Sizing ITB's for boost and IC configuring?

[Tippy]

So, I know the conventional wisdom is bigger the better for NA applications where all out max hp is required (until point of diminishing returns), but what about boosted applications?

I have a Carrera 3.2 (3.4) with stock intake port sizes (42mm IIRC) and I believe the OEM 3.2 intake are the same throughout until the runners meet the log parts of the manifold (assuming here?).

So, question is, do you run like a 44mm ITB (account for butterfly area diminished to get back to 42mm total area) or something like 50mm plus?

My brain is saying something like 44mm for good driveability (high velocity) but I see so many ITB's out there far larger making me have doubts.

Also, trying to figure configuring existing IC I have to work or if I'll have to go with a totally different end tank arrangement?

[Ken911]

Well mine isnt running yet. but i went with 43mm throttle bodies. my heads are ported to 41.6mm. The inlets are about 45mm the air horns going to the throttles are 80mm tapers down to 45mm. Jenevey recomended tapered throttle bodies. didnt get those but probably should have.

[Tippy]

So yours are basically 45 down to 43? Was yours configured to a particular proven build or hp range?

Just curious where to get data from. Jenvey didn't really answer my questions since they speak of NA mostly from what I gather.

[Ken911]

Yes it's a 45 down to a 43 then the manifolds are 43 down to 41.6. Not a proven build spent a lot of time on the phone with Chris at TK. Plus the guys at extreme when they were porting my heads. Looking for 650 at the wheels. I was not able to use the jenvey manifolds because they are too tall so I built my own. They are 1.5 inches tall

[Ken911]

here is a quick pic of the height

[Tippy]

Thanks Ken!

[TurboKraft]

What brand of t-bodies do you have?

[willtel]

You may want to send rsscotty a PM. He is with Rothsport and they have done some ITB turbo builds.

Rothsport 3.4 , ITB, Garrett GT35R build

[TurboKraft]

That's a great build. Stupendous drivability from a 3.4L.

Love those trumpets, plenums, and intercooler. ;-)

[Tippy]

What brand of t-bodies do you have?

GSXR 750. Remeasured and they neck down to 38mm. No bueno. I see Hayabusa's run bigger, may look into those.

[Tippy]

You may want to send rsscotty a PM. He is with Rothsport and they have done some ITB turbo builds.



Rothsport 3.4 , ITB, Garrett GT35R build

Thanks, known of them before. Going on the DIY (a.k.a. cheap) route.

There are plenty of sportbike throttlebodies folks have been successful with.

It's just I have bigger ports over the 930's or other older 911's that weren't boosted.

Didn't have a solid reference.

[TurboKraft]

If their throttles are 42mm, can the port below the throttle be machined out to match your Carrera ports?
And still leave a flange for a gasket to seal?

[Tippy]

Originally Posted by TurboKraft

If their throttles are 42mm, can the port below the throttle be machined out to match your Carrera ports?
And still leave a flange for a gasket to seal?

Unfortunately not.

[Ken911]

before i bought the jenvey throttle bodies I looked quite a while for some sport bike ones. I couldnt find anything that would work. they were either more expensive, too tall, wrong bore size, or not configured so that they could be set up in banks of three. I bought the ones from jenvey, then several months later the linkage and the horns. But even those you have to buy the regular ones not the short ones because the porsche linkage set up they have doesnt work with the short itb's.

[Tippy]

Ken, the Suzuki Hayabusa (1300cc) ones are singles you can separate and have a nice set of features to support them with rods and spacers to whatever widths you want.

They are 46mm up until 2008.

[jsveb]

You too Tippy?

Man, I feel left behind with the crap I am struggling with.

Looking forward to following your progress.