Holley COMMANDER 950 - Manual (Page 6)

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1.3 Multi-Point Fuel Injection (MPFI)
A multi point fuel injection systems meters the fuel to each cylinder individually via the fuel injector located just upstream of
the intake valve. The fuel is supplied to the injectors via a fuel pump. The MPFI is superior to the TBI systems because it will
generate better fuel economy, higher power output and improved throttle response. These advantages are mainly due to the
proximity of the injector to the intake valve and better fuel atomization. Most of the MPFI systems use one injector per cylinder
but in certain applications up to two injectors per cylinder are used to supply the required fuel for the engine.
MPFI system
1.4 Electronic Control Unit (ECU)
The function of the ECU is to "tweak" or "fine tune" the engine operation to obtain the most complete and efficient combustion
process. The ECU microprocessor receives input signals from various sensors from the engine and generates specific outputs
to maintain optimum engine performance. The engine operating modes controlled by the ECU typically include the following:
§ Baseline Fueling
§ Spark Ignition Timing
§ Cold and hot start
§ Acceleration enrichment
§ Battery voltage compensation
§ Deceleration cut/off or enleanment
§ Run mode (open loop or closed loop) ECU
1.5 Throttle Body Assembly (TBA)
The throttle body assembly (also called air valve) controls the airflow to the engine through one, two, or four butterfly valves
and provides valve position feedback via the throttle position sensor. Rotating the throttle lever to open or close the passage
into the intake manifold controls the airflow to the engine. The accelerator pedal controls the throttle lever position. Other
functions of the throttle body are idle bypass air control via the idle air control valve, coolant heat for avoiding icing conditions,
vacuum signals for the ancillaries and the sensors.
2 Barrel Throttle Body 4 Barrel Progressive Throttle Body