FYI on Bosh o2 sensors - an recent email from Performance Trends:
) Extend A/F Sensor Life A/F sensors (sometimes called O2 sensors, lambda sensors, wide band sensors, uego sensors) are very useful for measuring the engine's A/F ratio. A/F ratio indicates how rich or lean the motor is running. Running the motor too rich or lean and you lose power. You also risk damaging it from detonation (spark knock) if too lean, or washing oil off the cylinder walls or building up deposits if you are too rich. for an FAQ about the correct A/F to run for different fuels.
We've gotten feedback that the newer Bosch LSU 4.9 A/F sensors (with the D shaped instead of rectangular shaped connectors ) can sometimes have very short life. The older systems with the rectangular Bosch LSU 4.2 sensors are no longer available. The LSU 4.9 sensor does have some advantages with accuracy and not requiring recalibration, but we have sometimes seen very short sensor life, as short as 20 power runs or so. We've discussed this with some customers and it seems like heating them up quickly from room temperature, or heating them up often reduces sensor life. Some things to consider to extend sensor life would be:
Keeping your A/F controller powered up all the time. One customer says he keeps it powered up for months at a time and has not had a problem with sensor life. Remember the sensors can be hot so when you swap them between engines on your dyno, do not get burned.
Start the motor to get some exhaust heat to the sensor to start it heating up. Then power up the sensor and controller so the sensor's heating element does not have a big job to do, just maintain a high temperature.
Avoid anything that could produce condensation that could accumulate upstream of the sensor. Water drops that could come in contact with the hot sensor could cause a sharp temperature change and damage the sensor.
