NOx is produced by high temperatures and pressure. In other words when the
engine is loaded. That is why the dynamometer tests are needed for emissions
testing that is looking for NOx control. The primary emission control
devices consist of the three way catalyst working with the O2 sensor and for
many vehicle exhaust gas recirculation (EGR). Excessively lean mixtures not
only increase NOx under load but also prevent the catalyst from reducing the
NOx. Over advanced ignition timing and increasing compression also increase
NOx production.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
John Bange
Sent: Monday, June 18, 2012 5:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: AFM adjustment; clockwise or anticlockwise?

On Sun, Jun 17, 2012 at 4:32 PM, John Meeks <vanagon@gmail.com> wrote:

> Is the best way to verify this adjustment to find someone with a NOx
> sniffer?
>

Nah, you can just use a wideband oxygen sensor. NOx is a secondary effect of
lean mixture, so you might as well measure mixture directly so you can tell
if it's rich also. I got a cheap AFM off eBay years ago that had been
horribly maladjusted and got it to work with my wideband O2 meter. I have
the older version of the Innovate Motorsports LM-2:

http://www.innovatemotorsports.com/products/lm2.php

That, plus an O2 sensor socket to remove the stock  lambda sensor and plug
in the LM-2 wideband sensor, and finding the issue with an AFM isn't too
hard.  NOTE: you must run the engine warmed up, in open loop, and aim to
bias a little towards rich rather than the stoichiometric 14.7:1 ratio.
This was YEARS ago, but as I recall, the Bosch book says Digifant ECU
defaults to the WOT table on open loop, which ought to read somewhere in the
neighborhood of 13.5-14 air to fuel ratio.