Barry Gardner wrote:

Bill Freeman asked:

I wonder if those pumps can be run at
reduced voltage to reduce the flow rate yet retain the output

pressure?

Many aircraft fuel injection systems have two speed boost

pumps, with high

being only used for TO and climb, and normal used for

everything else.

A voltage regulation system to lower the voltage to 8 volts for

cruise and

use 12 volts for TO & climb might work, depending on the motor
characteristics.

You should know that the stock Mazda fuel pump has such a
two-stage resistor built into it. I'm measuring the voltage back
at the fuel pump with a gauge. At idle, it runs about 8.8 volts
and on boost, it goes up to 10.8 volts or so.

Do you have a scope? Are you sure that is DC? 
The best way to modulate a pump motor is with pulse width. Switching
a resistor in series with the motor waste a lot of electrical power.
It would take a big resistor. Perhaps a fusible in line resistor.
PWM fuel pump would be a neat thing for Tracy to add to his EFI. (Sorry Tracy :-))

I can't seem to find the gallons per hour spec for the stock
pump, however. The racers, who want more than 250 HP out of the
13B usually upgrade the pump, however. Of course, if you were to
have two pumps, one in each wing, you might be well served with
the stock pump or ones of still lesser output to decrease the
volume of the return flow.

FYI.

Barry Gardner
Wheaton, IL
87 Turbo II

 
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