ESE's works engine tuner

[wobbly]

Well it all depends upon what has changed , and thus if that change is an advancement.
If , by lifting the outer edges , you have also increased the port duration , then that will have the biggest effect on performance - especially if more timing/blowdown was needed to begin with.
But we all know the effect of excessive Ex timing , a big reduction in power spread.

Edit - is the outer edge hooked toward bore center properly ?

[TZ350]

- is the outer edge hooked toward bore center properly ?

Maybe not. Looking at your picture it looks like our efforts with the hook are to shallow. Will look at it again and dig more out if its needed. Thanks.

[wobbly]

Thank Frits , its his diagram of well known and long proven geometry.

[Frits Overmars]

Thank Frits , its his diagram of well known and long proven geometry.

You are very welcome Wob.
As I wrote the other day, everything that I make available via https://1drv.ms/u/s!Atyzb5b7jtWNmVcX...5eKjL?e=nxuw41
and via open forums such as KiwiBiker and Pit-Lane.biz, and even via Fakebook, may be freely used and distributed.

[SwePatrick]

Still developing my EFI setup, this week i changed the fuel strategy, far from done.
I´ll tune it today.
But it appears promising:

[wobbly]

Having dyno and track tuned a 3YL/4DP TZ250 Yamaha to a win at Eastern Creek last weekend I have continued doing some development work for the future.
It has surprised the hell out of my by not responding in any way to the usual duct CSA reduction.
The stock exit is 37.5 dia and it likes nothing else except a 40 header forming a step. This increases front side and overev.
Its super finicky with intake length tuning and reed frequency , and will deto with even tiny increases in Com /MSV/Ignition/A/f or CE.
The other thing I wanted to nail down definitively is that for years many people have been extolling the virtues of cranks with cork in the balance holes , or full circle webs and or stuffing the case around the reed
to decrease the volume. I know both cases are not the same , but having measured one side and increased the volume to the usual 1.3 ratio , I now know this is all bullshit.
Sad really as the owner has a couple of super expensive filled and full circle cranks as well as a special kit version.
The pipe reacts as per normal , except it has to be alot shorter than I would expect to peak at 12500.
Its very difficult with the short stroke to get the needed STA , but its making the actual port power capability in the sim.
Anyway here is some info about the thing - Im now looking Hi and Low for a pair of 4DP - 11 or 4DP - 20 cylinders to put on it , please contact if anyone knows where a pair are hidding.

[F5 Dave]

So what are we looking at? The 70 hp looks right for a '91 B at rw. That's what Ansteys old one was on Chris's DJ they got it a bit better than that. I have the runs somewhere but don't even think I can run djpep without creating a virtual machine.
Sim looks like much higher revs. Is that what you are now aiming for ?

[wobbly]

Yes , the short stroke means the only way to generate power is by holding up the torque at much higher rpm.
13,000 is nothing to a 50.7 stroker.
The stock 3YL/4DP cylinders and pipes made max power of 75 @ about 11300 , and the solenoid powerjets just make it rev on forever.
Fast enough to win the class but nowhere near what is possible.

[Javier Ruda]

The pipe reacts as per normal , except it has to be alot shorter than I would expect to peak at 12500.

Hello wobbly, just an idea. When the fresh mixture must be pushed back in the cylinder it will find an exhaust port that is diminishing the height until it finally closes. Compared to a longer stroke engine the shape of that port could have a worse Cd on a short stroke engine because it will be not so “square”, needing an additional time to push back the mixture.

[katinas]

Having dyno and track tuned a 3YL/4DP TZ250 Yamaha to a win at Eastern Creek last weekend I have continued doing some development work for the future.
It has surprised the hell out of my by not responding in any way to the usual duct CSA reduction.
The stock exit is 37.5 dia and it likes nothing else except a 40 header forming a step. This increases front side and overev.

Hi Wobbly, could this be related to Yamaha 4DP more downward direction of ex duct. The roof angled down 22 degrees, the floor 42 degrees. And the floor angled down nearly from the cylinder wall, just about 3 mm off.

Other thing that looking so extreme from outside, is YZR 500 2001 exhaust duct arrangement.

[Frits Overmars]

the short stroke means the only way to generate power is by holding up the torque at much higher rpm.
13,000 is nothing to a 50.7 stroker..

13,000 is nothing to a 50.7 stroker from a piston speed point of view. But the time.areas in a short-stroker are a different cup of single malt,
preventing you from holding up the torque even before you reach 13.000. No free lunch, as usual.

[skako]

Hello wobbly, just an idea. When the fresh mixture must be pushed back in the cylinder it will find an exhaust port that is diminishing the height until it finally closes. Compared to a longer stroke engine the shape of that port could have a worse Cd on a short stroke engine because it will be not so “square”, needing an additional time to push back the mixture.

You made a good point Javier.
I have noticed this with some that had very wide and low exhaust ports, to satisfy STAex. The tests were not very encouraging. This is where the hydraulic diameter comes to the fore, which increases the Reynolds number and friction factor, which act to reduce Cd and fluid flow.
A compromise between STAex and Cd factors should be guessed.

[41juergen]

Having dyno and track tuned a 3YL/4DP TZ250 Yamaha to a win at Eastern Creek last weekend I have continued doing some development work for the future.
It has surprised the hell out of my by not responding in any way to the usual duct CSA reduction.
The stock exit is 37.5 dia and it likes nothing else except a 40 header forming a step. This increases front side and overev.
Its super finicky with intake length tuning and reed frequency , and will deto with even tiny increases in Com /MSV/Ignition/A/f or CE.
The other thing I wanted to nail down definitively is that for years many people have been extolling the virtues of cranks with cork in the balance holes , or full circle webs and or stuffing the case around the reed
to decrease the volume. I know both cases are not the same , but having measured one side and increased the volume to the usual 1.3 ratio , I now know this is all bullshit.
Sad really as the owner has a couple of super expensive filled and full circle cranks as well as a special kit version.
The pipe reacts as per normal , except it has to be alot shorter than I would expect to peak at 12500.
Its very difficult with the short stroke to get the needed STA , but its making the actual port power capability in the sim.
Anyway here is some info about the thing - Im now looking Hi and Low for a pair of 4DP - 11 or 4DP - 20 cylinders to put on it , please contact if anyone knows where a pair are hidding.

Hey Wob, sorry to say, but you made my day!
I'm working of that 4DP setup on my 1 cylinder bike now since a long time and didn't got that engine running well... So I gave up on the 4DP cylinders and modified 3XV R cylinders. As beeing from a street bike with the japanese 45 HP restiction, these barrels have low timings giving a lot of possibilities for mods. Finally I need to grind down the cylinder and will put the engine together soon, will report back. I can send you my .pak file, not sure if all data are correct.. (with an street air box setup and your older proposal for a pipe).

[wobbly]

So joy of joys , thats is a 5 port with a drum PV that closes off the Aux ports ?
Would be cheap as well. , but alot of work - yes please send the .pack. , really interested.

So Frits , you believe I am kicking a dead horse trying to make better power at 12500 with overev to 13,000 - thats about 1200 past the original.

[F5 Dave]

Watch for cracks between aux and main. Not sure how prolific or isolated to example I saw.