[urq] Into the CIS abyss

Buchholz, Steven Steven.Buchholz at kla-tencor.com
Thu Nov 18 18:45:34 EST 2004

... while I agree wholeheartedly that an AFR meter is highly
recommended, frankly I don't consider a bar graph LED attached to the
OXS signal to be an AFR meter ... 

... there is a DIY-EFI project to build your own AFR meter using a
"wideband" OXS (BTW, I hear prices are coming down on WB O2 sensors) ...
check out www.diy-efi.org for more info ... look out for links for
"WB02" ...


... another tack ... someone posted here about an off the shelf unit
...here's a link:


... for $350 it looks like a good price ... looked like they had some
cool accessories for it too ...

... getting back to the CIS tuning ... I think the first thing I would
recommend is to read through the widely available Bosch documentation on
the CIS system to gain a full understanding of how it works.  For
example, you could have done the same thing as cranking all ports 45
degrees by reducing the control pressure.  In fact, assuming that your
OXS feedback is working you should expect the duty cycle on the OXS Freq
Valve to compensate for the richer mixture.  It seems to me the
adjustments for the individual ports might help with balancing the
cylinders ... such as richening or leaning particular cylinders based on
the inspection of the spark plugs after a run ... 

... please don't take this as me trying to tell you not to tweak your
fuel distributor or other CIS components ... more power to you as far as
I'm concerned!  I think that you might be able to find more variables
you might want to play with to try to gain the upper hand over the old
WX ... for example ... the control pressure regulator (AKA warm up
regulator) has vacuum ports on it which should allow you to impact
mixture by applying pressure or suction ... you should be able to do
similar things by changing the duty cycle on the OXS Frequency Valve.  

Steve B
San Jose, CA (USA)
> O2 meter is a must on a turbo car.
> It's easy... one wire to +12, one ground and one spliced into 
> O2 signal.
> That's all.  I have Autometer on my '85 and am very happy with it.
> -----Original Message-----
> Last night I ventured into the black abyss of CIS 
> experimentation. I know to
> some that's a 4 letter word, but have mercy.
> Since I acquired my WXd 83 URQ (and 2 motors since) it has not been
> consistant or impressive at full throttle. Ever!
> So- I pulled 2 fuel distributors from the local boneyard. The 
> plan was to
> have 1 to experiment with, one stock with which to return to the
> hinterland's original spec, and my original.
> I put one on the car last night and adjusted the allen screws 
> under the caps
> next to the fuel lines out (counterclockwise- rich) 45 degrees each.
> The preliminary results are YEEHAAAAAAAAAA! Full throttle as it was
> intended
> to be. All the way to redline, and not just in 3rd gear. I 
> will now  check
> the plugs routinely for indications of rich/lean etc. The 
> frequency valve still
> dials right in, so I don't feel I have gone over the edge 
> with  mixture.
> Maybe I should put together a fuel ratio meter? Anyone who 
> has done that and
> could talk a non electric dummy through the process would be greatly
> appreciated.
> More real life driving impressions to follow, but so far it 
> is an amazing transformation.

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