EFI Butterfly Alternatives

[Peter Delaney]

Slightly out of left field, but has anyone had experience with the "sliding plate" setup for throttle control (as opposed to the conventional butterflies) ?

The concept has been hovering in the back of my mind since I saw a few vintage Brabham F1 cars with this setup on the Repco engines. Then I saw the following post which shows much the same thing on a flat 8 Porsche engine :

http://www.gt40s.com/forum/porsche-917-talk/21795-917-flat-12-engine-drawings.html

It stands to reason that this type of arrangement would totally solve the linkage/synchronisation problem between butterflies on each bank (once machined right, they should stay right forever) - you would only have to get the left & right banks synched.

Maybe there is a problem in terms of the linearity of the throttle opening for road use (or maybe an issue with keeping things clean & sliding freely without a tear-down between races) ?

Any experience or ideas ?

Kind Regards,

Peter D.

 

Pete, i'm pretty sure the Cosworth DFV has sliding plate system too. I imagine getting it to slide freely AND seal well would be a challenge.

 

According to my book "Anatomy and Development of the Grand Prix Car" by Sal Incandela, the DFV used sliding plates up right up until it's retirement in 1983. I need to read more into what advantage it would have, but I would imagine that a butterfly would have an advantage in terms of airflow and distribution from the trumpet into the actual throttle body. A sliding plate would probably cause the air to tumble into the throttle body/carb at part throttle operation.

 

[Peter Delaney]

Tim, I reckon that you are right regarding the sliding & sealing - both would be difficult to maintain on a road car unless you had better things to do !

Joe, I guess that race cars are pretty-much "On & Off" the throttle - not to much care given to driveability in road traffic on part-throttle settings ! It makes sense that a butterfly valve will give a more even & balanced air flow "down the hole" than a sliding flat plate, so maybe that's another reason why we don't see this used on road cars ?

(Not hard to tell who is on the verge of retirement, & is looking to fix things that ain't really broke) !!!

Kind Regards,

Peter D.

 

Tim, I reckon that you are right regarding the sliding & sealing - both would be difficult to maintain on a road car unless you had better things to do !

Joe, I guess that race cars are pretty-much "On & Off" the throttle - not to much care given to driveability in road traffic on part-throttle settings ! It makes sense that a butterfly valve will give a more even & balanced air flow "down the hole" than a sliding flat plate, so maybe that's another reason why we don't see this used on road cars ?

(Not hard to tell who is on the verge of retirement, & is looking to fix things that ain't really broke) !!!

Kind Regards,

Peter D.

Well....not necessarily since the DFV was a road racing engine, some consideration had to be given to driveability. I can't imagine that having an on/off switch under your right foot was good for mid corner stability. I think you're right in that the major advantage of a sliding plate is synchronization and balance. But for overall driveability, the butterfly is a better choice IMO.

 

[Rick Muck- Mark IV]

The early Gurney-Weslake small blocks used a sliding plate throttle system. They were used on both Dan's Can-Am and Indy cars with the 289/302 engines. He also delevoped it for the Ford 4 cam engine.

AAR claimed a power advantage over the butterfly Hilborn system, I have no idea of how the mid range was.

Rick

 

[Richard Timte]

The carbs on my shifter Karts (125 and 80) are of the slide type as are most carbs on motorcycles (at least they were). One thing I can say is that this is not a on/off setup at all.