Obviously the larger a throttle body, the better it flows. With turbo, how important do you think that is? I ask because my current setup has a 56mm throttle and I'm wondering if it would be worth it to go larger or if the gains would be minimal. Goal on this build is about 380-400whp. 2.5" charge pipes. A 56mm throttle comes out to around 2.25". Just wondering how much of a difference the slight bottle neck may cause if any...



12.6 @ 114.6 MPH

Hmm.. I have always read that the gain is minimal which is why I never persued one.

The gains are minimal is the throttle body is already sufficient for your air flow level. Now getting up to where you want, a larger one would be the proper size. Look around I posted a link to a throttle body calculator at some point somewhere, else just google it.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
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Jon, any idea about that link? I searched and came up with nothing on here. Google only lead me to some pretty complicated and confusing calculators.



12.6 @ 114.6 MPH

The pretty complicated and confusing calculators sound about right. This is the good one. Its how I proved that the stock size throttle body is perfect for all bolt on builds. Your text to link here...


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Leafy (Club Jeffie FEA man) wrote:The gains are minimal is the throttle body is already sufficient for your air flow level. Now getting up to where you want, a larger one would be the proper size. Look around I posted a link to a throttle body calculator at some point somewhere, else just google it.

There's no way you can make that a definitive statement.

If you assume at ambient air pressure, then I would certainly agree with you. However, if the throttle is on the high pressure side of the compressor (like most turbo setups), then it's not going to make nearly as much difference when compared to a draw through system (like most roots supercharged setups). Now, if he were planning on achieving this with a large turbo which can support the same flow at lower pressures, then there's an argument to made there. My guess is the outlet on that turbo is no larger than 2" OD, so a larger throttle isn't going to provide significant gains.




I have no signiture

I can say that its enough power that a monster throttle body up to 89mm in diameter is when the throttle will start acting like an on/off switch. I'm getting something around 59mm to 72 mm as being good for 400 hp on the 15 psi boost area.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Sorry use what formulas you want, but with 2.5 piping a 56mm TB is a restriction. Major big? Maybe not. On a eco we made 314whp on stock TB, stock intake manifold. I think a larger TB would of helped get that a little easier.

It will also help the car drive better in normal driving.



FU Tuning

Leafy (Club Jeffie FEA man) wrote:I can say that its enough power that a monster throttle body up to 89mm in diameter is when the throttle will start acting like an on/off switch. I'm getting something around 59mm to 72 mm as being good for 400 hp on the 15 psi boost area.

Who said anything about 2 bar? There's no way he'll get that kind of flow on an L61 without a radical cam, not to mention that
1) unless he has a 60 trim, the compressor won't support that kind of flow at 2 bar either and
2) the small T3 turbine will restrict the flow further.




I have no signiture

^^^ Sorry, I just realized it's an LD9...my argument still stands.




I have no signiture

At 3 bar the numbers change minimally.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Whalesac wrote:

Leafy (Club Jeffie FEA man) wrote:I can say that its enough power that a monster throttle body up to 89mm in diameter is when the throttle will start acting like an on/off switch. I'm getting something around 59mm to 72 mm as being good for 400 hp on the 15 psi boost area.

Who said anything about 2 bar? There's no way he'll get that kind of flow on an L61 without a radical cam, not to mention that
1) unless he has a 60 trim, the compressor won't support that kind of flow at 2 bar either and
2) the small T3 turbine will restrict the flow further.

For what its worth, I plan to have boost around 15-20psi. Current turbo is a T3/T04E 57 trim. Cam wise, I'm running stock LD9 intake cam along with the secret exhaust cam.




12.6 @ 114.6 MPH

You have a 56mm listed in your profile how much bigger are you going to go?

jason norwood wrote:You have a 56mm listed in your profile how much bigger are you going to go?

65, 70... not sure if I even should. 65 would be a hair over 2.5", 70 would be equal to 2.75". Like I said, IC piping is all 2.5". That gives an ID of roughly 2.25" which is almost equal to the current TB size of 56mm. However then there is loss from the throttle plate and bar so it does equate to a slight restriction. Ive got an old LS1 TB I was going to adapt for this project (75mm/3"). Not sure if it would be wroth it though. I don't want a throttle so large it acts as an on/off switch while cruising, but I also don't want to use something if its much too small.



12.6 @ 114.6 MPH