3B Motronic Control on WGFV with Charlie Spring

["Paul C. Waterloo" <74543.407@compuserve.com>]

As some of you read, I have a 91 200q that I just put in a "charlie" spring
for testing. I'm really trying to figure out why I don't have the right
power with my stock spring.

The car makes a lot more power with the charlie spring installed. I
couldn't really explain it to myself, so I added a WGFV monitoring circuit
discussed a couple of weeks ago. I have now tested both set ups with the
monitoring circuit and have interesting results, not what I expected. My
results:

WITH CHARLIE SPRING

When I installed the charlie spring, it took a while for the computer to
"learn". I hit 1.8 in first gear the first time I got on it. Now with the
charlie spring 1st gear gets no more than 1.6. Most other gears hit 1.6
unless I've been in wide open conditions and now I can see 1.7 after a
little bit, with 1.8 shortly in 5th gear today on the highway. Man.....I
thought the top end was fast with the stock spring.....it totally smokes
above 70 MPH!

I got very nervous about the increased power and took it out until I could
hook up the WGFV monitoring circuit. With the circuit hooked up, I
explained why I got a ton of power with about 1/8th to 1/4 pedal. The thing
would indicate 1.3 and the power was HOT! Comes down to the WGFV not being
put under any duty cycle, or if it is, just for a little bit at first, then
it turns off. This is consistent with the low throttle. Watch the duty
cycle come on, lift just a little bit, the duty cycle goes back to zero,
feather the gas, and the duty cycle stays at zero, and the power is on!
Even when I hit WOT, the light only comes on at 100% duty cycle for a short
period of time before it backs off.

WITHOUT CHARLIE SPRING

So I had to put the stock spring back in to see how the WGFV acts. To my
surprise (I thought the duty cycle would remain constant at the same
throttle/acceleration scenarios), it had a much higher duty cycle under all
conditions. If I hit WOT, it goes to full duty cycle and then to something
less than that for the whole time. Much less power. During 1/4 - 1/8
accelerations, it comes on at some level higher than the stiff spring, than
it won't go off if I feather off the throttle. With the stiff spring, I can
get it to go off just by backing off, with the stock spring, it is
difficult to get it to turn off. 

So now I know why I have the huge low power differences (the WGFV is under
0 duty cycle) and large power differences at WOT (I don't get high boost
numbers when using the stock spring, 1.4, 1.5).

MY QUESTIONS

If I'm rarely seeing more than 1.7 bar, but the WGFV is under a different
duty cycle, what I'm I gonna damage?

1- Turbo for very high speeds (WGFV is not operating, so turbine is getting
really spinned up). This would only be a problem if it let loose?

2- Buring pistons and head gasket? Just because the WGFV has a lower duty
cycle, does that mean the engine is getting leaned out?


Why does the WGFV duty cycle change with different spring pressures, what
is providing that feed back to the ECU?

TIA, learning a lot

Paul

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Paul Waterloo
Brookfield, IL

91 200q

EMAIL: 74543.407@compuserve.com
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