Cat bypass question?
04-03-2011, 09:09 PM
#1
Drifting
Thread Starter
Cat bypass question?
I hooked up my cat bypass.
The secondary 02 sensors got warm, so I just unplugged them. Car runs fine and surprisingly no check engine light.
Does any one see issues running this way? I think the 2nd 02 just tell you if the cats are working.
The secondary 02 sensors got warm, so I just unplugged them. Car runs fine and surprisingly no check engine light.
Does any one see issues running this way? I think the 2nd 02 just tell you if the cats are working.
04-03-2011, 09:14 PM
#2
Race Director
what does "the sensors got warm mean"?
You'll probably be fine if you open air the sensor, but I don't love running like that. If you just unplugged them, you'll probably get a check engine light at some point soon.
Somebody has to sell an 02 sensor "malfunction indicator light eliminators".
You'll probably be fine if you open air the sensor, but I don't love running like that. If you just unplugged them, you'll probably get a check engine light at some point soon.
Somebody has to sell an 02 sensor "malfunction indicator light eliminators".
04-04-2011, 12:09 PM
#6
Burning Brakes
I think the big question is whether the secondary O2 sensor simply tells if the cat is working properly OR if it takes a reading and sends that to the ECU which adjusts the fuel mixture accordingly. If it's the second one I don't see how running it in open air could result in the engine running "normal". I'm curious as to the answer...anyone know for sure? I know it's been discussed before but don't ever remember reading anything definitive.
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04-04-2011, 12:32 PM
#9
Burning Brakes
Thanks Quadcammer...so is it your opinion that running the second O2 sensor in clean air (or in a "spacer" like many import tuner cars use) has no ill effects on the car?
04-04-2011, 12:35 PM
#10
Race Director
That is a "mil cover upper thingie" not a delete.
Reason just covering it up is no good is because if you have another malfunction you won't know about it, unless you check the car with the scanner regularly....plus its a little bush league if you ask me.
Oh the car will run fine, no question about it. I don't like just leaving the things in the open air.
There has got to be some resistors or something that can be spliced into the rear 02 wiring to make it think the sensors are fine.
Reason just covering it up is no good is because if you have another malfunction you won't know about it, unless you check the car with the scanner regularly....plus its a little bush league if you ask me.
There has got to be some resistors or something that can be spliced into the rear 02 wiring to make it think the sensors are fine.
04-04-2011, 07:47 PM
#11
Nordschleife Master
Just plug them in & run it. I don't see why you would not have them screwed in.
Yes, they get hot, they are in the exhaust, & are also heated.
If you get a CEL, you can get O2 spacers, they can shut off the cel.
Yes, they get hot, they are in the exhaust, & are also heated.
If you get a CEL, you can get O2 spacers, they can shut off the cel.
04-04-2011, 09:46 PM
#12
Race Car
DO NOT RUN YOUR SECONDARY O2 SENSORS IN A CAT BYPASS PIPE!!!!!!!!!!
Your secondary O2's read the air passing them and are looking for a specific value that is supposed to be different from the pre-cat O2's, they tell the ECU that the cats are working (or not) and adjust the A/F mixture accordingly. If you run both sets in a bypass pipe the O2's read no different and the system goes into a lean mode (this would be the best way to burn holes in your pistons!)
If you run the post cat O2's in fresh air, the system goes into full rich mode. Not a big deal other that smell of unburnt fuel and you will get a CEL in time (within usually 100 miles) once the ECU realizes the extreme differences in O2 readings.
The safest thing to do is to have your ECU chip flashed with the post O2 variables flashed out. Steve W or most chip tuners can do this for you.......'course you must have their chip
Your secondary O2's read the air passing them and are looking for a specific value that is supposed to be different from the pre-cat O2's, they tell the ECU that the cats are working (or not) and adjust the A/F mixture accordingly. If you run both sets in a bypass pipe the O2's read no different and the system goes into a lean mode (this would be the best way to burn holes in your pistons!)
If you run the post cat O2's in fresh air, the system goes into full rich mode. Not a big deal other that smell of unburnt fuel and you will get a CEL in time (within usually 100 miles) once the ECU realizes the extreme differences in O2 readings.
The safest thing to do is to have your ECU chip flashed with the post O2 variables flashed out. Steve W or most chip tuners can do this for you.......'course you must have their chip
04-04-2011, 10:52 PM
#13
Race Director
DO NOT RUN YOUR SECONDARY O2 SENSORS IN A CAT BYPASS PIPE!!!!!!!!!!
Your secondary O2's read the air passing them and are looking for a specific value that is supposed to be different from the pre-cat O2's, they tell the ECU that the cats are working (or not) and adjust the A/F mixture accordingly. If you run both sets in a bypass pipe the O2's read no different and the system goes into a lean mode (this would be the best way to burn holes in your pistons!)
If you run the post cat O2's in fresh air, the system goes into full rich mode. Not a big deal other that smell of unburnt fuel and you will get a CEL in time (within usually 100 miles) once the ECU realizes the extreme differences in O2 readings.
The safest thing to do is to have your ECU chip flashed with the post O2 variables flashed out. Steve W or most chip tuners can do this for you.......'course you must have their chip
Your secondary O2's read the air passing them and are looking for a specific value that is supposed to be different from the pre-cat O2's, they tell the ECU that the cats are working (or not) and adjust the A/F mixture accordingly. If you run both sets in a bypass pipe the O2's read no different and the system goes into a lean mode (this would be the best way to burn holes in your pistons!)
If you run the post cat O2's in fresh air, the system goes into full rich mode. Not a big deal other that smell of unburnt fuel and you will get a CEL in time (within usually 100 miles) once the ECU realizes the extreme differences in O2 readings.
The safest thing to do is to have your ECU chip flashed with the post O2 variables flashed out. Steve W or most chip tuners can do this for you.......'course you must have their chip
04-04-2011, 11:07 PM
#14
Burning Brakes
http://www.mkiv.com/techarticles/oxy...sor_simulator/
https://www.speedforsale.com/suprapa...nly-p-323.html
Almost all OBDII cars will trip the CEL if you run no rear sensor or no cat.
They make O2 sensor simulators that trick the ECU into thinking there is something there. The air/fuel mix should not be affected by the rear sensors reading a little whack.
I would take this as a great excuse to have the ECU re-programmed though, thats the best way to handle this.
https://www.speedforsale.com/suprapa...nly-p-323.html
Almost all OBDII cars will trip the CEL if you run no rear sensor or no cat.
They make O2 sensor simulators that trick the ECU into thinking there is something there. The air/fuel mix should not be affected by the rear sensors reading a little whack.
I would take this as a great excuse to have the ECU re-programmed though, thats the best way to handle this.
04-05-2011, 09:00 PM
#15
Leaving the secondary sensors strapped up out of the way is not a problem if you are running a bypass. Doing this will cause the engine sensors to believe it can make the fuel mixture richer. A richer fuel mixture means your engine will run cooler. Leaving the secondary sensors in without cats will be a problem because the engine will sense that it is running too rich and will lean out the engine to the point of eventually causing damage.
I tried running my car with the cat bypass pipes on for a little while, but I did not like the smell. My car did not throw any codes with the secondary sensors strapped above with zip ties.
I tried running my car with the cat bypass pipes on for a little while, but I did not like the smell. My car did not throw any codes with the secondary sensors strapped above with zip ties.