ESE's works engine tuner

[Drew]

Why would it run rich ? it has plenty of air going through the 38mm inlet

Still limited (turns out by fuck all) by the 24mm ball valve. Feeding it more gas doesn't change that.

[Ocean1]

We figured that a bigger carb with a 24mm insert acted like a flow straightener aligning the air column before it negotiated the 24mm restriction.

I vaguely recall test data related to output corrections to orifice plate based flow meters that showed that across a significant velocity/viscosity range an orifice plate returned lower overall pressure differential than a staged reduction in cross section. In other words a flat plate with a hole flowed better than an hourglass shaped restriction.

Put that together with the fact that a reduced bore gate valve usually flows better than a reduced bore ball valve at partial openings and the fact that you don't actually need a venture in your "carb" and you might have a case for experimenting with a thin flat gate slide over a thin 24mm orifice.

[Yow Ling]

Still limited (turns out by fuck all) by the 24mm ball valve. Feeding it more gas doesn't change that.

the ball valve is 38mm
the inlet to the plenum is 24mm
the disk valve is shut aprox 50%of the time
when the disk valve is open the inlet is 38mm
while the disk valve is closed the 24mm hole is constantly flowing
seems you chose the wrong 24mm orifice drew

[TZ350]

Given up on the big carb idea, inlet tract becomes to long and its hard to package.



but could this work? a 24mm carb feeding into a plenum chamber and the 34mm rotary valve inlet feeding directly from the chamber to the motor. That way when the motor takes a gulp (duration 200 deg) it sucks full atmospheric pressure through a high flow 34mm bell-mouth and the restrictive 24mm carb has much more time (duration 360 deg) to refill the plenum.

The motor ran OK and it drove well on the track too.

http://youtu.be/YxiEo8cgopg

http://youtu.be/p4ef-WUO1Qs

It was fuel dropout building up in a big puddle in the bottom of the plenum and doubts about how much oil was actually finding its way into the motor that stopped the project and got us looking at EFI.

Also the realization that there was not as much of a power increase as expected for the increased inlet area and that pointed to restrictions somewhere else.



So power dramatically improved when we increased the transfer port area by opening up the rear transfers. But its looking like the time is coming where another look at the plenum might be worth while.

I have elected to go the EFI way but a plenum arranged in such a way as to drain dropout fuel into the motor might work well, but its probably easier to fit something like that to a more conventional piston port engine than my RV carb on the side setup.

[TZ350]

I vaguely recall test data related to output corrections to orifice plate based flow meters that showed that across a significant velocity/viscosity range an orifice plate returned lower overall pressure differential than a staged reduction in cross section. In other words a flat plate with a hole flowed better than an hourglass shaped restriction.

Put that together with the fact that a reduced bore gate valve usually flows better than a reduced bore ball valve at partial openings and the fact that you don't actually need a venture in your "carb" and you might have a case for experimenting with a thin flat gate slide over a thin 24mm orifice.

Good idea, I have a copy of the old British Standards somewhere and now you mention it, I recall early mechanical fuel injection manifolds had a thin slide throttle plate.

[husaberg]

Good idea, I have a copy of the old British Standards somewhere and now you mention it, I recall early mechanical fuel injection manifolds had a thin slide throttle plate.

So how come you are not using the slide throttle come variable timing Neil made up first? As it is much shorter than the ball valve.

I will not accept to many variables ALREADY as an answer Rob

[TZ350]

That is on Neils F81M, and was for varying the closing point of the inlet valve. He is currently working on something similar which will be a fly by wire throttle. I am using the Ball Bellmouth throttle with TPS he made for me.

[Ocean1]

Good idea, I have a copy of the old British Standards somewhere and now you mention it, I recall early mechanical fuel injection manifolds had a thin slide throttle plate.

Perfect. Be interested in any experimental results you might find.

[jasonu]

Still limited (turns out by fuck all) by the 24mm ball valve. Feeding it more gas doesn't change that.

My point is that only some of the fuel supply is restricted by the 24mm restrictor/carb/??? If you have another set of injectors outside of the 24mm restriction as prescribed in the rule book then surely that is outside of the rules.

[husaberg]

That is on Neils F81M, and was for varying the closing point of the inlet valve. He is currently working on something similar which will be a fly by wire throttle. I am using the Ball Bellmouth throttle with TPS he made for me.

It does both,........... add restrictor, hello throttle tps and 24mm intake in one ultra short package

[TZ350]

It does both,........... add restrictor hello throtal tps and 24mm intake in one ultra short package

But I want a short 38mm intake.

[F5 Dave]

My point is that only some of the fuel supply is restricted by the 24mm restrictor/carb/??? If you have another set of injectors outside of the 24mm restriction as prescribed in the rule book then surely that is outside of the rules.

Yes you are totally right. He should restrict the inlet by the flow size of the injectors too. 23.95 ought to do it.

[husaberg]

But I want a short 38mm intake.

So where is the intake restrictor going to be then?

HE GOES BACK AND LOOKS A PICTURE....
Then he laughs and says oh thats dubious. fiendish........
So an airbox feed by an 24mm "dummy carb" flowing just air..........mmmmmmmmmmmm.....

It was on PG100 Rob.

[TZ350]

So an airbox feed by an 24mm "dummy carb" flowing just air..........mmmmmmmmmmmm.....

Yes it used to flow air and fuel, and with EFI it will be the same equivalent amount of air, and the fuel gets added elsewhere.



So ... Yep, an old 24mm carb is pretty much equivalent to a 24mm carb.

[Flettner]

You need one of these Rob,



I would machine a 24mm restrictor, totally smooth with no throttle piston at all, best air flow and absolutly legal! You might want to add some more volume up where the old aircleaner fitted, more volume is better, but who am I to tell you.