In SX Microcontrollers, SX/B Compiler and SX-Key Tool, william wrote:

Dan,

I think ECU design is a bit science mixed with a bit of art.
It could this art portion that creates myths surrounding ECU design.
We need to keep a clear and logical mind to separate myths from facts.
GAF has stated quite clearly that injectors only go on or off, no in betweens. I tend to agree.
Why would any injector manufacturer want to design a injector that can work with 2V when they know that 
every electrical device in a car runs on 12V? Beats me.

He also mentioned that at high RPMs, the injectors are on about 90% of the time.
On this point, I want dispute.
As far as I know, injection only starts at the end of the intake stroke and has to stop before the power stroke.
That means, at the most it should be injecting fuel only 25% of the time.
At normal cruising RPMs, I would expect the injectors to be on less than 5% of the time. 
So considering that 95% of the time, the injectors are in off state, over heating of injectors would not happen at all.

GAF has also recommended MOSFETS that can handle at least 200V.
I tend to disagree with this recommendation.
Assuming the injectors has a inductive coil inside it, yes it will induce a high voltage when it is switched off.
But by having a free wheeling diode across each injector, the voltage build up should not exceed 24volts.
Based on this explanation and my experience, I would continue to recommend the IRL510 as the injector drivers.

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