Cross-posted from the DFI board, 'cause this board has more traffic:


Multi-Throttlebody Application?
I've got a theoretical question here. Would it be possible to use a stock-type throttle body with a stand-alone system like the Holley 950 or the Tec3?

I ask because I am planning a wierd custom build-up. I am trying to build an EFI version of a Tri-Power intake, using an Edelbrock/Offy 3x2 manifold and three TPI throttlebodies. As I see it, only one throttlebody needs to retain it's electronics, and the rest will just be stripped down to the butterflies.

I know that there's no real performance gain between a 3x2 and a big 4-bbl, but I'm going for a custom look, in homage to the Tri-Power Pontiacs of the '60s.
The engine will be in the 383-400 ci range, so it won't be looking at real high revs. I'm looking at a 389 with a 6" rod, but that may prove to be too expensive, and I may settle for a 383 or 400.

Most of the fabrication I can handle, but I want to know if I can make the electronics work. Any thoughts/suggestions are welcome.

 

On a tri power setup the center carb is the only one with an idle curcuit. Setup the TB the same, IAC & TPS on the center one, the other two closed at idle. Some aftermarket ECU have provisions for progressive throttle linkage, that would be useful for this.

 

I would reccomend finding 3 small single-bore throttle bodies. 3 stock throttle bodies will be WAAAAYYYYYY too much on pretty much any engine. Granted the effects may be different on a 3x2 manifold than on a stock TPI setup with the large plenum, but I still don't think this will be anywhere close to optimal.

I've seen GM port setups with other single-blade throttle bodies (One comes to mind that used a pair of audi throttle bodies). As long as you can find one that uses the .5 to 5 volt TPS reverence like the stock one, you should be able to wire it in and make it work.

I would think that figuring out how to get a MAF or MAP sensor to know out what is going on would be more interresting, but I suppose that with enough tuning, using the MAP value from one of the 3 plenums would probably be sufficient. I don't know 3x2 manifolds at all, but if they share a plenum area I suppose this wouldn't be an issue. If all 3 have individual plenums, it might be. But... if only the center carb on a 3x2 provides the idle air & fuel, I suppose that would mean that all runners pull from a common plenum.

 

Well 3 TPI TB's would flow in the neighborhood of 1800+ cfm, but I doubt any tripower manifold available will come anywhere near equaling that. Provided you could delay the opening of the two secondary TB's, I don't think it would be unmanagable, certainly not optimal, but I don't think that's your goal.

 

It doesn't matter how much the throttle body flows!

If the intake only flows... say... 300 cfm well guess how much air is gonna move through that throttle body ? Yeah, 300 cfm.

So the only limitation will be the amount of air your intake is able to flow.

Although delaying the opening of the other two throttle bodies should make tuning the whole thing much easier.

 

According to your philosophy, a monoblade throttlebody on a stock 305 wouldn't cause any adverse effects, yet there are countless timeslips out there to support the idea that to big of a throttle body will hurt performance. It's no different than putting a 1300 cfm carb on a stock 305 and jetting it down.

 

I don't think te original poster mentioned anything about having a fast timeslip. We all know (including the originator of this post) faster ways down the 1/4 mile.