Re: Injector Duty cycle calculations

["Bruce Plecan" <nacelp@bright.net>]

> I bought a new set of injectors (24lb SVOs) to replace my stock 22lb
injectors.
>  The car is a 1990 IROC 350 with the 730ECM.  It has a 52mm TB, MiniRam,
>  AFR heads, 218/224cam, 2800 stall, and 3.73s.  I switched to 24lb
injectors
> because I was calculating 100+% Duty Cycles with the 22lb injectors.  Now
> that I have the 24lbers installed I am still seeing high duty cycles (90%
> at 6500rpms).

I fail to see the problem, if the plugs look right, and the performance is
there.

  I am running a PROM where I used an injector flow constant
> of 28lb/hr and have the pressure cranked up to 50psi.

Remember as you crank the pressure up, you reduce the volume that the pump
can produce.  Put a fuel pressure guage in the return line to make sure you
got enough volume.

> Diacom shows an injector pulse width value of 8.3ms at 6500RPMs.  Is this
> a 90% Duty Cycle?  I am using the following formula:
> RPMS / 60(sec/min) / 1000 (ms/sec) * Pulse Width (ms)  * 100% = Injector
> Duty Cycle

I'm dumb, I just remember 10msec at 6K is 100%, so atta glance your about
there.

> Since the 730 is batch fire this equation appears to be correct.  However,
>  I viewed some Diacom run from a '97 LT1 and saw injector pulse widths of
> 10ms at 6500rpms.

If the 10 is correct, then he's not in a SEFI mode.
10 at 6.5K batch means he's static (injector always on).

 Given that that ECM is sequential, I don't understand
> how those duty cycles could be so much less than mine?!  This car is even
> more seriously modded than my car (224/236 cam, AFR heads, manual, 58mm
> TB, 4.10s).
> Am I missing something here?

Really sounds like he's batch

  Is Diacom reporting wrongly?

Might give em a call, and ask if there are issues about this.

  Any help is
> seriously appreciated because I am getting ready to sell the 24lb
injectors
> that I just installed (this past friday - two days ago!) in order to buy
> 30lb injectors.

Get some used GN ones, I just bought a set of 6 for $15.  For the price of
checking them, I can't lose.
Grumpy
>
> Thanx!
> Tim
>
>
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