Injector Duty cycle calculations

[Scot Sealander]

timsiford at hushmail.com wrote:

> I bought a new set of injectors (24lb SVOs) to replace my stock 22lb 
> injectors.

Need to stop you right there.  That is only a 2/22 or about a nine
percent
increase in injector flow rate.  I think if you need a bigger injector,
you need to go at least 20 percent larger.  


> 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). 

So you dropped from 100 percent to high nineties.... Hmm, a 9 percent
change
in flow rate should do that.  :-)


> Diacom shows an injector pulse width value of 8.3ms at 6500RPMs.  Is this
> a 90% Duty Cycle?

Yes.

 
> 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.  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).

I really don't know what GM is sending out in the 1997 data stream.

 
> Am I missing something here? 
> Is Diacom reporting wrongly?

I don't think so, in either case.


> 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.

Gonna give a decent deal?  I would not mind working on a 24 pound
chip for my car.  Only need 6 though!

Scot Sealander


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