[BlooDReigN]

Originally Posted by 5spd GT

There are many factors to why people get gains from throttle bodies.

They didn't match the inlet the first time and then dynoed it again after they port matched it.

They dynoed on different days with more mileage on the engine (you gain horsepower that way).

I have yet to see a back to back dyno with a bigger throttle body that gained power.

One way to tell if it is the day/dyno showing the gain is if you see a gain across the powerband. That shows that it is inaccurate, because if it is showing a gain at 2,500 or 3,500 rpm it is off. Reason being is because, as in your example, a 75mm TB would flow plenty at that rpm, why would the 90mm TB gain it more horsepower if the 75mm can easily keep up at that RPM.

I hope that made sense.

What I would like to see, in which I have yet to see, is a back to back dyno. I imagine if any gains it would have to be in the upper rpms.

I'll have to dig out the MM&FF mag I saw it in. My guess is that it made the gains because the 90mm throttle body is the same size as the opening on the intake causing less turbulence or something. It was a surprisingly large difference though for going from one throttle body to another. I can't remember exact numbers though.