Q45 90mm tb's on rb's

[blues14]

ok, I am a self admitted ebay junkee and i keep seeing these Q45 90mm throttle bodies when i search for rb parts. do they bolt up? do they really offer any worth while advantages?

[CursedGTR]

No they do not bolt up you have to have the greddy manifold or something else like it that is designed for it or you can modify your stock one. I had a greddy Manifold on a RB25DET with a Q45 Throttle, it made a difference for the better and I was quite happy with it.

[matt_calgary]

more airflow + more fuel = more power (well on a general basis)

If you have ever seen the stock RB throttle body next to a 80mm TB, the 80mm looks huge!!! I think you need an adapter plate as well for it to work.

[stiergott]

um no, it bolts straight on. if you want it to work the way it should you need to enlarge the intake hole. its all aluminium so its easy to do.

[Eikon]

We've discussed before that it's not necessary to use a Q45 TB. It's overkill unless you are going to build the hell out of the thing. I think even the stock RB20 TB will flow enough air to pretty much max the capability of the engine.

In fact some beleive that you can actually have a TB be too large. It might actually slow the flow of air into the manifold. The theory was that a slightly smaller opening would actually create a faster flow.

I don't know the validity of the second part... But the first is right on.

You can use a 90mm Tb if you want... but why spend the money when the stock one is big enough to work.

[Shocker]

but what if you got it for free.. from a blown Q45 ...

[Bluefire]

um no, it bolts straight on. if you want it to work the way it should you need to enlarge the intake hole. its all aluminium so its easy to do.

Wrong the q45tb cannot be bolted directly to the stock intake mani. You need an adapter or the greddy manifold.

Also it is true you can have too big of a tb, but the q45 works just fine on the RB.

-Bluefire

[Kansei240sx]

We've discussed before that it's not necessary to use a Q45 TB. It's overkill unless you are going to build the hell out of the thing. I think even the stock RB20 TB will flow enough air to pretty much max the capability of the engine.

In fact some beleive that you can actually have a TB be too large. It might actually slow the flow of air into the manifold. The theory was that a slightly smaller opening would actually create a faster flow.

I don't know the validity of the second part... But the first is right on.

You can use a 90mm Tb if you want... but why spend the money when the stock one is big enough to work.

By a physics stand point Eikon, you'd be correct, and i'd have to agree with, i know a friend whos got the RB25DET Greddy intake mani setup and had a stock Tb and then got the bigger Q TB, and he said it runs slower and laggier, becuase for one, on the q tb, there is more surface area for pressure to build up on the q tb, therefor it takes more pressure, which would be ok... but not for a stock turbine, and if you have more pressure built up it stacks up making the air molecules more dense as apposed to having a less dense amount of air. I hope that made sense.

[blues14]

good input guys,,,, i was just curious cuz i always see them go for about 90 bucks......overkill for my power goals.

[DrifterTom]

i have to agree with our rb elders. the throttle body is unnecessary and does slow down the air. i was stoked about outfit my rig with one and my boys that build supra's(the baby ones are 750whp+. they know their shiat and they did every thing they could to talk me out of it. only looking for 16 low and 20 high boost myself though.

[240sxed]

yes, there is also an adaptor made by greddy so you don't have to use a 90mm throttle body for the greddy manifold.

Since im running a fmic greddy intercooler, im actually gonna run the smaller throttle body , but if i ever get bigger piping and a bigger turbo, im gonna stick the q45 back on, it does look crazy, like it could suck up small animals.

Wrong the q45tb cannot be bolted directly to the stock intake mani. You need an adapter or the greddy manifold.

Also it is true you can have too big of a tb, but the q45 works just fine on the RB.

-Bluefire