Pop off valve question

[clnilsen]

Ok., I was looking at the tech article on the web site http://www.pelicanparts.com/techarticles/911_pop_off_valve/911_pop_off_valve.htm

and to me, it looks like the pop off value is backwards in the picture. It looks like it opens INTO the airbox, not to the outside. I'm thinking of tacking this fourth of july weekend.

Especially this picture


Am I just not looking at it right?

Thanks!

Chuck

[Jdub]

That is the correct orientation. Think about the slant of the filter proper when in place. The valve could not open *as fully* if it were 180 degree changed in orientation, but as you see it in the pic the valve can open so that the back of the popoff valve is essentially parallel to the filter slant when it is forced to open.

Don't forget to put a dab of silicone sealer on each end of the pin when you install this sucker, and lay a nice full bead around the base to prevent any air leak and subseqent weird idling that is sometimes traced to leaks through the popoff valve.

John

EDIT: Ah, yes, I do note your post asks why this is not vented to atmosphere but rather into the airbox. That's fine: the way it is meant to work. There is no pressure *against* the valve within the airbox and so no force against the popoff valve opening. However, I will defer to smarter folks who can speak on this matter.

[wckrause]

The area where the air filter sits is not technically the "air box". The air box is the enclosed area under this that sits between the throttle body and the intake runners. It's pressure in this area caused by an intake backfire that gets vented through the pop-off valve into the area where the air filter sits.