[s-cars] Air Fuel Gauges, Wide Band Sensor Type

[SJM Autotechnik]

Bob, and others

As you likely have heard, these so called A/F gauges that use the standard
heated 3 or 4 wire O2 sensor with 0-1VDC output have no real capability to
accurately measure the A/F ratio below the stoich point of 14.7 to 1. These
3 or 4 wire heated O2 sensors were designed to switch or transition the
voltage output from high to low and low to high as the A/F ratio crosses
14.7 to 1

Of course this hasn't prevented the proliferation of these A/F gauges and
many folks driving around with a false sense of security that their turbo
engine is running rich enough under load.

There is a A/F gauge that uses the newer Wide Band O2 sensors, and can give
a more accurate A/F measure from about 10 to 1, up to 30 to 1 A/F ratios.

A company based in Australia sells kits and complete gauges here

http://www.techedge.com.au/vehicle/wbo2/default.htm

There is also a Wide Band O2  discussion list here

http://autos.groups.yahoo.com/group/oz-diy-wb/

Most of the 20V Turbo chip sets I have tested using a portable 4 gas
exhaust analyzer have A/F ratios down close to 10 to 1 at full boost, full
load to keep the exhaust temps within a safe range. These tests show CO% up
above 9.0 % but with very low HC ppm levels below 100ppm showing good
ignition and combustion.

HTH

Scott Mockry
SJM Autotechnik