ESE's works engine tuner

[wobbly]

Crap transfers can easily be subjected to "over scavenging " a term coined by Erv Kanemoto about trying fatter pipes on a TZ750 when going from 100 Dia up to 110 Dia.
That is the overly efficient steeper angled diffuser looses more power to short circuiting than it makes power by better scavenging.

So yes its a balancing act as always - your longer diffuser might be better , but my choice would be a shorter diffuser % moved to the left on a short header , but with a smaller belly diameter
to reduce the angles.
One thing that really helps this situation is grinding the A port front wall to point back closer to the boost port face , 1/3 from the boost port face to bore center is a good guide.
This works very well in things like LC/RD/YPVS/350 race engines.

But excess short circuiting due to fat pipes , and or insufficient A port front wall angle , cannot be modelled effectively in a one dimensional sim code , so the dyno is the only one unable to lead you astray.

EDIT - a straight line ignition will instantly kill overev , needing a dramatically shorter pipe to retrieve the power past peak - as is seen in the KZ designs.

[dutchpower]

Erv Kenemoto

[andreas]

Hibernation mode, also reverting back to 0.7 sheet (what was I thinking?)
Corr typo in the first drawing mid section length.

[andreas]

I did some speculating regarding the advantages of the the increasingly converging baffle. I'm not sure if the reasoning conveys from the scribblings, but being the baffle has a restricted useful length before possitive effects of the furthest part is eaten up by the part that is still in the 2/3 dip.
So it might be that the wave profile is the key, more suitable for pushing fresh mix, and is better tailored to fit the regime.

[wobbly]

Having a 3 angle increasing convergence gives an asymmetric amplitude return wave form.
Having the steepest portion at the furthest point from the piston , gives an increasing return pressure wave as the piston is closing the port - exactly what is needed for extracting all the remaining energy.
This will generally increase peak and overev power .
A one piece steep cone will give more peak , but the then it drops dramatically after peak - and looses front side power.
The 3 angle can easily be tuned to give more power everywhere.

[andreas]

Note taken.

[edgefinder]

There was talk of the Mikuni or Keihin carbs with full length needle jets to top of bore with a series of tiny holes the whole length. It makes me visualize an even spray of fuel thats somehow better than just spewing up from the bottom. This video of FCR's on a Ducati at 33,000 frames per second tells me carbs work work pretty good already. Alex at 2T stuffing might get some good information with a high speed camera looking down the carb like this

https://www.youtube.com/watch?v=9KSc_KNGKYg

[wobbly]

I have seen fast frame video's of a Lectron/Mikuni and a SmartCarb/Fuel Injection.
Seems one of the reasons the carbs that use a needle with a flat on the engine side work so well , over a wider range of weather , is they atomize the fuel droplet size much smaller.
EDIT - those fuel droplets in the FCR's are huge.
The idea of a hollow needle with a multiple series of vertical holes is in fact no better at atomization than the normal emulsion tube/needle , with or without a shroud for main jet air correction.
Its been done several times , including pumper carbs.
I haven't seen video of that , but the dyno doesn't lie.

[andreas]

Party at local shop. TM 450 and 89&93 Honda CR 500.

[TZ350]

Third place in New Zealand F5 (50cc Bucket) Road Race championship.

There were plenty of other faster riders but I rode and finished all the races in the series. Preparation and consistency beats faster talent to the podium once again.

[husaberg]

There was talk of the Mikuni or Keihin carbs with full length needle jets to top of bore with a series of tiny holes the whole length. It makes me visualize an even spray of fuel thats somehow better than just spewing up from the bottom. This video of FCR's on a Ducati at 33,000 frames per second tells me carbs work work pretty good already. Alex at 2T stuffing might get some good information with a high speed camera looking down the carb like this

https://www.youtube.com/watch?v=9KSc_KNGKYg

this is a promo shot of Yoshimura MJM

it also seemed to be a bit of a gimmick.



It seems to make odd farty noises.

Third place in New Zealand F5 (50cc Bucket) Road Race championship.

There were plenty of other faster riders but I rode and finished all the races in the series. Preparation and consistency beats faster talent to the podium once again.

Congrads Rob..

[TZ350]

this is a promo shot of Yoshimura MJM

We have a MJM carb on one of the RG50's. No more power but it seemed to throttle better than the standard needle/needle jet carb. We liked it. It got past the power dip better than the std OKO carb. The improved throttle response made this one a keeper for us. From experience we know that what works on one engine may not be great on another so we keep an open mind. Best by Test.

[ken seeber]

this is a promo shot of Yoshimura MJM


It seems to make odd farty noises.

Congrads Rob..

And I always thought the fuel was meant to go into the engine...

[husaberg]

And I always thought the fuel was meant to go into the engine...

Well sometimes it seem that airfuel mixture goes 2 or 3 times past the mainjet.....

[Grumph]

Having a 3 angle increasing convergence gives an asymmetric amplitude return wave form.
Having the steepest portion at the furthest point from the piston , gives an increasing return pressure wave as the piston is closing the port - exactly what is needed for extracting all the remaining energy.
This will generally increase peak and overev power .
A one piece steep cone will give more peak , but the then it drops dramatically after peak - and looses front side power.
The 3 angle can easily be tuned to give more power everywhere.

Sinply out of curiosity, how does the very early TD pipe with effectively a part - spherical end cone align with this ? Certainly the steepest portion is at the furthest point from the piston, if nothing else.