The measured mass of Oxygen is determined at the inlet and is unchanged there after. mass at the air inlet is the same as mass at the heads. It does not mater how the pressure and temperature changes through the blower or intercooler. If we are well tuned using the MAF then as the temperature/humidity/pressure varies at the MAF (air inlet) the relative changes at the head inlet port can be calibrated and the air temperature at the heads is a redundant measurement.
We are fueling to accommodate the Mass of O2 not the air flow because air flow varies once past the intake due to pressure /temperature changes. Once the tuning is correct based on the MAF, calibration for air temperature is a relative function where ever you choose to measure it.
Heat soak is not a consideration when the engine is flowing moderate amounts of air. However if the inter-cooler fails, then all bets are off.
the engine runs in closed loop most of its life when the manifold is under vacuum, this may preclude moving the temperature sensor to the manifold which would interfere with the restart EPA requirements.
but then again I could be wrong.
Quote:
Originally Posted by Duke
Maybe I can simplify this from strictly an engineering perspective.
The IAT at the air box determines the mass floww of air. The temperature after the intercooler determines the volume flow of air into the cylinders. The lower the temperature the lower the volumetric flow rate. Since the blower is positive displacement and the cylinder volume is fixed, the intercooler outlet temperature sets the blower discharge pressure.
All things being equal, lowering air charge temperature to the cylinders will produce the same horsepower with less boost pressure.  |