Date: Sun, 12 Nov 2000 13:15:45 +0000
Reply-To: Mark Keller <kelphoto@ISLANDNET.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@ISLANDNET.COM>
Subject: Vanagon ECU Settings
Content-Type: text/plain; charset=us-ascii
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Gary,
I agree with Darrell on the Bosch Book. I obtained a copy from a
listmember to read and found cartesian graphs of power and O2 voltage.
Incidentally the Max. power curve was at .84 volts, and then declined to
a max. fuel burn efficiency at .15 volts. The Ecu will not allow the
leaner mixture to set, as the voltage reaches .3 volts the ECU calls for
more fuel via a longer injection pulse. The ECU on mine, as I did
exactly what your doing, tends to reduce fuel when the voltage reaches
.75 Volts.
I might note that I was seeking a max. power voltage at wide open
throttle, WOT, when at 3600 RPM and greater. The author, Alan Probst,
noted that injection pulse times are nearly maximum. He was referring to
all engines with bosch fuel injection. And since It's been noted on this
list that the orifice size on the stock injectors is smallish and the
waterboxer runs at 3600 RPM for 60 mph in my automatic I felt that this
was an issue to look at .since this is when a max. fuel delivery issue
could be noticed.
That is the Bosch Book indicates that as the engine rpm increases in
this range, the injectors could be open almost all the time. A slightly
undersized injectors, a weak pressure regulator or fuel delivery issue
could cause the engine to lean out when in this RPM range with the
throttle opened for high power.
The bosch Book has a section on what works and what doesn't' as far as
tinkering with the system, a la perfomance chips, and odd sensor input
diddling. The author, says that increasing fuel pressure is among the
simplest and most effective quick improvements to an otherwise healthy
fuel injection system. Better fuel atomization was on his mind. But I
felt that since the 3600 Rpm range is right where most of us drive. The
fuel delivery issue was probably one that some vanagon have and don't
know it. The only real test is to do what you and I did, run Darrel's
Digi-tool, or a volt meter while driving the van and check for a .75-.84
volts while under max throttle at 36000- 4400 RPM Range.
My van test originally at a respectable .7 volts. But I wanted the max.
I installed the adjustable pressure regulator that Robert Lilly
suggested, and now run at .84 volts at the 4000 RPM and WOT Throttle.
I also adjusted the spring and wiper setting on the AFM. Mainly I
wanted a low .3 volt at slight coast, 16" on my vacuum gauge, and a .84
when below 8" vacuum. Of course this is open loop. The closed loop
setting are the interaction between the basic setup and the computer
program modifying the pulse time to get the O2 voltage back in the
approx.3- .7 volt range.
Sincerely,
Mark Keller
91 Carat. "Lazarus"
I on digest modes so Pmail is ok
Date: Sat, 11 Nov 2000 19:43:09 -0600
From: Darrell Boehler <midwesty@MIDWEST.NET>
Hi Gary,
I suggest you read the " Bosch Fuel Injection & engine management" =
book. It does a good job of explaining various bosch systems and fuel =
management components. This is not intended as a cop out it is the best =
source of informantion about the questions and observations you mention. =
Darrell
--- Original Message -----=20
From: Gary Stearns=20
To: vanagon@GERRY.VANAGON.COM=20
Sent: Saturday, November 11, 2000 4:47 PM
Subject: Digifant Operating Specs
Maybe only Bosch or VW engineers know this, but the list has amazed =
before...Over the past few months, I have run our '88 with the O2 sensor =
disconnected (open loop). I did this so that I could manually adjust =
the AFM spring tension and wiper static setting and live with it awhile =
under various conditions without fighting with the ECU. Lots of =
fiddling later I do have open loop settings that allow the WBX to run =
right. Rock steady idle (though cold is still an issue) and plenty of =
power. Today I again connected a digital multi-meter to the O2 sensor =
while still keeping it disconnected from the ECU. This setup allowed me =
to drive with the multi-meter propped on the dash. I had found earlier =
that our engine will not run right (too lean, stumbling acceleration, =
lousy throttle response) with O2 sensor outputs in the .5 range where I =
had seen the list suggest that they out to be. I find that my manual =
S.O.P. (seat of the pants) adjustments have left me with O2 outputs in a =
fairly constant (doesn't fluctuate too much) .75 to .88 range. I next =
reconnected the O2 output to the ECU while keeping the multi-meter =
connection piggy-backed as well. Now the O2 output changes quickly as =
the ECU is trying to adjust. Output appears to go from .55 to .90. A =
little more lean hesitation at lower rpms, but the high rpms seem to run =
more cleanly.
My question (finally) is: what O2 sensor output range is considered =
normal with the ECU adjusting things? I thought that the O2 sensor / =
ECU combination attempts to adjust for no excess oxygen or a 0.00 =
voltage. Our WBX might run at this level, but it would run terribly. =
At what output levels does the ECU go "out of range" and give up =
defaulting to open loop again? With non-spec AFM settings am I forcing =
it to go open loop or even fluctuate between open and closed? =20
Thanks-
Gary
