[Diy_efi] High-voltage P&H IDM

[Phil Lamovie]

Hi David,

It is possible to drive high-Z with higher voltages.

I worked on a project that utilized such injectors and a 45 volt switch
mode power supply (for a total of 60 volts) enabled fuel pressure of
350 psi to be handled.

The real question here is why you think that this would help in the
"big injector-bad idle' scenario.

The problem is two fold. Speeding up a slow injector (opening time)
makes it behave more like a peak & hold injector. This still leaves
you with linearity problems at very small pulse widths.

It also causes a drop in available resolution. If your adjustments are
say 0.01 ms speeding up the injector from say a 3.00 ms idle pulse width
to a 1.5 ms idle pulse more than doubles the increment fuel step flow change.

If the dead time is now say 0.6 ms instead of 1.1 your effective time of
injection has changed from 1.90 ms to 0.90.

It also has helped you into the injector bad linearity zone which you were
trying to avoid in the first place.

Why not fit a 5th injector (or more) to deal with the fuel supply issue and
leave the smaller injectors to deal with 95% of the driving duties which
are at sub atmospheric conditions. (i.e. pre boost)

hth

phil