Throttle body stacks … Air flow and performance

[jondee86]

As I understand it, it is the total tuned length from the valve
head to the open end of the trumpet, that is important. The tuned
length determines at which rpm bands you will achieve torque peaks
due to the "ram" effect of reflected waves in the intake.

Having the open end of the trumpet close to a bulkhead can have two
effects. The first is simple interference with the airflow into the open
end, and the second is interference with the reflected waves. If the
distance from the bulkhead to the open end was adjustable, you may
even be able to obtain some benefit from "tuning" the gap.

A trumpet with a fully rolled lip is said to improve the airflow from
behind the stack. This air has to make a 180 degree turn. However,
the improvement in flow is somewhat less than obtained by just
having a nice trumpet with an elliptical curve or better still, parabolic
curve. Allowing air to enter evenly around the whole circumference
of the trumpet would be good for efficiency also.

Using a trumpet with a plain flaired lip and putting a flat plate hard
against the back of the lip would be a nice arrangement.

Cheers... jondee86