I read old topicks concerning turbochargin and TBI, but still thinking of turbocharging my 305tbi . Here is a list of what I'm thinking:

- two hybridturbo (probably Garret T03/T04)
-fuelpressureregulator which senses boost
-blockked EGR and warmingsystem in intakemanifold
-350 injectors
-no mods in engíne
-boosts max 0,5bar
-intercooler
-maybe bigger cooler for transmission oil

Can this kind of combination run? What modifications are still needed? What about MAP an timing adjustments?

I have TH350 transmission. How does kickdown works with boost?

Thanks for tips!

By the way, I really wanna do this, not any kind of supercharger

!

 

With enough money you can make anything work. However, there is no way to tune boosted set-ups on a TBI system. It is all a stab in the dark. The bad thing about adding boost to a stock 305 TBI is that you could make more tunable power for less by going the 350 TBI route.

 

On knight registries they had a posting for a twin turbo setup. I am trying to locate the link but having bad luck.

 

Okay! Let's assume that I have 350TBI and I want to turbocharge it . I think broplems are same when we are talking about TBI engine? Besides here in Finland turbos prices are quite reasonable.

 

What is our jurys opinion about this:
http://www.perfectpower.com/products/smt6.asp

Is it suitable for tuning uder boost?

 

I am sure Dewey will chime in. He will tell you exactly why you cannot really tune forced induction TBI set-ups. Your money will be better spent elsewhere.

 

I'd say your best bet is to look into converting into a 7749 setup. Search the DIY-PROM board for that.

 

I didn't sign up for the wiring diagrams for that SMT unit, so i didn't get alot of details on it.

The funamental problem with boost on our cars is a couple of things, 1 fuel pressure, you have to not only increas fuel pressure in a 1:1 ration to just compensate, you also have to increast it above that to add fuel, while an FMU can do this, they few who have run FMU's with TBI have had some tuning problems. you might be able to use something like vortecs super fmu. Computer wise, someone else nailed it, you best bet is to conver to the 749 ECU, this is great and all, until it comes time to idle, since it handles injector firing diffrently. it is not a huge problem, and easily overcome.

You could also use a 2bar MAP in our computer, and revalue the fueling tables in the ECU. again, not ideal, you loose resolution. it would be a crutch and work under WOT, but you would lose part throttle drivability.

The other option, is to conver to the C950 from holley, it should handle driving our injectors alright. it can be had with both 2 or 3bar maps, and also has WB02 capabitility's.

all of this is just trying to get it to work. we haven't yet begine to deal with some of the other issues.

If it was me, i would really consider converting to some sort of port injection. IMHO tbi really isn't the best choice for turbo/centerfugal type of boost, it is a GREAT fit on roots blowers though.

i guess some other things to bring up here, are what kind of power levels are you looking to run. on a stock 305, the kind of power you can produce before you have alot of problesm, can easily be obtained NA, it is alot cheaper and easier to get that power. if you are talking about the 700+ HP range, then turbo's are the right route, but you will need alot more than a stock 305

 

Twin turbos makes life alot more complicated then needed. While everyone talks about lag, it's often the guys that have never driven a turbo'd car, or just some lil 4 cyl., that harp about it. A single would do you just fine, and be alot less work.

While it makes life maybe more complicated, maybe just do a 4.3L and use a set of Syclone exhuast manifolds. Just use what GM's spent millions developing. It'd be interesting seeing a TBI 4.3L turbo 3rd Gen.

And you'll want to use a 749 ecm.
Might even get one, and start tuning with what you have to get it all down pat before getting hip deep in the new combo.. You can keep it all plug and play, so swapping out ecms is a 10 sec job.

 

For the cost to turbo one of our cars.... couldn't you just supercharge it. I've seen many of these new "prochargers" on the market used at the local track, and I'm sure someone has one for a thirdgen.

One thing I was thinking of (Correct me if I'm out of line) was the heat generated off these headers. I had to put a cat back on my car b/c of new visual smog inspections, and man does that bitch get hot. With those exhaust temps, I don't see how you could benefit to a worthwhile degree by trying such a profound feat as to mock up your own customs headers, exhaust and intercooler.

This is assuming that you would never even attempt to put boost through stock LO3 Heads and cam.

I do agree that twins aren't necessarily needed b/c the amount of boost you would generate with a single would be plenty enough to create one hell of a tuning nightmare

 

Problem with one turbo is that it boost so late. With handmade twinhybridturbos I can get boost much ealier. Anyway exhaustmanifolds are easier to make for two !

About prices. Just talking about bare chargers. Two hand made hybridturbos specially for my project will cost 1300eur. One ATI ProCharger 2900eur. I think the difference is huge? I can make necessary mods by my self. I was thinking of using orginal exhaustmanifolds. Only mods are 2 flange and couple of curves .

Okay, when we think about mods, which are very similar n both cases (turbo vs. blower).

I have to make same mods to fuel- and timingmanagement. Same mods for intercooler. Same mods for tbi (some kind of boost container). Same mods for lubrication and cooling system for charger.

Only obstacle seems to be MAP-sensor and timing. If I put zener-diode to limit map-sensor value to ecm (max.4,7V). Is then problem solved? I think then with boostsituation it will give 100%fuel from injectors?

 

Really?.
I can be well into boost before the stall speed of the converter.
Lots of GNs stage at 15+ PSI of boost at, ~3,500 RPM. Matter of fact, I crack into boost at about 1,500 RPM, at small throttle openings. How much lower do you want it?. And run 24+ PSI, on pump gas. If you want to ask the board members Saturn5, RBob, Prevost, or Jeremy, they'll all tell you about how seamless my car is from N/A to boost mode. Any engine that's over 2HP/CID, under some circumstances is going to take time to react, lag is just what they call it in a turbo car, in a N/A it's just being below where the cam is starting to work. Both will take a down shift or a moment for the engine to build a few revs, or EGT to start making HP.

 

If it really works with one turbo, I will try it. Then it is very cheap to execute .

Can you tell me more about turbos specks? What kind of turbocharger are you using in your car. Where have you located it? Is it hard to make exhaust system? Manifolds must be very long?