Throttle Body Size

[MikeH686]

for anyone who's been keeping track of my build I've gotten the new motor setup in. I'm looking to get a new throttle body but unsure of the size to get. My charge pipe from the turbo is 2.5" which equates to 63-64mm my old combo I had a 75mm on it. Wondering if I should bump up to an 80mm. Any insight would be appreciated here's a few pics.

 

[RangerJoe]

I am no FI guru, but if your current TB is already bigger than your pipe, and you are forcing air in, I doubt it would make a huge difference. If I was going to step up, I would go to a 90.

Joe

 

[Chuckman]

How big is the discharge on the turbo? Imo I wouldn't let any of the cold side be smaller than that, inter cooler is going to steal enough flow as it is.

 

[MikeH686]

Discharge of compressor is 2.5" or 2.25" it's a vsracing 76mm

 

[Real time recon]

A lot of complaints on line with BBKs (including mine). They tend to have a 'whistle' sound(that comes & goes) at different RPMs.Some say it due to rough casting of internal air passageways .

 

[MikeH686]

It'll be an accufab or Holley I'm just looking more so for sizing

 

[NIKwoaC]

I am no FI guru, but if your current TB is already bigger than your pipe, and you are forcing air in, I doubt it would make a huge difference. If I was going to step up, I would go to a 90.

Joe

Agreed. Usually my vote is as big as your intake manifold can tolerate, but when your current throttle body is already much bigger than everything between it and the turbo, it might be a moot point.

Just curious, why is the charge pipe so small?

 

[a91what]

With a turbo the charge piping does not need to be any larger than the turbo outlet.. a 2.5" pipe will flow over 900cfm before the velocity goes over mach. In boost the cfm stays the same but the density increases. You want a throttle body that will flow at least what the engine is capable of NA. A accufab 75mm is probably more than enough, they flow 750cfm if memory serves.

 

[MikeH686]

It's a 363" motor

 

[a91what]

It's a 363" motor

spinning to what rpm?
a 363 spinning to 6500 rpm using a cfm calculator
Street: 580
Racing: 750

with boost the engine can only ingest as much air as it did in N/A trim, boost simply makes the air denser.

 

[MikeH686]

Probably 7000

 

[revhead347]

I would imagine that there wouldn't be any advantage to going to a bigger throttle body.

Kurt

 

[MikeH686]

Your probably right I might stay with an 80 though because I plan on going to around an 80 to 85 mm turbo something close to sbs484

 

[NIKwoaC]

What size can your elbow accommodate?

 

[a91what]

If you plan on stepping up the turbo just buy once. Go as big as your elbow will allow. 90mm accufab flows a chit ton of air and they look amazing.

 

[MikeH686]

I think it's a Wilson elbow and never measured it but I would assume at least a 90

 

[NIKwoaC]

If you plan on stepping up the turbo just buy once. Go as big as your elbow will allow. 90mm accufab flows a chit ton of air and they look amazing.

Yep. Honestly I don't understand why they even offer 80s and 85s when most intakes are either 75 or 90. People like options I guess.