Throttle Body Sizing?

[jdmser]

I'm looking for opinions on sizing a throttle body for my soon to be RB24. So far I've heard a lot of different theories and I'm still having a hard time sifting through all the info. I know that the larger the throttle body the less throttle response but, I've also heard that small increases in flow can net large results. Now this will primarily be used for drag so some throttle response loss is acceptable if more top end can be gained. Just wanted to see what you guys thought. I've been thinking of going with a 80mm unit.

[DriftingisLame]

Pick up a copy of Forced Induction performance tuning by Graham Bell. Under the Intake chapter he states HP levels for given inner diameter's of Throttle bodies. He states the 60mm throttle body should always be retained for power levels under 450 hp, anything less and it is unnecessarily large, looses throttle response and gains next to no power.

I believe our stock RB20 and RB25 throttle bodies are 63mm. I dont think you'll ever need to change yours.

[jdmser]

If this setup doesn't make more than 450hp I will leave this forum and never come back.

[Nissan2367]

I run a q45 90mm and i have no complaints. I have the greddy intake with stock turbo and my throttle responce is awesome... I would just get a Q45 its cheap and gives room for more upgrades... cant really go bigger

[DriftingisLame]

If this setup doesn't make more than 450hp I will leave this forum and never come back.

Well then you probably should have listed your power goal. Then we can tell you what size throttle body is ideal.

[jdmser]

We'd like to see final numbers around the 750-800hp mark but for this year I'll only have supporting mods for around 500-550rwhp.

[Bluefire]

Throttlebody sizing for forced induction applications are simple. you can go 70mm, 80mm, 90mm, etc... You won't really lose any power by going bigger, but you do risk losing throttle response. Also you won't really gain from it unless it actually becomes a restriction. And FYI, a 90mm can handle over 1000 hp. But IMO the loss in response is barely noticeable. I've felt cars with the stock tb and ones with a q45, and they felt pretty much the same.

[eh?]

Sounds like you definitely want the larger TB if you are going to drag. You can add timing down low to add some responsiveness if need be.

[LovesBigTurbos]

bigger is better!!!