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Low turbo boost '86 5KCSQ
In message <email@example.com> Alex Kowalski (firstname.lastname@example.org) (Law Guest Account) writes:
> It's strange that your boost is increasing when you disconnect the WG
> valve. Like you, my belief was that the valve functions under boost to
> keep the WG _closed_ longer than it would with the spring alone...maybe
> your hoses are mixed up or my brain is, but this has been posited many
> times by many different sources -- it would be a big surprise to me.
I thought that - until I hooked a boost gauge up to the line between the
wastegate frequency valve and the top of the wastegate.
That thing doesn't just _switch_ between supplying boost and vacuum to the
upper chamber - it postively _vibrates_ between the two. Once the ECU takes
control from the spring, it buzzes. Scott Mockry has a test lead that plugs
into the wastegate frequency valve - it shows just how intensive the ECU's
control efforts are.
> All of this is leading me back to Phil's post some time ago about how so
> much "tolerance" is built into the F.I. system to compensate for leaks,
> goofy sensors, etc., and the importance of trying to get the car back to
> spec. with everything tight.
Definitely. Very important with the MC/MB/1B design.
Committee Member, UK Audi [ur-]quattro Owners Club