91 200q WG Spring Info (long)

["Mike Miller" <MikeMilr@email.msn.com>]

I had a WG laying around from an 86 5kt. I have had a low boost problem (1.6
max) for quite some time that no one has been able to fix. I decided to
clean up the WG and install it to see if it would help anything. While
cleaning it, I had the spring out of it and noticed that it felt quite a bit
stiffer than the one I had in the WG on the car. Quick simple test was to
install the new, stiffer spring and try it out. Before you say that the 91
200q does not get more boost from a stiffer spring, try removing the spring
all together and see what happens. (No boost at all). To make a long story
short, I now get 1.8 boost in all gears. Where it used to require full
throttle to get to 1.6, I now get that at about 1/4 throttle. Makes the car
much more fun to drive  :-).  I do not know if my old spring is "tired" or
if the new spring is masking another problem - however, the car has run
great for over a month.
There were no part numbers or colored dots or any ID at all on either of the
springs. The WG part numbers are slightly different - I can get them if
anyone wants them.  Here's some specs and differences between the two
springs and WG's:

For reference sakes, the old spring is the one that was originally on the
car and has been removed. The new spring is the one from the 86 5kt WG.
Measurements are approximate. Inch measurements taken using a steel ruler
calibrated to 64ths - pound mesurements taken using baby scales and/or
bathroom scales. I figure that the spring is compressed 1.125 inches when
installed in the WG using the 5/16 top spring pad. This was measured by
placing the WG cap on the WG and the measureing the gap between the cap and
WG. The total travel of the WG valve is about 5/8 inch - this gives a total
height of the spring when the WG is fully open of about 1.5 inches. To get
the measurement of a fully compressed spring, I took two pieces of 2x4 (1.5
inch thickness) and placed them on the scale side by side with the spring
between them, then pushed down until the I contacted the wood. I'm not sure
how much the actual reading means, but the difference in the force required
to get the springs compressed that much was over 50%.  Both springs have 5
working coils. The new spring is what I would consider to be one gauge of
wire thicker. My micrometer was not available when I was doing these
measurements. Using the calibrated eyeball method, I would guess the wire at
about .100 (1/10) for the old spring and .125 (1/8) for the new one. The
styles of the top spring holders between the 2 WGs was way different - the
one with the 5/8 in thickness didnot compress the spring as much as the
other one. Crude ASCII art:

     _____
    /           \
   /             \                         ______
_/               \_    versus   _/             \_ with a hole in the middle.

 I used the shorter one  to get max compression. The taller one allowed the
base of the spring to be nearer the top of the WG Cap.


Thickness of the top spring holder  - old - 5/16in                new -
5/8in
Spring Heighth                                  - old - 3.25in
new - 3.05in
Spring diameter                                - old - 1.5 in
new - 1.5 in
Force to compress 5/8 in                - old - 9lbs 4 oz            new -
13lbs 12oz  (baby scale)
Force to compress *to* 1.5in          - old - 24 lbs                 new -
38 lbs (bathroom scale)

Have fun with the data. Any of you other 91 200q owners that have lower
boost might want to check that spring and see if maybe it is tired. I do not
know of a source for new springs if it is.

mike miller - renton, wa
91 200q