DIY_EFI Digest V1 #180

[WERNER_HAUSSMANN at HP-Loveland-om2.om.hp.com]

Hi Josh

I don't know as much as Jim. (He let the 'Alfa' guy have it, and rightly 
so.). But then Jim seems to like the digital ECU better.  I don't have 
access to the Motronic units in the junk yard. 

1. You can't get a good idea what the mixture is doing with an O2 sensor. 
The O2 sensor is only useful to tell you if the mixture is rich or lean, 
not how much.  

Try to find someone with a CO meter. or emission meter.
Using a dynamometer, accelerometers, or time trials is too hard. You need a 
way to measure the AFR in the garage so you can see what happens when you 
change something. A CO meter is the easiest.  I have never been able to 
make a O2 sensor do that.  Besides I don't think you have a place for an O2 
sensor.


2. If you change the spring slightly, or the fuel pressure slightly, at one 
point (say no load, 3000rpm) the rest will stay close to calibration. Jim 
is right, changing the spring position screws up the calibration, 
especially if you change it a lot.  The idea is to calibrate it at cruising 
and at WOT.  You should have a trottle switch that closes at WOT.  You set 
it up for say 13:1 at cruising, and 12:1 at WOT or whatever you think makes 
sense.

3. Start by measuring the AFR at 3000rpm.Check it at part open trottle, 
and check it again shorting the two wires that go to the ennrichment. 
They are  shorted for WOT (wide open trottle, check the box on the 
trottle body, two of the three wires).  When shorting the enrichment you 
should see the AFR get richer.  (also a good way to test the CO meter). 
Depending on the type of ECU  you might be able to do the tuning in the 
ECU. I am only familiar with the Bosch ECU that uses the O2 sensor.  (I 
don't use that feature)

also check out http://proffa.cc.tut.fi/~k124775/Injection.html


The above is a first step no matter what you plan to do.  You first have to 
be able to measure AFR or any changes you make.


Best regards
Werner


______________________________ Reply Separator _________________________________
Subject: Re: DIY_EFI Digest V1 #180
Author:  Non-HP-joshk (joshk at tanisys.com) at HP-ColSprings,shargw2
Date:    6/26/96 8:24 AM




OK, I hear that you are the guy who knows how to modify the analog 
ECU to make the car run leaner (whatever).  I can plug in an O2 
sensor and measure the mixture without the air pump, no sweat.  I can 
also tighten the spring in the AFM or add a resistor (whatever) to 
make the car run leaner in range of operation where the AFM is in the 
game (warmed-up, above idle, below 3000 rpms or so, right?).  So then 
how do I recalibrate the whole system to make it run leaner (and the 
right amount leaner) at idle, 3000 rpm+, cold-start, etc ?

Thanks for your advice.

_____________________________________________________________________________ 
Josh Karnes                                                 joshk at tanisys.com 
Renaissance Man                        http://www.tanisys.com/~joshk/home.htm 
Tanisys Technology                                     http://www.tanisys.com 
Austin, Texas                      '78 BMW 530i | '72 Datsun 240Z | IZCC #308 
_____________________________________________________________________________
           *** opinions expressed herein are MINE, ALL MINE!! ***