wastegate dumping. . . been there doing that

[Nate Stuart]

----- Original Message -----
From: <Schwnnbkr1 at aol.com>
Subject: Re: wastegate dumping. . . been there doing that


>     So it's safe to use a blowoff valve only for the wastegate, because it
> vents to the exhaust anyway. This bleeds off what could be backpressure
then,
> but only when you're shifting or slamming the throttle shut?

Now things are reallly getting confused. A blow off valve vents pressurized
intake air, nothing to to with exhaust gasses AFAIK. That is soely the
purpose of the wastgate.

> So it's unsafe
> to use a blowoff valve  in the intake system, but safe to use it
post-turbo
> in the exhaust system, got that.

Nope, not unsafe to use a blowoff valve on the intake system, just on
metered air. For example I have a 'bypass' valve post turbo, pre throttle
that just dumps to atmosphere between shifts. However my air is not metered
until it get into the intake manifold, thanks to EFI.

> Now if the bypass valve vents boost from
> post-turbo (cold side) to pre-turbo (at the turbo inlet, during shifts and
so
> forth) then wouldn't it be best to have a blowoff in the exhaust and a
bypass
> in the intake, or is that just moronically redundant? (just a radical
idea)

The idea with the bypass valve is to keep the turbo impeller spinning (by
reducing the pressure at it's outlet) so that lag is reduced when you open
the throttle again in the next gear. By passing less exhaust gas through the
hot side you will effectively slow the impeller even quicker, not a
desirable effect.

Later!
-Nate
'89 90tq
www.newtsplace.com/90tq