my friend has a '81 turbo trans am which isnt very great from what ive heard but maybe kinda rare.

were pulling the engine out of it and looking at how the turbo is set up i was thinking about making a flange that goes between the carb and the intake manifold. my dads a CNC programmer so he could very easily make this for me the only thing i would have to bite is the cost of a big brick of aluminum.

ok heres how i would do it, make my own exhaust manifolds, maybe just run stock manifolds flipped to the outlets are facing upwards and are in the front of the engine, then make a custom Y-pipe with a welded on flange for a single turbo, it would be located somewhere near where the turbo is at on the GN/TTA. after the exhaust leaves the turbo id just have a custom downpipe running underneath the passenger side manifold and out through the stock route for exhaust


cross section of the adapter, made in paint, bear with me please



i know that it would full the fuel/air mixture through the turbo and it would be compressed and then forced back into the engine so you would have to keep the plumbing as short as possible from the carb to the manifold, so maybe for an intercooler run a small one like from a subaru or from a SVO turbo mustang?

with this setup you wouldnt have to buy a box for your carb but youd need to buy some type of cowl induction hood, probably a big 4 incher or maybe taller because the whole block under the carb would be about 6 inches tall, but i think it would be pretty easy to do. any questions, comments, suggestions? is there something im missing here? this is just an idea i was to know opinions

 

So I take it then you want to use a draw-thru set up since that is what the 81 Turbo T/A is? Ask me how I know. Which would mean that you don't need a pressure box on top of the carb. Well intercooling these things is alomost mute unless you want the fuel to puddle up and start a fire. Not to say that it couldn't be done if you did the work, but just by the nature of the draw-thru it is difficult at best. I'm still trying to get what you want to do. Bare with me. So you want to make a plenum to put on your Chev motor I assume? The good aspect of the draw-thru is that you can run unlimited boost(whatever the motor can handle) since the carb will not be pressurized. Just trying to figure out what the actual outcome you want. Use the turbo T/A set up and related pieces?

 

That is almost identical to the old Martin Turbo kit.
The Martin kit also has a vave between the upper and lower chamber to bypass the turbo when the turbo is not making boost.









Some more pictures here: http://jobyteknik.homeip.net/fredrik...turbo_systems/

 

Or maybe something like this....

That kit is up on ebay here..... draw-through kit

 

The main problem with draw-thru is that you need a special seal on the turbo.

 

IMO, dont do draw through. Your throttle response wont be as snappy as will blow through and your A/F will always be off somewhere in the RPm range. My buggy was REAL rich at idle and just right at WOT. That being said, a benefit of draw through is that you really dont need an intercooler. I ran a VW sand rail with a T3. The turbo and intake came off of a 301 T/A but the turbo was a custom hybrid I had built that used the trans am intake and compressor but with a T3 turbine housing. Anyway after a run I would come back to the pits and the intake would litteraly be dripping with condensation and the intake was freezing cold. I thought it was the funniest thing and cant really explain it but I figured the intake charge was colder than ambient at that point.

 

It was cold because some of the gasoline was turning from a liquid into a gas while in the intake. This state change is endothermic; meaning energy (heat) is absorbed from its surroundings as it happens. This is a definite plus for a system like this, although alky injection works on the same principle and can be applied to any FI (or NA) application.

 

Hey Larson-

My buddy in FL did a mid engine sandrail with my old 1776cc bottom end, used a junkyard T2 from a Suburu, made a flange off the four into one header, made a plenum and had it draw through a $50 swap meet 600 Holley double pumper. It did 7.49 at 94 in the 1/8 on 26X8" slicks. Real laggy on the bottom, but when the boost came hang on!

I can imagine the lag and idle roughness problems associated with the use of this type of draw through system in a street application. Which is probably why those old Rayjay and Martin systems went by the wayside years ago.

 

those old turbo kits are interesting, almost exactlywhat i have planned..

the reason id do this draw through type of design would be because i could probably have it done and finished for around 500 bucks and i could do most of the work myself. i wouldnt care so much about idling and stuff but the AF mix variation thing has me kindof weary, but knowing other companies have tried this type of system and it works, it may not work very well but it would work, not to mention it would be a good winter project for me..

what kind of special seal do i need on the turbo? is there a special kind of turbo i need? i didnt think there was much variation on the types of turbos. i imagine the special seal is to keep the AF mix away from the hot expanding gasses on the other side so it doesnt blow up, but i would like a little more detail with this so i dont blow up my motor..

right now im making about 250 (crank) hp from my 305, how much of an increase do you think i would see with this kind of set up? i know i probably wouldnt want to push that much boost but at the track id try to push as much as i possible could, im hoping that it would at least put me to around 325 hp at a medium boost level, does that seem too steep? how much pressure would you recomend running in this type of set up?

sorry for all the questions but im really interested in this and want to learn more, knowledge is power

 

Isn't that interesting....never heard of that setup before. Pretty neat!

 

On a draw thru turbo system you have vacuum in the compressor housing during part throttle. That will pull oil from the turbo into the intake.

You need a special turbo with a carbon seal on the compressor side to stop oil from leaking into your intake under vacuum.

 

aah i see, are you able to put a carbon seal on any old turbo or do you have to get one that was manufactured with a carbon seal?

 

Carbon seal turbos are uncommon and I don't know what turbos you can modify.

 

I know all Rajays and probably most Airesearch also were sealed for fuel use.Your limited to about 425 hp with the biggest Rajay.Every now and then you will see the type of carb adaptor you have drawn up for sale on e-bay.Usually used on RV's and as a matter of fact they say RV Turbo right on the adaptor.Those also used engine water to heat the plenum up to help fit lean tip in.
I can tell you now it needs to be designed to where fuel will go directly into the engine without going through the turbo untill boost.If not it will be one hard to start ,backfiring, turbo laggin' SOB and you'll hate it.The Martin kit shown above was about the best draw through available since you didn't loose your hood clearance.They had a kit for Vettes and Camaros and another for trucks which is the one on the yellow motor. Those kits went for well over a thousand bucks in the day,the Accell kits were around 850.

 

Hey if it isn't Mike from Eldorado- haven't seen you on the S series board in awhile.

I remember you had pitures of some draw through setup you were going to install on your Z28 or something?

 

Eric! What's up.Yea I wanted to put it all on my truck but no way would the exhaust manifold fit.I haven't put it on the Z yet.A couple years ago an Electric company truck pulled out in front of me in the Z and I smaked him a little.I've about got it all fixed but I manage to get 10 more projects going at the same time.I did put some effort into it a week ago and worked on the distributor and fuel lines.My latest purchase is a 57 Chevy 2 door hard top.Lots of money and time going to be needed for that one.I'll have to wait for the kid to get out of school next year before I start since his insurance and up keep are mucho bucks!As a matter of fact today I'll be spending about $180 on a clutch ,throw out bearing and clutch master cylinder for his 89 Bronco.DAMN!!