[urq] Throttle Body Port

[Buchholz, Steven]

... you are not on boost 100% of the time, and yes, there are check
valves that prevent the positive pressure from filling the reservoirs.
Sometimes the vacuum signals from the TB are used to directly actuate
functions ... the vacuum advance on distributors is a classic example.
I looked at the IST Maint & Adjustment doc and saw a vacuum plumbing
diagram on page 13.  In this diagram it shows a single vacuum line from
the TB, and this line is used to switch the evaporative emissions
system.  The vacuum reservoirs used for things like diff lock and
climate control come from the manifold proper ...

Steve B
San Jose, CA (USA)
> 
> Unless there is a check valve, I don't see how anything in the intake
(post
> turbo) could be vacuum only....
> 
> > I'm still trying to confirm what this port does exactly.  Not what
it is
> > being used for, but weather it is alsways vacuum  and directly
> > proportional
> > to the airflow through the throttle body and weather the engine is
under
> > boost or vacuum doesn't matter.
> >
> >
> > [What exactly does the throttle body port on the UrQ(and others) do?
By
> > that, how does it behave?  Is it using venturi effect to induce
increasing
> > vacuum as flow through TB increases.  Is it always vacuum - even
under
> > boost.  Is its highest reading at max flow?