Can I use a Holley 4 bbl throttle body with my GM com?puter and chip

[Chevelle45466]

Can I use a Holley 4 bbl throttle body with my GM computer and chip? I read about some one setting up the computer for 4 injector drivers.


Also if I wanted to use a Camaro with TPI just for wiring or electrical to get multi port injection Could I use the Holley Stealth ram and a 58mm Throttle body I all ready have? Or other MPI set ups.

My 406 in my 95 with Vortec heads and a bored 50mm TB and 90lb/hr injectors, LT headers, no EGR, GM tbi/Vortec intake, hydraulic roller cam, 9:01 comp and a custom tune at best gets 12-13 mpg.

I'f I'm on it it gets less than 10 but it hauls that heavy 1/2 ton fast. But not as fast as it sucks gas.

Little help. Would a 4bbl 4 injector or MPI be better.

[Fierobsessed]

Your engine sounds exactly like mine, with exception to your engine having more displacement.

I'm willing to bet that changing the throttle body won't fix any of your problems, and that most of your mileage issues can be fixed in tuning. Problem is, that its not easy, and there is no magic solution. I would reconsider your lack of an EGR, as that does have an effect on gas mileage, and is not so detrimental to performance. I have some solutions for hooking it up, The headers can make it a bit more challenging though. An EGR does have the effect of reducing effective displacement (which at 406 cubes, you have a LOT of) and it lowers the cylinder temperatures which reduce the short term chance of detonation. Enough about the EGR. I am willing to bet that your induction system (TBI and Intake) are more then sufficient to feed your engine, and still keep it running conservatively, AND pass emmissions.

Im running a 355 Vortec (stock long block) with 1.6 rockers, GMPP Intake BBC TBI with 90lb Injectors, Stock L05 exhaust till next weekend, when the thorley Tri-Y's make their way on. My EGR is installed, but disabled because I was having major stumbling issues on throttle tip in, which went away as soon as the EGR was disabled. The problem seems to be that I have an after market EGR. I too only get around 12 MPG, In a Van. I believe most of my mileage issues are coming from cold tuning, It surges a lot when sitting still. Also I strongly believe that the Intake gaskets are leaking since ambient temperature severely effects the engine till its fully warmed up, to the point where some cylinders don't want to fire. Im getting the GM gaskets... hopefully soon. Once warmed up, it will pass emissions easily. On cold startup its pretty poor, downright stinky.

Few questions for you...
Do you do your own tuning? How are your BLM's looking? Do you have drivability issues? What have you done with your tune that deviates from the stock code? What kind of power do you think or know that it's producing?

[Chevelle45466]

Makes an easy 375 to 400 horses at the flywheel plus lots of torque 1800 up. I had the chip burned for no egr and the current parts combo. If I would have used a set of 96-98 SB Vortec headers or manifold I could have used EGR. Down state in IL no emissions check. So no cat long tubes 2 into 1 flowmaster the2 out.

I did notice they stuck the O2 sensor in only one bank of the exhaust. Been a while since I had it hooked up to my laptop. Dropped my fuel pressure and help make it less rich and snotty.

I do have and irratic idle after it warms up but I think the TPS needs adjusted. My fuel injectors i had apart and put back together but re-used the gaskets and rings screens in them. I bought a rebuild set from the place I got my injectors and it should help.

It just seems like I'm leaving a lot on table by the throttle body and some inefficient injectors. A higher pressure modern injector and a throttle body with a progressive linkage for the secondaries.

No leaks in vacuum that I know of. I have a BB radiator in it when I almost dropped a Vortec 454 in. This 400 runs cooler than my other stays at or under 160. I was thinking a 180 or 195 would help clean up the burn. I also polished my cyl head chambers while I ported and polished the rest.

The truck hauls and has tremendous pull to 5000 and a little more but got a funky flat spot there. It has the comp beehive springs and lifters on a Custom Cammotion cam.

But unless I drive like my grand mother it just eats gas like no tomorrow even with 3.73s and a 30 inch or more tire. They are 20's with street tires.

Think injectors first then a fuel pressure regulator with the vacuum port for at idle to drop the pressure a little more. Still a little rich there. Then maybe put the O2 sensor back farther to where the pipes come together. Get it to read both cyl banks.

[xch3no2]

I'm pretty sure if mileage is your goal the Holly won't help any. When you say custom tune do you mean live or mail order? I would tune it yourself, or get a good live tune.

[Fierobsessed]

Your TBI at 13 PSI should be good for 340 HP or so, and with bumped up pressure shouldn't have much trouble feeding 400. But its still going to be difficult to tune. I still don't see a new TBI solving any of the issues you are having. It's probably just a waste of money.

I don't think seperatly operated secondaries are an option with a 4 injector TBI either. It kind of flies in the face of logic to have two blades remain closed when large quantities of fuel is being thrown at them. Unless I am missing something.

The temperature thing is a pretty big factor in MPG. You might run into a problem where the vehicle is running in closed loop, but its not updating the BLM's because it isn't hot enough. This would cause it to disable learning. You may not even be in full closed loop at idle either. You really need to have the engine running at 180 degrees at the coldest in my opinion. This makes the computer happy.

Using a Vacuum regulator on the TBI is a great idea. It does mess with the tune a bit, but it helps SO much when it comes to the effective range of the injectors. So it's some time working on the VE table that should clean up what that changes.

All TBI engines (that I know of) have an O2 sensor on only one bank. Generally this is OK, since that one bank takes samples from two cylinders that run off one injector, and two cylinders off the other. So it sees an overall engine balance sufficient to make good accurate corrections.
My Thorley headers have it on only one tube. So I'm adding a heated sensor at the 3" collector for the whole header.

It sounds to me that you bought a tune if thats correct. I am not a big fan of this. I've always said that the only way to tune is to LOG A LOT of steady state conditions, Fix the VE table, Fix AE tables, and attack specific problems, then repeat. Buying a tune has no way of compensating for YOUR engine. If anything, that tune you bought should be used as a starting point if it runs somewhat ok.

[Chevelle45466]

The 4 barrel throttle bodies now have a progressive secondaries that open slower than the front. Edelbrock, Holley, have 4 injector 4 barrel throttle bodies. Even mine ported with the KN FIPK kit seems to be limited in air flow.

I was thinking of a different computer all together just let my stock one and chip run the trans.

yes it was a mail order very detailed chip I bought. I have been tuning some with what I have the fuel pressure mostly.

So even with the chip set at 160 degrees it is not getting what it should?

I do have the Datamaster TTS i think have used it very little yet.

The EBL Flash by Dynamic EFI interest me more than burning my own chips. Also i can use the wide bannd to better dial in air fuel ratios right?

[wrench-head]

If you get the older non-progressive linkage it might work. I have both styles, never tried either, but agree that fueling the closed rears isn't going to help.