ESE's works engine tuner

[Vannik]

Couple of videos of 294cc boxer engine with carburetor and new type of exhaust

EngMod2T has no problem simulating it. It is a 2into1 with funny joint angles.

[jbiplane]

EngMod2T has no problem simulating it. It is a 2into1 with funny joint angles.

Hi Vannik

Can you try to simulate my engine with this king of exhaust and compare with my experimental data?
I can provide any information for this.

[peewee]

But I have never seen a duct in a competition type engine that is too long.
Plenty that are way too short - especially those that have a female header plug in as part of the cylinder.
Having the really good guide of 75% smallest and 100% again at the header makes choosing the areas simple, and they work.
I would be interested to see the result of using both bmep and bore/stroke shortening multipliers in a severely oversquare project.
In the example I did ,the lengths seem quite usable , if the actual cylinder is a bit longer then I doubt it would have much negative effect.

maybe i dont understand your terminology. exh passage is bore face to exh spigot exit , measure through the center ? header is first section of exh pipe that slips over the exh spigot ? and what is the 100% you refering to ?

[wobbly]

Guide for EngMod users collated by Neels.

[Matt@TYGA]

Hi chaps.

Fiddling with some combustion chamber shapes, and will try a few once I've decided on what to try.

Just thought that I'd throw this out there for the blokes that know more than me (which is lots of you).

The pics attached have basically the same volume chamber. The differences being the height of the chamber (also spark position) relative to the top of the piston, and the size of the radius that comes off the squish.

On the left, the rad is tangent to a vertical line drawn. On the right, as you can see, it isn't tangent and the chamber more resembles a hemi than a bathtub.

Both have the same squish clearance (parallel to piston), and same squish area ratio

So given this, what do you guys think would be the difference, and more importantly, why?

Thanks,

Matt.

[Muhr]

For once, I have a little luck, the casting was successful.

Here are some more pictures on the cylinder. finish is okay, took some control measures and the deviation is basically non-existent.
would be fun if someone has 3d printed a cylinder so we can compare.

[dutchpower]

Looks promising Muhr

What about the cost

[Muhr]

Looks promising Muhr

What about the cost

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

[wobbly]

Jan tested both designs on the Aprilia and opted for the bathtub.
I have done direct back to back tests on TM kart engines and the bathtub is ( only slightly ) superior in that application as well.
That engine has a conical piston shape ( the squish angle continues to almost a point ) at 4* so dropping the plug has less effect.
If I was permitted by the regs I would use a toroid and bring the plug down even closer.
The logic I have for this is that if you draw a line parallel to the squish, this will be the direction that the turbulent flow exiting the closing gap will enter the expanding bubble
of burning combustion.
This turbulence is, in effect , creating a situation exactly the same as advancing the ignition - the advancing flame front is sped up by the eddies created thru its volume.
Thus if the center of the bubble ( the spark gap ) is closer to a line exiting the squish, we get the maximum effect of the increase in burn speed.
Dropping the plug even further with a toroid has made more power, and suppressed deto in every case I have used it.
It works best on flat top pistons - 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.

[Matt@TYGA]

Thanks Wobbly.
I'll do another design to drop the plug a bit further and compare. Thankfully I don't have any regulations I need to stick to.
Regarding the EGT sensors you've previously mentioned, do you mind sharing the link again... Or I guess I could search for it. Another question is how to log the EGT vs rpm. I have a dynojet dyno but not sure if it's possible to link up the sensors to log the output. It's a pain trying to watch several things at once and then the EGT is only a guess as I'm not logging it. Logging it independently of the dyno software is also OK. No problem hooking up another lap top if that's what it takes.

Cheers

Matt.

[wobbly]

Exhaust Gas Technologies in USA, clamp on Stinger ( exposed tip - is fastest ) probe with mini K plug is easyest,and are the only commercial egt with a guarantee.
DynoJet is easy to datalog egt,they have a input box specifically for sensors, then you have a readout on screen with warning capability etc.

[Matt@TYGA]

Thanks again Wobbly. I'll get in touch with them.

Should make my life a little easier

[lodgernz]

I would for sure use the 75% and 100% area guidelines.
But try this as a thought process.
The guideline lengths relied on 125cc square engines with really high bmep.
So modify the duct length total of 2X Bore by your actual numbers.
First the bmep.Say yours is 12Bar and the Aprlia is 15Bar,so we have 53X12/15 = 42.4.
Then we have the bore to stroke ratio 42.4 X45/53 = 36
So now assume your effective bore is 36
Times 1.5 = the 75% area position = 54 and the 100% position = 2X36 = 72
So this gives a slip on transition length of only 72-54= 18
Make this 22 long with the smallest CSA at say 50.
Seems reasonable to me,but the real proof is in the mach number at peak power of the 75% CSA = 0.8
Do the lengths come close to achievable ?

But I have never seen a duct in a competition type engine that is too long.
Plenty that are way too short - especially those that have a female header plug in as part of the cylinder.
Having the really good guide of 75% smallest and 100% again at the header makes choosing the areas simple, and they work.
I would be interested to see the result of using both bmep and bore/stroke shortening multipliers in a severely oversquare project.
In the example I did ,the lengths seem quite usable , if the actual cylinder is a bit longer then I doubt it would have much negative effect.

Thanks Wobbly. I'm struggling to get my head around those numbers, but I'll juggle them a bit and see what pops out the end.

[wobbly]

Here is the Aprilia RSA125 Pack file zipped.

[jonny quest]

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

I've had the same thought, and have been meaning to try that.

Tyga, look into YZ125 piston 06-18. And that head shape. I've found that design to work the best.