maximum ON before damage

[Phil Lamovie]

Hi John et al,

Injectors that are higher resistance 10 -16 ohms are saturated
inductors and require no current limiting. They can be left on
indefinitely as long as they have been designed correctly.

They are a bit slow to open and thus have a higher minimum ms before
stability is reached. approx. 2.5 ms.

Lower resistance injectors are high current devices that must be
handled with respect. They will draw 3-5 amps and will self destruct
in seconds with out current limiting. The usual ratio being 4:1.

They are fast to open 0.4 - 0.9 ms and thus need to be limiting very
soon after saturation.

The limiting factor with any injector is the max. time in ms available
at max. rpm. If that rpm is say 6,000 rpm we have 10 ms total.

If it takes 1.2 ms to open (saturated type) and 1.1 ms to close you
only have 7.7 ms left. Just to make things difficult the first period
of 1.2 ms has NO flow. So really that 2.5 ms lower limit (for
stability's sake)
means you have 2.5 -8.9 ms to play with.

Now the required flow needs to take place in this window thus the duty
cycle limit of approx. 80%. Don't forget that at minus 20 deg C the
accelerator can still be floored and you can't run out of duty cycle
at any air/water/manifold vac or the valves will say ouch.

Once again I must ask are you pulsing once per revolution or every
second  / If once your figures don't add up. If every second your
choice is incorrect. The sequence is not an issue. How often do you
fire No. 1 injector ?

If you apply a table with load vs rpm values instead of you falutin'
volumetric eff. table you would find that the map sensor response of
1-3 ms is sufficiently fast to react within 1/4 of a revolution even
at moderately high rpm. If your code does a run through in under 10 ms

you will never miss more than 1 p/w correction.

You might be in the middle of an output event as the vacuum drops but
most throttle movements  take  200 - 300 ms from start to finish and
thus many injection cycles b/w start and finish.

As to the 40 ms pulse... I don't think so. The maximum fuel required
is more a function of poor combustion at low rpm than anything else
but given a max. p/w of 8.5 at 6000 rpm then the pulse width at full
load 1000 rpm  would be 8.5 plus the excess fuel required due to poor
tumble, swirl, vaporization etc. etc. Probably no worse than 4 -5 ms
extra will be required. Don't forget to decay this in proportion to
the rate of change of rpm (derivative of PID )

This still points to a short coming that you have imposed with your
12.7 ms upper limit.   Full load plus cold air plus cold water plus
acc enrichment will put you badly in debt even at low rpm.

8.5 + 20% + 60% + 5 ms = 17.24 ms

Your in the pursuit

Phil