I was working on my car with a friend of mine and he was talking about how the butterfly valve in the GSR IM restricts it and by removing it you gain 5-10 whp...fact or fiction?

 

the butterfly valve is there for a reason.
you might get a small gain, but it isnt worth it IMO.

 

i woudnt touch that if i was you. one thing leeds to another!

 

you'll lose some low end torque and power

 

Yes, it is true that the butterflies do create drag in the intake manifold. However, removing them will not help. You can replace it with a Skunk2 manifold if you really don't want the secondaries.

 

If you get any noticable gain, it will be at the very top of the rev range, somewhere around 6k to redline. The loss in low end torque from functional butterfly plates isn't really worth it.

 

I believe on the Toyota Celica GT-S there is some kind of butterfly valve in the intake itself rather than the manifold, which is commonly removed to gain a bit of power. But that doesn't really apply to the two-stage manifold in the GSR. I don't know how you would even get inside there to take it out.

 

That manifold is one of the reasons a B18 makes a little more power than the B16, leave it there.

 

The manifold actually comes apart.

 

yeah look real close, the back of the main plenum drops off. you can get to them then.