Dsagers

As many of you already know, this is about the best board around, especially when it comes to performance mods.

Have a DFI TBI question, and I’ll be up front, it’s not in an F Body, but since this is the best place for info, I’d like to ask for help from anyone here who knows the answers.

It’s a 1994 truck, which uses the 4L80-E transmission, so I need the factory ECM to control the transmission. Also have a DFI 6.32 computer with a Fasttrack piggy back system.

I'm trying to get everything ready to change out the engine and will need more fuel than the stock GM TBI can provide for the new engine.

The important stuff is a 540 ci BBC, Merlin 269cc oval heads, mild porting and 124 cc chambers. Cam is a hyd roller designed for a street supercharged engine. Whipple supercharger at 6 lbs of boost. Pistons are -15 cc reverse domes, and rated at 8.0:1 compression with the heads.

Max RPM will be 4500 as this is in my tow truck.

So here are the questions. No way can the stock TBI provide enough air & fuel, injectors simply are too small.

Right now the stock 454 has a Whipple and additional fuel is covered by an FMU, the DFI is sitting on the shelf. Whipple says my current FMU fuel system is an very old design and even though it’s run nicely for 120K miles, the design is too undependable to risk burning up an expensive new engine.

What I need to figure out is how make the DFI / factory computer run 4 or more injectors instead of just the two injectors from the original GM TBI.

One option is that I have an Accel 1000 cfm throttle body with four 72 lbs/hr injectors in the base of the TB. However these are not factory injectors and I believe are a different impedance. If I use this 1000 cfm TB is there a way to convert the computer to match the injectors?

A second option is to use an older Holley 4D 950 CFM TB with the four injectors. Again, how to match up the injectors and the computer so I don’t let the smoke out of the drivers.

Or, if anyone has taken a different route and already invented this wheel, please share your info.

Thanks

hectorsn

Have you called Accell to get their opinion? It might just be able to power the 4 inj's. However, I think you're cutting it close even with 4 72lb/hr inj's. I know that's a lot of fuel but that's a lot of engine, too. What's it going to be pushing, close to 800 ft/lbs of torque? I'm sure there is an aftermarket ECM that can do what you want but I'm also sure you're asking questions as you don't want to buy another ECM. I'd also assume that running a manifold other than the one you have is out of the question since that's what the Whipple was made for? How about this, can you put port injectors on the manifold and run a dry throttle body? Had to ask although I'm sure you've already had the thought.

Dsagers

Thanks hectorsn

Interesting enough, the Whipple is made to fit on top of a GM TBI manifold. To use a different manifold, just have to make it the same height and then center the compressor in the same location.

Still back to the question of keeping the factory ECM to control the 4L80-E, and then firing 4 or eight injectors.

BTW, good advice, I'll call today.