RE: Injector Duty cycle calculations

[Mike Rolica <mrolica@meridian-mag.com>]

Well.. on mine the 24lbs injectors were running at 6.5@6500
<mailto:6.5@6500> , 26lb inj constant..55psi...
I hav a similar prob and some knock....
Your fuel pump may be not strong enough...
Mike Rolica
Plant A,
Magnesium Products Division
Strathroy

(519)-245-4040  Ext. 244



	-----Original Message-----
	From:	timsiford@hushmail.com [SMTP:timsiford@hushmail.com]
	Sent:	Sunday, July 23, 2000 7:45 AM
	To:	gmecm@diy-efi.org
	Subject:	Injector Duty cycle calculations

	FELP

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

	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

	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).  

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

	Thanx!
	Tim


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