Clt (coolant temperature) – AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual User Manual

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EFI Components

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CLT (Coolant Temperature)

The coolant temperature sensor (CLT) is a variable resistance thermistor (thermal resistor) that

sends a return voltage back to the ECU based on the temperature of the engine coolant. This

sensor can also be used for virtually any other type of automotive fluid if it is located in that

liquid’s respective reservoir. Unlike other types of sensors that emit voltage signals to the ECU,

with CLTs the ECU outputs a +5V signal to the CLT and the sensor’s resistance determines the

return voltage. The AEM Infinity is compatible with virtually all CLT sensors.

The CLT provides the ECU with engine temp information. The AEM Infinity modifies the base fuel
calibration during start and warm up based on the CLT input. In addition to adding fuel, a CLT
can signal to the ECU to modify ignition timing at varying engine temps for optimum
performance. On race cars, ignition timing is typically advanced during warm up to heat the
engine faster. Race cars use an ignition based warm up because usually idle speed motors are
not used. On streetcars, where clean emissions are important, we reduce timing based on CLT
input to light the catalytic converter(s) off sooner.

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Coolant Temperature