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patkeefe patkeefe is offline
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,850
I have a stainless steel airbox. I blew up the factory plastic one on a backfire after I installed the turbo. This is because I put in a plumbers plug, as the boost pressure was opening the standard popoff valve, and cinched it down pretty good. It was in too tight.

I also blew two seams out of the SS airbox...same reason. So, finally, I welded the SS box back together, coated all of the seams with JB weld, and pressure tested it in a big tub of water. I put six plumbers plugs in the outlets for the manifold runners, plugged all of the other holes, and rigged up a fitting for my air hose from the compressor.

Test was this...put in air pressure at whatever low PSI (I only run around 6PSI boost). The plumbers plug (the IMChappy method) is not tightened down too hard during the test. So, for example, if I put in 5 PSI and the plug blows out, I tighten the wingnut incrementally. I repeated this until I could hold 15 PSI without blowing out the relief plug.

Now, I set my regulator to 50 PSI ( I had a hard time figuring out the equivalent pressure a backfire pressure wave would carry, and I don't remember what it was), with a ball valve in the system, such that I could simulate a pressure wave. You'd be surprised how far out of a tub of water and across the lawn you can launch a plumbers plug doing this. I think I was blasting the plug out at about 100 PSI after awhile.

Anyway, I now have my right hand calibrated to tighten the wingnut properly to contain the boost pressure, and still allow for popoff. If I was smart, I would have put on a regular hex nut and tightened the plug with a torque wrench.

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Patrick E. Keefe
78 SC
01 Boxster
Old 06-11-2011, 06:52 PM
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