Re: "Blue" wastegate spring

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

In message <34F21442.2071@teleport.com> "Scott Mo." writes:

> If the installed WG spring tension is higher than stock then you would
> normally see the behavior mentioned, where the WG solenoid duty cycle is
> shut off (Test LED light stops blinking) as the engine speed climbs at
> WOT. 

Yes, that accounts for it.  I think there may be so much pressure exerted by 
this particular spring that the MB wastegate _never_ opens.
 
> The ECU senses that enough boost or too much boost is being made so it
> shuts off the WG solenoid. When the WG solenoid is shut off and connects
> the upper WG cap to the intake boot at the turbo intake, the WG upper
> cap will see a slight vacuum at sustained WOT operation. This will
> reduce the boost ~0.1 bar over what the WG spring alone will make with
> the upper cap connected to atmosphere.

My logic too.

Now - I think there are two possible causes for the problem:
 
a) Someone has fitted a WR-type spring, possibly even an uprated one, to the
   MB in question.  Perhaps it was someone who knew a little about tweaking,
   but not enough to realise that the MAC12D works differently to MAC01/02.
 
b) Someone has fitted a WR wastegate, perhaps ignorant of any difference
   between the WR and MB.
 
I've asked Tony to check the wastegate part number on the tag tonight - if it 
turns out simply to be a WR wastegate then we've solved the problem.
 
Is the MB's wastegate (034 145 705A) used in any other applications?  200TQ?

Any of our resident MB owners care to measure the length of their springs?

-- 
 Phil Payne
 UK Audi [ur-]quattro Owners Club