Engine Sensors
In order to provide the
correct amount of fuel for every operating condition, the
engine control unit (ECU) has to monitor a huge number of
input sensors. Here are just a few:
- Mass airflow sensor - Tells the ECU the mass of
air entering the engine
- Oxygen
sensor(s) - Monitors the amount of oxygen in the
exhaust so the ECU can determine how rich or lean the fuel
mixture is and make adjustments accordingly
- Throttle position sensor - Monitors the throttle
valve position (which determines how much air goes into the
engine) so the ECU can respond quickly to changes,
increasing or decreasing the fuel rate as necessary
- Coolant temperature sensor - Allows the ECU to
determine when the engine has reached its proper operating
temperature
- Voltage sensor - Monitors the system voltage in
the car so the ECU can raise the idle speed if voltage is
dropping (which would indicate a high electrical load)
- Manifold absolute pressure sensor - Monitors the
pressure of the air in the intake manifold
The amount of
air being drawn into the engine is a good indication of how
much power it is producing; and the more air that goes into
the engine, the lower the manifold pressure, so this reading
is used to gauge how much power is being produced.
- Engine speed sensor - Monitors engine speed,
which is one of the factors used to calculate the pulse
width
There are two main types of control for
multi-port systems: The fuel injectors can all open at
the same time, or each one can open just before the intake
valve for its cylinder opens (this is called sequential
multi-port fuel injection).
The advantage of sequential fuel injection is that if the
driver makes a sudden change, the system can respond more
quickly because from the time the change is made, it only has
to wait only until the next intake valve opens, instead of for
the next complete revolution of the engine.
