Shutting fuel off whie driving.

[Ord Millar]

-----Original Message-----
From: Frederic Breitwieser <frederic.breitwieser at xephic.dynip.com>
To: diy_efi at esl.eng.ohio-state.edu <diy_efi at esl.eng.ohio-state.edu>
Date: Wednesday, March 31, 1999 1:50 PM
Subject: Re: Shutting fuel off whie driving.


>> As an "electronocally challeged" participant,
>
>Being a non-electronically challenged participant, I will add...
>
>> I'd use a resistor and an led connected to the
>> injector harness.  Not sure of the exact value.
>
>A generic Radioshack LED with a 1K ohm resistor in series would
>display light when the injector is fired, however even at idle, it
>would be difficult to see it going on and off.  Lets see why.
>
>Assume a V8.
>On true sequential injection, one injector pulse per intake stroke,
>would result in 50 injector pulses per rotation at an idle of 800
>RPM.  800 rpm / 8 cyls = 100, 100 / 2 (four stroke) = 50.
>
>At 800 RPM, the led would pulse at or about 50 hz, which your eye
>really cannot see, and would view as constant illumination.

<SNIP>

Wait a minute.  Number of cylinders has nothing to do with it.  If the
engine is at 800 RPM, any one injector will fire 400 times / minute, or 6.6
times / second.


Flashing at this rate would not appear as constant.  However, the pulse
width at idle would be so short that we might not even see it flicker.  In
fact, the duty cycle will always be so low (12.5% max on 8 cyl) that the LED
will only ever appear dimly lit at best.