Injector Duty cycle calculations

[Roger Heflin]

On Sun, 23 Jul 2000 timsiford at hushmail.com wrote:

> Roger:
> 
> >  I went from 22->30lb ones.
> 
> What is your current setup?  Did you notice any wierdities at idle with 
> the bigger injectors?

My current setup is !ENGINE.  The last engine I was running had 30lb
injectors (93 Lt1).  

And if you are using tunercat, at least on the 93 LT1 his injector
constant is off.  It reports the stock injectors to be 24lbs which I
know not to be the case.  With it programmed to 30 lbs by my
calculation the engine ran real good.  The best on this motor was a
12.52 at 110.4.

But I spun a rod bearing road racing (130K), the new motor is supposed
to arrive monday, and will be a 409LT1 SBC, with a 230/244-112 cam.

 > 
> >What rpm are you measuring on the 97?   
> 
> 6350rpms, 10ms

Based on my motor, the injector times are already going down pretty
significanlty at that rpm.  You might also check what his is at 6000.

> 
> > And what fuel pressure is he running? 
> 
> Don't know exactly.  But, I do know that its less than what I am running 
> with the same injectors.

Running to higher rpms make more of a requirement of injectors, since
higher rpms mean less time to be open.  If his peak is alot lower than
yours is then that would do it.

> 
> >  If that cam is a 224/236-114, it has run out of power a
> >couple of hundred rpm before 6500.  
> 
> Its a 224/236 -112
> 
> >What were the O2 sensors reading in both above cases, 
> 
> 860-880mV

That is probably a bit on the rich side.
> 
> Thanks for the help Roger.  I appreciate it!
> 
What kind of times are both cars running? With the above times I was
running about 7.3 ms at the 5800 rpm peak with 30lb injectorrs which
translates to about 9.125 ms on 24lb injectrors.   My O2's were
running in the 820 range, and may have been getting close to the lean
side, thought we found no signes of detonation when we got the engine
apart to fix the spun rods.


				Roger

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