ESE's works engine tuner

[F5 Dave]

Yet Beta just last year changed their 300 from 72x72 to 73x69.9. Not really much of a change, but why go that way rather than the other?
And they hardly needed to, I have a 21 engine and it is fantastic for purpose.

[wobbly]

Thanks Frits , the disparity in my CCR description never even occurred to me - criticism fully accepted.
The " bigger is better " thing came from the fact I have never ever , had to make a case smaller - its always been longer rods , cylinder spacer plates , pockets around the mains , reed spacers
etc trying to correct a small volume.

[skako]

......
I did, Skako. You can find the axial angle calculations below, and as you'll see, transfer durations do not play a role. But a transfer timing of 144°?
For an engine with only two transfer ports I think it would be best to use the radial angles of the A-ports below and the average of the axial angles of the A-ports and the B-ports.
Attachment 352448

Thank you Frits,
I will try to post a video of the simulations. The simulator simply took me to angles of 144°. I combined different exhaust pipe designs and transfer times. The goal was to achieve greater power and elasticity (wider power range combined with gear ratios).


https://streamable.com/279h89

[Frits Overmars]

The " bigger is better " thing came from the fact I have never ever , had to make a case smaller -
its always been longer rods , cylinder spacer plates , pockets around the mains , reed spacers etc trying to correct a small volume.

Same here .
And it's my pleasure to show your input below:

[skako]

Same here .
And it's my pleasure to show your input below:
Attachment 352453

Frits,
Do you have perhaps a scavenging efficiency graph as a function of scavenging (volumetric) ratio for your type of transfer channels.
Which known and measured scavenging type best describes your transfer channels.

[Frits Overmars]

Frits, Do you have perhaps a scavenging efficiency graph as a function of scavenging (volumetric) ratio for your type of transfer channels.
Which known and measured scavenging type best describes your transfer channels.

What kind of graph would that be Skako? Efficiency along the Y-axis, OK. But what about the X-axis? Primary compression ratio? Revs? Throttle position? Mixture strength? Engine temperature? Environmental temperature? Environmental air pressure? We can handle 2-D graphs and 3-D maps. But 7-D...?

The 'known and measured scavenging types' you mention remind me of the Yahama papers, the various SAE-papers and Blairs "Design and Simulation of Two-stroke Engines".
But a lot of research has been done since then. My name appears on some of the publications, but it really was Jan Thiel who carried it all as far as we are now.
So if you feel the need to give it a name, think of him.

[Peter1962]

...
Undersquare means: the bore is smaller than the stroke. So an engine with 54 mm bore and 54,5 mm stroke is (granted: just) undersquare, or long-stroke as I prefer to call it.
And long-stroke Honda, Yamaha, Suzuki and Aprilia engines did win a GP or two....

Frits, I know see that I wrote my question extremely clumsy...
Of course in GP racing, the bulk of GP's were won on 54 x 54,5 bore to stroke engines (what i should have called 'square')
In gp mx, in the 250 cc class all engines are long stroke. (66,4 x 72 )

You write that square engines like the 300's from KTM, or Beta, Sherco and TM are the optimum way to go.

That was what I thought, since all the modern 300cc two strokes are 72 x72 and being very succesful...

Sure, if you already have a twofifty on the shelve and all you have to do is overbore the cylinder. From a technical point of view it's not the best solution, but try telling that to the bean counters. A factory that would design a new two-stroke 300 and that has NO plans to make a 250cc version, would definitely come up with a long-stroke 300.
...

Thank you for a your answer. I assumed (wrong) that square ratio would be the optimum in a 250 or 300 MX engine.

[Peter1962]

Yes, it has the option to design a 5-port scavenging systems based on Frits' recommendations, giving the results in either Blair or FOS geometry.

Thank you, Neels.

[skako]

What kind of graph would that be Skako? Efficiency along the Y-axis, OK. But what about the X-axis? Primary compression ratio? Revs? Throttle position? Mixture strength? Engine temperature? Environmental temperature? Environmental air pressure? We can handle 2-D graphs and 3-D maps. But 7-D...?

The 'known and measured scavenging types' you mention remind me of the Yahama papers, the various SAE-papers and Blairs "Design and Simulation of Two-stroke Engines".
But a lot of research has been done since then. My name appears on some of the publications, but it really was Jan Thiel who carried it all as far as we are now.
So if you feel the need to give it a name, think of him.

I meant something like this graph

[Vannik]

I meant something like this graph

That is the single most difficult thing to find! There used to be a special test bench at QUB to measure it but is has since been scrapped as QUB has moved away from engine development. They printed over a thousand cylinders to test but I have not been able to find the results anywhere. Honda built their own but according to Prof Blair they could never get it to function correctly. Today the characteristic is an output of unsteady moving piston CFD simulations which is another ball game altogether.

[F5 Dave]

I was going to say it looks uncomfortably like something from a Eugenics site. But I decided against it. Until Friday night happened.

PS search Adam Ruderfords(?) Bad Blood podcast BBC fir a balanced history from a Biologist.

[TZ350]

TwoStroke Stuffing .......

[pete376403]

TwoStroke Stuffing .......

Soeedway bike frame? Many years back a guy I competed against was seriously looking into putting a KX500 motor into a Jawa DT frame but rules wouldnt allow two stroke in speedway

[TZ350]

.


Many thanks to Speedpro for his help with turbine housing for this.

A turbo charged Suzuki RG with a aftermarket 65cc big bore cylinder. The next project after I get the Kawasaki F81M 250 running properly on Methanol.

[edgefinder]

The beauty of the turbo rg50 is you can use all the power a lot and it can't get out of hand try to hurt you. Good for tuning driveability