Frank J. Bauer dassault systemes of America email:fjbauer@dsavm.e-mail.com Subject: indy pop-off valves the typical indycar has a listening tube that goes from the pop-off valve to the driver's helmet. as soon as that thing whispers in his/ her ear, it's time to feather the throttle. as graydon says, there's no way a driver wants that valve open! like throwing out an anchor... frank