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Intake Air Temperature

OBD2 Technical>Interpreting OBD2 Data>Intake Air Temperature

Air intake temperature is used to correct fuel quantity (pulse width) since air temperature effects air density. (colder air is much more dense) Approximately 70°F is generally used for 0 correction, temperatures above will result in less fuel to compensate for the lower air density, and conversely temperatures below 70° will result in steadily richer (by volume) mixtures. Bad readings will effect ECM attempts to keep the air to fuel ratio proportional.

Deliberate IAT Sensor Distortion
OBD2 systems use the IAT, MAF, and HO2S sensors to regulate the fuel to air mixture. To keep the exhaust as clean as possible, the OBD2 systems will attempt to run the system fairly lean. Performance enthusiasts would prefer a richer mixture, at the expense of fuel economy and clean emissions. A fairly simple way to get a richer mixture is to replace the IAT sensor with one that claims the air is cold and dense when it really isn't. Such devices are inexpensive, fairly easy to install, and comprise the majority of the 'performance chip' upgrades advertised on certain popular auction sites (see below) The increase power claims are mitigated by the actual outside temperature, the amount of inefficiency in the stock fuel map (most maps make the ratio richer when heavy throttle is present anyway), and the amount of compensation that will be done when the O2 sensors see the results of reduced oxygen in the exhaust.

IAT Sensor Tweaks on EBAY

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