Downstream O2 eliminators

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Aside from the emissions/legality concern, will a "dummy" device designed to do away with downstream oxygen sensors (used in a compatible application) affect performance or engine longevity any calculable amount?
 
I'm aware of the non-fouler trick. In this case, the moron that replaced the engine in a new customer's '02 F150 (4.2L V6) a few months ago cut out the cats and the downstream O2's, replacing them with several feet of flex pipe clamped at each end. (Yee haw, welcome to Kentucky.) The expense of new cats is out of the question for him (he could barely scrape together the money for me to do intake gaskets) and with the downstream sensors completely gone, a set of eliminators is half the cost of two new sensors that are just going to get non-foulers put on them to keep the CEL off. However, the local exhaust shop (going to put some proper pipe in place of the flex for a good price) won't do the pipes unless they put sensors in them, claiming it'll ruin the engine shortly if they aren't there.

I just wanted to know if I was under the wrong impression about the function of the downstream sensors or not. It appears I was correct.
 
I believe there's a small set of cars (mid 90s Chrysler's) that actually use the downstream oxygen sensor to work in tandem with the upstream

Otherwise, eliminate/space away
 
In my experience, the only people that say that 02 eliminators are bad are the ones who want to sell you a new cat...
 
Downstream O2 sensors are part of a second closed feedback loop for the engine module,
they monitor if the up stream O2 are OK and if the Cats are functioning correctly.

You can bet OEMs have lots of code running to validate all O2 since they are critical
to smog controls! The O2 signals change as an engine starts cold and runs til hot and
beyond, the system checks they are outputting correctly under all conditions.

So fake O2s won't cut it.
 
Originally Posted By: i_hate_autofraud


Downstream O2 sensors are part of a second closed feedback loop for the engine module,
they monitor if the up stream O2 are OK and if the Cats are functioning correctly.

You can bet OEMs have lots of code running to validate all O2 since they are critical
to smog controls! The O2 signals change as an engine starts cold and runs til hot and
beyond, the system checks they are outputting correctly under all conditions.

So fake O2s won't cut it.


Fake 02's and Stacked Non-foulers do, in fact work. I've used both probably 100 times with complete success.

The post cat 02's are just an emission monitor for the convertor's performance. Most cars, true not all, but atleast 80% do not use the post 02 data for anything else.
 
Originally Posted By: bdcardinal
If you want to get technical, Ford calls the rear O2s "cat monitors" in a lot of publications.


Ha, nice.
laugh.gif
 
Yeah, since this is a Ford I actually have the Ford OBD manual for '01 and '04 that goes in depth about how all the various emission systems work. The rear O2 is just for cat monitoring.
 
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