My Fiero is a bit of a conversation piece in my parking lot. The question came up among the observers (3-4 regulars) of my vain efforts to get it running : " How can the injectors fire in banks, wouldn't it be putting gas in a cylinder that does not need it?" Good point, how does that work?

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If you ever have a questions about the sincerity of the circle of Fiero owners on this site, take a look at:
"In Memoriam: Fiero Members"

Pretty impressive.....

Avatar is of an actual Fiero on fire

While it is counterintuitive, experiment has shown that the absolute timing of a fuel injector pulse makes very little difference in engine operation. As an extreme case of "batch fire," you can consider a carburetor or throttle-body injector, where fuel delivery is essentially constant.

In batch-fire pulsed fuel injector systems, if a cylinder's intake valve is closed the fuel just accumulates as a very rich pocket on the back side of the valve. Once the intake valve opens, the fuel-rich pocket enters the cylinder along with enough air for complete combustion. Then, during the compression phase, turbulence causes the fuel to be more uniformly mixed with the air before combustion begins.

Even in the more sophisticated sequential timed pulse fuel injection systems, at high RPMs fuel is often delivered with the intake valve still closed, because otherwise there just isn't enough time available for the complete fuel injection event.

[This message has been edited by Marvin McInnis (edited 06-04-2008).]

It is beneficial for the fuel to spray against a closed valve, the heat of the valve will evaporate the fuel much more completely so that when the valve opens a nice load of fully evaporated gaseous fuel gets sucked into the combustion chamber. Gases mix much more completely than fluid droplets or spray.

JazzMan

Most cars are a batch fire fuel injection system. It's cheaper and effective.