After spending many hours sifting through wires,sensors,more wires and sensors I got my 89 GTA running smoothly. I spent 1670.00 and many hrs. chasing bad grounds and poor sensors as well as a bad ecm. On my 87 GTA I dropped a 500hp carbed AFR headed 383 in and now have a beautiful engine bay and a car that runs 11 sec. 1320's. It is far more fun to drive and I will now be spending my spare time upgrading brakes and handling instead of chasing wires and fumbling with plugs and sensors. My first TPI third gen had about 4000 in upgrades and made about 300fwhp and although it felt fast ,it ran out of steam at about 5300rpm. With proper carb tuning and well matched engine upgrades available to even the lower budget folks (like myself} I find it unusual that tpi still draws so many enthusiasts. Please enlighten me.

Rob
Edmonton AB.
87 GTA Mod
87 IROC stock
89 GTA stock

 

Frankly I would say that TPI (and TBI) cars are far much more efficient than carburated ones at least for a daily driver...

 

I agree about the efficiency aspect but I think alot of us Third Geners drive these cars for fun and also enjoy working on them with buddies and such. I found my experiances working on the TPI engine more frustrating than anything and I couldnt get at the engine bay to detail it properly after a Sunday drive. My 670 cfm Holley Street Avenger carbed 383 with AFR 195's is getting 18mpg on the hwy in OD. Hard driving is another story and I would estimate 10 or 12mpg. I read the SA design book on tuning holleys and it was well worth the time. The car drives exceptionally well with a 2500 stall converter and revs to the moon when called upon. [xr 288 cam]. Im not bashing the TPI system but imho I find the carb motor far more fun to drive and maintain. By the way there isnt any e-testing here so I guess Im lucky when it comes to modding choices !

Rob

 

In a lot of states like California you have to be smog legal if you want to drive on the streets. The carb in place of the TPI will not fly. However with my next round of mods hopefully I can get into the low 12's with my smog legal TPI.

 

why TPI instead of a carb?

1, i can tune from the drivers seat.
2, i like the driveability i have with TPI.
3, no choke, runs perfect from cold startup.
4, i like the fuel mileage i get with TPI..
5, no carb that will need to be rebuilt.

you can get the same performance from TPI that you can from a carb, but it will probably cost more.
fuel injection is not for everyone, but it is for me.

if i were to build a weekend warrior, it would probably not be carbed, more than likely it would be something along the lines of an LS1.

 

ya I here ya, I guess Im still bitter about all the time and money I have spent on past tpi motors . This is my first 500hp car and it was sooo much easier to build than my TPI stuff that I am wondering why I never did this before and why anyone in an unregulated state continues to tinker with TPI. Question: if your car is registered in a state without emission regulations than can you drive it through states that have E-testing ?

 

why anyone in an unregulated state continues with TPI are for the reasons i listed & probably a few other ones.

to your other question, yes, you can drive your car to any state that has emission regulations even though your car wouldn't pass there, you can even stay there & drive it for some time, how long you can stay there & drive it depends on the state, it seems like i read that california is like 3 months. if you move to an area that has emissions testing, then your car must pass the test there to be titled & licensed in that area.

with that kind of power, i bet that car is a joy to drive, & probably a hand full at times too

 

Tuning from the driver's seat-- that was my original goal....until I priced Accel DFI and a display in the dash! No matter whom I asked the Stock and Aftermarket TPI induction seemed to be limited to 350 to 400 hp. In order to break the 500hp barrier I was told complete aftermarket EFI system {SR/DFI,etc.} or carb! My budget dictated carb motor and I am amazed at how well this car runs with such old technology! Fine tuning the mid range and transition circuts certainly changed my EFI only mindset! When money allows I am going for the DFI with dash display ,but for now the carb setup has far surpassed my expectations! I understand why fuel injection is popular but the original TPI systems seem so troublesome to me and yet remain very popular?

 

Your right , It can be a handfull sometimes, and Im glad I didnt build this car in 1987 when I was 18 !!!

 

what limits the TPI is the intake itself, a factory LTR TPI intake just can't breath, they are just too small to move much air, & forget about making anything above 5000 RPM with one. FIRST has a LTR TPI intake that can breath, but its not cheap at $1000.00
thats why the LT1 conversion intake is somewhat popular, they give good power & aren't RPM limited like a LTR TPI is.

the factory ECM can handle lots of power, with the right engine parts & tuning 500 isn't a problem for it.
i forget what Craig was getting from his car, over 600 i believe.
for the most part the aftermarket ECMs still haven't got to where GM was in the first part of the 90s.

*edit*
i guess the should say there are people on the boards here that are making some good power running a LTR TPI, how much i don't know, but i believe there are some in the low 11s & probably some even faster.

"Im glad I didnt build this car in 1987 when I was 18 !!!"
LOL, i hear that

 

I don't know that TPI's are really that popular of a swap. I know the hot-rod crowd like's 'em because they're cheap (for FI) since you don't have to buy Accell/DFI, you can just buy a wrecked thirdgen or c4. Plus, FI is kinda like the cool ticket in hot-rodding.

For a thirdgen? Holy cow, you couldn't pay me to put a long tube runner TPI in my car unless it came that way. I'm keeping mine because to me, it's the way the car should be since it came that way, but a swap? No no, I'd go stealthram or SR, maybe a mini-ram. Like I said, there's some intangible pride about having the long tube runners in there, and it being a factory "TPI" car, but there's no mistaking that other intakes will make more power. It's funny, even the local Mustang guys will check out the LS1/LT1 cars trying to find out what kind of power they have, but when they see my, they almost instantly respect the TPI and strike up conversation even though they know it's not a match for (most) of them. It's like I get street credit for sticking it out with the TPI!!! LOL

For the sake of a swap, I agree with your feelings about the TPI. Now if you could afford a different FI set-up, that'd be different. FI is the way to go, assuming you can afford it!

 

I deal with this kind of question all the time. People often comment how complicated TPI (or fuel injection in general) is, and how simple carburetors are. Its all a matter of familiarity. I am very comfortable with fuel injection, but to be perfectly honest, I'm intimidated by a carb. I don't know enough about them to be comfortable with them, although I have rebuilt a few before.

In actuality, I find carburetors much more complicated than TPI. A typical Holley has over 120 adjustments. On a TPI intake, you set TPS voltage, and minimum air. There are no other adjustments, although it involves more parts to get running.

If I wanted to tune from the drivers seat, I wouldn't pick up an ACCEL, Holley, or any other unit. On a typical street driven application, I don't find it to be reasonable in comparison to what a factory ECM offers. The factory unit is much more easily attainable if it fails, cost much less, has more flexibility and control, has diagnostic abilities, the only downside I see with it is the lack of user friendliness. With a $185 emulator, you can tune in real time. The cheapest aftermarket unit out there is much more than $185.

 

Why? Because it was there.

 

lol

The age old question.

TPI is a restriction in itself, it isnt without merits however, building a car to maximize TPI takes more work than most people are willing to deal with or take the time to do properly.

They can also be a real PIA to get it to the ground when u get them there. They ET on torque, its why u see stupid low mph on a TPI car that can crack low 12's or high 11's and they are out there. But the entire package tends to be a well thought out setup.

I ignore the Superram(unless u live in states with open hood type emission inspections) its overpriced, but it does work and that counts alot if your talking full emissions legality where u live.

I would adapt a single plane or run a Stealthram and wont have to worry about a 5000rpm ceiling anymore.


Aftermarket injection setups arent impressive for the $$$$$ they cost. They still do not have as many functions as a factory ecm and the common ecms/software on our cars is literally picked apart and able to be modified at will. U can do as much as your knowledge lets u or even use a mildy patched stock mask and manage a much more serious buildup with it. Whether u need it to be emissions or not, its almost unlimited for anything you would drive on a street. U could be tuning it yourself for about $100. Want to get fancy and tune on the fly add $175 or get a real wideband 02 and make your life a lot easier your looking at $200-350 depending on what u buy. (realistically you could use the wideband on even a carbed engine for tuning as well, works great actually :-))

Even if it sounds like I hate carbs I dont. I love QJ's and have tweaked and tuned many on CCC cars and straight QJ's. I have my days and problems where I swear up and down and tell my friends I'm putting in a LS2 with a carb just so I have something different to play with that isnt affected by electrical gremlins lol So I feel some of your pain.

Ultimately its whatever makes u happy, I do like the start up and driveaway capabilites if injection, but with enough playing with a carb u can get too almost the same point. Doing either one properly for cruising, WOT, startup both hot and cold takes a serious amount of time.

The same applies to a spark curve, even identically built engines have subtle differences from one to another to make them a little different as far as fueling or spark requirements go.


But hey, if it makes you happy and you like it, go for it :-)

I havent seen two cars from here the same yet and it would get really boring if everyones was the same.

later
Jeremy

 

Definetly pros and cons with both systems and the thing that really got me was chasing a surging idle problem. There must be about 20 causes for this and I went through most of them. I eventually found if I disconected the o2 sensor and stayed in open loop it ran fine. I believe now that the injectors may be worn out and the o2 sensor was compensating for a lean condition on idle? At any rate it drives and idles fine in open loop mode so I just left it that way until I get the ambition to yank the injectors and have them tested. Meanwhile the 500hp carb car is providing great thrills for my kids and I on Sunday drives around the city!

 

For a race car, you cant beat a carb. Its cheap, reliable, and there are thousands of books out there on how to tune it.

But for a daily driver, you cant beat fuel injection. Not just TPI, but any fuel injection. We all recognize the limits the long tube runner setup places on us, but over the years we have found many ways to get around that. I took my long tube runners and had them siamesed.

 

i like tpi b/c everyone else doesnt lol...

as for power...they can do it. The long tube runner design isnt horrible..ive seen cars with 390rwhp and 465rwt with a tpi..even though it was the accel runners and base.

Im keeping my tpi just because so many people switch to a carb or another intake. Id like to keep mine...eventually ill swap my heads for some dart iron eagles or something. Im just curious to see much power i can get out of her before swapping the intake


plus the tpi looks cool

 

and as for building it when you were 18..

my ***..im 17 and this car has drained the life outta me with problems and money...sometimes i wanna sell it so bad, but then you go for a drive and all of its little imperfections go away...touching..i know haha

 

As far as I am concerned -- If you want about 300 horse, run TPI, if you want more, run carb

I'd guess you are probally more on the rich side than the lean side. And I'd guess that to be more of a camshaft issue than anything. If you've got lots of valve overlap, your 02 sensor detects that, and richens the fuel mixture by a fair bit. Thats why if you set it to open loop by unplugging the 02 sensor, it runs better.

You gotta be smart when working with EFI. You can't just look at whatever code is tossed, and just throw parts at it. You need to use your knowledge of how an engine operates, and how the various EFI sensors are suppost to operate, and using a scanner to check those sensors, determine what might be the cause of the problem, rather than just replacing whatever sensor might be sending an incorrect reading due to an entirely unrelated problem.

Personally, my biggest reason for getting rid of my q-jet in my 3/4 ton is those -30 mornings. I can't stand how difficult it is to get the truck to start, and stay running at those temps, and how once you do get it started, it bogs and sputters, and generally runs like a peice of crap, lol

The choke only really helps to -25 or so, then it just doesn't matter. Having a standard tranny on the ice, its important to have something that isn't gonna stall out on me by bogging while trying to accelerate onto the highway or something.

Other advantages include awesome low rpm torque, which is great for getting my truck moving with the bobcat behind it, and the ability to run at some pretty intense angles offroad

Sure, TBI does the same, but TPI is just so much cooler, and can be made to perform tons better

I'm from about 25 minutes East of Edmonton, just south of Highway 16 nearby Ardrossan, BTW

 

There are some on this board with TPI(modified) with way more than 300 horsepower. Some are pass the 400hp mark. I expect before the year is over there will cars way pass the 400HP mark with modified TPI. These will be 350-355 motors. By modified TPI I mean high flow intake manifold, runners and modified factory plenum.

 

Yeah, I'm talking factory intake though (of course with some porting, etc)

I know you can definitely get more power out of an aftermarket intake, but not all of us can afford that kind of stuff, lol

 

I like TPI for a daily driver. It starts up good, runs nicer than a carb, alot of go fast parts. If I had a strip car it would NOT be tpi. I also like the torque produced by the tpi setup, even though it lacks high end hp. It is possible for a tpi L98 car with just bolt ons to make a little over 300 crank hp. It all depends on what you want to do with your car.

 

I went carb. I'm going back efi, MS computer and custom intake. I guess in FL we don't have the cold morning problems, but other than that, my carb is as issue free as EFI. I'm running in the 11's, get 20-21mpg highway, and 17 in town(average). Pump the pedal once, hit the key and she's running. It'll idle fine by the time I hit the end of the driveway. Nothing wrong with a carb. Just takes a little time and a little tuning. Funny, same thing for efi....
I'm going back simply because efi is cool.

 

Madmax made 330 rwhp with stock runners. I believe he had an aftermarket intake. Not sure if the plenum was modified. This is with an A4 so he is past the 400HP mark at the crank.

 

Thats pretty awesome power output with a relatively stock intake!

Got a link to his setup? I'm about to build another tuned port engine for a buddy, and wouldn't mind taking a peek at what he did to build his to make over 400 horse!