PTS Flowbench Forum

Forgive me if this question is in the wrong section; it would seem to me that a flowbench would be the right tool to determine whether enlarging (by cnc machining) the I.D. in front of and behind the butterfly would produce an increase in rate-of-flow.

My premise is that where the butterfly (unchanged in diameter) and the surrounding wall area that is required to ensure it functions properly at idle has remained untouched. To me there is actually no increase in rate-of-flow as the cross-sectional area has not increased...irregardless of any machining upstream or downstream.

The claim by those who offer this cnc porting is that "venturi effect" has air velocity...and therefore a measurable gain in HP/TQ.

Any thoughts? Furthermore anyone here interested in helping me test?

Thanks...

p.s. I should add that the machining process only takes the upstream / downstream bore from 80mm to no more than 83mm...

Here is an idea of what can be done with a Harley throttle body. The stock 50mm butterfly was kept, all work was done before and after.

You are modifying the coefficient of discharge (Cd) or discharge coefficient (Dc) how ever one wants to say it that the throttle bore "sees" (call this your orifice)

That/those hints should give you some additional reading on the net not related to TB's but, orifices in a pipe which is the same principle . . .