Wastegate, how does it work?

[Burl Vibert]

John Shost wrote:
> 
> Here is a pictorial
> <http://www.rs4.org/quattro/technical/s4-engine/engine17.jpg>
> 

Only problem with this is that the wastegate on a 5000 works in
the opposite way.  The frequency valve is used to add pressure to
the wastegate to increase boost, not decrease it as in the
diagram for the S4 wastegate.

I don't think it's a pressure leak as it did hit 1.6 and
overboost cutoff as mentioned.  Hard to do that with a large
pressure leak.  Also pressure leaks are often vacuum leaks as
well so often there are other problems such as rough or no idle.

As the wastegate has stuck shut at least once perhaps something
is screwy in there, only takes a few minutes to pull the cover
off and look at the spring and diaphragm. Perhaps add a slightly
different spring or a washer or two before reassembly.

Burl Vibert
1987 5kcstq 
Kingston, Ontario