Mike,
You are partially correct that the distance to the
collector will affect the readings. It will take
longer for the O2 sensor to reach it's operating
temperature, but once hot enough, readings will be OK
(but see my comments below about these guages).
Many cars today use an internally heated O2 sensor,
which brings it up to working temp very quickly. It
has a seperate wire for the heater voltage, which is
wired to be on whenever the ignition is on. You should
be able to get one for << $50.
As for the 'guage', be aware that the common O2
sensors these use are NOT wideband. They function like
an on-off switch in the presence of Oxygen. NO oxy,
off, ANY oxy, on. This point is commonly called the
stoichometric ratio, or lambda. The Engine Control
Computer (in closed loop mode) continuously monitors
the O2 sensor for lambda. If rich, it cuts down on the
injector pulsewidth. If lean, it increases the
pulsewidth. Note that it *never* holds steady, the
pulsewidth cycles back and forth (and so the O2 sensor
switches) continuously.
Now, since the 'guages' have no control over the
mixture, they can only really report that the mixture
is under or over lambda, but not by how much.
Although this can be somewhat useful, be aware that
lambda is fine for emissions control, but not so great
for either best power, or best economy.
In an ECU controlled car, when you open the throttle
past a certain point, the ECU drops out of closed loop
mode, and delivers more fuel than lambda, to get max
power.
There are some newer cars that use wideband O2
sensors. These O2 sensors can cost $100-250, plus the
electronics to manage them is somewhat complex and
expensive. The commercially available WB O2 meters
cost >> $1000.
There is a project underway to make WB O2 available
for around $300 with sensor. Beta prototypes have been
shipped, but they are not yet generally available.
Hope this helps
Carter Shore
--- "Graziano, Michael" <michael.graziano@csfb.com>
wrote:
>
> All,
>
> I'm once again contemplating installing an air/fuel
> ratio gauge. I know
> that install should be relatively easy, but I'm not
> sure on the location of
> the sensor. With a manifold, it would be easy. But
> where would I install
> the sensor with 4-2-1 headers? I would think all
> the way down by the
> collector for the 2-1 part would be too far along in
> the exhaust to be of
> any use.
>
> Any ideas?
>
> Mike
> '78 Midget (Twin HS4's and 4-2-1 headers)
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