ESE's works engine tuner

[husaberg]

Just sent an email to Neels.

The answer is NO, wtf is going on - how hard can this be.

might i suggest as many users as possible on ask the same question (respectfully) in this thread) worth a crack?https://www.kiwibiker.co.nz/forums/s...post1131243035

[Wos]

WOS, 15* BTDC is an optimum advance number that occurs when the static compression plus the dynamic compression created by the Delivery Ratio and the Trapping Efficiency combine
to reduce the pumping losses of compressing that retained charge, and if it all works together the peak cylinder pressure occurs near 15* ATDC.
If you can get away with more advance then one or both of the compression cycles is sub optimum.
Having to retard the ignition, leads to the opposite conclusion.

Thanks for detailed explanation Wobb!

[Jan Van Hamme]

Deleted post

[husaberg]

Just sent an email to Neels.

KB's top dog has replied for Neels to try now.

[Vannik]

might i suggest as many users as possible on ask the same question (respectfully) in this thread) worth a crack?https://www.kiwibiker.co.nz/forums/s...post1131243035

After more than a month I am back! Wow, talk about serious withdrawal symptoms.

[Jan Van Hamme]

After more than a month I am back! Wow, talk about serious withdrawal symptoms.

Welcome back, Neels. I am delighted to be able to read your contribution once again.


@Wobbly, Mach 0.8 and 51% gives less power when I simulate it. What I have also found is that when Engmod generates a fospipe on my engine, it results in a stinger diameter that causes a Mach of 1.
And that Mach 1 does not cause any detonation in the fos exhaust or in my own exhaust.
I think something is wrong and will send a pack file to you and Neels.

[F5 Dave]

Thanks for making the effort. And for Spank for sorting the issue. It must be hard for amateurs to cope with odd issues.

[Peter1962]

After more than a month I am back! Wow, talk about serious withdrawal symptoms.

Great news ! Welcome back, Vannik.

[wobbly]

JVH, having Mach in the stinger nozzle means that tube is sonic choked. ie it is impossible for more flow to happen - talk to GPT about this.
If its not getting into deto, then that simply means the TubMax is very safely low.
IMHO, with a bigger stinger @ 0.8 Mach ( plus with MSV @ 40m/s ) and way more compression to push the TubMax up near the deto limit , it will make alot more power.
The only question to ask is will the new squish configuration cause piston clipping - I doubt it, as for example Jan has said the RSA didnt hit at 0.4mm/14000 rpm.

I did ask sarcastically " how hard can it be " - what was the actual problem with Neels access here?

[Jan Van Hamme]

JVH, having Mach in the stinger nozzle means that tube is sonic choked. ie it is impossible for more flow to happen - talk to GPT about this.
If its not getting into deto, then that simply means the TubMax is very safely low.
IMHO, with a bigger stinger @ 0.8 Mach ( plus with MSV @ 40m/s ) and way more compression to push the TubMax up near the deto limit , it will make alot more power.
The only question to ask is will the new squish configuration cause piston clipping - I doubt it, as for example Jan has said the RSA didnt hit at 0.4mm/14000 rpm.

I did ask sarcastically " how hard can it be " - what was the actual problem with Neels access here?

Wobbly, Msv 40m/s
Squishband 50%
Compression 12.7
Stinger mach1
Squish 0,65mm
Stroke 57mm
Tubmax 960
Deto @ Tubmax 970
Thanks that you will look at it over the weekend.

[Frits Overmars]

having Mach in the stinger nozzle means that tube is sonic choked. ie it is impossible for more flow to happen...

In sonic choked flow, lowering the pressure downstream of the throat will not increase the flow velocity past Mach 1, and neither will raising the pressure upstream of the throat.
But raising the upstream pressure will increase the gas density and thus the mass flow, even if the throat velocity remains Mach 1.
One more pedantic point: Mach 1 flow in the stinger may not be Mach 1 all of the time. The practical limit of Mach 0,8 may be an average value derived from practical experience and your Mach 0,8 flow guideline may contain instants of Mach 1. But we must proceed with caution there; Mach 1 all of the time will be risky.

[wobbly]

Here is a stinger nozzle Mach trace at peak power.
In this and all the other cases I have simulated if 0.8 Mach is exceeded it means ignition or compression has to be reduced to some unexpectedly low value
as the retained pipe pressure is overly excessive.
The peak velocity is occurring as the main wave descends down the rear cone and enters the stinger - this plot is logged 1/2 way along a 25mm long nozzle.
Subsequent peaks and troughs, are reflections and superpositions off atmosphere, the nozzle entry and the step up to the main stinger tube, I assume.
I do not know if going sonic creates a shock wave at the nozzle entry - maybe Neels can enlighten me/us.

[ApolloMotoMoto]

After more than a month I am back! Wow, talk about serious withdrawal symptoms.

Welcome back, Neels!

[ApolloMotoMoto]

Wobbly, Msv 40m/s
Squishband 50%
Compression 12.7
Stinger mach1
Squish 0,65mm
Stroke 57mm
Tubmax 960
Deto @ Tubmax 970
Thanks that you will look at it over the weekend.

0.65mm squish???

Come on man, what are you afraid of?



0.01 x stroke is nearly guaranteed safe from clipping.

So, going larger than 0.57mm squish is just giving up MSV potential for no good reason at all.

Strong caveat that this number "40m/s MSV" is more of an imperical tuning symbiote that has been discovered over COUNTLESS engine examples...

But, from having attempting this same game myself, you are going to make sacrifices "trying to find" 40 MSV when you fully enforce all of the statoe of the art design guidance as Wobbly has clearly laid out.

Its NOT easy to get there, the CR being high enough to get your TubMax into the "making power" region is limiting the MSV somewhat, higher CR = lower MSV for all other geometries being equal; the compression is "resisting" the acceleration of the squish event.

So, maybe you have been limiting CR to sneak out some extra MSV, but as Wobbly has correctly pointed out, now your TubMax falls into the toilet and your doing weed-eater stuff.

You need to use ALL of your available "squish gap" potential, period. Or you WILL be leaving power on the table.

0.65mm squish with 57mm stroke is just screaming "but WHY though???" to my eye.

The aprilia RSA is ~54mm stroke.

Wayne just gave you the key reference;


"The only question to ask is will the new squish configuration cause piston clipping - I doubt it, as for example Jan has said the RSA didnt hit at 0.4mm/14000 rpm."

54mm stroke and they could safely use 0.4mm up to 14k.

To scale that to your 57mm;

0.4 / 54 = 0.0074 squish gap per mm stroke

57 x 0.0074 = 0.42mm

I suggest you plug 0.42 squish gap in and see how much easier it gets to achieve that 40 MSV with useful compression; and you shouldn't need near 55% SAR to do it

[Jan Van Hamme]

0.65mm squish???

Come on man, what are you afraid of?



0.01 x stroke is nearly guaranteed safe from clipping.

So, going larger than 0.57mm squish is just giving up MSV potential for no good reason at all.

ApolloMotoMoto,
The reason why I thought not to go too small with the squish is the following:


A 125RSA has a squish gap of 0.7mm
It could well be that the crankshaft is made of 15NiCr13.
The bearings in which it rotates are BC1-1442-B cylindrical roller bearings (found in the datasheet by Jan Thiel & Frits Overmars)


My crankshaft is from a Yamaha DT200. (I don't know what material it is made of from the factory).
I have to press the crankshaft apart and back together.
The bearings are ball bearings.
I suspect that the distance between the two bearings (support points) on a DT200 crankshaft is greater than on a 125RSA.


Although the piston speed is much lower in my application than in an RSA, I thought that with much lower crankshaft rigidity, a lower steel alloy, and less stable ball bearings... I should be cautious about the squish distance.
There is someone working behind the scenes for me, for which I am extremely grateful, who has a wealth of experience that could fill an Olympic swimming pool...I have now also heard that it may be less and that there would be no contact between the piston and the head. I am waiting patiently.

Thank you for your insights and help. I am just a private individual, not a competitive rider or anything... but I am a 2-stroke enthusiast at heart.
Jan