ive read where you can program out the o2 sensors. whats the upside and downsideof this?
thanks,
steven

 

This would probably have gotten a better response in one of the ECM mod boards.

But just think about it for a second. No O2 sensor=no fine adjustment made by the computer to improve air/fuel ratio. Which means a possible lack of performance and fuel efficiency.

 

You need 02 sensors on closed loop fuel injection systems. Late model EFI systems (later LT1 and LS1 set-ups) implement aft-cat 02 sensors. These are used to relay feedback to the ECM that the cats are working properly. Only the 02's prior to the cats are needed for the ECM. You can program out the aft-cat 02's.

All 3rd gen fuel injected cars had only one (prior to cat) 02 and it must remain.

 

upsides - ....um....none.


downsides - .....you have a $1000 fuel injection system that runs like absolute crap and makes you mad.

 

UPSIDE = no more $30 part every time it goes bad. But I would imagine the decreased mileage and drivability outweigh that.

 

The purpose of the O2 sensor is to give feedback to the computer during normal driving about the air/fuel ratio in the exhaust system. This is how the computer makes adjustments to fuel delivery to keep the car running well.

Without the O2 sensor, your vehicle might drive poorly during normal use because it doesn't have that feedback system (no feedback is 'open loop' and having feeback is 'closed loop') to tell the computer what to do next for fuel delivery. This means it could use too much fuel or too little fuel. I'm not certain, but if there is no O2 sensor I suspect the computer would revert to the pre-programmed fuel maps. The real risk here is running too lean (too little fuel) and burning up a piston or valve. That's an expensive repair.

Once again, I'm not completely sure about this but I suspect your car doesn't always use the O2 sensor anyway. During initial startup the O2 is bypassed until it is heated and can accurately read air/fuel ratios. Another condition where it is bypassed is under full throttle. The factory O2 sensor is a narrow band sensor and is not calibrated in the air/fuel range where the engine operates during full throttle. So the computer bypasses the O2 sensor and reverts back to pre-programmed fuel maps. If you want to go faster, you alter the pre-programmed fuel maps. This is what companies like Hypertech do. They are restricted by law to change cruise and part throttle settings because it will alter the emissions output. But full throttle is fair game. The O2 sensor is bypassed anyway and they just tell the engine to use different fuel and timing maps.

So... I think the answer to your question is do not unplug the O2 sensor. And yes, it is bypassed during full acceleration and you can play with those fuel and timing settings for better performance.

 

Bypassing an O2 sensor is for OBD2 cars with the extra sensor to monitor the catalytic converter function.

 

Sure you can tune it out. It probably would not be the best thing unless you drive the car with over 30- 50 percent throtle at all times. Getting rid of the o2's would probably make it smell rich when idleing or cruising. Almost all fi race cars dont run o2's. Why cause the car is never in closed loop cause its at 3/4 to full throtle at all times. I would suggest leaving them. Why would you want to get rid of them anyways? I see no gain.

 

In the LT1 realm, when converting to obdi(94-95 LT1) from obdii(96-97), the 2 extra O2 sensors in obdii aren't needed.

 

thats because they are post cat o2's