If anybody is thinking of trying this with a throttle body
mounted where the mass air flow sensor is mounted don't do it.
It will collapse the box when the throttle is closed.
It is designed for a slide throttle mounted near the engine.

It could be beefed up to do that by making it out of
1/4 inch thick PVC foam and glass or carbon  fiber on
both sides.
Paul Lamar

That the setup I have, airflow sensor followed shortly by throttle. The
plenum and runners are made of pvc tubing segments joined with
fiberglass. Plenum is 6" dia. round pvc with a wall about 3/8" and the
four runners are 1-1/2" and 2" pvc pipe, joining a sawed-off piece of
the aluminum stock intake manifold that has the secondary injector fuel
rail.

It has worked for several hundred hours now. But I suppose knowing the
vacuum limit on the stuff would be good to know.

Perry

A six inch round plenum is a lot stronger than a 9 by 8 by 4 inch high
box.

A four inch square extruded aluminum plenum will also work fine with a TB.

Paul Lamar

You got me worried about my pvc pipe intake manifold, but a quick google
search shows:

http://www.uni-bell.org/faq.html

Q: Can PVC pipe withstand a vacuum?  If so, what is the maximum vacuum
that PVC pipe can withstand?

A: Yes, PVC pipe can withstand vacuum pressures.  According to research
conducted by Dr. R.K. Watkins at Utah State University, vacuum pressures
cannot collapse an underground PVC pipe that is properly encased in a
soil envelope and exposed to normal service temperatures.  In fact,
quick calculations show that even under conditions of elevated operating
temperatures of 100oF, the pressure required to collapse most PVC pipe
is greater than atmospheric.  In other words, the pipe can withstand a
complete vacuum.

Vacuum pressures are generally not considered a favorable occurrence in
water distribution systems of any pipe material.  However, if the
effects on the entire system are taken into consideration, PVC offers
adequate strength and safety to withstand vacuum pressures.

Perry Mick

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