get drunk talk two-stroke. I'll probably be there too.
Maybe you can gate-crash :whistle:. In fact I'm sure you can, because none of us knows all members by face. Just drop in. But don't tell them I told you.

[Frits Overmars]

:violin:307711:violin: I love it.

[Frits Overmars]

The EFI is touching 28, but its still very reluctant to come back on the throttle after rolling off.Maybe it helps if you not only watch how far the throttle is opened, but also the rate at which it is opened.


camping with every one else will be fun and the local RSA does a real great Saturday night dinner We could never persuade an RSA to do that.... What's your secret?

[F5 Dave]

[TE=TZ350;1130814439]307710

The EFI is touching 28, but its still very reluctant to come back on the throttle after rolling off.

It will be a pig to ride so I guess I will take my laptop to Tammers and the weekend for me will be all about starting off the back of the grid and adjusting the EFI map to try and get the Beast track ride-able.

I am looking forward to it as I might have more luck getting it right by riding it than trying to tune its low to mid range on the dyno. Anyway the weekend away camping with every one else will be fun and the local RSA does a real great Saturday night dinner ..... Yum ... :p[/QUOTE]


IlI'll be there with a bike that performs considerably better or considerably worse than last year, either my lap record falls or it stays. But the Thai place is best.

[TZ350]

We could never persuade an RSA to do that.... What's your secret?

:laugh:


Maybe it helps if you not only watch how far the throttle is opened, but also the rate at which it is opened.

Yes, thanks, now to find that map and give it some gentle adjustment .... :bash: the fun continues.

[jonny quest]

At BDC is it always best to have the floor of the transfer ports the same height of piston crowns edge?

[speedpro]

Evidently.

I've been thinking that a clear unobstructed port would flow more than one partially blocked by the descending /ascending piston. Given that, my thought was to divide the transfer port. The upper portion of the port where it enters the cylinder would be completely unobscured for whatever time the piston was fully below it's lower edge. Against that would be the reduced flow from the lower portion due to inertia and being, % wise, obstructed for a greater time impeding flow. It could end up with a well shaped and directed column in the cylinder as another benefit as the incoming stream through the upper portion of the port would not have the side of the piston interfering with the flow direction.

Given that we have been discussing variable height transfers, and one way of going about that is to remove the outer portion of the transfer duct and then fit a machined outer shell with the mechanism fitted, it wouldn't be too hard to fit a thin divider at the same time, maybe. With a divided port you may simply be able to block off the upper portion when desired though that doesn't achieve engine throttling. It would increase blowdown when desired.

[190mech]

Yes,the transfer flow across the top of the piston greatly helps piston cooling..

[peewee]

i cant think of one good reason to have the piston poking up above the transfer floors at bdc. i thought about this alittle and the piston top will create a ledge for most of the transfer period but at bdc the piston will be completely out of the way for a brief moment. if the piston top edge doesnt sit flush with the floors youll always have a ledge through the full transfer period which doesnt seem like a good idea

[TZ350]

the weekend away camping with every one else will be fun and the local RSA does a real great Saturday night dinner ..... Yum ... :p But the Thai place is best.

It could be Thai ..... so many great places to Eat and so few Saturday nights ..... :facepalm:

[F5 Dave]

Its slim pickings in Taumarunui now the cafe at the end is gone.

[jonny quest]

I swear I remember reading a post by Jan or Frits in the Aprilia Pit Lane thread commenting that having piston below transfer floors was best for power, i just can't find it anymore.

[peewee]

i dont recall them saying its good to have the piston below trans floors but i remember jan saying he saw good results by raising the exh floor. possibly thats what your thinking of

[F5 Dave]

And that having a step in the transfer floor (too low) was bad and a gap (floor too high) was bad for piston cooling.

[Frits Overmars]

it wouldn't be too hard to fit a thin divider, maybe. With a divided port you may simply be able to block off the upper portion when desired though that doesn't achieve engine throttling. It would increase blowdown when desired.Like you say, it's no good for throttling, so at the moment it's no good for me. But apart from that, putting a curved divider in a curved duct may well improve the flow.
Because of inertia, gas flow through a curve concentrates against the outer wall; the pressure at the outer wall is higher than at the inner wall. This pressure difference causes cross flow turbulence, therefore flow resistance. This resistance is proportional to the ratio between the outer radius and the inner radius of a curve
(this is one of the reasons for wanting the largest possible inner radius in a transfer duct).

Let's look at an example: a curved duct with an outer radius of 30 mm and an inner radius of 10 mm. The radius ratio is 30/10 = 3.
Now we put a curved divider with a radius of 20 mm in the middle of that bend, so we will effectively have two curved ducts laying one on top of the other.
The radius ratio of the outer duct is 30/20 = 1.5 and the radius ratio of the inner duct is 20/10 = 2. Both have become less turbulent than the original single duct;
it more than outweighs the small loss of cross flow area caused by the divider's thickness and the wall friction which has about doubled, but which is small compared to the turbulent losses anyway.

Now you may wonder why we don't put even more than one divider in a curved duct. Well, we do, sometimes. Take a look at the airconditioning ducting in large buildings. From the outside you hardly see any curves; you see square angles. But inside there are series of curved dividers: less flow resistance, less need for power-guzzling fans and less turbulence-induced noise.
Now all you need to do is put curved steel dividers in the sand cores of the transfer ducts before you cast your cylinder :D.