ESE's works engine tuner

[jacobson_se]

Jan did you see any improvments in laptimes with the light pistons?

[F5 Dave]

Did the finance team see an improvement of the lapdancers with an 80% margin? That's fleecing it.

[jamathi]

Jan did you see any improvments in laptimes with the light pistons?

We never tested this difference on a track (as far as I know)
On the dyno there was no difference at all..
I do not see a very light piston as an advantage.
Except vibrations of course!
The difference was 20 grams if I remember well.
The 'light' piston lost power after some 5 dyno runs.
The 'heavy' piston still gave the same power after 30 dyno runs.
And a cast piston was better than a forged one.
But there was no big difference, maybe only 0,2HP

[Muhr]

In both 3D and 2D the walls were modeled as no-slip, but for 2D I made the walls adiabatic. This was all steady state, so that's a known difference from reality.

Hi something that came to my mind. What model do you use for turbulence

https://www.simscale.com/projects/mu...radie-stinger/


An interesting thing is that carbon dioxide has a speed of sound at 267 ms at 20c. do not know if it is right to use it but air also feels wrong.

300 g exhaust gases. The composition is:
180 g of carbon dioxide
70 g water vapor
50 g of other substances (= 36.0 g of carbon monoxide, 9.5 g of hydrocarbon, 3.0 g of nitrogen oxide, 0.25 g of sulfur dioxide, 0.25 g of soot, 0.001 g of lead, 0.0006 g of aldehydes, 0.00025 g organic acids, 0.00025 g ammonia, small amounts of bensopyren.

[OopsClunkThud]

Hi something that came to my mind. What model do you use for turbulence

https://www.simscale.com/projects/mu...radie-stinger/

I'm using SST in both the 3D and 2D. I used air as the fluid, that's another refinement I need to make.

Here's a link to the simscale 3D: https://www.simscale.com/projects/Oo...junction_flow/
I set the walls as no-slip, constant temp, and matched the cylinder, piston crown, exhaust header... to the values in engmod
The input pressure and temp were matched to the engmod at the respective crank positions as well.

In the 2D I'm trying to configure things as close as I can to the 3D (SU2 is not as intuitive as simscale)

[Muhr]

I'm using SST in both the 3D and 2D. I used air as the fluid, that's another refinement I need to make.Here's a link to the simscale 3D: https://www.simscale.com/projects/Oo...junction_flow/
I set the walls as no-slip, constant temp, and matched the cylinder, piston crown, exhaust header... to the values in engmod
The input pressure and temp were matched to the engmod at the respective crank positions as well.

Nice! I chose to put a reduction instead of a back pressure and that I have a lower temp (it behaves a little strange when you only have one medium).

Here is a simulation with an end time of 0.0002 s

[ceci]

Sorry, I am very insistent but I think that here there are possibilities that the performance of the 2S engine will be improved

[lohring]

The NACA reviewed a very large number of two stroke designs. I don't think they missed many possibilities in the pre tuned pipe era.

Lohring Miller

[ceci]

The NACA reviewed a very large number of two stroke designs. I don't think they missed many possibilities in the pre tuned pipe era.

Lohring Miller

CROSSFEED SCAVENGING FOR MULTI-CYLINDER TWO CYCLE ENGINES
Does this work (I don't mean the US3289656A patent, if not the concept), I don't know, so far only the testimony of wobbly makes me think so.
For this to work of course you need a tuned pipe

[andreas]

CROSSFEED SCAVENGING FOR MULTI-CYLINDER TWO CYCLE ENGINES
Does this work (I don't mean the US3289656A patent, if not the concept), I don't know, so far only the testimony of wobbly makes me think so.
For this to work of course you need a tuned pipe

I didn't read the patent through, but is it not about delaying the charge, with a cylinder that is 90* behind? I don't see the resemblance to Wobblys sea doo.

[ceci]

I didn't read the patent through, but is it not about delaying the charge, with a cylinder that is 90* behind? I don't see the resemblance to Wobblys sea doo.

The video is the same as wobbly, with the difference that express conduits are used for it (wobbly uses the exhaust pipe itself).
Advantages, because you can incorporate some type of mechanism as a valve that controls and closes when the engine needs it.
Where do you think the Wobbly sea doo engine crankcase would have the lowest pressure be it, before TDC, at TDC or after TDC?

[andreas]

That video, you made it? I'm not sure what you mean. The sea doo engine has a y-pipe I think, the lowest pressure would vary in respect to crank angle, and why it made more power is not really cuncluded either, if I follow.

[ceci]

That video, you made it? I'm not sure what you mean. The sea doo engine has a y-pipe I think, the lowest pressure would vary in respect to crank angle, and why it made more power is not really cuncluded either, if I follow.

If you mean the video of the 3D figures, if I did it, if what you mean if I have done something like that with a real engine, NO, doing it is not within my reach.
The bottom line is: can cross feed work on engine twins?

[andreas]

At least I can't think of any reason why it would be benficial.

[ceci]

And adding to the effect of having very high exhaust duration you can cut the skirts short such that the port is open a few mm when the piston is at TDC.
Wreaks havoc with the jetting , but in the project i tried that we were using big pumper carbs.
Very easy to adjust the fuel curve as was needed - but I doubt a normal carb could be made to work.
This setup on a " stock " 950 SeaDoo gave an added 8 Hp in about 80 , so 10% - enough for the title at Havasu.
On a 1180 twin race motor the bump was 15 Hp in 120 so a little less.

That fact intrigues me, filling (supercharging) supplement volume charge for the exhaust why it happens.
How to get that little supplement volume of cargo to the exhaust:
The depression of the main exhaust creates a venturi effect and attracts it
the inertia of the incoming mixture forces it out through this small slot.
Which of the two causes can it be?

I believe it's the split suction wave from the single diffuser that find it's way into the tdc side crank case. Or it's explained on previous pages.

Can you give both at the same time?