Best way to control boost pressure...

Gerard gerard at
Tue May 20 21:27:20 EDT 2003


What is the best way to control boost pressure? Is it from the bottom of
the wastegate (through the hose that pushes the gate open) or from the
top (through the hose that closes the gate)?

Assuming that the wastegate spring used is a stock Audi 5kt/200t item
which is the usual 0.4 bar. Assume that the required boost level to be
used is 1.0 bar and that this boost should be as controllable as
possible. Assume that the bottom air feed hose has been rigged with
either the stock restrictor or a pop-off valve (full open after a
certain pressure) to control the point at which the gate starts to open.

Now using either a pressure regulator or a solenoid valve, would it be
best to control such a gate by feeding air to the top of the wastegate
(pushing against the pressure from below) or to take control of the
pressurised air after the pop-off valve before it pushes the gate open?

I think this quite sums up to: is the S4 setup better than the 5kt/200?
:) I've seen the article on where they rig up the S4
wastegate to control boost creep. I was just wondering if that is better
over the way it is done on the MC engine.

Just thoughts inspired by latest acquisition. A new solenoid valve. :)
My very last purchase for a long, long time. :(


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