Tuning NB 02 lean for smog test (mot uk)

[Gelf VXR]

I'm sure I've read this being done on here but cannot find the post?

If I wanted to program the psuedu NB output of an LC-1 to switch slightly leaner than stoich.

At my last test I had tailpipe lambda 1.006 (limits 0.97-1.03)


From the programmer text

1.1V = 0.958 lambda (richer than stoich)
0.103 = 1.022 lambda (leaner than stoich)


0.97V = 0.064 difference between upper and lower limit

0.064V = 0.01 lambda

If I program the LC-1 as below would this work?

1.036V = 0.958
0.039V = 1.022

[mr.prick]

Why not just change the commanded AFR.

[Gelf VXR]

It will be in closed loop for the emmisions test

[mr.prick]

I mean change {B3601} Ratio of Air to Fuel for Stoichiometry.
Your OS may have a different parameter number.
This will change the CL and PE commanded AFRs.

[Gelf VXR]

My os does not have any calibrations of that type

thanks thou

[gmh308]

My os does not have any calibrations of that type

thanks thou

Which OS do you have?

[joecar]

Can you program the NBO2 switch points in the PCM calibration...?

If you do get it leaner, watch out that NOx levels increase (as you go leaner)... are the smog authorities measuring NOx levels...?

[Gelf VXR]

The only table for idle airflow is {B1829} minimum desired airflow per gear.


My OS is 02596734

[Gelf VXR]

Can you program the NBO2 switch points in the PCM calibration...?

If you do get it leaner, watch out that NOx levels increase (as you go leaner)... are the smog authorities measuring NOx levels...?

I don't think so, the results of my previous emmisions test, it does not list NOx


Natural idle

engine speed 450 to1500 rpm manual check pass

CO =< 0.30% 0.3% pass


Fast idle test

engine speed 2500 to 3000 rpm manual check pass

CO =< 0.2% 0.12% pass

HC =< 200 ppm 14 ppm pass

Lambda .97 to 0.93 1.006 pass


I have aded the attachment image that shows the effects of AFR on the various emmisions