Re: lambda sensor

[Simon Favre <simon@domain.elided>]

Yes, a lambda sensor is the same thing as an O2 sensor. I know Wes Ingram
runs his race cars with them fitted. There are several things to remember
about O2 sensors:

1) All lambda-type O2 sensors are basically the same. A one-wire sensor
has only the sensing element. The voltage is picked up at the wire, and
the body is the ground. A 3-wire sensor has a heater element to get it
up to temperature faster, that's all. A 4-wire sensor has the sensing
element isolated from the body, so a separate ground wire is needed.

2) All modern EFI systems use the lambda sensor as a switch. The computer
constantly runs the mixture from lean to rich and back again across the
ideal point. This is like an auto-zeroing or chopper-stabilized system
to cancel out noise. The EFI brain does not use the sensor in analog
mode.

3) Aftermarket O2 meters do use the lambda sensor in analog mode. On a
car with EFI, this is probably a waste, because of #2 above. On a car
with Spica or Webers, they can really help tune a car for performance.
All the aftermarket O2 meters are based on the National Semi LM3914N.
The design is virtually straight out of the National Semi databook. For
the irrepressible do-it-yourself types, a schematic is available at:

  ftp://ftp.team.net/misc/o2meter.pdf

4) All generic O2 sensors use the same thread as an 18mm spark plug.
That's not 14mm, like in an Alfa engine, that's 18mm, like in some big
American lumps of pig iron. You can get a fitting to add an O2 sensor
at any auto parts store. The thing to look for is called a spark plug
non-fouler. Get the 18mm, gasket-base spark plug non-fouler and cut
the threads off. Drill out the center, if needed, then weld into the
exhaust as close as possible to the motor, but after all runners are
combined into one pipe. V-6 and V-8 motors can run 2 sensors, and 2
displays, or have a left-right switch for the display. ** USE ANTI-
SIEZE ON THE O2 SENSOR THREADS. **

Simon

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