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Better gas mileage - TBI or TPI?

Blaze

Blaze

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Just wondering. I am getting a 1990 K5 Blazer with a 350 TBI in it. I have a complete TPI setup in my shop that I could easily put on the engine. I know the TPI would be a better setup as far as power goes, but just wondering about MPGs.

I don't really care because I have a minivan to drive (hey, it was free) to get good mileage, but my wife was asking me what the gas mileage of this thing was so I figured I'd ask. Good excuses are always the best reasons for upgrades. :haha:
 
Im sure mileage would be better with tuned port.
After all every manufacturer on the planet currently uses multipoint EFI
 
odin said:
Im sure mileage would be better with tuned port.
After all every manufacturer on the planet currently uses multipoint EFI
Click to expand...

And they mostly sell smaller vehicles with smaller engines and smaller tires :D

I'm with Stomis; I don't think you could numerically justify the swap for the sake of fuel efficiency.

Now, for the sake of power or coolness, sure...

-- A
 
You would get a definite power increase though...does that count?:whistle:
 
tho a dry manifold has a lot of advantages over a wet, it's not always the best solution.. TBI does have a few advantages over MPFI.....
 
odin said:
Ok, I'll bite.
Such as?
Click to expand...

tend to be a bit torquey-er on the bottom end, whereas MPI have the topend advantage.... a bit simpler to work on...

and vastly cheaper to buy injectors for! :haha:
 
Not the TPI setup off of the old small blocks, these things have all kinds of lowend grunt and run out of steam at like 4500rpm.
 
I agree with ya Blaze. Ive run both TPI and TBI and Tuned Port has the most low end response of any other system.

Cant argue about the injector pricing though.:haha:
 
odin said:
I agree with ya Blaze. Ive run both TPI and TBI and Tuned Port has the most low end response of any other system.

Cant argue about the injector pricing though.:haha:
Click to expand...

You can get flow matched rebuilds for $100 now though. Plenty cheap and I agree with torque and cool factor!:thumb:
 
well, unlike most people, I work on both daily on dozens of motors and thats what I've seen... tore down a MPFI 502 this morn as a matter of fact...
 
This is only marginally on topic, but my Ford 250 has about the worst of all possible setups.
Its multiport fuel injection, but it bank fires instead of individually firing the injectors on the intake stroke.
Plus, it uses a MAP sensor instead of a MAF.

They make a kit that replaces the wiring harness, computer, and adds the MAF to give true multiport FI.

From everything I have read, it does not help the milage very much, but does give better throttle response.
Almost certainly does not pay for its self.

Still got it on my list though. Gonna do it for the cool factor, and the fact that it gripes me I have 8 injectors and they fire 4 at a time.
Why did they not just go with TBI?

Of course, some vehicles using the same engine had true mulitport, not sure why they did not put it on the trucks.
 
odin said:
Just to clarify, Im talking specifically about TPI (86-89 Corvette Camaro)
Click to expand...

Me too, my question was specifically about the Vette/F-body TPI vs TBI.

I've owned a bunch of both and have swapped TPIs onto TBI engines before. Down low torque is much improved but they run out of steam before you even hit 5 grand.

I just never cared about gas mileage enough to notice a difference when driving these cars. :haha:
 
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