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Author: gearhead greg
Time: 07/31/00 10:04 PST
This is a reply to message no. 3129 by dr funda
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multi point fuel injection
I think you have it wrong Doc Funda.  Sorry to point it out.  MPFI does not force fuel into the cylinder, it injects fuel into the intake manifold before the valve.  Direct Injection in SI engines is a new and expanding field but there are few manfactured DI gasoline engines these days.  MPFI reads engine parametrs from engine sensors and calculates the proper amount of fuel to deliver to each injector.  The primary sensors are engine speed, engine load (either manifold pressure or mass air flow) and for feedback, an exhaust gas oxygen sensor.  The pressure or mass airflow is used to determine the amount of air entering the engine.  Knowing the mass airflow and a desired airfuel ratio, you can calculate the amount of fuel to be delivered, divide by the number of injectors and calculate the desired pulse width from the injector calibration.  The O2 sensor is used to trim the amount of fuel delivered to maintain stoichiometry.

MPFI uses the computer to control the performance of the engine.  At any poitn, depending on its algorithm, it can provide max power, minimum fuel consumption, minimum emissions.  A carb is optimized for one operating condition and cannot be changed.  
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