converting tbi to tpi

[maroman88]

swaping a TPI into my 88 camaro, just the TPI system not the engine. i got it from smokingss out of an 88 GTA 350. i have started to take stuff out and was wondering if anyone has any tips or suggestions that may come in handy. so far i got the fuel lines out and the main wiring harness that goes through the fire wall disconected and few other things undone......

[9secfirebird]

nothing other than inspect the parts you have and make sure you have all the odds and ends for the swap

[j0n]

http://www.thirdgen.org is your friend :D

[V]

I found some other parts i have to give you. youll need the throttle cable too which i have for you along with another relay type box that mounts on the firewall by the brake booster. I'm going over all the parts from the gta in the next few days and anythigng tpi related i'll put aside for you. and i'll drop them off as soon as i get a chance.

[The Fixer]

Are you putting the setup on a 350, or a 305? If a 305, you will need 19lb/hr injectors instead of the 350's 24 lb/hr injectors. And definitely search thirdgen.org - there's information for re-pinning your TBI harness to become a speed-density TPI harness.

[Untamed]

What is the benefit of going SD (speed density) over MAF? I thought for 88's and such, MAF was the typical setup for a TPI?

[Tru2Chevy]

Not really related, but if you want to sell off your TBI stuff, I may know someone that wants it....shoot me a PM.

- Justin

[The Fixer]

What is the benefit of going SD (speed density) over MAF? Â*I thought for 88's and such, MAF was the typical setup for a TPI?

I don't know if there's a benefit, per se, I was really making the suggestion because I didn't know if he acquired the whole engine harness from Paul to make it a MAF setup. When swapping from a GTA to a Camaro in '88, it can become a problem because the GTAs had VATS (the key with the chip in it) and the Camaro didn't, so there are differences in the wiring harness.

I'm a fan of MAF myself, having swapped a MAF system from an '87 IROC into my '88 Monte SS.

[maroman88]

yea thanks paul i was wondering how the throttle cable and the trans cable would be long enough lol, i can pick the rest of the stuff up whenever you have it all aside and tru2chevy i might put all the TBI performance stuff on the 92, but not sure yet. steve i did get the entire wiring harness out of the 350 gta, what kind of differences would there be?

[The Fixer]

Â*steve i did get the entire wiring harness out of the 350 gta, what kind of differences would there be?

I'd recommend borrowing (or buying if you don't have it already) the GM Electrical Service Manual for the '88 F-body. Since both harnesses are from the same year, it'll be a big help.

The only thing I can think of off the top of my head is the issue with VATS - whether your car has it or not. If not, you'll either need to swap in the column and key from the GTA, or have a chip programmed to disable VATS.

[V]

as far as i know, 88 did not have vats yet, my old 88 gta(also tpi auto and digital dash) didnt have it. and from what ive read in the past only 89-up had it, but i could be wrong. I dont have the keys from this GTA, the column was drilled out to start it, so i cant tell if it was Vats or not.

[The Fixer]

and from what ive read in the past only 89-up had it, but i could be wrong. Â*I dont have the keys from this GTA, the column was drilled out to start it, so i cant tell if it was Vats or not.

Ah. Well, it could be '89 then. If you were using a screwdriver to start the car, that wouldn't work if it had VATS anyway. Sounds like he'll be OK using the '88 harness then. :)

[maroman88]

woohoo8)

[NJSPEEDER]

the biggewt advantage of speed density over MAF is that the MAF represents a huge restriction in the intake run. remove that and the engine will love you :)
too bad you are ditching the tbi, it is a very strong system. jsut never got any respect for som ereason.

later
tim

[maroman88]

i like the TBI, i have 2 lol, and i worked on this one for a while now, see signature, but im bored and i always want to change something and this seemed like a nice winter project. now if only i had a second garage to work on this car in.....daddys firebird stole my garage! what happens by removing the MAF, wont it throw the check engine light?? or is there a by pass. also do i really need to buy one of those cheesey thottle body coolant bypass kits or could i just plug the hole?

[Untamed]

IMO, the TPI system looks sexier under the hood. TBI looks like one step up from having a carb.

I should have my own 88 Trans Am next Sunday, with a 305 TBI in it. I'd like to swap to TPI, and drop in a 350 (yes Al, I'll take your suggestion), so the TBI in mine will be up for sale.

[NJSPEEDER]

i love some of this stuff. everyone rides the tpi nutsack sooo bad. tbi is capable of jsut as much power while using less expensive parts.
while it is true to get ultimate power you would want port injection, for a street motor i wouldn't spend all the extra money on good tpi parts.

later
tim

[Fasterthanyou]

TPI does look good. I'll never forget it when a thirdgen.org member said it looked like a metal spider humping the engine :) . TPI is great for a 305, I wouldn't want TBI or carb on a 305. Any motor that's close to square was designed for low rpm torque. A 350 with a mild cam and long runners is a great street motor because of the mid range power the TPI gives.
I like TBI because I've studied it to death. I can do anything with TBI that you could do with a carb but I have EFI benifits. I've done enough with both to tell you that TPI is great but it's not worth the $$$$ for the parts, especially not on a 350. The biggest problem with TBI is it's lack of knowledge base. TBI is seen as the imbetween EFI and so less desirable... I see it as perfect for new low budget high tech engines :) .
Another note; heavy vehicles need as much torque down low as possible (unless you've got a 6+ speed tranny) so TPI belongs on trucks. That's my belief. I also believe in light weight high reving high horsepower v8's for lighter vehicles. An ideal engine for a 3300-3700lb thirdgen is a 350-383 for the street, lighter and the 327 is looking good, for ultra light weight cars like a fiero with a v8 I'd build a 302 and build it to rev. Obviously for drag racing you want the biggest motor and like I said, TPI isn't made for bigger motors. The runners are too long and you'll notice EVERY dyno with mild TPI setups on big engines peak torque at a very low RPM and it just drops right off causing a flat horsepower curve... not ideal. A good TPI setup for big motors and flat out horsepower would have much shorter tubes and an aggressive tapper. Kind of like an Edelbrock RPM intake or Victor Senior :wink: . Oh, and looky their, TBI bolts right onto either of those intakes. Why haven't you seen more high horsepower TBI setups... because people are affraid and it isn't as easy to tune as a dry flow port injection system! Oh well, to each his own.

[maroman88]

well i was going over the new tpi harness and one major difference seems to be for the fan hookup, the firebirds batery is on the drivers side, camaros on the passenger side.....gotta do some "custom" wiring, yay! wat kind of wire should i use?

[Untamed]

Erm, my 88 TA has the battery on the passenger side, with the intake system for a TBI on the driver side. The TPI goes to the passenger side.

[maroman88]

ok well right now im attemping to swap TV (tranny kickdown) cables and its being a pain tryin to get at the bolt! Â*also its guna be a major pain in the ass to modify the wiring to switch the battery and the charcol canister.(firebird wiring harnes in a camaro) battery and charcol canister are on opposite sides in my car vs bird. other then that the wiring is in and as soon as i swap tv cables te intake manifold and distibuter can go in along with the rest of the TPI


any tips or pointers at this point???

[maroman88]

ok i have a bit of a problem, everything is installed and it wont start, the fuel pump isnt runnging so there must be a bad ground somewhere, the batery isnt dead, the headlights work. also i have a massive pile of little hose, vacum hose?, that might go to the charcol canister? someone wanna take a picture of how this is supposed to look and where they all run to. also on this harness (from an 88 TA) there is no thick single red wire that runs to the alternator and no wire that runs to the power steering. theres a few othe odds and ends left to go over but i neeeeeeed help

[Tru2Chevy]

Have you checked for power going to the fuel pump? And do you know that the fuel pump works?

- Justin

[maroman88]

yea fuel pump is new....nothing gets power, no door chime or hazards, just headlights...

[ar0ck]

Hey Maroman, if you need a camera for pictures, maybe I can follow you to your house from bergen.

[maroman88]

i got a camera, i jus need pictures of a TPI already in a car so i can see what goes where

[Untamed]

Check the fuse for the fuel pump. On TA's its in the center top of the fuse box. Dunno about Camaro's, though each slot should be labeled.

And it may seem silly, however make sure your battery is connected. A friend of mine was one second shy of calling a flat bed when he realized the ground wasn't connected. Another friend had a bad terminal on the hot - some corrosion formed under the shield and ate away enough copper to prevent it from channeling. Both are pretty easy fixes unless your battery cables are as tight as they can be already.

[maroman88]

ok i got the engine to turn over finnally. the harness where it goes through the firewall on the drivers side was the problem. the conector for the main thick red wire was not connecting wit the other side when plugged in. only problem now is that it wont start, i think its the battery from sitting for so long, so ill jump it tomarrow hopefully

[maroman88]

no luck battery is fine, it just keeps cranking and makes some hissing and popping noises but wont start

[The Fixer]

1st question, do you hear the fuel pump prime when you turn the key? Did you swap in a high-pressure pump?

If both of those are OK, then look to the firing order. Maybe the distributor was dropped in 180* out, or the wires are crossed.

[maroman88]

yea the pump primes no i didnt get a new fuel pump and i checked the plug wires 105 times lol, im guna go double check the fuel lines now to make sure that gas is gettin through....

[The Fixer]

yea the pump primes no i didnt get a new fuel pump

I'd bet that's your issue. The stock TBI pump is rated much lower; they run about 12 psi at the fuel rail. TPIs need around 35-40 psi at the rail, or it will not run. Time to hit up the parts store for a TPI pump, then drop the tank and install it in your stock sending unit.

[maroman88]

there was some presure, i got shot with gas when takin the lines apart but that was as far as i got, we had a working house fire so that shot the rest of the day to ****. i dunno how i would put the distibuter in backwards, it went in the only way i could get i back in, i made the marks of where it was when i took it out and put it back in the same place but could the timing be so far off it wont start? i just really aernt lookin forward to spendin 100 bucks and doin a fuel pump swap............

[The Fixer]

i just really aernt lookin forward to spendin 100 bucks and doin a fuel pump swap............

I don't blame you, but even if you put an adjustable fuel pressure regulator on it, you'd never get enough pressure to have those injectors flow properly. You gotta do it!

[maroman88]

grrr, but it wont run at allll, not even for a second, without gettin the fuel pump

[The Fixer]

grrr, but it wont run at allll, not even for a second, without gettin the fuel pump

I doubt it. The stock TBI pump flows maybe 1/3 of what it takes to pressurize the injectors; not enough fuel mixed with air and spark to get it running.

[maroman88]

ooooooo fine, ill start looking at prices for fuel pumps...