Rotospeed

iTrader: (8)

i may have the intake parts and the a turbo manifold lind up... but i dont know what turbo to run. i've got a s4 turbo... can that be seald to work good?


its a 12a and i want to go turbo but i dont have lots of $$$$$$
eney help would be grate. --thanks--

defakto

Sealed turbo? Not sure what you're asking for here.

Only things you need sealed on a drawthrough is everything between the turbo and engine on the intake system. A turbo is "sealed" by nature otherwise it wouldn't produce boost.

Just out of curiosity why did you choose to go with a drawthrough setup? You won't be able to intercool and you'll be pretty limited to what you can do with it performance wise.

Rotospeed

iTrader: (8)

i was told that the gas will leak around the shaft of the turbo. and that it needs to be seald difirent than it normaly is.

drawtrough for the price. if i can do it for a lot less then blow through i can afford it.

Re-Speed.com

iTrader: (3)

Both will need a, turbo manifold, turbo, intake manifold and carb at the least. If you go draw through you will need to purchase a carb and make an intake manifold. You already have a carb and intake manifold on your 12A so I do not see how draw through would be any cheaper. A boost sensing regulator and boost prepping the carb for blow through would be offset by the special intake manifold needed and carb to go draw through.

Just my thoughts,

-billy

defakto

I would seriously spend the time and extra money on a blow through, you will be much happier with it performance wise.

XLR8

iTrader: (52)

Draw through setups are not only dangerous but very limited.

I would recomend a blowthrough setup. Much easier....and safer.

jim_chung

iTrader: (2)

I don't think that comment is entirely accurate. Drawthu is limited in boost but its not inherently dangerous. I've been running boost at 6 psi for a year without any problems and that nearly doubles the stock bhp which is more than fast enough for a 22 year old car and its equally dated braking system.

Driveability is the key, no sense making monster hp if you can't even drive it daily to the supermarket.

Man_in_black49464

iTrader: (1)

Buy the Holly intake manifold then buy a blow throu holly carb (about 800$)
Then make turbo manifold buy a garret 45 and your set, everything else is up to what you want to spend.

Its will be cheaper to do a T2 Swap.

XLR8

iTrader: (52)

Sure it is....

I am glad you have had no problems with your setup. I'm not saying it's a time bomb, but many people have had issues with draw-threw setups. You are drawing a AF mixture through a turbo, and in some circumstances, a glowing turbo. It was very common in the 80's, until they figured out a better way to run the setup. Just because you have had no issues, doesn't mean it's not flawed or there isn't a better way.

www.rotaryshack.com
Robert knows his stuff.

Jeezus

iTrader: (4)

Draw Through:

Simpler
Low pressure system, so no change occurs in air density at the carb
No compressor bypass valve required
Prone to Icing under 50*F

Blow Through:

Better throttle response
Better cold starting
Reduced emissions
Permits an Intercooler to be used.

"Weighing the merits, there is virtually no reason to build a draw-through system unless one lives in a year-round hot climate and never intends to produce serious power"

Maximum Boost, Corky Bell

If you need any more help or info, I can just retype whatever you want from the book to help you understand.

EDIT: Ok, I am bored, just going to type it anyways...

"LAYOUT OF A DRAW-THROUGH SYSTEM

The primary concern in the draw-through layout is that the air/fuel mixture be permitted to flow downhill at all times. This condition is not possible due to the compressor inlet scroll, but no other item should be allowed to serve as a low point. Fuel tends to droop out of the mixture and puddle at low points. Puddling will badly upset the cold idle and low-speed response.
A water jacket added to warm the carb mount and bottom of the turbo scroll will alleviate cold fuel puddling. However, the mere thought of purposely adding heat to the intake system should be considered nothing short of revolting. A further addition of heat may be required to prevent carburetor icing when operating under boost. Typically, a correct air/fuel ratio will create about a 45*F temperature drop when the fuel vaporizes in the carburetor. This temperature drip, combined with a cool, damp day, will frequently cause throttles to freeze wide open when operating under boost. A fine circumstance, cured only by adding yet more intake heat.
Sizing the carb for a draw-through system should take into account the basic cfm Capability of the engine without considering the turbo. The reason for this is that cfm ratings of carburetors are based on atmospheric pressure drops only, whereas the turbo can violate these conditions by changing vacuum conditions after the throttle plates. Consider that the only way a carb with atmospheric pressure above the throttle plates can flow more air on a given engine is to have lower pressure, created by the turbo, after the throttle plates. In other words, the turbo creates a bigger pressure drop across the carb.
The draw-through carb system has a hidden pitfall in the area of selecting a suitably sized carburetor. This pitfall is created by the odd circumstances that allows one cylinder at a time to breathe through the sum of the carb throats open at that specific time. For example, imagine a dual-throat carb mounted in front of the turbo, all of which is mounted on a four-cylinder engine. Although the carb cfm rating may match the system just fine, we have a situation wherein each cylinder is breathing through the two throats. That equates to putting four dual-throat carbs onto a four-cylinder engine -- certainly a situation that would be badly overcarbureted. The disaster comes about from the fact that the one cylinder drawing through two throats yields a very slow air velocity at the carburetor venturi. This sends a weak vacuum signal to the main jet; hence, lousy fuel metering. The situation is somewhat alleviated by having more cylinders, yet the fundamental problem remains. The proper solution to the problem is the selection of a carb with a small primary(s) and vacuum-operated secondaries."

REVHED

I've seen some plenty powerful draw through setups. Back in the day the fastest untubbed car here was running 9's with a drawthrough.

Rotospeed

iTrader: (8)

ok ok... i get the idea. thanks for all the info. some things came up and i'm going to whait a while before i go turbo. so when the time comes i mabe doing a blowthrough set up