Wideband air/fuel install question

lightblade · Feb 8, 2009

I have an autometer wideband air/fuel gauge with bosch wideband sensor can i just remove one of the o2 sensors and install the bosch sensor? Like one of the aft sensors? Thanks.

klaw · Feb 8, 2009

I don't know about anyone else, but I drilled a hole just below my cat on the driver's side and welded in a threaded bung. I mounted the Bosch sensor in the new bung and left the other sensors alone. It works great and was dead on with the AFR measurements taken during my dyno tune session. Someone said it's better above (before) the cats but I'm not sure and not keen to move it now.

It's apparently important to mount the sensor so that the sensor end (inside the exhaust pipe is lower than the other end (the one with the electrical connector). I was told it helps to keep condensation off the sensor tip and avoids corrosion. It also helps to ensure that the electrical connection is tucked up nicely out of the way where it won't snag on anything.

Gearbanger 101 · Feb 8, 2009

According to Innovate Motorsports, the ideal placement for the bung is about 6-8" after the exhaust collector....and that's before the cat. If there isn't that kind of room to spare, just make sure you get it between the two, closest to the cat. Putting the sensor right in front of the collector can overheat it and shorten its life span.

klaw · Feb 9, 2009

Brian - Do you happen to know why it's preferred to have the sensor before the cats? Is it related to how quickly the sensor gets hot or how hot it gets? I was told that the reading would be off if it was after the cats but I have reason to doubt that.

walter · Feb 9, 2009

klaw said:
Brian - Do you happen to know why it's preferred to have the sensor before the cats? Is it related to how quickly the sensor gets hot or how hot it gets? I was told that the reading would be off if it was after the cats but I have reason to doubt that.

I would think that an accurate reading of what happens during combustion has to be made as close to the engine as possible and not after the cats because their filtering of gasses and particles would alter AFR readings.

NastyStang113 · Feb 9, 2009

This reminds me ... I need to put my Dynojet Wideband Commander in my car ...

Gearbanger 101 · Feb 9, 2009

walter said:
I would think that an accurate reading of what happens during combustion has to be made as close to the engine as possible and not after the cats because their filtering of gasses and particles would alter AFR readings.

Correct.....the closer to the source you can locate it, without overheating the sensor, the more accurate the measurement will be. Installing the sensor after the cat will result in "leaner than reality readings". Also, the sensor should be mounted at the top of the exhaust pipe between the 10:00 and 2:00 position at the top of the exhaust stream. Mounting it below these angles could result in condensation accumulated on damp days, or short trip cool down leaking back into and damaging the sensor.

klaw · Feb 9, 2009

Gearbanger 101 said:
Correct.....the closer to the source you can locate it, without overheating the sensor, the more accurate the measurement will be. Installing the sensor after the cat will result in "leaner than reality readings". Also, the sensor should be mounted at the top of the exhaust pipe between the 10:00 and 2:00 position at the top of the exhaust stream. Mounting it below these angles could result in condensation accumulated on damp days, or short trip cool down leaking back into and damaging the sensor.

When I had my dyno tune done, the tuner's AFR's were measured with a probe in the tailpipe. Does that mean that my tune is probably a bit fatter than the dyno card indicates?

Gearbanger 101 · Feb 9, 2009

When the tuner takes the reading via clamping the sensor into the end of the tailpipe, most will apply "corrections" to the figures to accommodate for the difference in readings. Either way....this method is always going to be a "best guess" scenario. The most accurate way of sampling the A/F ratio is doing so upstream from the cat.

klaw · Feb 9, 2009

I hate "corrections" - that's why I did the IAT sensor relocate even though I was told that the MAF temperature sensor could be "corrected in the software" for the supercharger and intercooler effects.

Gearbanger 101 · Feb 9, 2009

In that case I would take you car in to an exhaust shop and have bung welded in. You can always thread a plug into it until its time to take it to the dyno...at which point all the have to do us unscrew the plug and screw in their sensor in its place. Remember....have it welded in somewhere between the 10:00-2:00 possition, but also somewhere that it will be accessable from all angles.

klaw · Feb 9, 2009

easily accessable - ya funny!

I think I'll put an extra bung in when I change over to LT's

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