Innovate Motorsports LM-2 - Manual (Page 38)

Document # 31-0008 LM2_Manual_1.3.doc 38
6.2 General measurement requirements
The LM-2 measures the air-fuel-ratio by measuring the amount of oxygen in the exhaust
(for lean conditions) or the amount of unburned or partially burned fuel (for rich
conditions). You should correct for the following in order to get optimum results from the
LM-2
1) An exhaust leak will allow oxygen to enter the exhaust stream and therefore
will measure leaner than the engine is actually running. For correct
measurement, air-leaks in the exhaust MUST be prevented under all
circumstances.
2) Missing ignitions (where the air-fuel mixture does not ignite) also pump
unburned oxygen into the exhaust and cause the LM-2 to measure lean.
3) The only circumstance where the LM-2 will measure richer than the engine is
running is if the pressure in the exhaust tract is excessive (and the engine is
running on the rich side to begin with).
6.3 Vehicles with ‘smog-pumps’
Older fuel injected vehicles with a ‘smog-pump’ actually inject air into the exhaust
stream to aid their catalytic converter in the burn-up of unburned or partially burned
fuels. This additional air will make the exhaust look leaner than the engine is running.
For an accurate measure, install the LM-2 sensor up-stream of the outputs of the smog-
pump. If this is not possible, temporarily disable the smog-pump by removing its drive
belt.
6.4 Single Cylinder Engines
These kinds of engines are difficult to measure at the tail-pipe using an Exhaust Clamp.
The oscillations of the exhaust gas are so large that a lot of outside air enters the
exhaust and prevents correct measurement. Sometimes it helps to temporarily wrap a
piece of heat resistant cloth around the exhaust clamp to prevent outside air from
entering the exhaust.
6.5 Diesel Engines
Diesel Engines and gas turbines run at wide open throttle at all times. They do not have
a throttle but regulate power by the amount of injected fuel. The LM-2 can still be used,
but measurements at idle will read as lean.