[urq] wastegate diaphragm

[urq]

Gary, I forgot to congratulate you on getting the diff locks and console
panel sorted!

... I remembered one thing that happened to me on the 5kCSQ which created a
similar situation ... if the upper chamber on the wastegate is sealed it
will in effect stiffen the WG spring.  Of course on the WX the upper chamber
is intended to be vented, but I've seen on some cars there is small diameter
(4mm) vacuum line attached to make it look "right" ... well, the MC engine
has the WGFV attached to modulate the effective WG spring rate.  On my Avant
the line got pinched very close to the wastegate cap and I experienced a
situation similar to what you describe ... 

Yes, having that extra boost feels good ... but it may not feel good for
long!  :-)  I remember one day I surprised a supercharged Buick ... and
myself ... when I had the Shrapnell Knobben adjusted a bit too high ... 

Hey, are you running a stock MAC-02 in your car?  If so, I'd be a bit
surprised to hear that the fuel pump didn't shut down.  If your car is
chipped then there's probably nothing to worry about, but if it is stock you
might want to look into the pressure transducer.  Looking at the IST, at
anything above 2500RPM the limit is set at 1.9 bar, which is less than
22PSI.  

Good luck!
Steve B
San Jose, CA (USA)

-----Original Message-----

Which side of the diaphragm are you testing?  If you're testing the upper
chamber I would agree that you would expect to see that it holds a good
vacuum.  The bottom half is where the manifold pressure is applied, and that
side has the rod which goes to the wastegate proper.  I've never tested the
lower chamber for how good a seal it makes, but I wouldn't be surprised if
it was leaky.

It could be that the wastegate mechanism is sticking or the WG spring is too
stiff or binding.  You may want to pull the cap off and verify that you can
move the wastegate up and down, and that the spring is good.

Steve B
San Jose, CA (USA)

-----Original Message-----
Hi y'all!
 
My car is running great! 
Diff lock panel is in place, both locks work, and the LEDs work too!
But, it's boosting up to 20-22psi, even at 1/3 to 1/2 throttle, 4500 rpm.
It feels like the timing gets retarded during this, which is good.
Problem is it doesn't hold vacuum. Visually I can't find a hole in any of
my WG diaphragms. Also, I just replaced the hose.
 Could there be another leak source? A cracked WG cap?
 
TIA
 
Gary