Draw-thru turbo

[Anonymous]

Anyone here running a draw-thru turbo ? If so, what are the pros and cons ? Seems like an easier setup over the blow-thru, minimal carb mods, no BOV, no inter/after cooler. I'm sure it has it's drawbacks or everyone would be doing it !! Also, I've seen some turbos glowing red hot !! Would there be an issue of detonation in the turbo itself due to air/fuel being in the turbo ? And lastly, is there a specific turbo to use in the draw-thru application ? I read something about carbon seals versus piston ring seals. Any info appreciated. (by the way, the books are ordered )
Thanks, Darrel

 

[XFlow_Fairlane]

well on a blow through you don't have to run a BOV or intercooler. But you can't on a drawthrough or else you will puddle fuel in the intercooler or expend air/fuel mixture to atmosphere. also the packaging on a drawthrough is a little tougher (you should try and keep it all down hill to the motor so that puddled fuel will not roll into the turbo) on a drawthrough you will also need to size the carb to match the HP you are looking for.....so a 300hp drawthrough needs a carb rated for 300hp (like a 650cfm carb or so) instead of a stock carb. so if you move up in the power range you will need to keep going to bigger carbs. I am not sure how well a 200 would idle on a 650 holleysince I would think it would be getting one poor vac signal.

 

[Anonymous]

I don't have it running yet, but I have a turbo from a 3.8 Buick with the carb mount that I'm mounting on a 250 in a Bronco. Advantage to me was cheap to start out with and set up, but if it works well, I will swap to FI and a blow thru setup which should work even better.

 

[Anonymous]

What carb are you going to run on that set-up ? I'm thinking of putting a Holley 1850 (600cfm) on my 250 and draw-thru. Or I might go for the "wow" factor and sync. 2 smaller carbs. I'm researching now to find out why you couldn't put an intercooler between the manifold and turbo on a draw-thru set-up. If it's a matter of lag, couldn't you up the boost a little ? Can't wait to get the books I ordered !!!
Darrel

 

[wallaka]

I'm researching now to find out why you couldn't put an intercooler between the manifold and turbo on a draw-thru set-up. If it's a matter of lag, couldn't you up the boost a little ?
Darrel

There's a couple reasons. The first is that fuel will drop out of suspension and make the engine lean out and go boom. The second, and most important, reason is that a backfire will ignite the large volume of fuel-air mixture that's inside the intercooler and make you go boom. So it's not a good idea.

 

[Stubby]

You should never run an intercooler with a draw thru system unless you are building a bomb.

The large volume of air/fuel mixture in the intercooler combined with one pop back thru the intake will blow it up and kill everyone old enough to die!!!

 

[Anonymous]

I realize you can't have the fuel mix in an intercooler. I was thinking of cooling the exhaust flow at the manifold, before it went to the turbo and carb.

 

[Stubby]

The hotter the exhaust the more boost, within reason. Cool it and lose pressure.
When you get your books you will understand.

 

[Anonymous]

Thanks guys. I appreciate the responses.

 

[Anonymous]

I was going to use the Buick QJ that came stock with the system, reasoning that it was already matched to approximately that size of engine.

 

[FrankBoss]

draw threw system work very well with larger carbs... I use to race turboed 2.3L that were carbed...I would use a 660 center squirter on mine with after market VW turbo parts... Dont be afraid of the drawthrew... You cant use a IC with one but with modern ignitions and fuel pumps they work very well..


Frank Canon

 

[matt1967]

how do you get a draw through engine started? is there a primer line that runs directly in the intake? I'm using a stock 3.8 GN turbo that was/ will be draw through carb'd but I don't get how fuel could get from the carb into the intake in short order.

 

[Anonymous]

Take some dry grass clippings or leaves and dump them in your carb and turn the starter. You'll be surprised how fast they get sucked into the cylinders.

 

[Anlushac11]

Way back many many moons ago when I had my draw through 1979 2.3L Capri Turbo RS (Mustang clone) we used water injection with water/non detergent winshield washer solvent mixed and injected into intake above turbo but below the carb. Worked like a poor mans intercooler because forcing water to steam the phase change takes alot of heat energy out of the intake charge.

Used a Hobbs switch to activate the water injection when the boost hit. You have to use a very fine input source or too large of water drops hitting the impeller can cause erosion on the blades.

At teh time there were several water injection kits on teh market. Not saure who makes one now but there are several do it yourself guides on the net.