Low turbo boost '86 5KCSQ

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <s4474719.074@wppost.depaul.edu> Alex Kowalski (audial@aol.com) (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.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club