Re: 3B Charlie Spring?? and new results with WGFV

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

I've gotten some advice from a few people, thanks for the input. I decided
to make the circuit discussed the other day to measure waste gate frequency
valve (WGFV) duty cycle. Here's what I found:

Engine: 3B 20v turbo

Symptoms: With a new, stiffer waste gate spring, I found a lot more power
after the spring worked itself in, no longer hits overboost. Car seemed to
pull hardest when starting at about 2,000 RPM in second or third or fourth,
just put the pedal down about 1/4, the thing pulls hard when you get above
1.3 bar, max boost is usually 1.6 or less.

However, if you put the pedal all the way down, you don't get as much pull,
even if it shows the same boost or more.

So I made the circuit, and hooked it up. Real easy to make if you have ever
soldered anything together. Ran the diodes inside the car so I could look
at them. It's best if you can see the boost gauge and the diode at the same
time. 

So when I went out on the road and put the gas 1/4 of the way down, the
diode lights up a little bit, then seems to go out, as if the WGFV was
pulsed a little bit and then turned off again. When the WGFV is not being
energized, and the boost is at 1.4, it's a true 1.4, the turbo is
pressurizing the intake to 1.4 and nothing is bleeding the pressure off. So
it's smooth and powerful.

Now when I put my foot all the way down to wide open throttle (WOT), the
diode immediately goes full on, which means the WGFV has a constant or
close to constant 12 VDC (full system voltage, 100% duty cycle). This means
that the waste gate is opening, bleeding off pressure. Now the turbo is
working against this and pressurizing the intake at the same time. Now if
the gauge reads 1.4, it's actually a combination of some pressurzation rate
and some bleed rate which is something like 1.4 at the manifold. But I bet
the pressure wave going into the intake is much different as compared to
less pedal with the WGFV being closed.

Very interesting, makes a lot of sense. Now I'm gonna put the old (original
lower pressure) WG spring in and see if the WGFV acts the same way. If it
does, I'm assuming the computer is calibrated for a certain mechanical
pressure spring. If it changes, the computer has feed back into the
motronic unit to control duty cycle of the WGFV.

I'm sure I'm learning what a lot of you already know. I'll post results.

Paul

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Paul Waterloo
Brookfield, IL

91 200q

EMAIL: 74543.407@compuserve.com
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