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Re: [Tech]: O2 sensors
>From: "Dave Ewing" <rabbit16v@prodigy.net>
>snipperoony<
>The answer to this actually depends on your knowledge of your fuel system.
>I would suspect if you know enough about your fuel system to >be able to
>keep it from either fouling your plugs by drowning them in >fuel or burning
>a valve by creating a "too lean" situation, and you are willing to take the
>risk, experiment with it.
Well, keep in mind that the adjustments that you can make are _idle_ mixture
(via the 3mm allen) and fuel flow at each injector. (via adjustment screws
at each injector line. DO NOT MESS unless you can accurately measure fuel
delivery at each injector. Pre-set, not inteded to be adjusted, and once
changed, a pain to get back the same) Basically you are limited to the
factory preset, unless, like you say, you are very daring and experimental.
You can adjust idle mixture, but that will have little effect at higher RPM.
>Since the early CIS systems are not electronic at all (atleast nothing like
>CIS-E systems), I wouldn't see any problems with atleast >experimenting but
>keeping an eye on the air/fuel mixture of course!! >HTH!!
There are electronics. The frequency valve, mainly. The fuel distributor
that has a frequency valve attached is pre-set to give 14.7:1 AFR when the
duty cycle is at ~50%. When I bought my 78 someone had tried to install an
O2 system, but the frequency valve wasn't buzzing. So even when I adjusted
mixture to stoich at idle, whenever the motor was revved, it would run lean.
Put in an earlier fuel distributor built without the frequency valve, and
now it's fine.
Basically, without knowing what the frequency valve will do without an O2
sensor connected, (i.e. 0%, 50%, 100% duty cycle, etc.) it is difficult to
determine if it will work. Unless it sticks at 50% duty cycle you won't get
good mixture at higher RPM.
IMHO, if you're abandoning the O2 sensor, also retrofit the fuel distributor
to one that does not have the frequency valve. It would save some serious
tinkering/tuning time. The end result would be the same.
HTH
Jonas
85 Scirocco 2.0
78 Scirocco 1.8
For direct reply: jonas@metabolex.com
http://www.geocities.com/scirocco2l8v
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