As a former owner of a TBI 2.8 Blazer and proud new owner of a 3.1MPFI 92 Firebird, I was just wondering what the difference was. I mean, I worked on my Blazer a lot (one of the reasons it's gone) so I know how the TBI works...but mechanically and perfomance-wise, what's the difference. I haven't been able to drive my bird a lot yet because it's in the body shop, but my mom used to own a 3.1MPFI Beretta...and it was pretty fast. I think it ran a 16.3 or 16.8, can't remember.....

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DRIVE IT LIKE YOU STOLE IT!

 

A TBI is just a carb with injector(s) well a MPFI has 1 injector per cylinder. MPFI is suspsed to make more power over TBI, be more economical, but in theory follows the same ideas as TBI...

 

Basically, a TBI is nothing more than a computer-controlled carb (in its appearance and, more or less, its function.) Multi port uses intake runners with an injector at each end. MPFI is more accurate, and as Brian said, more powerful and fuel efficient. TBI is cheaper to produce and easier to fix...hence why GM used TBI on various engines for as long as it did!

To give you an idea of the power difference between TBI and MPFI stock, here are some numbers:

TBI 2.8 = 120hp, TBI 3.1 = 125hp
MPFI 2.8 = 135hp, MPFI 3.1 = 140hp

Port injection doesn't make a monumental difference, but it is a noticeable one.

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Jason E
'89 Camaro RS 2.8
Hypertech chip/K&N filters/Accel 8.8 wires,coil/RapidFires
Eclipse CD and 100x4 amp/Boston plates and 6x9s

JasonEE98 on AOL IM

 

I get 32 MPG with my TBI 305.

Coop got 37 once.