Vacuum divider ciruit and MAC11 mods

[Richard Tanimura]

Kurt,

I like the way you think. Lets keep to the electrical analogies. True, you
want R1 + R2 pretty big to keep the leak to ground (outside air)low. The
transducer can probably be seen as a capacitor since it doesn't leak much to
ground. What you might see is a time constant 1/R1*C that is pretty big.
This will give a lag in your pressure signal. The larger R1 (and C) is, the
larger the lag.

The CPU is using the pressure signal to determine WGFV pulsing, fuel, etc.
If you have a big lag in your feedback loop, you might have some automatic
control problems.

Just some idle speculation on my part.

Rich

-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Kurt W. Deschler
Sent: den 12 januari 2004 19:03
To: quattro at audifans.com
Subject: Vacuum divider ciruit and MAC11 mods



I would appreciate any feedback about using a series of air flow
restrictors to extend the range of a the MAC11 pressure transducer. I
think the following circuit would work:

Vacuum Source >---Flow Restrictor1---T----Flow Restrictor2---< Outsize air
                                     |
                                     ^
                             Pressure Transducer

My intuition is that this circuit should behave like a resistor network
Pout = Pin*FR1/(FR1+FR2). Fluids experts?? Clearly this would make a
vacuum leak, but if the restrictors were small enough, it should be
negligible. I was thinking a FR1/FR2 ratio of 4:1 to extend the transducer
range to 2.5 bar. The higher ratio keeps the leak side is smaller, which
is good. Ay ideas on how much flow is needed for adequate response? Could
even put a check valve on the atmospheric side so that the leak is not
present under vacuum to work around high idle (split linear curve?).

Longer term, I have a cheapo 2+bar setup in mind using a vacuum divider
and the cold start valve as a 5th injector. I would line to alter the
MAC11 program to open the cold start valve, and lean out the injectors at
the same threshold so that the rest of the boost map can be calibrated
with the cold start valve open. Any feedback on altering the MAC11 boost
sampling loop would be appreciated as well.

	-Kurt
	'87 5kcstq



_______________________________________________
quattro mailing list
quattro at audifans.com
http://www.audifans.com/mailman/listinfo/quattro
---
Incoming mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.560 / Virus Database: 352 - Release Date: 2004-01-08

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.560 / Virus Database: 352 - Release Date: 2004-01-08