STUB25

Just looking for some refrence diagrams for conversion. Also wondering where the hot air sensor in the open air element goes on the TPI unit, or is that just replaced by the MAF?

RCR

What years?

91banditt2

iTrader: (1)

i'm doing this swap and my years are 89 TPI motor going in a 91 TBI.

JuGrNuT350

I'm converting 92 SD into a 90 TBI so it would help me a lot if I could get the diagram's too.

Thanks,

-Timbo-

topdown

Use a 91-91 Z28 Wire Harness and ECU and plug right in. The ECU can come out of many different GM cars with multi-port (a salvage yard can find one for you), but you'll need the correct EPROM for your car(a stock or modified 91 305 TPI PROM--assuming your using the 305). To connect the fuel lines to rail you'll need stock lines from any TPI equipped vehicle. Your current map sensor and other sensors will work fine. The new harness won't necessarily use all the sensors on the TPI so if it's not on the harness don't worry about it. Just hollow out the MAFS since it will no longer be functional. Your VATS will remain functional. If TPI is from 350 the injectors may or may not be too large (22lbs/hr instead of 19lbs/hr). Not too bad of a project with a little homework!

redbird_400

Hey topdown, do you do this for a living or something. Just that it seems you know a lot about this. I'm doing the same here, tring to install a TPI instead of TBI. Hey do you know a web site with all this info on it and maybe some pics? Oh yeah one more thing is there that much of a difference between the two or its probably just the way they look right?

topdown

I've just been down the TPI conversion road before and did plenty of research along the way. As far as the difference between TPI and TBI...TPI is multi-port injection meaning an injector for every cylinder...TBI uses injectors above the throttle body which doesn't allow nearly as good of even distribution to each cyl nor as good of atomization(smaller fuel particles=better burn). The long blocks are basically the same from carbs to TBI to TPI--a carb can be converted to TBI or TPI by adding the sensors and ECU. Anyway..trying to keep this short and simple so if you have any other questions post away and I'll see if I can help you through the process...as far as diagrams go--I don't know of any specific to the conversion...Good Luck

91banditt2

iTrader: (1)

so i'm going to need the under dash harness aren't i?

topdown

NO! The engine bay harness plugs into the ECU under the dash, goes through the fender area into the engine bay, attaches at all its points and then plugs into the fire wall on the Driver side. The under dash harness plugs into the ECU, connects to all its points including the fusebox and the same firewall harness. One Harness is all you need!

topdown

Before anyone runs out and throws down $400 on a wire harness from GM w/no return policy I'd better clear something up. The 91-92 Z28 harness and fuel lines I mentioned will work fine in any other 3rd gen f-body, but if your doing this conversion in anything else you will need to have your wiring harness customized or get a painless wiring kit and the fuel lines need to be spliced differently. ALSO I forgot to mention (sorry) that your fuel pump will need to be upgraded to a high pressure unit. It's a direct replacement for any TBI equipped vehicle but you need to drop the fuel tank and that is a dreaded job in these cars! A TBI pump runs around 10-12 psi where a TPI/Multi-port pump runs closer to 40+ psi. A factory replacement will be fine but seeing as the pump is so hard to replace you may want to look into an aftermarket unit. Something to remember is that a High Performance pump will work harder and probably wear out sooner also, so if you don't plan alot of mods the factory replacement might be best.

topdown

Hey 91bandit, I just read some of your other posts and I see your situation. Use a 91-92 z28(or T/A) wiring harness w/ correct ECU and EPROM and eliminate the harness and ECU your using now. The harness you have could be converted but it will cost more than a brand new harness and will be harder to diagnos problems in the future. 91-92 z28's had VATS also so it will function normal...as will all dash guages and acc. and service engine light.

91banditt2

iTrader: (1)

so all i would need is a Speed Density harness?

now what about the fuse block would i have to swap it out for a 91-92 TPI car or can i leave it in and use it?

and thanks for your help.:rockon:

topdown

Leave it in...it will work fine.