ESE's works engine tuner

[dutchpower]

Ign. 1000 30

6500 30

17500 26

14500 19

16000 10

17000 9

[dutchpower]

Exhaust latest test 22.7

[wobbly]

I have never been able to understand why people in general ( tuners ) seem to think that spinning any under 125cc engine to 12,000 is " thrashing " it do death.
The 125 Aprilia GP engines were reved to 14,000 all day , and today we apin the 125 kart engines to 15,000 on a regular basis to delete gerchanges between corners.
Having a 50 or 85 making max power at 15500 , in terms of piston speed and inertial forces on the crank/rod/bearings is simply using the ( very ) safe rpm available.
If you can hold the torque up , having peak power 3000 rpm above that 12,000 level will effectively add 25% more Hp , and have no deleterious effect on power "range " or reliability.

And that Bidalot pipe is so last century , with many design features that could be dramatically improved with a days work on a computer screen.

[dutchpower]

And that Bidalot pipe is so last century , with many design features that could be dramatically improved with a days work on a computer screen

2 days is that oke for you to post pipe that give more !!!


https://www.youtube.com/watch?v=qi37...&start_radio=1

[koenich]

Thanks for sharing! 23 HP is impressive...

Absolutely agree with you Wob, however the aftermarket cranks (even the most expensive ones) for the Derbi engines are usually crap and for the endurance races (main race 8h) I tend to want to keep the revs down.

[wobbly]

Hey Dutch , you send me the .pack file ( PM me and I will send email ) and I will spend a day on the pipe and post the results.
All the time listening to Mr Zappa , as I do regularily.
Yellow snow is quite inspiring , except when its in your eye.

[F5 Dave]

My reservations were based on archaic Suzuki engine that would die at 13,000. Rebuilt them every season to ward off mishap.

Fed Yamaha parts (non competition as per intent, 's' or otherwise on 'motors') I figured 13000 peak with sharp cut off should be ok. First engine did a billion miles and still had the same crank in it after 10 years. Clearly no where near limit. By then the Derbi engine had same TZR rodkit fitted but I never got around to increasing the revs as I wanted to see how a Spanish engine held up otherwise.

It's gone now, but clearly if I'd been paying attention to what was going on overseas it would have gotten me over my false fear.

[polcat88]

What they said before me - except to add that having the Aux at the same height as the main is never a good plan.

Can you expand on this statement, Wobbly? Specifically what are the negatives and how much difference in height would you recommend?

[wobbly]

Sure I love expanding.With a 3 port you have several elements interacting.
Firstly , is that when you stagger the Aux below the main port the initial wave front exiting into the duct has a high amplitude.
This has the effect of recovering the maximum energy from the remnant Blowdown pressure above the piston when the port cracks open.
Thus a high energy " pulse " travels down the duct and into the header , then eventually into the diffuser.

Once this wave front has been formed , and on its way , the lower positioned Aux then rapidly bleed down any remaining pressure into the duct.
BUT , be aware that the path length from the Aux ports , often around to bore center , is way longer than that of the main port - as they are effectively in a perpindicular relationship.

Open all three ports together , and you have two downsides.
First is that the initial opening area is much larger - thus the wave amplitude is reduced.
And secondly the two largely differing path lengths effectively " smears " the wave formation in time.
These two effects combine to reduce the wave fronts energy available to be used for scavenging by the diffuser , or plugging by the tailcone.

Timing variation of the port set varies according to the actual setup.
First case would be the obvious Aprilia.This had reverse stagger transfers , so the Aux ports floor were able to be very low - achieving a ton of area , without causing drastic short circuiting from the A port roof.
This , along with the main ports powervalve action , meant that the Aux ports were optimally positioned at around 9* of duration lower. This height still achieving sufficient Blowdown STA to match the transfers capability.

Then we have a TM125 R1. With slightly less power capability , matching the Blowdown STA needed results in an optimum of near 5* duration split - some what affected also by the factory refusing to use pin plugs ,that
would allow the Aux timing width to be increased, as well as the duct entries to be less tangential to the bore.
This translates to just over 1mm of height difference on the 54.5 stroke , and reducing the height difference immediately kills front side and peak power , with a gain of some overev power right at the very topend limit.
Way less total area under the curve.

[tdc211]

quote
These two effects combine to reduce the wave fronts energy available to be used for scavenging by the diffuser.

i was sort thinking along this line above. idk, been i definitely thinking something like that.

every time i have gotten greedy for a little more blowdown (when power is good) and raising subs just a tic higher , it just goes to hell in a hurry.
seen that quit few times.

[dutchpower]

Hey Dutch , you send me the .pack file ( PM me and I will send email ) and I will spend a day on the pipe and post the results.
All the time listening to Mr Zappa , as I do regularily.
Yellow snow is quite inspiring , except when its in your eye.

Think i get 2 answers

[tdc211]

Like 5 years ago. Guy that helped me time to time iced races a 3 port cr250. I stripped the plating. Welded up the sub roofs alot lower. Reported, Cant remember timings. Just used the sim. That and thin reed custom block made way more power . I have the chart on a old laptop. He won alot that season. Next season 1/2 thru it cracked on a bridge. Was junk unfortunately.

[polcat88]

[QUOTE=wobbly;1131161616]Sure I love expanding.....


A thorough and logical expansion! Thanks Wobbly.

[ceci]

Hi Katinas.
I want to ask you if this may be one of the reasons why you get a better result in the 1st model than in the 2nd model.
The Zhukowski pulse that I think occurs when passing point B to point A, creating the pressure pulse which when reaching the end of its path is returned to a positive pressure pulse which coincides with the opening of the transfer (point D exceeds point C) obtained supercharging

[katinas]

Hi Ceci
Yes, the pressure fluctuation in trans tunnels at closed phase period (aprox 10 degree duration) helps to charge at higher revs.
But maybe your words, nicely confirms test that did not work. Most interesting and informative was 4 scheme test, when engine completely stop at 5000 rpm. as positive pressure blocked intake process when arrive at wrong time.

3 and 4 types is very similar, except that 3 type, with extended transfers deeper in the crankcase and with relatively higher position of intake tunnels, works in normal way.

I am still testing on the road, but finally tested things on my friend,s dyno, so many tests.
This is rear wheel dyno graphs of 1 and 2 types.
PS. 1 type now with slightly opened crankcase to trans, about 1/4 of original 2 type area, for better transition from mid to high range.
PS. Engine Honda NS 250 modified for only one horizontal cylinder, vertical blocked, 57 mm bore and 50.6 mm stroke 129 cc