i just wanted to thank everyone on the tbi boards for all the help when i was haveing tbi related issues

i just finaly gave up with tbi after doing so much to it and and only pulling a 16.1 out of it . mind you it spun pretty good bad track prep
i may have been able to get it into the mid 15s but i got tired of really haveing to work to even be able to get into stock tpi range
haveing a car that would run a 16.1 but also as it got a little hot run 16.7 was also annoying

so far tpi has corrected the hot powerloss issue

a few pluses for tpi so far have been no speed limiter
no more vacuum leak sound from the open element

and just the seat of the pants driveing is better so far
and the tbi heads really do make up for tpis off idle responce

im wondering why gm didnt put the "tpi heads on tbis" and vice versa
the powerband feels so nice

and for anyone else thinking converting to tpi get the correct harness for the car i used a firebird harness in a camaro and there was alot of cutting and spliceing as a result

once again i wanted to say thanks for all the help you guys have been

 

YOU WILL THANK YOURSELF many times every day that you did the right thing
tpi is way easier to tune in my opinion,looks modern compared to the carb look.did you change the cam at the same time cause the tbi cam is absolutely CRAP!?
congrads to you

 

I went through the nightmare of swapping a Firebird harness into a Camaro... I feel your pain. You should take that thing to the track and tell us what it runs.

 

The SOTP feel can be decieving. You can only really feel the torque, not the power. FWIW, my daily driver feels 'fast' becuase its got a peaky power band, but the 0-60 time is a whopping 12 seconds. Teh camaro doesnt feel that much faster, but it can do 0-60 in around 5 seconds on a cool night.

OTOH, the tuned port part will help prop up the mid range where teh power falls off with the swirl ports.

As Ive been saying for awhile now, one of the biggest issues with TBI is the fact that its a wetflow system and the fueling drifts alot with the stock ECM. Thats why you probably had the high temp slow down. The fuel has a tendancy to really skew things, not to mention that alot of teh TBI setups dont use an IAT, which can cause a huge rich condition at high temps.

I gave up and went to MAF, which is probably teh best mod I ever did. This makes TBI work more like TPI and other port fuel injecton systems. I havnt had to tune it much at all. All Ive really had to do was pull a degree or two of timing in certain areas for the 90-100 degree days. Accurate fueling is everything.

 

I'm not trying to start a TBI vs. TPI war, but TBI was not the reason why you couldn't get out of the 16's.

Most if not all of your gains from the swap is going to come from changing from a speed density to a mass air flow system. The modifications you made to the SD (tbi) setup threw the tune out of wack and required a retune to correct. With the MAF setup you won't have to change much at all to keep the fuel in the ball park.


Dimented, I agree with what you are saying but this issue really doesn't become apparent untill you've tuned system to the extent where you are trying to control that last few percent of fueling. It sounds like to me that azrael never even got close to that level of a tune. Kinda like worying about the color of the floor tile before you ever broke ground on the house.

 

True...

I do know where hes coming from, though. With a performance manifold and a CAI, even with tuning I had alot of performance issues with the stock computer. Really annoying to have it run good at one point, and totally dog out another. The inconsistency drove me nuts. Although I think a TPI conversion was a bit drastic to fix the problem. With EBL or similar and some more tuning, alot of the issues could have been alieviated. That and itll need some mods to detune the 'tuned port' part of it when it comes time for a bigger cam and better heads.

The mid range torque can be fun, though. Me and my brother had an 89 TPI GTA with a 400. Man, that thing could do some serious burnouts.

 

I've never seen anyone do a TBI to TPI swap and regret it afterwards. Congrats!

 

how do you adapt a MAF to TBI?

 

i converted from tbi to speed density tpi
i did it for more then the reasons i posted

i keep thinking id wait and see what tbi can do but after doing all the free mods and better gears alloy drive shaft and open element
i just figured that it would have pulled far better then a 16.1

a Friends stock tpi iroc running with a tbi motor under it he blew up the 1st got a tbi motor cheap and just tossed the tpi on it and that even running badly and with 2.73 gears
keep mirror to mirror with my tbi made me think that it was time for tpi

that and being Finlay seeing how slow my car was
so far I'm very happy and don't thing ill ever regret it

but when i got this car 2 years ago i let my girlfriend race me with my old 3.1 6shooter when i saw my modded 6 shooter school my tbi
i knew there was some issues
it took a major tune up and other things just to make it as fast as a v6 camaro
it wasnt until i gave this car the same gears as the 6 3.23 did i finally beat that car
sure the tbi was faster on the freeway but from a dig is where its at to me

so i went and got a tpi as my fathers iroc always made mence meat of my 6
so i figured what was the difference and the only one was tpi

i can truly say that the tpi swap as of yet has been the best mod so far

I'm right with cars that where blowing me by 2-3 car lengths before
and the lack of a speed limiter is nice aswell
btw the front tires in the pic where my rears lol one thing thats nice about the C-4 brakes can use 4 rear rims

 

If you never tuned it, then youll never get anything out of TBI, especially with the stock ECM, which really sucks. Same thing with TPI. Right now your not too far off, and the TPI has full IAT compensation, which allows it to run better (to a degree, given how its set up). With cam swaps and stuff, youll be back in the same boat. IIRC, there was someone here with a modded TPI car that was only doing 15's due to lack of tuning. Converted over to TPI for the same reasons, and went no faster. I remember getting beat by TBI'd civic hatchbacks because of teh total lack of tuning. It will absolutly kill the performance.

Everything needs to be tuned. Basically, its like slapping an untuned holley on an engine and wondering why it blows smoke and runs extremly slow.

 

I used an LT1 style MAF and 93-95 TBI PCM, which has additional inputs that can interface with the MAF. The PCM must be reprogrammed to accept the MAFs input and calculate the fueling, but once that was done, it worked like any other fuel injection system. Somewhere around here the source code is floating around for it in one of my old posts. Basically you load teh code onto the PCM, plug the MAF in, and set up the calibration.

Theres alot of bad blood with mass air flow from the old MAF vs. SD wars, but MAF really does work, and works well with TBI. Makes it much easier to tune. The only thing that has to be done for the steady state fueling is to calibrate teh mass airflow table. Would make a nice add-on to EBL

TBI itself works exactly the same way as a carb, so the performance isnt an issue. It really comes down to getting the fueling right. Once that is done (thru tuning or whatever), it works fine.

 

You naysayers never give up LOL! Congrats on the swap.
I did mine a few years ago and it produced 14.9 @ 93.

 

Never said MPFI/PFI didnt work. Just another means to get fuel into the motor. Ive thought of trying out MPFI for yucks, but the price tag was too great to convert over (700+ for everything). The one big advantage Ive always liked with TBI is that if the weather isn't overly hot, you get free thermal turbocharging if your using an unheated manifold. On days where the temperature is below 80 degrees, the fuel in the manifold cools the intake down to around 35-50 degrees F, offering greater power with no strings attached.

On that same note, TBI is also the hardest to tune system in stock or near stock form. Like a carberator, it has some unique requirements that have to be addressed when setting up the fuel management (IOW, dont use teh stock computer). If its done right, the entire system is autonomous year around and needs no attention. In this case, the user did no tuning whatsoever, so its sort of biased in TPIs favor.

 

So what's now involved in smogging it. That was a main reason I went from carb to TPI and then back to TBI for the visual pass ... I would like to convert to TPI but I really hate the fact of going to a referee ..... As tempting as it is sticking my edelbrock lower/SLP runners/ edlebrock headers and really feeling the power that my L-98 should have ...... The REF has me keeping my TBI LOL.

 

Also I was looking at the original posters pictures and I am just curious to what extent that LO-3 exhaust system hurts TPI's performance ... Or has it been changed? Also his injectors kind of look like grey top vette multec's is this true too? .... Also curious internally speaking if he has had cam/head swaps? Or is this a bone stock LO-3 .... My TBI combination seems to run pretty strong, but can't really compare mine to his.

Gotta say though he kinda inspired me to drop my polished TPI stuff on my engine and really detail my engine compartment LOL.

 

You may have a hard time getting it thru, unless there is a provision that allows for equal or later FI systems, but that doesnt sound like the case. Basically, the MAF will look like TPI, but with a carb hat of some sort and a large MAF. The ref will probably be all over it for not having the thermac and all that junk that doesnt do much in cali. The stock air cleaner and exhaust is EXTREMLY restrictive. Might want to look into 50 state legal stuff with CARB exemptions. Its absolutly killing your performance.

 

my tbi always felt strong but as soon as id pull up to something i figure had some speed i was taught a lesson in the fact that my car wasn't as fast as i thought it was no matter what i what i did to it

the tpi i put on was from a 90 formula 305 manual with G-92 as far as i know the injectors are stock
i had to get the the camaro air ducting elsewhere

my lo3 mods where all of the free mods listing on the site along with gmpp versions of the sensors for faster reactions along with a breather and open element

the long block is stock with 112k miles i figured if really the only difference from having a lo3 and lb9 was induction the tpi heads would only flow better up top and lose some of tbis low end

but the tbi stock heads seem to work very well with tpi
the 187 heads give me the off idle of tbi but then tpi takes over and gives me a ton of torque where tbi faded off and the 187 heads don't flow well above 5000 just about where tpi doesn't flow well
so it works out very well
I'm thinking about an Lt-1 cam or a L-98 cam as right now my sd's stock tune is looking for the l98 cam so I'm down on power from where i should be

but none the less its a major difference engine runs smoother its faster and Ive already notice a major increase in fuel mileage

i don't live where i need to be smogged so i removed air injection but i do still have the stock lo3 cat

as soon as i get a chance ill see what it runs now
i know the tbi could have gone better then a 16.1 but it would never hook correctly it just sucked i would put more money into my tbi to get 15s and watch Friends with tpi running 14s with no mods

but it seemed like every time it took off with a good hook it would also run closer to 16.5
then if the temp went up a bit it would run a 16.6 and if to hot 16.9 all depending on air temp and how long i was waiting to make a run

i just got tired of the performance being at different spectrum's just because the car is a little warm

tpi seems to only lose a little from being around 100 to all the way up till almost at overheating the power is still there where as tbi used to turn into a real dog


about the exhaust

well every speed density 305 had the same exhaust setup as the tbis

hence the reason why stock for stock speed density is better then maf

speed density made more hp and the same torque with a crappier exhaust

maf got the 2 3/4 Sd got a 2 1/4 but stock to stock SD made 205 to mafs 190

other then the g92 with that got twin cats something i have but have yet to install


but really i suppose its time to move this thread over to the tpi forums

all in all tpi did what i wanted tbi to do but couldn't for whatever reasons

my goal is the have the best parts from the top 3rd gens basically a b4c
ill be swapping in some dual cats along with there proper manifolds soon

as much as i want headers i cant afford the slps i want so ill wait till i can
budgets for everything

 

As they say, Ignorance is bliss. I don't say this to be degrading but by not understanding how the ECM works leaves a big black hole in your understanding of how these cars work.

All you had to do was get into prom tuning and all the pieces of the puzzle would come together. The stock TBI ecm is quite a bit more finicky than the later model tpi SD systems. Which is probably why you felt such an improvement. Fast355 did a rather comprehensive TPI vs. TBI test and found that TPI only outpowered TBI in a very narrow rpm range. He also mentioned that TPI tune had quite a bit more timing than the TBI tune, which also effects power quite a bit. DynoDon found this out with his test.

In reality the difference between the two systems when properly tunes is such a small margin that just a few degrees of timing will make more of a difference. Most folks who have TBI are much better off spending the money they would have spent on a TPI setup on other mods.

I see this has fallen into a TPI rocks TBI sucks type post so more power to you, have fun with your TPI.

 

Good job on the swap man, but you should have looked into things more. And thinking your car will go from a 16.1 to a high 14 doesnt make any sense at all.. The 305tpi your talking about has different heads/cam etc.. I don't claim to know squat compared to any of the gurus on here but you should have taken the tuning route. And 16.1... can you drive? i ran a 15.6 with just 3.42s.. its just a matter of mashing the pedal to the floor

 

Hmmm... where to start...

 

Exhausts

No TPI car shared the same exhaust systems that the TBI car used ... A TBI cars exhaust looks like a LG-4's exhaust system ..... If they did it's news to me, I've never seen a TPI car without a 3 inch Y-pipe

 

The 90-92 305 TPI's with automatics, and the 5-speeds without G92 got the TBI/LG4 smaller exhaust system (2 1/4") with a single cat. They were rated at 205 HP. The 305 TPI 5-speeds with G92 got the larger 350 TPI exhaust system (2 3/4") with dual cats. They were rated at 230 HP. All 90-92 TPI's have the larger 350 camshaft, regardless of G92 package or not.

 

TPI is the shizzzzz.... don't let the HSR or Victor Jr. Guys tell you otherwise.

Welcome to the club!

 

the point was gm fine tuned the speed density setup so much more that it was able to make more power with a crappy exhaust

i didn't mean it as they just took the maf out and put in a map sensor and bam 15 hp

and BMmonteSS Ive read all the threads posted by fast355 but
he has been the only one that ever seems to get results out of tbi

and for tpi only having power peaks in certain areas well thats fine as the are where you need them
and for mind you my car is a daily driver for the summer but its also my toy
i don't need a 400hp rocket with that only gets 14mpg
i wanted a car that could keep up with or be faster then most of the family sedans and trucks out there

i really got tired of silverados smoking me just because ya they have ls based 6.0 but they also weigh alot more to

i mean every time i took my tbi to the track when I'm running only a second faster the 4.3 blazers and then to get smoked by an escalade at the track its embarrassing
why do i blame the tbi
because simply put i put tpi on top of the exact same motor and and now 5.0 gts that used to have 4 car lengths by the time i got to 70 now they only get as far as my front bumper that tells me alot about how crappy tbi is

or how i put 4 car lengths on a tbi rs last night the feeling was great that wow all i did was tpi and now i don't have to be the loser all the time anymore

it really sucked dumping money into a car and when Friends got in the car they say thats it thats all its got

at lest now i can throw them back in there seat

all the major tbi guys talked about using different manifolds to get more power

well did that but i also changed my comp and added 6 more injectors

and not only am i much faster I'm also getting 4 more miles per gallon

like i said before i tried to work with tbi but i grew up with tpi camaros

i tried using what i know about making tpi fast into making tbi fast apparently its much different

i know putting gears on a tpi car do great things
i did see a difference with tbi swapping to 3.23s but it just didn't do as big a jump as tpi cars do

maybe its just because now i stare under my hood and see this great looking intake i guess even if it wasn't any faster id be happy cause it doesn't look carbed

or maybe the best thing is ill never have to hear someone at a car show say man why the hell did you put a carb on that then having to explain that no really its fuel injection
really i just got tired making up excuses for why the car was slow
i had so many reasons for this swap only 3 of them related to driving it

Ive always preferred mpfi every car Ive owned was mpfi this was my 1st tbi
but really i guess i was just a tpi guy that happened to have tbi car
i only got the car because it was cheap or else i would have just got a tpi car to begin with

sorry for the rant but its just how i feel at this moment in time
for some reason this is something i could ramble on and on about
but i think I'm done now lets just say I'm very happy with the results i got
no matter how many people tell me i could have done more with tbi then i did
it wouldn't matter
I'm very happy with it and really thats all that matters

i really didnt mean for this to turn into bash the tbi but its the same way 350 tpi guys to when they swap over to mini ram bam they go alot faster as its better suited for a 350 then tpi is you the intake that was designed to make a "305" act like a 350

 

No problem with the rant...glad to hear someone tell it like it is.

Everybody enjoys TPI...only a select few "rave " about TBI.

 

Most people have a very poor understanding of how a wetflow system actually works. Thats one reason why tbi performs so poorly in the hands of the uninformed. Once you understand teh system, and gear the fuel management to a wetflow system, and actually tune it, it performs like anything else.

Im one of those people whos had BOTH systems. One mass airflow TPI, the current one mass airflow TBI. The TPI wasn't bad for what it was, but was always a little mushy off the line. That, and those damn Botch MAFs cost 300 dollars a pop when they broke.

 

cool.
and now that you have TPI, swap the TPI manifold for something else... and the heads.. and the cam.. and the shortblock to something thats not a 305.. and you'll have yourself a motor!

(modding a l03 is an uphill battle.. that only ends with something thats not an l03)

 

I envy you guys that can wakeup one day and say I'm just going to get my tools out and put TPI on my car or drop in a bigblock LOL .... If we did that a smog station would laugh at us

 

but its stock... all that i did was the air filter.. honest.

 

 

After I smog my trans am in december I am going to add TPI to my L-98.