ESE's works engine tuner

[SwePatrick]

It costed just under 900 euros, but one should know that the one I chose to do was considered to be very complicated piece to manufacture because of the many small channels I designed

For one or two cylinders?

If my new cylinder works well i might reverse engineer it and get one casted.

[Matt@TYGA]

So a couple of extra choices here with toroid chamber.

The toroid is pretty severe in an effort to keep the volume as is but bring the plug close to the firing line of the squish.

The first sticks with the dome top piston, whereas the second is essentially the same piston with the top of the dome turned off flat, and the plug lowered.

The volume and squish area of all these designs is identical by the way. Just playing with shapes.

Any thoughts?

The plan is to machine inserts for the VHM head covers and test the theories on the NSR150SP.

Also have an extended and water cooled spigot for the exhaust port to try. The plan wuld be to test the pipe we have, and then have a pipe with a header shorter by the same amount as the spigot is longer, so that the tuned length doesn't change.

All very exciting, just need 25 hours a day, 8 days a week to get it all done.

Anyway, better get on with boring work.

Cheers,

Matt.

[jfn2]

Wobbly:

"but my opinion is that the best piston shape is an angled edge,its width = the squish,then a flat top.
Will be testing that soon" - WOBBLY

In a paper from Pune, India (sae # 931510) they were testing different combustion chambers and also different piston dome shapes and they found that the shape of the dome with the dome angle the same as the squish angle then a small deflector upwards than a flat top to work the best. I tried this on a Yamaha KT100 engine and it seems to work well but I do not have any proof.

[Frits Overmars]

In a paper from Pune, India (sae # 931510) they were testing different combustion chambers and also different piston dome shapes and they found that the shape of the dome with the dome angle the same as the squish angle then a small deflector upwards than a flat top to work the best.

I did not succeed in locating SAE 931510. What was the BMEP of the tested engine?

[Haufen]

Wobbly:

"but my opinion is that the best piston shape is an angled edge,its width = the squish,then a flat top.
Will be testing that soon" - WOBBLY

In a paper from Pune, India (sae # 931510) they were testing different combustion chambers and also different piston dome shapes and they found that the shape of the dome with the dome angle the same as the squish angle then a small deflector upwards than a flat top to work the best. I tried this on a Yamaha KT100 engine and it seems to work well but I do not have any proof.

I did not succeed in locating SAE 931510. What was the BMEP of the tested engine?

and what were the criteria that defined "what works best"

[jfn2]

Frits:
The paper is titled 'Study of the Effect of Combustion Chamber Design on Performance of the Small Two Stroke Gasoline Engine'
Authors were.... Marathe, Chikhalikar, Malekar, Sarveswaran by Bajaj Auto Ltd, Pune, India.
Engine was a 2 stroke s.i. engine forced air cooled used for 2 wheeler (scooter) application
57 x 57mm bore and stroke
145.45 cc
cr= 10:1
22* BTDC (constant at all speeds)
rotary valve
20mm carb

Here are some pages I hope answers most questions.

[Muhr]

For one or two cylinders?

If my new cylinder works well i might reverse engineer it and get one casted.

For one! Of course, it's not the most economical, but the expectation that this will be an optimal cylinder is low. I have CFD the shit out of this cylinder so should give me a lot of data.

[jfn2]

I left out some of the pages because they dealt with emissions. On the last page it says all combustion chambers were tested at the same ignition timing. Conclusions were:
combustion chamber has significant influence on emission, SFC and power output.
Deflector type combustion chamber is found to be the best in respect of emissions, SFC and power output. Faster burning rate is observed with this combustion chamber due to its typical geometry.
Combustion chamber having no squish zone is found to be inferior than all other combustion chambers with squish.
Further work as out lined above will be undertaken to assess the effectiveness of different combustion chambers with respect to emission levels and fuel economy.

[Haufen]

On the last page it says all combustion chambers were tested at the same ignition timing.

Thanks for sharing the paper.

Ouch. That's a bit like comparing the laptimes of three riders on three bikes, then running one in the dry, one in the wet and the last one in the snow and then concluding that the rider who rode in the dry is the fastest by far because he had the fastest bike.

If you want to compare combustion chambers, ignition timing should be adjusted for max torque (MFB50@ ~8deg ATDC) at a fixed A/F ratio. You can then vary e.g. A/F ratio and note when engine knock begins (leaning) or how rich you can get before 4-stroking occurs (richening).

What has been done in this paper is to check which combustion chamber performed best for a given spark timing and carburetor setting. And that is not always the same chamber as when you'd "max out" each chamber. The "winner" might probably have been the same in both cases, but much more and also smaller differences could have been discovered in the mid-field. Did they even write if the bowl on the asymmetric chamber was near the exhaust port or near the boost port? This in itself can already make a considerable difference.

[wobbly]

Yes I agree Haufen.
If I have learned anything,the most significant from dyno work for years now its that Jan told me all his pipe testing was inconclusive as the fueling
wasn't optimized for each change.
I wasnt till the egt was baselined for each new pipe, then changed to produce max power did the real potential of each design emerge.

In that paper I can see that the so called " deflector " setup would help power etc, as the squish action is in fact being directed up at the plug.
But approaching the limit, an offset chamber is a complete waste of time.
This idea was sold to Yamaha by that burgler of the first order Doctor Joe.
It showed up on the TZ250G head, and that would severely detonate before even getting close to the correct jetting.
One side has no MSV, the other side is huge - maybe fine for an outboard , but no free lunch for a race engine.

Matt - the toroid as you have drawn it is exactly as I have used in all manner of race engines with great success.
The latest being the record breaking TZ350 LSR engine. ( PS,get the water closer to the threads ).
But again, as it allows much leaner and or much greater advance to make more reliable power without deto ( every case is different ), simply swapping from a hemi may not produce instant results.
The angle/flat top is exactly what I am soon to test, but not with a toroid as the KZ kart rules include a compression cc measurement thru the plug hole at TDC and this design traps
air at the highest point doing this.

[Haufen]

The angle/flat top is exactly what I am soon to test, but not with a toroid as the KZ kart rules include a compression cc measurement thru the plug hole at TDC and this design traps
air at the highest point doing this.

Just curious, do the kz rules allow only one spark plug hole? and do you have to have an actual spark plug in each of them or can you put an aluminium insert in the "measuring hole" during operation?

Thanks for the pack file. Although I get an error trying to import it on V5.6.9, I can already confirm deviations on the port shape and roof angles of the main transfer ports and deviations on the roof angle of the boost port (at least, and so far). I will see if I can get the sim running and do a re-evaluation on the molds I made before providing any numbers. Looks like there were at least some small changes made after Jan left.

[2T4TSim]

Here is the Aprilia RSA125 Pack file zipped.

Many thanks Wobbly for this RSA file. After the evening to reload it completely in Dat2t , it runs and is much better than what I expected form my Pit-lane readinds...

Regards
Alain

[wobbly]

The tech people use a threaded screw in gauge that has a smaller hole down the middle.
The volume of the smaller hole is the same as the plug threads.
This was introduced as some smartarse ( not me for once ) was running a smaller chamber volume than was allowed, then drilling blind holes at an angle from the threads.
This then measured correctly to the top of the plug hole with a burette , but was a smaller volume within the chamber , with the spark plug installed.

Not that this is really relevant , as in the case of the KZ engines , no one runs the minimum allowable volume, as this completely kills the overev power.
If the gauge wasnt used you could also release the trapped air from a toroid using an angled drilled hole into the highest point.

There is also a semi " stock appearing " rule ( even though I cant find the actual words ) that means the parts of the engine must " look " like those shown in the homologation papers.
Extra holes are not allowed, even though " removing material " is allowed but adding anything isnt.
This is why my attempt to feed cold water into the cylinder by moving the transfer hose to point at the boost port ( with a new threaded hole ) was rejected.

PS Edit - I have version EngMod 5.6.9e, the latest.
Neels put out this update recently and was concerned other versions would not open packs if not up to date.

[jfn2]

On the last page of this paper they said they are extending the experimentation with MBT ignition timing. Also we have to remember this was done in the early 90's with possibly thinking of the 70's.

[TZ350]

Attachment 336537Attachment 336538Attachment 336539Attachment 336536Attachment 336541Attachment 336540

NF4 MC21 Exhaust and Vertical port angles.

Comparison of transfer port angles between a Honda RS125 NF4 and NSR250 MC21 cylinder.