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Old 07-23-2010, 11:28 AM   #1
Brock31
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Default Which O2 sensor would you trust?

When logging, I will usuall log bost AF sensor #1 and my Lc-1. I do this for a couple of reasons which aren't really important to this thread.

I replaced my front sensor with an OEM denso about 8 months ago. My Lc-1 has been in for a couple of years.

I was doing a bit of OL MAF tweaking today and I noticed a pretty significant (0.8) difference between my logged LC-1 reading and my front O2 sensor reading. When in OL, (which I realize the front O2 shouldn't be used solely for) generally it is rich enough to peg the front O2 at 11.25. I noticed that the front O2 was reading 11.4 and up in a few spots while my LC-1 was reading 10.9.

So, my question is this:

Can the reading off the front O2 be reliable when in OL and AFR's are leaner that 11.25?

Also, I probably need to recalibrate my LC-1.
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Old 07-23-2010, 12:42 PM   #2
quazimoto
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I would not rely on the front O2 sensor for WOT. Should be plenty of informative threads on here and Romraider on this. Part of it has to do with the front O2 sensor being in a pressurized area. And for the most part if I plan on doing some logging I recalibrate my LC-1 before so. Innovate Motorsports recommends constant recalibration of your LC-1 for best performance. It in their users manual.
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Old 07-23-2010, 01:33 PM   #3
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also depending on how far back your lc-1 is there will be some delay from sensor to sensor. so for your question, no, this is why we have to get widebands in the first place...
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Old 07-23-2010, 02:14 PM   #4
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The front o2 cannot be trusted, at all, in boost. The exhaust manifold pressure throws off the readings.
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Old 07-23-2010, 04:21 PM   #5
Brock31
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Quote:
Originally Posted by quazimoto View Post
Part of it has to do with the front O2 sensor being in a pressurized area.
Ok that makes more sense. I just wondered what could make one sensor read differently if it is in the same exhaust stream (aside from one being wideband and the other narrow). I can see how being under significantly higher than atmospheric pressure could make a difference.

Do you "free air " calibrate yours every time? I only do this every few months?
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Old 07-23-2010, 05:08 PM   #6
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i only do mine every few months but it wouldnt hurt to do it before a logging session to be sure its as accurate as possible.
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Old 07-23-2010, 05:31 PM   #7
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I do mine every few months. Most of the time I do it while driving though because I don't feel like pulling it out of the downpipe. In decel the injectors shut off and the engine just pumps straight air through the exhaust, so I just get up to speed, let off the gas and start decel, wait for the wideband to read straight air, then tell it to recalibrate (making sure not to touch the gas until it's done).
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Old 07-24-2010, 01:36 AM   #8
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Neat trick.
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Old 07-24-2010, 10:48 AM   #9
Brock31
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Quote:
Originally Posted by the suicidal eggroll View Post
I do mine every few months. Most of the time I do it while driving though because I don't feel like pulling it out of the downpipe. In decel the injectors shut off and the engine just pumps straight air through the exhaust, so I just get up to speed, let off the gas and start decel, wait for the wideband to read straight air, then tell it to recalibrate (making sure not to touch the gas until it's done).
It is definitely a pain in the a** to pull the sensor every time I want to calibrate aspecially since I've got an awesome homemade copper heatsink on it.

This is a neat trick. I'll have to give it a try.
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Old 07-24-2010, 09:49 PM   #10
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It is definitely a pain in the a** to pull the sensor every time I want to calibrate aspecially since I've got an awesome homemade copper heatsink on it.

This is a neat trick. I'll have to give it a try.
I never remove mine either. I will just first thing in the morning after the car has sat all night is just recalibrate it in the downpipe.
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