Nissan ECU Tuning

satanstinydevil · Joined: 27 Apr 2008 Posts: 3

Is this number actually valuable? Using the Alpha and the o2 sensor number, is there any way to calculate the AFR?

I have NIStune and am learning with it. I have the car running, but have to adjust for the bigger injectors (Nismo 555). Just trying to see if I can find an alternative to buying an AFR.
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-Noob

datsunboy · Joined: 26 Jul 2005 Posts: 209 Location: New Zealand

best bet is to go ask same question on the forums for NIStune
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1970 Datsun 1600 CA18DET Project

The point of life is not 2 arrive at your grave all preserved & in mint condition, but 2 slide in sideways, scratched & bruised screaming F**K WHAT A RIDE!!

darkhalf · Posted: Tue Apr 29, 2008 6:11 am Post subject:

I've never looked into the alpha from consult too closely, but I dont believe you would be able to use it as an AFR meter replacement. Suspect its used for trim reporting at best, but would need to invetigate it

The narrow band O2 sensor indicates if the AFR is above/below stoich.

The curve on these is very sharp (hence the term narrow band) so accurate AFRs cannot be derived

You will notice in your log player voltage bounces between 0 and 1 volts as the ECU adjusts the fuel leaner / richer against what the O2 sensor is reporting

This adjusts the injection, so the resulting burn is around 14.7:1

satanstinydevil · Joined: 27 Apr 2008 Posts: 3

okay, well what o2 voltage corresponds to a 14.7 af ratio? this is really helpful stuff, by the way
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darkhalf · Posted: Wed Apr 30, 2008 1:29 am Post subject:

About 0.5 volts should be 14.7 depending on characteristics of narrow band sensor used

The ECU uses a lean value and rich value. When the input O2 sensor voltage hits one of those, then it will adjust injection length to achieve the opposite

The Z32 address file has some definitions used for example might be 0.3 volts lean and 0.7 volts rich

What results is an oscillating reading from the O2 sensor when in closed loop as the ecu tries to maintain the voltage between these two points

satanstinydevil · Joined: 27 Apr 2008 Posts: 3

Thank you for the information. This helps me a lot and gives me a lot of information I can explain to my parents.
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-Noob