Adding another O2 sensor

[Walter Sherwin]

Actually,  you have a good idea there!..........By placing one standard zirc
oxygen sensor at each header collector, and by running the outputs up to a
toggle switch mounted in the cabin, you will have the ability to flip back
and forth to determine whether the fueling is balanced from bank to bank
(assuming you are still running bank fire).  You could then use one ALDL
scan tool device to observe either O2 output, and make a comparison either
while at idle or while on the road.  Would make things "nice" when tracking
down a bad cylinder, or injector, or combo.

Now let's say you find one day that the fueling is "off" between banks, due
to say recent porting & runners & etc.,  and that your cylinders and
injectors are in fine working order.  Are you then SOL for adjustability
without reverting to elaborate sequential EFI control?  Absolutely not!
Accel make a plug-in product called the "VIC" (short for Variable Injector
Controller) which can offer +/- 10% BPW adjustment per injector, while using
your conventional bank fire ECM triggers and wiring.  It's as simple as
twisting a knob per injector, and then locking it into position.  Kinda like
having SEFI, but without all the other associated hassles.  Two O2's,
together with some plug reading and a VIC, could get you to where you need
to ultimately be for balanced fueling.

However, for the two zirc O2 bank readings to be meaningfully comparable to
each other, you'll want to make sure that your sensors share the exact same
ground plane.  With custom exhaust parts inserted in the ground path(s)
between your sensor(s) and the ECM O2 LO sense circuitry, it would be
prudent to either:  1)run a braided ground strap from one header collector
to the other, OR   2)see a recent post to this list regarding standard zirc
O2's with redundant external ground leads built-in (GM and AC Delco P/N's
were supplied).

Carry this dual O2 concept one step further.............You could even
purchase a couple of cheap (but useful) Halmeter AF30 O2 monitors, and stick
them side by each on the dash.  This would expose a huge wealth of insight
with regards to comparative O2 trends and magnitudes between banks.  If you
later got "fancy", you could probably datalog the raw zirc O2 signals and
get to the point of examining each individual cylinder event on a trend
basis.  Although this approach would not necessarily be super accurate in
terms of absolute A/F ratio,  it would at least be somewhat repeatable and
illustrative for comparo purposes between cylinders.


Walt.




> Car = 1990 IROC-Z
> From the factory these cars have one O2 in the driver's side exhaust
manifold.
>
> Since I will be installing Hooker long tubes I have been contemplating the
> installation of an O2 sensor in the passenger side header as well as the
> driver's side header.  Then, I was thinking of running a SPDT toggle
switch
> so that I could switch between the O2s to determine how one side of the
> engine is running as compared to the other side.
>
> Just figured I would throw this out into the air since the list is pretty
> dead today.  Besides the obvious con of the extra expense ... can anyone
> think of a reason not to do this (besides the whole geek factor)?  Would
> the fact that O2s are not accurate be enough of a reason for not doing
this?
>  If so, then why is it that later F-bodies run an O2 sensor for each side
> of the engine (one for each bank of injectors).
>
> Heh heh - wouldn't it be cool if WB O2s were cheap and we could install
> a WB O2 into EACH primary tube of the header and then tune each cylinder
> for maximum power through sequential fuel injector tuning?  That would be
> really cool.  Yea - I know I am just wishing ... sometimes its cool to
wish.
>
> Tim

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