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Subject: Re: BSFC
From: Dave Dahlgren <>
Date: Fri, 19 Sep 2003 05:26:19 -0400
Here is the reply without the original message so it will get past the 'me too'
message length filter..

The pressure problems you state are very injector specific as well as ecu
specific as to the available drive current. with a saturated injector, which
really has no business on a racing engine, or a low impedance injector with
insufficient drive current this can happen at times. Flow is controlled by
pressure across the injector not the pressure in the fuel rail. The injector
opening load only sees this as well for the most part. I have run in excess of
125 psi using bosch injectors that you can buy and are not F1 parts. Atomization
is everything when trying to make HP. It is not good to go big on injector size
and run low pressure this makes for poor atomization and you are screwed before
you even start. You do need to have a realistic projection of how much power you
are going to make before you start. It is the difference between a professional
and a backyard hacker. Then pick the injector to match the rpm and flow rates at
some pressures that will make for good atomization.

The number of ohms that an injector coil has is an interesting number does not
not describe impedance which is what the injector driver sees. There is a lot
more to it than that do an internet search and i suspect a lot of info will show
up. A good example is a Bosch 403 has a ohm reading of 2.0 and requires 2.5 amps
to function correctly while a Rochester 989A reads 2.2 ohm and needs 4.0 amps...

Another thing i have seen thrown around the net is the use of an external
resistor bank to run low ohm injectors with a saturated driver or one that can
not provide enough current for the injector. Stay away from this fix there is a
reason for the way the coils are wound and if you try this fix all you will get
is lazy opening times and erratic flow rates.

I have already commented on the duty cycle and will leave it alone here, other
than to say you are wrong..

The low voltage flow test is equally bogus for a whole list of reasons as well..

Dave Dahlgren

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