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Old 07-07-2015, 01:58 PM   #21
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<p>
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Originally Posted by Joe Perez View Post
</p><p>&nbsp;</p><p>Thank your for posting Joe. From the article:</p><p>&nbsp;</p><p>
Quote:
</p><p><strong>Summary points:</strong></p><p>&nbsp;</p><p>When engine conditions are stable there was <strong>no noticeable (significant) difference in readings</strong> before and after the catalyst.</p><p>When mixtures were altered rapidly or/and conditions changed there was a delay until the post reading stabilised.</p><p>&nbsp;</p><p>Exhaust is best sampled before the converter if possible, this avoids delays, gains a slight increase in accuracy, faster sensor heating (closed loop), less moisture condensation exposure and less gas transport delays.</p><p id="376">
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Old 07-07-2015, 02:22 PM   #22
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This guy did it on his Audi S4:



Quote:
after logging with it in the driver's side dp pre-cat, and then later the same day, on the same tune, with it stuck in the tailpipe.
looks like close to 0.3 AFR leaner on average after the cat. In some spots almost half an AFR difference. I'd consider that borderline significant.

I swear I did this test back in 2006-07 and saw close to 1AFR difference leaner after the cat.


Still, pointless debate aside: you should be using the front o2 signal wire if you want the MS to get your readings...
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Old 07-07-2015, 02:44 PM   #23
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<p>
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Originally Posted by Braineack View Post
This guy did it on his Audi S4: &nbsp;looks like close to 0.3 AFR leaner on average after the cat. In some spots almost half an AFR difference. I'd consider that borderline significant. I swear I did this test back in 2006-07 and saw close to 1AFR difference leaner after the cat. Still, pointless debate aside: you should be using the front o2 signal wire if you want the MS to get your readings...
</p><p>&nbsp;</p><p>Idk, just relaying what a Bosch Engine Managment book said. I trust the OEM level of engineering over some guy with who&nbsp;knows what level of acuracy and precision sensors with unkown calibration he used. Just the diffence between and ETAS wideband&nbsp;properly calibrated with Cal Gas and an inovate free air calibrated is often 0.4+&nbsp;AFR difference.&nbsp;</p>
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Old 07-07-2015, 02:52 PM   #24
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Quote:
Originally Posted by cyotani View Post
I trust the OEM level of engineering over some guy with who-knows what level of acuracy and precision sensors with unkown calibration he used.
Agreed.

And in that spirit, I again point to the fact that in OEM applications, the post-cat O2 sensor is expected to produce different readings than the pre-cat sensor. If the two sensors produce the same output for any length of time, this is indicative of a failure of the catalyst, and will result in the setting of a P0420 diagnostic code and the illumination of the CEL.

It is true that, in closed-loop operation, the difference between the two is mostly temporal in nature (the rear sensor lags behind the front sensor), however this is still a very good reason not to place the primary O2 sensor behind the converter.
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Old 07-15-2015, 04:04 PM   #25
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The sensor is behind the cat just temporarily until I get the rest of my turbo exhaust parts then ill install it in the correct position. I just want to be able to get a decent base tune so tuning for boost wont be as difficult.

Today I rewired the LC2 output to go to the front o2 sensor input. The sensor is still physically behind the cat, Im still not getting any reading in TS. I have EGO port 1 set to normal EGO and I calibrated it and everything. Any ideas??
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Old 07-17-2015, 08:14 PM   #26
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I double checked all my wiring today and even wired the analog output straight to the ecu pin 2c. Still nothing on ts. I set both analog outputs to 0v=7.35afr and 5v=22.59afr.

On ts when I set wb input to ego1 I get a steady 7.40afr and when I set it to ego2 it bouces between 11.1 and 11.5.
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Old 07-22-2015, 07:16 PM   #27
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Old 07-23-2015, 10:15 AM   #28
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Try connecting to the LC-2 with Innovate LogWorks. See if it gives a good reading there.
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