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TBI vs TPI vs SFI

taildragger

Bow Hunter
City
Norman
State
OK
well, its coming up on project time and im not sure what kinda fuel injection i should go with, i am intending on buying a complete engine with brackets out of a chevy. I am curious as to which fuel injection system would be best for a daily driver and weekend warrior, i was also wondering whether or not its worth it to bump up to a vortec 350 if i have the money to finance it. And one more thing, does anyone know of a website or a store that i could contact to learn about how i'd wire the engine, any and all help appreciated

84 scrambler, t-5, 3.73, 32 baja wider track, 2.5+SOA, detroits front and rear
 
City
Houston
State
TX
With throttle body injection you still have a wet intake manifold just as with a carb but you won't have any problems like the carb has, but some cylinders will be richer or leaner than others. Throttle point injection has a dry intake manifold so all the cylinders get the same amount of fuel. All the injectore still go off at the same time. Sequential fuel injection has each injectors timed with the intake valves so the injectors open at just the right time. It theoretically is the most efficient and most powerful type. You won't be disappointed with any of these systems. The TBI chevys are probably the easiest to wire. The Vortecs have a lot more horsepower but don't seem to have any more torque than the TBI 350s. Vortecs get much worse gas mileage also if you care about that. I hope you're planning to swap in a better tranny with your new motor.
 

dadscj8

SOA Charter Member
City
Tucson
State
AZ
I got a fair price on my Holley Projection Sysytem a few years ago so that's why i went with it and what was said in the previous post is very accurate. The Holley works very well off road, i have no problems on the trails at all sorts of wackey angles, but i do have to tweek it from time to time as a daily driver on the streets. It is a cheap, ( relatively speaking), compared to the fuel injected systems out there, but those more expensive systems do preform much better of the open highway. I would say if you have the resources and you are going to also use your Jeep as a daily driver the throttle point or sequential injections are an excellent choice.

Phil Thompson
Junction City, KS
 
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taildragger

Bow Hunter
City
Norman
State
OK
TBI

alright, so from what i have learned from this post and some outside materials, it seems like the engines with TBI have a lower torque and rpm power range, usually torque peaks around 2400-2800 rpm if i remember correctly, Im just not sure if the TPI doesnt put out either the same torque or more torque in the lower ranges, so if anyone knows where i can find a graph of the torque and horsepower rpm range, i would greatly appreciate knowing where i can find it
 

CJATE

R-u-n-n O-f-t
City
NAPOLEONVILLE
State
LA
Okay, I'll throw my 2 cents worth in. I doubt you would notice much difference in performance between the two systems in your Jeep. I would favor the TBI system because it is far simpler than the TPI. The system is easier to trouble shoot, install and modify. Most importantly, it is easier to diagnose and repair off road should a problem develope. It is also cheaper and easier to install. The parts you may want to carry are also easier and cheaper to deal with. You can take off the air cleaner and see the injectors spraying and their pattern, try that with TPI.
 

hobbs

Basic User
TBI

I chose TBI for my small block Chevy conversion for 2 reasons. The first is that the donor engine I found had it. I guess that's the major reason...hehe. While getting it all to work I discovered a couple other advantages. It is a simpler system than the TPI and others. This is a big advantage, especially if you are "inventing" your system as I did. I took the entire engine, wiring harness, and computer harness out of the donor vehicle (1990 Caprice) and installed it piece by piece, with the help of the Caprice factory service manual. Another advantage is that TBI uses a much lower fuel pressure than the more sophisticated systems. I forget the exact inlet fuel pressure, but I think its about 13 PSI as opposed to 25-30 PSI for the others. Just something else to consider. hobbs
 
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