AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual User Manual

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Infinity User Manual

UEGO sensors use a “current pump” to determine the actual oxygen concentration within the
sensing element. The output is in the form of a very small current, which varies depending on the
air-fuel ratio. This is completely different from a narrow band oxygen sensor, which directly
outputs a voltage. The UEGO sensor design allows measurement of the exact air fuel ratio over
the entire operating range.

The following is a chart of typical AFRs. Note that every engine is different and this may not
be the optimum set up for your particular vehicle. The AFRs on this chart are very
conservative to minimize the potential for engine damage. These AFRs depend on the condition
that ignition timing and fuel octane are adequate enough to prevent knocking. The very low loads
found in the lower right corner occur during deceleration, and because there is no “work” being
done by the engine, AFRs during deceleration can be very lean. We have seen AFRs of 20.0:1
during deceleration runs.

Naturally Aspirated Piston Engines W/ Pent Roof Combustion Chamber

Air/Fuel Ratio

100

13.0:1

12.8:1

13.5:1

14.0:1

14.2:1

14.0:1

14.7:1

14.0:1

14.7:1

14.0:1

14.7:1

14.0:1

14.7:1

14.0:1

14.7:1

15:1

14.0:1

14.7:1

15:1

Idle

Maximum

RPM