Single wire and Three wire sensors do use the exhaust/engine as a ground.
On a single wire sensor this is obvious.
On a three wire sensor there is a sensor lead, and power and ground for the
heater circuit. The heater circuit ground is NOT shared with the signal
ground. The ground is through the threads of the sensor to the exhaust and
up to the engine.
A four wire sensor would be independent of the exhaust/ engine.
Five and six wire sensors would not be compatible with anything you could
cook up at home easily.
Rick
On Thu, Nov 17, 2011 at 11:02 AM, Bob Spidell <bspidell@comcast.net> wrote:
> re: "The sensor does not use the exhaust as a ground"
>
> I believe the one-wire sensors do. All the ones I've installed have come
> with a special (copper-based?) anti-seize to guarantee a good ground to the
> exhaust.
>
> Since three-wires have a separate ground I can see how it would work. I
> think the K&N guy assumed you would use their sensors, which I believe are
> one-wire.
>
> Bob
>
>
> --------------------------------
> Bob Spidell - San Jose, CA
>
> ----- Original Message -----
>
>
> You dont have to isolate the sensor, only the meter. The sensor is a 3
> wire type (heater, sensor, ground). The sensor does not use the exhaust as
> a ground. Its not theory. Been there done that.
>
> Gergo
>
>
>
>
> 2011/11/17 Bob Spidell < bspidell@comcast.net >
>
>
>
>
> Would be very interested in exactly how you did this. How do you isolate
> an O2 sensor? They emit a (very small) voltage signal, referenced to
> chassis ground, and I was told by K&N tech support that their indicators
> absolutely would not work on +gnd, because of their input polarity
> (isolation or no).
>
>
> Bob
>
>
> --------------------------------
> Bob Spidell - San Jose, CA
>
>
>
>
>
>
>
> You can use it on + ground cars with no problem. Just have to isolate it
> from the chassis. My car is also + ground.
> BTW it may be good to point out, that there are two different types of O2
> sensors awailable. The wideband and the narrow band. Though the narrow band
> may be usefull as a controll device, it is not particulary usefull when
> setting up an engine. Esp. if the negine is nonstandard.
>
> Gergo
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