ESE's works engine tuner

[wobbly]

TM KZ engine with 0.82 squish will kiss the head at 15500 , we rev them to 14800 all day.
In this application 0.82 is a little wider than mechanically possible , but any less and i have to retard the spark more to keep the overev, but this ruins the front side power. NFG,
I have just finished doing a rod model in SolidWorks and now have the rod inertia force ( less the combustion pressure ) at TDC
from Thomas Johansson so will do an FEA for the predicted rod stretch tonight.

[Frits Overmars]

TM KZ engine with 0.82 squish will kiss the head at 15500 , we rev them to 14800 all day.
In this application 0.82 is a little wider than mechanically possible , but any less and i have to retard the spark more to keep the overev, but this ruins the front side power. NFG,
I have just finished doing a rod model in SolidWorks and now have the rod inertia force ( less the combustion pressure ) at TDC
from Thomas Johansson so will do an FEA for the predicted rod stretch tonight.

You are punished by the rulebook that won't let you use a variable ignition timing.
Wob, it's too late in the day for me to do the math, but my gut feeling tells me rod stretch is not the main factor in dynamic stretch. I suspect crankshaft bending is the number one culprit.
Yeah I know, I keep telling everybody else that gut feeling should not enter the equasion

[wobbly]

Well said Frits , I have all the nominal bearing clearances , so I can add these to the rod stretch , and see how much extra
dynamic elongation can be attributed to the crank ( big end and small end pin bending I can add into the FEA analysis as well ).

[Wos]

Wobbly and Frits,

Nearby all calculations or simulations 😉...that i am not able to do..


Heard about seeing the touch of piston in builded up coal on piston surface...

Idea is to add /Find to add... a material for surface piston, that keeps footprint of head to measure, evaluate Real gap at highest rev...without doing damages anyway...that we as a non pro could not afford😥

Mayby kind of spray paint...or what ever

Ideas welcome! 😉

Wolfgang

[jamathi]

Tanks Frits,

One of best things in life...are Kisses����... when piston kisses head...slighty an smooth������

If i am right, rsa had 0,7 mm squish!?

This is more than 1%?

Reason?

Dont know the stretch of all involved parts at the yz 125 at 13000 in overrev... 0,7 works...no marks on piston... mayby next 0,65...

The only way to find minimum gap... seens to risk piston kissing head??? ���� ...����

Other ideas???


Tanks meister!

Grüße at all!


Wolfgang

The RSA piston did not touch the head with 0.4 squish.
It gave much more power until 12000, but would not rev whatever we did..

[Wos]

The RSA piston did not touch the head with 0.4 squish.
It gave much more power until 12000, but would not rev whatever we did..

Hey jan!✋👍

Wow 0,4 mm...thats a really strong rod and crank😎😲

Mayby squish has "blown out" spark...?

On the other hand...i am quiet sure you had best available ignition system

Whatever...kongratiolations to your sucesses!! 😉

Grüße Wolfgang

[wobbly]

I am guessing that under full load on the dyno the combustion pressure pushing on the piston would negate the bearing clearances and some of either rod
stretch and or crank flex. I think on the overun into a corner , with no throttle it would be sudden death.

[ken seeber]

Way, way back in those heady Ryger days (2015 = 8 years ago...time flies hey?) I did a calc of the net piston forces.
The main inputs being piston acceleration, its mass and the opposing forces provided by a known cylinder pressure trace.

The attached shows these net forces at various rpms.

Please don't ask me if these are accurate though.


Piston forces at varying rpm2.doc

[husaberg]

i was reading something about a tuned Ducati it went along the lines as when they reset the squish the power went up.. but also the Decibel's went down. I can understand the hp but with the Db's
Is it due to more complete or faster combustion? Do we have a physicist...

[jato]

Time flies alright! re crank flex about 20 years back i did the calcs for a short stroke (64mm) rm250 and (from memory) at 12000 rpm there was something like 11000 N of reciprocating inertia, diluted with 50% balance factor leaving the equivalent of a bit over half a ton of load carried by the main bearings. Ignoring combustion pressure to allow for upshifting and closing the throttle i then set up the rm crank supported by the bearing journals and carefully applied 550 kg to the crank pin... i can't remember the value now but the crank flexed steadily as the load was brought up to what it would see in service - possibly something like 0.2 mm (or more) at the middle of the rotor's taper

[Wos]

I am guessing that under full load on the dyno the combustion pressure pushing on the piston would negate the bearing clearances and some of either rod
stretch and or crank flex. I think on the overun into a corner , with no throttle it would be sudden death.

Longer time in my mind...

The squish gap in a kind of air cushion...the closer the more damping...

And maybe this has influence of the tilt of piston at tdc...

Clarify me if wrong! 😉

Thanks!

Wolfgang

[Frits Overmars]

i was reading something about a tuned Ducati it went along the lines as when they reset the squish the power went up.. but also the Decibel's went down. I can understand the hp but with the Db's. Is it due to more complete or faster combustion? Do we have a physicist...

We do. More effective squish = faster combustion = more time between end of combustion and initial exhaust opening = longer expansion phase = more combustion gas energy used for piston movement = less combustion gas energy left for noise.

[philou]

The RSA piston did not touch the head with 0.4 squish.
It gave much more power until 12000, but would not rev whatever we did..

do you have any idea of the power in millijoules of the ignition of the aprilia?

[jonny quest]

Polini had a variable combustion chamber... when cylinder pressure overcame pressure in cylinder head dome, it moved lowering compression.

I had read Yamaha had tried this as well. Why didn't it catch on?

[husaberg]

We do. More effective squish = faster combustion = more time between end of combustion and initial exhaust opening = longer expansion phase = more combustion gas energy used for piston movement = less combustion gas energy left for noise.

Thanks Frits

Attachment 314930Attachment 314931Attachment 314932

What is this head ... could it be a variable compression head????? Help Please.

Polini had a variable combustion chamber... when cylinder pressure overcame pressure in cylinder head dome, it moved lowering compression.

I had read Yamaha had tried this as well. Why didn't it catch on?

https://www.kiwibiker.co.nz/forums/s...post1130892885