Intercooler to TB pipe size ?
- Thread starter KWIKR 1
- Start date
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
90mm throttle body is slightly smaller than a 4" tube. I'd run 3.5 or 4"
Tim,
As you know I am running a set of stock GN turbos (lightly ported) on my TT SBC build and with that I am using a 75mm (3") Gen III (LSx-style) throttle body. The OD of the throttle body is 3.5" and the blade is 3", I am using 2.5" pipes off the intercoolers into a 3.5" merge at the throttle body.
Your throttle body size selection should be based on a few factors with the most critical being the CFM of the turbos, piping, intercooler and the throttle body. You don't want any one of these parts to present a restriction, nor do you want to oversize them so that they create other issues. It all has to work (flow) together.
However, if you are going to run anything smaller than the rest of the components it should be the throttle body as it will have the biggest effect on off-boost/low-load drive-ability. For this reason I am using only a 3" opening into the plenum as it is close to the stock size TPI 48mm (twin blade w/air foil) my EFI system was designed for; ~800cfm each. That is plenty of flow for my goals of +/-500hp.
These will give you an idea of what you are looking for:
http://www.efisupply.com/images/wilson/wilson_tb.pdf
Flow Tests 2.0
There is a rule of thumb CFM vs. HP calculator here:
Turbo and Supercharger Maps
All that said... the piping to your TB will be dictated by the flow figures of your other components.
As you know I am running a set of stock GN turbos (lightly ported) on my TT SBC build and with that I am using a 75mm (3") Gen III (LSx-style) throttle body. The OD of the throttle body is 3.5" and the blade is 3", I am using 2.5" pipes off the intercoolers into a 3.5" merge at the throttle body.
Your throttle body size selection should be based on a few factors with the most critical being the CFM of the turbos, piping, intercooler and the throttle body. You don't want any one of these parts to present a restriction, nor do you want to oversize them so that they create other issues. It all has to work (flow) together.
However, if you are going to run anything smaller than the rest of the components it should be the throttle body as it will have the biggest effect on off-boost/low-load drive-ability. For this reason I am using only a 3" opening into the plenum as it is close to the stock size TPI 48mm (twin blade w/air foil) my EFI system was designed for; ~800cfm each. That is plenty of flow for my goals of +/-500hp.
These will give you an idea of what you are looking for:
http://www.efisupply.com/images/wilson/wilson_tb.pdf
Flow Tests 2.0
There is a rule of thumb CFM vs. HP calculator here:
Turbo and Supercharger Maps
All that said... the piping to your TB will be dictated by the flow figures of your other components.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
The 90mm throttle body will support well over 2000hp. I've made over 1500hp with a 3.5 pipe feeding a 90mm throttle body. The only downside to the 90mm tb is it's sensitivity to slight throttle movement on street cars. It just takes a little time to get accustomed to it. I drove the car all the time with the 90mm accufab.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
None at all. Maybe there is a way to put a 3.5 outlet on your i/c when you get it.
