Slide throttles

[2nd.gunman]

i am considering making a slide throttle and individual trumpets for my new X-flow. it will be injected and n/a. was wondering if anyone had tried this before or had any ideas on materials, construction, logistics and any pros and cons of such a system.
i would be making a completely new mainfold to try and and get a straight shot at the back of the valve. would this hurt low end torque?

 

[Thad]

Slide throttle devices are hard to seal and very sensitive to grit. Can hang up. Ever wonder why designers stay with the simpler butterfly throttles.

 

[Anonymous]

I think part of why butterflies are used is that they produce less intake roar, but you're right, Thad. Slides are prone to wear from both dirt and vibration. Old Brit-bikes came with slide-type Amals which were rigidly mounted to the engine (vibration) and had little or no air filtration (DIRT!). As the slides wore, idle speed would wander, among other problems. I became a tech-whiz among some local bikers by applying a baked-on moly disulfide coating to their throttle slides, to build up the I.D. as well as give them a non-sticking dry-lubed finish. I have used the same process on homemade racing carburetors which used rotary barrel-valves for throttling. In this instance, the fit was not the problem, but both the valve and the carb body were aluminum, which would have been a friction problem without the molycoating. In production carbs with aluminum on aluminum, the slides are tin-plated or cad-plated or something, to prevent sticking.

The Japs quickly identified and solved the problems of slide-throttle carbs by rubber-mounting them and using good filters. But if the slides ever do get scratched up, the molycoat is still a good fix. Helps restore old SU's, too.

 

[Thad]

A CamAm efi developer named Falconer worked on flat slide throttle with two slides that moved in oposite keeping the opening centered in throttle bore. The injector sprayed into this hi velocity air flow.

 

[falcon fanatic]

Didn't Mustangsix try to set up a bank of Mikuni slide carbs on his Locost engine? I think he'd have something to say about this concept.

Also, Lynx makes a triple SU manifold for the Aussie head, don't they? FSPP has a pohoto on their site. That'd be a pretty kickin setup for these engines. As an aside, it is worth noting that there is now a FI throttle body with injector and TPS integrated that is a direct swap for any SU (1.5 or 1.75). Triple 1.75 injector bodies on an aussie head ought to be good for some serious power. Probably makes a nice scream at full bore, too.

 

[Anonymous]

I've read about Ryan Falconer over the years; he always has some really interesting project going.

In his book on carburetion, David Vizard has a picture and comments on adapting three SU's to an inline six. He likes those carbs, but they sure don't have a very good reputation around here for some reason. I've had a couple of old Brit-cars with SU's for short periods, and had no special problems.

But Gunner is talking fuel injection with slide throttles. Any special reason you want these? If you have a lathe, barrel-valve throttles are easy enough to make, and with the throttles wide open you have a smooth-sided tube all the way down the intake tract. You can do this with a slide, too, and maybe its just as easy.

 

[falcon fanatic]

Oops, you said xflow, didn't you? never mind...