vacuum connection under throttle-body

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Wed, 28 Oct 1998, Scott Mo. wrote:

> My 89 200TQ has a small hose fitting near the throttle plate (under neath),
> but this fitting provides vacuum only when the throttle is open  slightly
> (ported vacuum) and does not appear to be a good place to connect the
> bypass valve line.

Correct.  This vacuum port goes into the bore of the throttle body ahead
of the throttle plate when it is fully closed, so you see the pressure
spike from the turbo there when you snap the throttle shut, not manifold
vacuum.  If you use a fancy racing type bypass or blowoff valve which has
two vacuum ports, you could use this port under the throttle body to feed
the underside of the blowoff valve diaphragm.  This helps to blow the
valve open very quickly. 

Later,
Graydon D. Stuckey

"There's alot more to Jazz than just wrong notes"