onslaught_81

i basically just wanna know the difference...i keep reading about ppl planning to do either system but dont know what the difference is. and which seems to be better, yes this is an open invatation to argue like hell i guess.

mwatson184

Draw through means you stick the carb before the turbo. Drawing air through the carb, and passing on the air fuel mixture through the turbo (compressing it), and on it's way through the rest of the intake system.

On blow through, you have the carb after the turbo. Air enters the turbo, is compressed, is passed to the carb, fuel is thrown into the mix, and into the motor she goes.

Draw through advantages:
no need to modify carburetor
no need for a blow off valve
fuel system does not need a boost referenced pressure regulator or a high pressure capacity pump
maybe a few more...?

Draw through disadvantages:
Have to buy a special seal for the turbo (due to the fuel being passed through)
inability to intercool
intake icing
need for a larger CFM carb compared to blow through.

Blow through advantages
Ability to intercool (very important...more power safer)
"Small" CFM carb for the amount of HP made

Blow through disadvantages
must modify carb to keep boost in
High pressure pump, boost referenced regulator needed
no intake icing

I missed a lot of stuff, but that's the jist of it.

-Marques

mwatson184

Forgot to mention hard starts with draw through.

I would pick blow through any day of the week. Draw through systems are out dated, and will not yield the amount of power that can be made blow through, and are not as safe at an identical amount of power made.

custom13B

Well I had a draw thru on a turbo 12A and it definately is not as good as a blow thru. There still is a few mods needed even for a draw thru set up. Manifold referenced power valve 4 corner idle etc etc etc. In all honestly having been there for 3 years with this set up. By the time you modify everything to work on any carburated turbo you could have went fuel injection. And be much happier! If you come across a carby turbo set up for cheap by all means go ahead. But I would suggest FI anyday. Think about it theres a reason those old carb kits are no longer made. And with T2 engines becoming more affordable it just makes sense. With any carb turbo system you will spend months tuning and modding that carb. Ordering jets and emulsion tubes...waiting for parts. Go FI and you wont be sorry...know what Im talking about here,custom13B

onslaught_81

nice thanks to both of you for the info...it's apreciated

WackyRotary

I think My blowthrough worked fine. Easy to tune. IS the fuel mixture perfect all of the time, NO. But it worked pretty good powerwise. IF you setup a blowthrough, you will go with a carb that is a performance carb that runs good with a rotary to start with. Realizing that it will never give 100% what EFI could, but its not hard if the carb has easy access to the jets/etc, like a weber.