3.1 preformance hint please...

[91corsy]

Hello,
I own a 91 corsica, and I wanted to do a unexpensive mods. First off I want to put better manifolds, and i need to know what GMs carried the 3.4l that would fit my 3.1. Also I heard a rumor that the throttle body on the 2.8 might be a good swap to improve acceleration. Please advise, as i am fairly new to the 60 degree v6s
Thanks
91corsy

[Berettaspeed]

well what is the price range to you that is"cheap"??? fast and cheap is not very easy. it can be done but its not easy.

for under 1000 dollars im sure you can do a 3400 engine swap. this will give you alot faster of a car, and........a new engine!!! it will be like a new...old car you will nee dto take out that 3.1 totaly though. sometimes if you find a good price you could get away with around 700 dolars total. some people have gotten engines for as low as 300 dollars.

otherwise a TB can be around 200 dollars. exhaust can be around 200.

the best bang for your buck ...i would say is the 3400 engine swap. There is a ton of info on this swap.

https://www.3400swap.com

and others but i don't know for sure.

[91corsy]

what about junk yard stuff?? throttle body upgrades, exhaust manifold swaps...inexpensive stuff from the local'Pull-A-Part' that would interchange fairly easy!

[SHOoff]

Like he said. Go for the 3400 swap. If you have to, hunt through the junk yard and find an entire 3400. The swap that bad mofo in there. You'll not be disappointed.

[Berettaspeed]

nothing comes to mind with finding 2.8/3.1 parts in a junk yard.

doing manifold swaps you would have to get almost the whole engine and just the same amount of work as the 3400 swap...if not more. its very simple if you have some knowlege of cars and the basics on how thet are put together.

you can get under drive pulleys around 100 bucks??? i don't know the exact price.

[91corsy]

I should also mention I have a MPFI, not a SFI, that shouldn't complicate with the swap right??

[SHOoff]

No. That's how your computer is programmed. Basically if you swap to the 3400, you'll have a MPFI 3400. Cuz you're still gonna use your ECU and all the wiring for it.

[91corsy]

I thought the MPFI was the intake system, the SFI has only one injector (on the throttle body) and MPFI has an intake per cylinder... please RSVP, because i am a bit confused now

[Doubt_Incarnate]

MPFi has 6 injectors fired in sets, TBI has one or two on the throttle body and SFI has 6, but fired sequencialy as each cylinder needs.

[vsop4me3.1]

well I'll probally explain this wrong but
MPFI multi port fuel injection pumps gas into the cylinders I think like four at a time while
SFI sequential fuel injection pumps individually as needed, but at the upper RPM sfi turns to MPFI

both have 1 fuel injector per cylinder (total 6)

how'd I do?

EDIT: damn I type too slow

[91corsy]

ok that makes more sense.... so ur saying SFI is better than MPFI?

[WhiteRaider]

so ur saying SFI is better than MPFI?

SFI is slightly better than MPFI at lower speeds. The difference is nothing you would ever notice. At higher RPMs, the SFI can't keep up and reverts to MPFI anyway.

The MPFI computers control the SFI engines just fine and are widely hacked and widely available on the cheap in the junkyards. You probably have a 7730 ECU in that Corsica which is one of the preferred computers to use.

[SHOoff]

Well.... SFI is better than MPFI. Better Idle, gas mileage..... crap like that.

But you're looking to modify your vehicle for more power, which suggests that you're probably going to use it to race something else. Which is going to probably put the engine into 3000+ rpm operation, or Power Enrichment mode, at the least. Either of which, will put it back to MPFI.

When running an SFI motor with your MPFI ECU, you just need your MPFI injector harness.

[Guest]

For the most complete info on swaping a 3400 or building a hybrid for a J-body go to www.domesticcrew.com.

L-bodies are very similar.

We are also adding more info for other vehicles as well.

[91corsy]

Thanks!!

OK I think I got it all figured out, SFI (Sequential Fuel Injection) is MPFI (Multi Port Fuel Injection) at higher RPM, and SFI at lower RPM. Which makes better fuel economy.