o2 sensor placement cause extreme lean condition?

s300 and SManager software questions & answers
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Level5
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Joined: Tue Jun 14, 2022 9:48 am

o2 sensor placement cause extreme lean condition?

Post by Level5 »

This is my first post here, I apologize if its already been covered, or if it is a stupid question.

Just finished putting together my new setup, b16a, skunk 2 pro 2 cams and full valvetrain and ported head, stock block, gt35 63 56 turbo, rdx 410cc injectors (will install FIC 1000s on the dyno). I have s300 installed and my AEM wideband wired in to d10 with stock o2 sensor removed. I made my own basemap to start the car on and calibrated my injectors and wideband input.

when I started the car with it being NA and the wideband in the header with full exhaust, it ran fine for the most part. a tad rich but nothing alarming. After installing the turbo, the wideband is in a bung on the downpipe that is not even an inch from the end of the pipe, and the downpipe is open because it doesn't meet my exhaust. also the bung on the downpipe a little messed up so the wideband only threaded about half way down. I can see the tip of the sensor is still in the exhaust flow though. After starting the car it read extremely lean (22 ish AFR) after about 10 seconds of idle and it not getting any better I got worried and turned off the car. It seemed to be running normally though.

So I am wondering if the fact that the o2 sensor is only half an inch from the end of the open downpipe would cause it to read an inaccurately lean condition.
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Spunkster
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Re: o2 sensor placement cause extreme lean condition?

Post by Spunkster »

Yes that will be a problem.
Level5
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Re: o2 sensor placement cause extreme lean condition?

Post by Level5 »

How far from the end of the exhaust would you recommend? I assume it doesn't have to be that far because there are people running hood dumps where the entire pipe is like a foot long. Would 6-8 inches be alright?
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Spunkster
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Re: o2 sensor placement cause extreme lean condition?

Post by Spunkster »

The sensor should be located 6-8 inches after the collector, with 18-24 inches of exhaust pipe after it. That's the ideal location for the sensor to monitor the unburned oxygen in the exhaust while also preventing ambient oxygen creeping up the exhaust pipe and throwing off the readings.
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