Pressure fitting placement
on Tuned systems

For Boats and Cars:

Just about any place is OK, although it is best not to place it on the header tube because it might weaken the tube there. It is also better not to tap into any part of the muffling section of a muffled pipe system, or behind the baffles of a Quiet pipe system, since there can be unusual pressure waves there.

For airplanes and helicopters:
(See drawings below)

For tuned pipe systems:

It is best to use a Thin-wall pressure fitting, either a straight or a 90', as the wall thickness of a tuned pipe is very thin and doesn't hold threads very well. The most consistent pressure is found where the pipe first reaches its apex in width. However, this may be inconvenient. Many modelers choose to place it in the header plate. The problem here is a possible pressure spike which can develop when the aircraft is in a power dive, out running the system tuning. The spike may flood the engine causing it to lean or die. (This seldom occurs, though.)

For wizards:

It should be placed 1/4" in front of the muffler braze line. Please note: the internal tube may stick back this far in some of the wizards, so make certain that you do not damage it drilling or tapping for the fitting.

Note: Never place the pressure fitting on the header tube or the muffler part of a tuned pipe.

(Please note a standard threaded pressure fitting is shown. This is only for placement; we suggest a thin-wall pressure fitting be used on tuned systems.)

(If you do plan to place a threaded pressure fitting on the plate of the header pipe, we suggest you place it so the pressure fitting comes through at the rear of the exhaust hole.)

Macs Products
7935A Carlton Rd.
Sacramento, CA 95826