Me and my roomie were discussing this last night for a while, but i wasn't totally satisfied with our limited knowledge of the subject:

when installing a turbo setup on cars/trucks where the O2 sensor is very close (6-8" from head), where should the O2 sensor be placed - before or after the turbo?

And in another case, if the O2 sensor is a good distance downstream of the turbo, will the lower exhaust temperature lead to an incorrect O2 reading? (all this is assuming the stock ECU is still being used)

2/24/2006 12:08:16 PM

right after the exhaust housing, either in the "o2 housing" or cast piece at the top of the downpipe, depending on your setup

2/24/2006 12:17:23 PM

if its obd2, one in the downpipe right before the cat, and one right after the cat.

2/24/2006 12:19:02 PM

the discussion started with reference to my 91 civic, which has the O2 sensor 6" or so from the head.

2/24/2006 12:21:55 PM

after

2/24/2006 12:29:44 PM

^

2/24/2006 12:53:40 PM

It really depends on what the ecu was originally calibrated for. Its after on my RX7

2/24/2006 2:19:48 PM

no it doesn't.

2/24/2006 2:21:27 PM

any car with an o2 sensor will have one b/w the engine and the cat which is used to check/adjust fuel trims.

obd2 cars will have an additional after-cat o2 sensor to check cat efficience, which is for emissions

[Edited on February 24, 2006 at 2:29 PM. Reason : clarity]

2/24/2006 2:29:08 PM

would it not be reading a rich condition if the exhaust temp is lower (due to exchange of energy through the turbo)? ... and then wouldnt it adjust to a leaner condition, which is unwanted?



[Edited on February 24, 2006 at 2:39 PM. Reason : -]

2/24/2006 2:39:09 PM

no

2/24/2006 2:45:05 PM

turbo it

2/24/2006 2:45:25 PM

could you tell me why it wouldnt then?

2/24/2006 2:47:47 PM

more specifically, why would it? do you understand the purpose and function of an o2 sensor? egt's don't affect one's reading (extremes aside).

2/24/2006 2:51:38 PM

ok, i was thinking about the extremes. (and yes, i had thought the O2 sensor got it's readings based on EGT -> higher=lean, lower=rich... I have since googled and learned.)




[Edited on February 24, 2006 at 3:02 PM. Reason : all better]

2/24/2006 2:56:37 PM

yeah, it takes most sensors ~600 degrees to work properly. anything above that and below meltdown level is generally ok.

[Edited on February 24, 2006 at 3:08 PM. Reason : .]

2/24/2006 3:08:08 PM

i need to replace mine after the cat. got CEL and open circuit code. wiring from O2 to box seems ok, possibly wire detached inside the box?

2/24/2006 5:02:44 PM

The reason for having it at the turbo outlet is to allow the exhaust to flow past it instead of just kinda sitting there under pressure before the turbine. It will still get hot enough to function properly.

2/26/2006 12:32:35 AM