contentsunderpressur

I noticed there are 3 sensors in the mid pipe. There is one on the passenger side pipe right above the converter and one mounted in the side of each converter. I need to know if the ones that are mounted in the converters are neccessary? or are they just there to throw the check engine light if the converters stop up? My 03 mustang had two upstream sensors that give the computer the readings for the engine to run right and two down stream sensors that was just for throwing codes in case the converters clogged up. The reason I'm wanting to know is because I'm getting the converters removed instead of buying an off road pipe. If I can just leave those two out and throw some MIL eliminators on them to shut the light off I will. If the car needs them to run right though I'll get the man to weld new bungs in for them.

socalwrench

The upstream 02 sensors are inputs to the EEC for adj. the fuel mixture. The downstream 02 sensors are make sure the cats are working correctly. You can't just unplug any of them, but you can pull them further out of the exhaust stream (effectively sensing less HCs) or use a tune to turn them off.

contentsunderpressur

The sensors that are mounted in the converters are the downstream sensors right? From the pictures I've seen I can see the upstream sensor on the passenger side but I don't see one of the drivers side. Is the drivers side upstream sensor mounted in the exhaust manifold? If the sensors in the converters are the downstream sensors I'll leave them out. I can put a set of MIL eliminators on them and tie them out of the way.

RAT281

mil eliminators will not work on an 08

socalwrench

Any 02 sensor before the cat is upstream, and after is downstream. MIL eliminators are just boxed resistors, and aren't really a solution. To do this right, use a tune that ignores the downstream 02 sensors.

contentsunderpressur

That's what I'll do then. I know the check engine light will come on when the converters are not present but the car will still run right correct? I'll get the tune but I need to use the car for a while until I can get the tune. I know the check engine light will come on but I'm ok with that. I just don't want to remove the cats if the car will not run right without the tune???

contentsunderpressur

Why won't they work? All they do is send the computer the resistance it's looking for the keep the check engine light off.

tx_zstang

No, they do a LOT more than that. The rear sensors generate a signal that roughly follows the alternating signal (from lean to rich) of the front sensors, and the PCM monitors the variation and amplitude of the signals to monitor the effectiveness of the cats.
If you live in an area where emission OBDII inspections are not performed, you can turn off the rear sensors in the tune, and remove them or do what you want with them.
Otherwise if you must retain rear O2 sensors, there are simple circuits and techniques that can be used to "simulate functional cat converters", but you still need the rear sensors somewhere to accurately do this.

DrDeaths01GT

Good question as ive wondered this myself.I have also wondered if having the rear sensors turned off on a car with the factory cats still on will do any good or make the car run like crap?

contentsunderpressur

So are you saying that if you don't turn them off or do something to simulate correct cat functions then it will affect the way the car runs? Can you tell me the techniques used to do this? There are many companies that sell off road mid pipes for these cars. There has to be another way to do this without buying a programmer and a custom tune. That's too much money for me to spend just to get a better sounding car.