Re: Aft O2 'simulator'

From: chris@slowcar.net
Date: Mon Jul 16 2001 - 13:47:33 EDT


|
| Well, without the cat, the postcat O2 will send the same voltage as the
| precat, both fluctuate between .1 and .9 volts, with the postcat hovering
| around .4, so we were thinking just a small resistor to reduce the voltage
| slightly would do the trick, since the computer wouldn't know any better. Or
| would it? Is it constantly comparing O2 sensor fluctuations to make sure one
| is following the other? The postcat reads much more stable, normally, cause
| of the effect of the cat. Except for mine, which died a few weeks ago.

    They do compare the readings and fluctuations; otherwise the sensor would
be pointless!

| Hmm...I was just going by my Haynes manual, which states "The downstream
| oxygen sensor (mounted in the exhaust system after the catalytic convertor)
| has no effect on PCM control of the air/fuel ratio." Quote.
| It goes on the describe the lower O2 content in postcat exhaust, and how it
| fluctuates more slowly, blahblahblah. Can the computer throw a code without
| tripping the check engine light?

   Yep, the computer can throw a code which doesn't light the MIL. As for the
first part - it's generic OBDII functionality (that there is an effect on fueling). This
was mandated by EPA, etc. in the OBDII requirements. The Haynes claims
the same thing for the F-body cars, but there is most definitley a change there -
so in this respect I would say the Haynes is just flat out wrong.

| Yes, the KatBox is perfect, except that it costs over $90...for that much, I
| could buy a high-flow cat and take me and my buddies out for beer and pizza
| afterwards....*sigh*...ah well, it'll all be moot when I swap in the 360
| anyway....

    I don't know if it's the same thing or not, but for our GM cars we have always
used "O2 Simulators" from casper electronics - around 50 bucks a pop. The
stock dodge O2 connectors will probably add a little expense.

Chris Bennight

|
| William
| 97 shortbed standardcab 2wd 2.5l manual, 18.8@75mph, 0.97 inst. g's. beat
| that.
|
|
|
|



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