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Air Temp senaor has control of timing advance
air temp sensor is zero to 5 volts
1 pin is ground and must be within
50mv of battery ground / negative
as measured from battery negative to sensor ground .
the other pin if fed 5 volts and the is a variable resistor that changes value with temperature
it has a negative temperature coefficient
high resistance cold , low resistance hot , the resistance is
irrelevant
the voltage is not , the voltage on the signal side will be close to 5 volts when cold and around 2.5 volts at 70f and about .5 volts at 210f
values are approximate and will vary
the 02 sensor will keep fuel trim at 14.7 to 1
no matter the value of the air temp senor , BUT
ignition timing will be retarded for high air temperatures and allowed to be
more advanced with colder temperatures
values were determined by the engineers that programmed the
system
which is why
under reporting MAF / MAP / IAT sensor can improve fuel economy ,
not by changing fuel trim
but
by changing the ignition timing advance map ... having said that
ignition timing map and MAP (manifold absolute pressure) sensor
are not the same thing although the MAP sensor's input does change the ignition timing map .
do not frak with the ignition timing advance map if you do not know what you are doing .... peak combustion pressure is partially controlled by
base ignition timing and the ignition advance map ,IF ignition happens too soon
peak combustion pressure will also happen too soon
which will destroy your engine
peak combustion pressure is controlled by the ECM to occur at
14 degrees ATDC except at idle and DFCO
tamper with it at your own peril
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