ESE's works engine tuner

[ApolloMotoMoto]

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

Jan

You super sure about that?

It was a MotoGP engine, and the squish gap IS a "tunable feature" of the engine. Are you super confident that everytime the RSA125's rolled off the paddock they did so set to 0.7mm squish gap???

I will repeat that Wayne shared a rather large clue, and if you do the deep dive (husaberg where are you!) this has been discussed probably 10-20 times over the course of this thread; what squish gaps WERE actually used in racing, what was tested on the track but never really "raced" and what was tested on the dyno. I can assure you it was not a static single numer over the entire racing pedigree of the engine.

I can absolutely assure you that no matter how "inadequate" your crankshafts are, they PALE in comparison to what I am playing with.

I build and tune "80cc Motorized Bicycle Engine Kit" engines from such fine makers as Jilin-Zeda Technology Corporation, Runtime Products, and Zong Dong Freight Corportation (not joking).

It is made with Chinese "cough" equivalent to something like SCM440, called CR40.

The videos you see on facebook of the fine manufacturing conditions that you will find in a shop with dirt floors, you can start to understand what I am working with.

I am certainly not running them as they come "out of the box" , and with correct preperation, mostly a good press fit and well trued, I am running my 42mm stroke at 0.30mm squish gap without clipping at 15k RPM's.


I totally understand your hesitation in theory, but in practice your concern is actually unfounded (especially if your piston speed is significantly lower than the RSA), and you are leaving a key piece of the Rosetta Stone un-leveraged because of it.

[Jan Van Hamme]

You super sure about that?
.

No, I'm not sure about that at all. That's just what I read and found in a datasheet.
I also have no idea how a racing engine is tuned when it goes on the track or on the test bench.
There are people with tons of experience and knowledge that far exceed mine, and there are also probably a lot of falsehoods to be found here and there on forums.
It's not easy to always make the right synthesis that would then be the correct one.
At the end of the day, I really value the practical experience and approach of those who have already proven themselves.
After all, the world doesn't revolve around just pressing the run button on a 5-axis CNC machine.

[Niels Abildgaard]

You super sure about that?

I
I can absolutely assure you that no matter how "inadequate" your crankshafts are, they PALE in comparison to what I am playing with.

I build and tune "80cc Motorized Bicycle Engine Kit" engines from such fine makers as Jilin-Zeda Technology Corporation, Runtime Products, and Zong Dong Freight Corportation (not joking).

It is made with Chinese "cough" equivalent to something like SCM440, called CR40.

The videos you see on facebook of the fine manufacturing conditions that you will find in a shop with dirt floors, you can start to understand what I am working with.

I am certainly not running them as they come "out of the box" , and with correct preperation, mostly a good press fit and well trued, I am running my 42mm stroke at 0.30mm squish gap without clipping at 15k RPM's.

Sounds interesting.Have You put pictures somewhere?

[ApolloMotoMoto]

Sounds interesting.Have You put pictures somewhere?

Yea I think I can find a few

[Niels Abildgaard]

Yea I think I can find a few

Very interesting.
How much is each engine ab China and how much modification is allowed in this class?
Can we have a picture of bike with engine?

[wobbly]

Here is my understanding of the issue - mostly from the usual on line conjecture.
Jan stated he had tested the RSA to 14,000 with 0.4mm gap and had no problem.
The engine, as delivered, was at 0,6.
Many team engineers at the track increased that to 0.7 as it was easier to tune and rev'd slightly harder.

Even with a crap crank and bearings, a 57 stroke at 9500 is a million miles away from clipping.
Here are the numbers I have 14:1, on E10 Unleaded, 0.6mm/50% = 40.8m/s , 9500 = 18m/s - safe as hell.

[ApolloMotoMoto]

Very interesting.
How much is each engine ab China and how much modification is allowed in this class?
Can we have a picture of bike with engine?

I'll see what I can dig up...


The "motorized bicycle" engine kits are ~$200 a piece to start with

There are many classes that allow various levels of modification;

There is the ChinaGirl "Series":

ChinaGirl SuperStock class for unmodified engines.

ChinaGirl SuperSport class allowing intake/ exhaust/ head/ ignition modification, by no internal engine mods.

ChinaGirl Superbike class allowing essentially ANY modification a person can dream up within a given displacement limit of 90cc, but it must utilize the stock Chinese cast carnkcases and cylinders (modification of these parts is allowed, just no "custom" cast/CNC crankcases or cylinders).

And, there is the "Formula" Series:

Formula 2 allowing for any SINGLE SPEED/DIRECT DRIVE configuration of air cooled 2-stroke engine design to compete with a displacement limit of 100cc.

Formula 1 allowing for any SINGLE SPEED/DIRECT DRIVE configuration of water or air cooled 2 stroke engine design to compete with a displacement limit of 125cc.

CNC crankcases allowed, ANY cylinder from any source that meets the requirements allowed.

There are NO fuel rules.

As of yet there are no "elecronics restrictions", anything you can dream up through electronic/digital controls is allowed until something shows up that requires regulation.

[Frits Overmars]

Jan stated he had tested the RSA to 14,000 with 0.4mm gap and had no problem.
Many team engineers at the track increased that to 0.7 as it was easier to tune and rev'd slightly harder.

46 years ago I was investigating the lower squish gap limit for the grandfather of the RSA, the Rotax 124. I ran it to 14.000 rpm with 0,4 mm squish gap and had no problem either (a well-set up RSA even revs to 14.500 rpm without problems).
Increasing the squish gap reduces the squish velocity and the combustion speed, raises the EGT and increases overrev, which in some circumstances can make life easier for the rider, even if it costs power. So that is what these team mechanics did.

We may need to define 'crap bearings'. The ball bearings in the Rotax 124 and the roller bearings in the Aprilia RSW and RSA are fine. The Aprilias with their 54,5 mm stroke ran a piston speed of 26,3 m/s at 14.500 rpm with 0,4 mm squish gap without problems.
But when I was searching the squish gap limit for the Rotax 124, I also had a 50cc Kreidler with its typical angular contact crankshaft ball bearings on the dyno.
The Kreidler with its 39,7 mm stroke, a much lighter piston and a piston speed of only 21,2 m/s at 16.000 rpm required a squish gap of at least 0,7 mm because those bearings allowed much more crankshaft flex. Crap bearings? They ran very light but shimming them was a pain and you cannot get away with the squish that roller bearings allow.

[F5 Dave]

Ahh thanks, my Suzuki 50 i set up as 0.5mm. I was running 2 base gasket and all was well. But if I reused the base gaskets twice the piston would tickle the head. 15mm pin from memory. I started running bigger pin and yamaha rod. Never thought to see if a stronger crank assembly could take closer squish.

[Vannik]

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

Seems I am only halfway back, I can get access from work but still not from home. And work has nothing to do with 2T engines so not really good to access from here.

Who do I contact about sorting it out all the way?

[husaberg]

Seems I am only halfway back, I can get access from work but still not from home. And work has nothing to do with 2T engines so not really good to access from here.

Who do I contact about sorting it out all the way?

Ask here.
https://www.kiwibiker.co.nz/forums/s...post1131243035
preferably quote Spankme. (thats not a joke)
https://www.kiwibiker.co.nz/forums/s...post1131243055

[Niels Abildgaard]

I'll see what I can dig up...


The "motorized bicycle" engine kits are ~$200 a piece to start with

There are many classes that allow various levels of modification;

There is the ChinaGirl "Series":

ChinaGirl SuperStock class for unmodified engines.

ChinaGirl SuperSport class allowing intake/ exhaust/ head/ ignition modification, by no internal engine mods.

ChinaGirl Superbike class allowing essentially ANY modification a person can dream up within a given displacement limit of 90cc, but it must utilize the stock Chinese cast carnkcases and cylinders (modification of these parts is allowed, just no "custom" cast/CNC crankcases or cylinders).

And, there is the "Formula" Series:

Formula 2 allowing for any SINGLE SPEED/DIRECT DRIVE configuration of air cooled 2-stroke engine design to compete with a displacement limit of 100cc.

Formula 1 allowing for any SINGLE SPEED/DIRECT DRIVE configuration of water or air cooled 2 stroke engine design to compete with a displacement limit of 125cc.

CNC crankcases allowed, ANY cylinder from any source that meets the requirements allowed.

There are NO fuel rules.

As of yet there are no "elecronics restrictions", anything you can dream up through electronic/digital controls is allowed until something shows up that requires regulation.

Thank You for pictures and explanation.
Sounds lot of fun for reasonable funds.

[F5 Dave]

No. It's obviously totally ridiculous.

Fortunately I like totally ridiculous

[Vannik]

Ask here.
https://www.kiwibiker.co.nz/forums/s...post1131243035
preferably quote Spankme. (thats not a joke)
https://www.kiwibiker.co.nz/forums/s...post1131243055

Thank you, I have done so.