Well, im looking into a turbo for the 305 tbi i have,
https://www.thirdgen.org/techbb2/sho...hreadid=252419
you can read more there...
im diff going to do it, since i see no other way to building the crap outta the 305, screw N/A where going turbo now!
What limits can i push that peanut, swirl port POS too!?
lol...

 

Why even bother to go with boost with a stock tbi when you can get the same results by spending less cash on the parts that are the bottle neck in the system? One major problem is that, in stock form, the tbi ecm cant see boost so you wont have any control over fueling with jsut the computer when the pressure goes above one atmosphere. It is possible to make it so the ecm can see boost and control the fueling correctly but its way over most peoples heads. There is also the fact that its a wetflow system so problems can arise with the fuel dist. On top of this is takes away from one of the major pluses of TBI, simplicity...

If I where to use a turbo I would probably go with a custom MPFI system with an ecm that was origionally used in a turbo application. No offense, but to me a turbo charged tbi is sort of a pipe dream. In reality it would be a pita to get it all to work properly and the end result may not justify the means, not to mention that youd have all that plumbing in your engine compartment

 

Putting a turbo set-up on an un-tuned stock head and cammed 305 TBI is like putting a baby on steriods. The end result is still weak. Your gains will be much less than if you do a proper heads and cam swap. It is pretty much impossible to tune a turbo TBI. Listen to Dewey and Dimented when they chime in. It is time to fight the real enemy. There is just to many problems with this to go on.

EDIT: Dimented beat me to it. Listen to him.

 

EDIT: Shifty beat me to it.

 

well then i guess all swap out TBI for TPI,
i liked TBI so much better tho....

 

No to TPI as well. It has just as many problems.

Need,

You have the right attitude, which is good. However you seem to be going about it all the wrong way. Just look around and see who is fast and what they are fast with. These TBI cars have been around for over 15 tears now. If they could be turboed and modded so easily we would have seen at least one make it by now over the last 1.5 decades. You can have a lot of fun with a 305 TBI car. Even if you can only get it to perform with a stock LS1 car you will be happy and have the sence of accomplishment. Just ride in one and I bet you would be hgappy if your 305 could do that. There is more to hot rod happiness than 10 sec timeslips. Keep your head up though and just be prepared to learn.

 

Shiftycapone, Is there any way you can make the tbi run on boost, if you swap out the heads and put a cam, maybe bigger injectors. There has to be a way to make a tbi run on boost.

 

it will run on boost.

if you figure out fueling, and the computer issues. boost is boost is boost. but you can blow as hard as you want through a straw, a garden hose will always move more air.

no one has said its impossible, we have hashed this subject to death over the last 5 years. guess what, there are SC'd TBI cars, there are probably turbo cars, but for there are cheaper and easier ways to get to the same power level.

<< RANT >>
what really gets me, and I rarely say it, but if you are having to ask these very basic questions, i doubt you are ready to take on a project like fabricating and making turbo's run. why beat a dead horse over and over and over again, every freakin' post i see about turbos goes something like 'I want turbo's Yo, so i can run boost, i'm going to smake vipers, and make my ***** buddys shake in fear. I'm going to the coolest guy in my town, please tell me step by step how to turbo it Yo, ohh btw, how many spark plugs does my car have?'
<< /rant >>

 

lol ....... What do you mean by fueling and computor? ( fueling ) bigger injectors, (computor) maybe work on a burn chip . Will that solve the isuess of the computor and fueling problems?

 

No, it won't. I won't even go into it. Just listen to Dewey and Dimented when it comes to tuning exotic TBI set-ups and be prepared to be schooled.

 

no the problem is, anything above atmospheric pressure the computer does see, it sees 1psi of boost as 0 vacume, and it see's 30psi of boost as 0 vacume.

 

so how do you make it see 1 psi of boost?

 

that is where it gets tricky.

there are 2 and 3 bar map sensors. but they aren't really compatable with our computers.

this is where options come in, and why it is typicaly easier to go with a NA motor, for this same power level.

You can swap computers. the 749 ECU from the SyTy's came with a 2bar map. they are set up to read boost. its not a direct swap, but doable.

Aftermarket, many of the aftermarket computer can handle this. the commander, DFI, gen vi and vii, ect.

or you can use a best referesed FPR, also knows as and FMU. this is not a great option for our cars. from the people who have done this, i hear that they don't really make an FMU capable of supporting the boost/fuel ratio needed for a TBI car. so you can do the best you can, but it will probably never run to its potentional.

 

who said i want to, I EM....
i kno i can turbo it, sure we all kno that it wont be the most powerful risible mod for a 305 tbi, but who ever said maybe in the next few years im not going to shall out for something bigger, and if you ask why not a 350 now or a better engine? my answer is my engines runs good, why pull it when its a great runing engine that has no probilems?? sure its not that fast, but i can make it fast in the mean while... and i found and have the parts to do it...

so why not?

 

Because it is limited. Sure it is fun and great way to start performacne wise but when you have goals of high power numbers it just falls behind. Lets just say this. I have done basically every mod to my 305 TBI and it only has 34,000 origonal miles. I cannot wait for the day when I can get rid of it. It only takes a few rides in various stock and modded LT1 and LS1 cars to convince you of this. Later on I will take the approach of 25THRSS who has a few scary cars and can play with a wannabe 12 second TBI car in the meantime.

 

What is that SyTy ???? What car is that? or computor is that?

 

What you have is a good running shortblock. The heads, cam, and jsut about everything else arnt of any use. If it still runs good then mod the shortblock. Itll be cheaper and easier to do so.

One thing your not doing is considering the fact that itll be dificult to adapt a turbo to the tbi. Ive never run, or owned, a car with a power adder like a SC or a turbo but the obvious limits imposed by only having two fuel injectors AND having to deal with boost would be difficult to overcome without having much knowledge of how it all works. Sure it would even be possible to maybe work over a standard TBI ecm to make it see boost and set everything up to make some serious power but if your a newbie then that sort of thing will be way over your head. I remember thinking the same thing when I first got my car and didnt really know anything about it but I came to the quick conclusion that it would be a pita to do it as a first mod.

If your just starting out then turboing a stock TBI car and having it work is little more then a pipe dream. There was somebody that SC a nearly stock L03 and got it to go 14's. Shaving about 1-1.5 seconds of the time of a pretty much bone stock car was nothing to sneeze at, but his words where somthign to the effect that by the time he slapped down all the money on the SC, there just wasnt enough left to make other mods to the motor to really let it breathe and stretch its legs. Do the more conventional mods first, itll be easier. A chip and some extra fuel pressure wont even come anywhere near to making it run properly.

 

I wish I had an exotic TBI setup. Just have a low compression 350. Basically stab it in first and the front of the car will come up and obscure my vision of the road while being pressed into the seat but its short lived and it fades out by around 4500 rpm. Never knew what 2-4 felt like, though, as they didnt exist at WOT. I have a feeling it would be one of those cuts a good 60 ft. but fails to deliver anything by the time it gets to the end of the track. I guess I have laid a good foundation but I have no money to put a house on it. I was thinking of maybe a zz430HP but those are close to 5k a pop and Id have a hard time justifying blowing that on such a ****ty car. Maybe Ill make a zz4 clone out of my 350 shortblock.

Of coarse I havnt used the car in quite some time as its broken. Ive been using this damn crustang. Not only does it have as much interior room as a clown car and is about the same size a s a civic but its slow as dirt. Ill start off at a light with the gas mashed to the foor and Ill speedshift the whole way down the highway and by the time I make it to 50, the next light turns red and I have to start all over again. OMFG IS THIS THING SLOW! I dont even want to hear those guys with LG4s and LO3s complaining. I didnt think it was possible for a car to be this slow. I really have to fix the camaro.

 

Don't we all.

Mine is nothing special either, i think the difference with us, is that we were not just happy with a car that ran ok after the mods, we wanted to understand the computer system, and wanted to try to get the 'perfect' tune. i don't even want to think about the number of hours i have spent burning chips, and driving around. and reading info from Grumpy, and Rbob about the way our computers work.

 

What is that SyTy ???? What car is that? or computor is that?

 

They Syclone and Typhoon they are turbo charged AWD S10's and Blazers. They use the 749 ECU. SyTy is the name they have picked up, I guess it is easier to type.

 

dude why not just go with a rocket engine since you are dreaming, hell, buy a space shuttle and put camaro emblems on it.. youd be the envy of all your buddies!


I think there is a new "Dream Weaver" in town... you guys probably dont remember those days though

 

i know that the syty wont not work correctly because they have 6 cy engines and i will be v8 now they have 6 injectors while'll i be having 2 so how will that work?

 

Well has anyone put a vortech sc on a tbi? if so, vortech sells a fmu for about 150.00. from there all you need to get is a 2 bar map (right or wrong) ?

If you do put on the fmu and a fuel regulator and a map , you should be fine to run boost?

What kind of fuel regulator are you talking about?

 

the FMU takes car of fueling under boost, you would not need to try to work something with a 2bar map in. the problem is the ratios available. search on the poweradder board for FMU and TBI, the people who have done this, have posted.

the syty computer will work, it was in other GM applications too. you just need to make sure the impedance is correct.

 

The 1227749 ECM can support TBI injectors. The same ECM was used in turbo sunbird applications with a single injector TBI. And, it will handle the fueling needs (ASSuming the injectors are properly sized) of manifold pressures above atmospheric. There are algorithms that add fuel under boost conditions.

I've recently installed a TBI where the CCC Q-jet used to be on my 81 Turbo Trans Am (301 ci motor with stock draw through turbo setup). This is using the 7749 ECM. I haven't had time to complete the fuel line supply/return hardware, yet. So, it hasn't actually been on the road. But, it does idle very nicely while sitting on jackstands.....

If you're looking for a quick-and-dirty boosted setup, you might want to look at something similar to this. (Before everyone chimes in with the drawbacks of draw through systems, let me tell you I'm very much aware of these.....) In 1981, the 301 Pontiac engine ratings were 200 HP/340 ft-lb w/turbo vs. 150 HP/245 ft-lb NA. E-bay has the turbo/carb/plenum hardware available quite often. There would still be a large amount of fabrication involved getting things to fit into a 3rd gen. But, you're pretty much stuck with some variation of that problem no matter how you go.

All of that being said... If you're completely convinced you want a turbo for bragging rights, cool-ness factor or to warm your hands on cold days, this is another possibilty. However, if you're just looking for more HP out of your 305, I'd concur with the previous posters and go with head/cam/exhaust mods. They'd probably be cheaper and easier to install compared to the turbo setup. Of course, if you plan on putting the two approaches together...... Hmmmm.....

 

here, its cheaper, easier, has more potential and makes more power.

alternative

 

If your planning on anything EFI related, you first have to learn about tuning EFI.

Go to the prom board and start reading.

Then spend some time on playing with your stock TBI.

By the time you learn about sanners, and tuning a TBI, you'll be in a position to really think about modifications.

 

problem witht that is its not always cheaper..you factor in the 2+ grand for the motor, and then what? You have a engine that has no intake or any kind of intake system..So you throw your stock intake and TBI ontop? uhh..id say that would choke out a 330 horse motor that you just spent all that money on..Then you replace the intake..and mabe even the TBI unit with a performance unit. Ok, now you run into the wall that most people dont want to climb over. Now its time for you to buy a laptop, a prom burning thing, some chips, and all that other stuff you need to burn chips. Plus learn the language of the ecm..for someone that wants power now, i dont think thats a good idea..unless you guys feel im saying something wrong. Im going through the same dilema now, my 305 is tired as hell and i want more power. no sense doing anything more to the 305, so i want to go with a 350. Now i dont know what would be better off, getting a 350 carbd setup, like the motor you posted above but in "deluxe" trim that comes with carb, intake, etc. Or to get the motor you posted above or something similar and adapt TBI to work for it. To me for a kid whos going to be going to tech school during the day and then working at night, a quicker way to make the power would be with a carb. I dunno, im a confused person right now...

 

I have a 79 Horizon that youd probably school me with, 1.7 ltr carburated VW engine and an automatic, there is no slower car, there just cant be.

 

What about nitrous on your TBIs? Wouldn't that be a fairly straightforward bolt on or do the swirl-port heads completely screw you with that kind of boost?

Or I suppose the boost from NOs is just as impossible to program the ECM for as it would be for a turbo?

 

People have run nitrous before... I never really like the thought of it as its only temperarily fast. Fast all the time is better. Thats why id sooner invest in a good motor before Id consider messing with a completly stock L03.

 

Well, this guy in Texas successfully supercharged his 91 TBI Camaro, so now we KNOW it can be done. Does anyone on here know this guy?

 

what it doesn't say in there, is what it took to get it running. He is not the first to do this. The point is, it is not very tunable, and will be A LOT of work to tune.

I'd be more than willing to do turbo's on my car, and do everything to make it run, and post everything i did, and document it. If everyone wants to donate to rund it.

Sitting Bull -- Nitrous is diffrent, it isn't 'boost' the MAP sensor still funtions normaly. Also with a Wet kit, it is adding the appropriate fuel with the nitrous, inedepently of the computer. the only computer change i would do for nitrouse, is drop the WOT spark a couple of degree.

 

I deal with turbos, and turbo cars on a regular basis.

I will say first and formost, there are less then a handful of these that are TBI. The simple reason, it is simply too much trouble.

I don't want to hear any comments about it, but I am working on an 89 Conquest TSi with an Eclipse 2.0 motor (and a T4E Turbo). And no, the Conquest is not FWD, it is RWD with a FWD engine mounted N/S.
This situation alone is a mojor pain. Anyway, the engine was choosen for MPFI, and they are good motors. I can spend less then a week tuning the computer and have it VERY fast.

Yes you can do ECM swaps, with the TySy/ GN/ TTA/ 88/89 GP and a plethra of Chrysler cars, but your going to have problems, ALOT of problems with tuning. Hell it is easier to T/C a CARB motor. I have seen a few of those, and they took the better part of 6 months to tune while SLOWLY creeping up the boost.

Yes boost is good, but if you can get say 120 HP (from 10 PSI) for 1/4 of the price of a turbo, why turbo? and have to deal with all those problems as well...

 

I'm kind of lost on why *tuning* a TBI boosted application would be any harder than an MPFI system.... I'm ASSuming both systems would have the necessary hardware (appropriate MAP sensor, ECM software that supports greater than 1 bar MAP, appropriately sized fuel pump, appropriately sized injectors, appropriately sized TB, etc.) If I have a system that has all of this, why would tuning be harder on one as compared to the other?

 

because the parts upgrading would be hell.
The magrin for forgiveness is higher with MPFI. It simply has fewer flow restrictions(not having to flow around the monster injectors - not to mention alot more fuel delivery potential) And yes I know about the 80 whatever Lb 454 injectors, but 2 80's cannot compare to 8 75 Lbers.

I should have said that tuning would be slower, and alot more finicky. You would almost need to tune for one setting then raise fuel pressure/boost, tune some more, then raise fuel pressure/boost and so on. Just slapping on a rising rate FPR would not exactly do it as it typically does for a MPFI.
Trust me I have seen it tried... many times... a guy went trough 5 engines tring. Burned all of them up by not listening and tried to jack everything up at once cause he set everything pig rich, so he thought he would be ok. He did not realize that once there is PSI the static (fuel) pressure needs to be tweaked in reference to PSI(boost). And that takes ALONG time to do.

I am only saying that a rising rate FPR on a TBI will only go so far, the rising rate is simply not enough. The fuel delivery is simply nothing compared to a MPFI car. Wet delivery systems are simply not the best choice for turbocharging. They have a much higher rate of failure under these conditions.
Tuning with a R/R FPR is a handful at best with MPFI cars. It takes alot of getting used to. Again trust me. You simply are speechless when all the sudden there is this HUGE fuel surge once it starts working, so you have to take fuel out and go through the long tedious process again. But after a while you just learn generic settings.

Just ask about how many of the 81 TTA's are still running under good turbo power? The motors have more then a tendancy to grenade when the carb hickups. That and the bottom ends were not that great either.

 

I don't know if I completely agree with the thought there are different margins of forgiveness between the two systems. Going lean on either one will grenade an engine at pretty much the same rate! But, my ASSumptions listed above were meant to take out the "TBI won't work on 1,000,000 HP motors because they don't flow enough fuel/air". I was ASSuming the TBI has the fuel and airflow capabilities to handle the motor requirements (like a mildly turboed stock 305 as per the original subject). I completely agree there's a threshold where the TBI TB and/or injectors just won't cut it.

I'm again ASSuming (I seem to be doing this alot here....) that the Engine Management System is able to comprehend and respond to "boost" as per the earlier post. For example, the 7749's ability to extend the injector pulse width relative to boost and RPM. I'd agree just slapping on rising rate fuel adjustment all by itself is a poor shortcut with its own sets of drawbacks. But, I'd expect similar, if not identical, engine behavior with EMS software that supports "boost" and can be calibrated to deliver the fuel properly. Effectively, set the fuel pressure once and tune accordingly.

And, regardless of TBI or MPFI, it's a good idea to stay on the safe side of things and slowly work your way up on boost. I don't see much of a difference between the two systems here if tuning shortcuts aren't taken.....

Actually, quite a few more 301s were removed (and are still being removed) not because of "premature/catastrophic" failure as much as for 99 additional cubic inches of engine. (And all the HP/Torque those additional inches bring with them for the ride....) True the bottom ends are weak. But, the basic turbocharging system used on these cars (draw-through carburated) was shared with similar-aged 231 V6 engines, too. I'd have to defer to anyone that has real statistics on these engines. But, I'm not aware of anything systemic that was carb-specific that caused the engines to fail. That being said, I'm sure someone somewhere had a fuel pump fail or some muck clog a jet during a WOT blast that destroyed an engine. I'd also be just as certain something similar has happened to someone running a version of MPFI, too!

Anyway, it seems like our differences in opinion lie in our ASSumptions of how the system is equipped. If the TBI can handle the air/fuel flows required of the engine with turbo *and* the ECM is smart enough to handle the different fueling needs under boost, there probably isn't much difference in tuning effort between TBI and MPFI. The sensitivity of the engine to going lean due to tuning, injector failure or fuel pump failure is the same between the systems. As we start taking shortcuts like FMU with 1bar MAP instead of boost knowledgeable ECM, I can see the tuning efforts going through the roof.

Of course, I could be entirely off base on this.....

 

I dont know if it would really be any harder using either an ecm that supports boost or maybe your own code that youve whipped up but you may be short on fuel with only two injectors. Youd still be handicapped to around 400 or so horsepower. Going MPFI allows for eight injectors that can supply a heluva lot more fuel then the tbi ones could.

 

That was kinda my point.
Yes, granted the 454 ones could probly get you to a steady 7-9 PSi. WHich would equate roughly to 90-120 HP. Which if things go correctly, about 4-430 HP total.

I did not say that if an injector fails on a MPFI that the engine would surrvive. That one piston would discentgrate rather quickly, but the other 7 would be "ok". If an injector, or a CARB or a similar "Wet" system delivery device were to fail, it would be much more likely that that AT LEAST 4 cylinders would fail, if not more. And the entire motor would be trash. At least with only one cylinder failure, you can do several things...
1. turn down the boost to make it home.
2. still have a complete salvagable motor. and be looking at replace 1 or 2 cylinders and their components.

When I begin tuning a Turbo motor that is MPFI, I can typically Start with the boost level at 7-9 PSi with a 1-3 R/R FPR (1 Psi boost raises fuel 3 PSi). And amazingly alot of time the stock components will handle it.

 

The tbi injectors seldom, if ever, fail. Theyre all but bulletproof. Ive seen the drivers have problems, though, but from what Ive heard it causes a no-start condition. Have an ecm with bad drivers. The car just wouldnt start one day with that computer.