Hey all,

So I found a TPI system for sale that I may go check out. I had a few quick questions.

- The system is complete (including wiring harness and dist. cover), minus an ECU. Were there different ECU's used between 305 and 350 cars?

- Which sensors/emissions equipment from a TBI set-up, if any, is compatible w/a TPI? If the TPI is from an earlier year car (Mine is a '91), will it still be legal to use on a same year/newer longblock? (It's just a visual inspection/tailpipe sniffer here).

- How do I tell the difference between an F-body and a Corvette TPI? (I hear there are some)

Thanks!

I'm pretty sure the ECU's between 305 and 350 are the same it is just the PROM chip that is different.

Don't know anything about emissions. Don't have any here so I ripped all that stuff off.

Main difference that I know of is the fuel rail on a vette the lines point straight out the front of the motor. On the F-body they make a 90 bend towards the drivers side. Also lower manifold on the vette has no exhaust crossover for EGR so it has a spot on the back of the intake where exhaust gases are introduced and would require extra pluming on an fbody.

the chip in the computer called a memcal can be identified bye it's three to four letters called a bcc Broadcast code.


http://www.hotrodlane.cc/Streetstories/choosetpi1.htm

I have a 91 firebird that had a 305 tbi. I put a 350 out of a 89 IROC in (after rebuilding it). Had to repin a few pins at the firewall and under dash. I used all of the emissions stuff from the IROC. Cranked right up no problems.

Of the 4 wires for the torque converter lockup on the 350 harness, one had to be repinned to match something on the firebird firewall. Left the other three as they were for future switch to auto and just put the 4th wire in with them unhooked. Could have been the wire for the backup light switch on the 5 speed. It needed to be pinned into the 350 wire harness so it would get plugged back in.

everything worked correctly including the check engine light.

No problem getting it inspected as they just do a visual and tailpipe emissions. But it looks EXACTLY like it came from the factory down to the air pump and charcoal canister.

I did need to move the battery to the driver side (IROC was on passenger side) which meant longer positive battery cable, and had to get an air cleaner for a TPI firebird as the camaro air cleaner setup won't work.

WHat year is the TPI from? I would think that the charcoal canister would be the same - maybe. air pump. Other than that you have the engine controls - like IAC which I think is different part number.

You can get a list of the parts you are concerned about and compare part numbers on autozone website.

Only the tune on the chip inside varied
Computer needs to match the harness you have
Computer type (85 -89 or 90 -92 ) will then determine if you are MAP or MAF system
Engine doesn't know / care what year intake or computer is on top


http://www.hotrodlane.cc/Streetstories/choosetpi1.htm
http://www.hotrodlane.cc/Streetstories/choosingtpi2.htm

Thanks for all the info! Unfortunately, the seller flaked out, so it looks like my search will continue.

It sounds like I'd be better off trying to find a complete system w/the ECU, or maybe even a cheaper motor w/one on it instead of trying to piece one together though. Maybe it was for the best!

Ok guys, I had just one more question about TPI.

So it's my understanding that 85-89 setups use MAF, and 90-92 setups are speed density? I'm still not entirely sure of the biggest differences between the two. I've heard that MAF is a little easier to work and tune, and that speed density usually requires a tune to work with even the slightest head or cam swaps, but that there's potential to squeeze a bit more power out of it? This is just what I've heard, so correct me if need be!

Basically, I'm wondering if a MAF system TPI is something I could quickly bolt onto a longblock (whether another 305, or 350 w/vortecs), and it would run ok without a tune? Or does it not really matter, do I need a tune for whatever setup I go with, no matter if it's MAF or MAP?

I've really never, messed with MAF but my general opinion of it is that it fails, I always hear MAF being the problem to engine troubles. I have SD and despite the fact my car sat for 6 years and has aftermarket injectors I've never had to tune it, it always starts first turn, and runs fine.

isnt the fuel pump needs to be replaced too?