Re: Injector opening time

[rrauscher@nni.com]

I have some hard data for this, over various fuel
pressures at that. Been wanting to post it, now I
have a good reason. A tidbit from memory is that
going from 10psi to 30psi, causes an additional
opening delay of 100usec (~720usec total).

(I can hear yelling of 'well, where is it!?').

As soon as I get home to where the data is, I'll format
it up and post it.

BobR.

>
>I don't know if there is any data, that is that specific.
>I do know that some of the oem gm port injectors will work down to slightly

>under  1 msec., and at 6K rpm, you can run 95% DC with some, so what ever
>the opening and closing times are they are very short.
>
>Just roughing things out.
>At 6K you have a possible 10msec time, and in 5% of that you can still get

>an injector to open and close.  that would be 1/20 of 10, or .5 msec for an

>open and close. or .25msec for a open or close average event.....
>
>Math ain't my strong point, so someone might 2x me.
>Again, just a seems logical to me thing, since I know of no other info..
>Grumpy
>
>
>
>
>
>> I wonder if someone could clue me in on the part of
>> fuel injector pulsewidth that is lost to just opening
>> and closing, no fuel delivered?  What I mean is if
>> an injector pulsed for 7 ms had an effective open
>> time of 5 ms, then a 12 ms pulse (2 ms opening
>> plus two times 5 ms open) would deliver exactly
>> twice the fuel of 7 ms
>>
>> The ECU I am looking at is the old 76 Cadillac analog
>> unit.  The pick-and-hold seems to put out a constant
>> 1.8 ms "pick" pulse which is fixed in length.  Then the
>> "hold" part of the cycle is controlled in length by things
>> like the MAP signal.  Extrapolating the absolute manifold
>> pressure curve to zero seems to give just about zero
>> hold time.  This makes me think the "pick" time is not
>> effective in delivering fuel.  I realize a pulse width vs
>> fuel delivered measurement would give the answer, but
>> I am not set up for this now.  So could anyone comment
>> on the ineffective part of the pulse width for both a
>> "pick-and-hold" injector, and a DC injector?  Bruce Roe
>> ________________________________________________________________

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