ESE's works engine tuner

[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.



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.



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



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....

[TZ350]

Page 180 links list to go here ....

[TZ350]

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



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]

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



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-gp12...tiques-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 ).
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)) mm

30 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 open

Moving 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.



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.



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



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....

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:


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.

mounted upside down

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

*edit*



Here we go. hopefully that's better