ESE's works engine tuner

[TZ350]

Attachment 336531Attachment 336532Attachment 336533Attachment 336534Attachment 336535

Comparison of transfer port angles between a Honda RS125 NF4 and NSR250 MC21 cylinder.

Honda NF4 RS125 and NSR250 MC21 Exhaust and Vertical port angles.

With the Power Valve set to open at 96deg ATDC thee is significant gaps around the PV blades.

The PV's are fiddly and difficult to get in and out so I cut a damaged cylinder to make a jig to make it easier for welding and grinding them to a closer fit.

[190mech]

Thanks for the cut cylinder pictures TZ350!It gives us a real view of how a decent port layout should look!!

[Frits Overmars]

Matt - the toroid as you have drawn it is exactly as I have used in all manner of race engines with great success. The latest being the record breaking TZ350 LSR engine. ( PS,get the water closer to the threads ...
The angle/flat top is exactly what I am soon to test, but not with a toroid as the KZ kart rules include a compression cc measurement thru the plug hole at TDC and this design traps air at the highest point doing this....
Not that this is really relevant , as in the case of the KZ engines , no one runs the minimum allowable volume, as this completely kills the overev power.

What would the true combustion volume of your toroid head need to be in order to pass the KZ-test?
You might give it a try Wob; I've seen surprising results from low compression ratios.

[husaberg]

Thanks for the cut cylinder pictures TZ350!It gives us a real view of how a decent port layout should look!!

What should be mentioned is Yamaha Suzuki and Cagiva would have liked to emulate the wide well curved transfer ports of both the Honda and more importantly the Aprilia.
Only they couldn't as the cylinder spacing and bore centers did not allow them to this there want the room. Hence they often used 6 main transfer ports
Yes they could have did it on the 125's and 250 v twins, but those bikes were only generally given hand me down tech from the 500's.
Both the Honda and the Aprilia layouts allowed for more room. thus more power and more championship wins

[Frits Overmars]

What should be mentioned is Yamaha Suzuki and Cagiva would have liked to emulate the wide well curved transfer ports of both the Honda and more importantly the Aprilia.

What never ceases to amaze me is the inner curvature of the Honda transfer ducts. Even in their most recent race engines it was only 12 mm at its tightest point,
compared to a constant 22,6 mm radius for the Aprilia's inner curvature - that's almost twice as big, which makes a big difference in flow attachment.

[husaberg]

What never ceases to amaze me is the inner curvature of the Honda transfer ducts. Even in their most recent race engines it was only 12 mm at its tightest point,
compared to a constant 22,6 mm radius for the Aprilia's inner curvature - that's almost twice as big, which makes a big difference in flow attachment.

I was under the impression they got it a bit better later on. That NF4 certainly doesnt compare well when overlaid with the Aprilias
They were still however better than most of the other japanese engines even if not as good as the Aprilia.
I think their lack of radius could in part be due to their perserverence with their giagantic bridged exhaust.
Which was likely by then weakness in design that due to corporate pride that they were not allowed to change even if the designer wished too.
I am inclined to hope (at least) they had trialed it, as they certainly had the resouces to have tested every possible solution and permutation to death.
Put it this way they certainly would have had a few Aprilia customer cylinders available for evaluation.
Just as they had a complete RGB500 when they were building the NR500.

I also recall Honda in the mid 90's had some intersting limits placed arround development of the GP bikes by the companies senior managers with regards to pollution and fuel efficiency that likely other manufacturers were not saddled with either. HRC were also hamstrung in regards to the NF4 RS125s in which it was a modified CR125 platform, they were only permitted to make radical changes every 5 years or so at most. That existing platform, like your own at Aprilia entailed the cylinders to be made to fit around the confines of the existing stud pattern.

What surprised me most of the Japanese was with Yamahas development was how often they changed their porting from bridged to 3 port and 7 transfer to 8 and more with every permutation between with changes back and forth with v angle when they earlier had had what would be classed as the best solution of a tripple ex with 5 transfers. They also abandoned the 54x54 bore and stroke for about 25 years as did Suzuki

There was a story from Burgess that they trialled an Ohlins for on the NSR500, not one change was made to the fork set up from what was delivered, yet Doohan lapped a second a lap quicker, There of course was never going to be any chance of him racing with it fitted but it shows that Honda was not prepared to race with a fork that was substantially quicker if it was not from a Honda owned company like Showa was.

[Muhr]

Checking what you can expect from the conrod before destroying the new cylinder
below 50cc conrod at 19000 rpm. Wonder what would happen at 30000 rpm? (but there may be other materials)

[Vannik]

Checking what you can expect from the conrod before destroying the new cylinder
below 50cc conrod at 19000 rpm. Wonder what would happen at 30000 rpm? (but there may be other materials)

The maximum stress is a modeling stress, caused by the sharp transition in the recess radius, real stress is probably less. Also it is a Von Mises stress, used for fatigue and not outright failure. What does the major principle stress look like?

[Muhr]

The maximum stress is a modeling stress, caused by the sharp transition in the recess radius, real stress is probably less. Also it is a Von Mises stress, used for fatigue and not outright failure. What does the major principle stress look like?

Well, of course, not the whole truth, looked at shape optimization.
(Seems to go in pieces at 24000)

[TZ350]

What should be mentioned is Yamaha Suzuki and Cagiva would have liked to emulate the wide well curved transfer ports of both the Honda and more importantly the Aprilia.

What never ceases to amaze me is the inner curvature of the Honda transfer ducts. Even in their most recent race engines it was only 12 mm at its tightest point,
compared to a constant 22,6 mm radius for the Aprilia's inner curvature - that's almost twice as big, which makes a big difference in flow attachment.

Thanks for the heads up about the inner transfer duct radius.



With the Power Valve set to open at 96deg ATDC there are significant gaps around the PV blades.

The PV's are fiddly and difficult to get in and out so I cut a damaged cylinder to make a jig to make it easier for welding and grinding them to a closer fit.

[wobbly]

Thats a good point Frits.
The min allowable volume is 13cc TOP.
But I know the magic number to shoot for is actually 13.6.
Below this you loose overev, above this the mid ( 10,000 ) is compromised.
So if I can do a toroid that measures 13cc on the bench, but actually has 0.6cc trapped as air above the threads we could have a winner.
Onto the CAD right now.
Cheers Big Ears.

[2T4TSim]

Many thanks Wobbly for this RSA file. After the evening to reload it completely in Dat2t , it runs and is much better than what I expected form my Pit-lane readinds...

Regards
Alain

All my apologizes Wobbly for the mistake.

Thanks again

Regards
Alain

[lodgernz]

. .

[husaberg]

Thanks for the heads up about the inner transfer duct radius.



With the Power Valve set to open at 96deg ATDC thee is significant gaps around the PV blades.

The PV's are fiddly and difficult to get in and out so I cut a damaged cylinder to make a jig to make it easier for welding and grinding them to a closer fit.

It might pay to spell out to the others that your new engine is a complete reversal of your previous incarnations of the ESE AC GP125
From memory the top end is completely std road NSR, the pipe is a stock 93ish RS Honda. The Carb is a 28 with a 24 venturi OKO.
but the bottom end is modified with a larger rotary valve a different gearbox and a de-stroked crank with a wider crankcase to accommodate a different gearbox and a more modern cylinder.
Normally you would have had a cylinder with hundreds of hours work and development. yet you are close to matching the best output obtained with the previous incarnations.
Is this correct?

[wobbly]

So here is the pack file of Robs GP-NSR110 Mod by me, to generate the power curve as published previously.
Rob or anyone can ask for details on any input for explanation.
As I said the ports ( including the RV ) are all "stock " as set up originally.
First page to explain is the Engine.
I went for 12 Bar at 12500 as this is what the STA say the ports are capable of.
Thus we have a fairly low bmep, and on AvGas this will happily take the 16.5:1 com input, used on short kart tracks where acceleration between corners is far more important than overev power..
This is proven by the TuBMax output with the stinger size optimized and a "normal " ignition curve that starts at 25* under the pipe
then heads for 15* at peak power.
The Ex length input is 10mm, to look at the Mach in Pipe 2 = the stinger nozzle.