Tom400CFI

I've been wondering this for a long time....here is the question;

Why not put the throttle body at the turbo inlet? Advantages would be minimal loss of turbo RPM during shifts (wheel would be in a "vacuum"), and there would be no need for a BOV.

Disadvantages? I'm not sure. Slower throttle response? IDK.

BrianCunningham

Not sure the seals are engineered for that

Boost. not vacuum.

Tom400CFI

They've worked on carb'ed draw through applications....as well as a carb can work w/a Turbo.

BrianCunningham

I'm actually old enough to remember those

Of course all modern roots blowers do what you thinking of

Tom400CFI

Seems like a good idea for turbos. In the old days, the detriment of draw though was getting the A/F ratio through the compressor, manifolding, and runners, all homogeneously mixed. With port EFI, that is not an issue. The only detriments that I can figure might be are slower throttle response, and possible over-speeding the turbo at part throttle. Not sure.


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Impala Balko

What about an intercooler... and i think during higher boost levels you would get compressor surge and Blow out the turbo, plus not to mention all the hot air you would be craming down your engines throat

Tom400CFI

No reason why you couldn't run an intercooler. Intercooler doesn't "care" where the throttle body is, or what the air density is inside of it.

As for compressor surge, you'll have to explain to me, how that would happen -any differently than w/the TB after the compressor. W/the TB before the compressor, the system won't know or care where the TB is a WOT....at part throttle, the turbo (both before and after the compressor) will be in a partial vacuum. Maybe I'm not understanding what you're saying about surge...

Not sure what is was, I found this definition of compressor surge on the Garrett web site:
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:

-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application

JoBy

You can mount the throttle body before the turbo, but you need a special seals. These (old) turbos were made for draw thru applications like with the one posted above.

On any modern affordable turbo you will draw oil from the turbo into the engine.

You can mount the throttle body before the intercooler, but make sure that you can not blow any pipes apart. If you do, then the engine will continue at 'WOT' naturally aspirated when you close the throttle.

This is a crazy Sweede running the TB before the intercooler on a 50 year old pushrod 1.8 liter Volvo engine. ( 500+ HP )

You see the TB at the intercooler inlet.