On Wed, 31 Dec 2003 19:07:22 -0800, L.W.(ßill) ------ III
<----------@***.net> wrote:

> I thought the pop-off valve was just to limit the power of the Indy
>type racer, like a restricter plate on a stock car's manifold.

The turbo wastegate limits max boost via signals from the ECU.

The pop-off valve or blow-off valve doesn't limit power, but protects
the impeller/ turbine assembly and intake system from harmfully
excessive pressure and stress. When the throttle plate slams closed,
the turbo is still spinning a gazillion rpm and providing boost. The
pop-off valve dumps all the high pressure air into the atmosphere,
resulting in that loud Pro-Rally noise. A bypass valve is much more
civilized and dumps the air via a hose back into the inlet to the
compressor.

I agree that turbos aren't usually suitable for off road use. Some
are, like this non-Jeep application, which is unfortunately out of
production:
http://www.airpowersystems.com.au/sa...int_turbo.html

For kicks, read the two magasine articles at the bottom. From what I
have heard, this system was mainly sold to Middle Eastern sheiks
looking for ultra-high top speeds from their Land Cruisers. There
aren't very many in Oz or the USA.

I have had a couple of high performance turbo cars and just loved
them.

John Davies
Spokane WA USA