Injector Duty cycle calculations

[timsiford at hushmail.com]

>Remember as you crank the pressure up, you reduce the volume that the 
>pump can produce.  

Yes - this is why I am thinking of switching to 30lb injectors.  I don't 
want to run 50+ psi at the rails.  I'm shooting for mid 40's.  

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

Yes - this is exactly what I am thinking too.  Let me ask you a quick question: 
 When the 730ECM reports injector on-time (pulse width), is this the amount 
of time the injector is on for ONE off-on-off session or the amount of time 
spend in a double-batch fire (off-on-off-on-off) session?  Its just hard 
to believe that Diacom is reporting 8.3-8.5ms at 6000+ RPMs.  That would 
mean that my injectors are actually on for 16.5 to 17.0ms per 4 strokes. 
 That's A LOT of fuel.  Does that sound correct?  Furthermore, when you 
consider the fact that my 24lb injectors are operating like 28lb injectors 
(due to the greater Fuel pressure) it makes 17.0ms of on-time seem like 
a A LOT for a naturally aspirated 350 for one 4-stroke rotation.  Any thoughts 
on this?  What does your EFI experience say?

>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).

Or Diacom is reporting wrongly for either his car or for my car.  We are 
running the same injectors, the same type of intake manifold, and the same 
heads.  His car is faster by a bunch (about 75 more hp - track proven). 
 I would think that he would need to have more fuel and therefore a greater 
pulse width.  This is just very wierd.  I just want to make sure that if 
I get the 30lb injectors that it is the right decision.  

>Really sounds like he's batch

When did GM switch to SEFI?  I made a slight mistake.  The car is a 1996 
Pontiac Formula with the stock ECM.

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

Will do.  Thanks Bruce.

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

I'll probably go with a set of SVOs.  I can't leave anything to chance given 
my goals.

Tim


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