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Discussion Starter · #1 ·
What do the voltages mean and what should I expect as a max reading?

Is there anyway of working out AFR from the voltages?
 

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I've been doing some research about this aswell and found the following list:

A/F ---- V
16:1 --- .76
15:1 --- .80
14.7:1 - .81
14:1 --- .84
13:1 --- .89
12.5:1 - .91
12:1 --- .93
11:1 --- .98

This list was made using a car on a dyno with an AFR meter to accurately get the corresponding AFR values with voltages.

I have several dynotests with AFR ratio line of several different RS250 with my current mapping (Fastchip Stage 1) and compared those AFR ratio's with my front O2 sensor voltage readout: they seem to be spot on!
 

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Pretty sure the R26 is a narrowband sensor though so you wouldn't get anything overly useful back. 250 is wideband i'm assuming by The Stig's post.
 

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Discussion Starter · #5 ·
I'm guessing I couldn't just swap mine out for a wideband B? Just trying to find an easy way to check AFR..
 

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Both are narrowband.

I also cross checked with the sensor voltages of my previous Megane II (2.0T) logs with my dyno run together with AFR line, and again it was pretty accurate. It was running a bit lean when I had it mapped due to injectors being maxed out, resulting in an AFR of 12.5:1. My logs show a 0.92V for that.

Installing a seperate AFR meter with a wideband sensor is always better. Even though the narrowband seems pretty accurate, don't trust it too much. Only use it to get a rough estimate of what it is running.
 

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You can replace the narrow band for a wide-band sensor, but you need a converter to transfer the signal back to narrow band so the ECU doesn't get confused.

Zietronix offer this including a gauge that can read the wideband signal.

http://www.zeitronix.com/
 
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