Re: Fuel Trim Cell 18???

[Roger Heflin <rah@horizon.hit.net>]

On Thu, 1 Jun 2000, Glen Beard wrote:

> Jody Shapiro wrote:
> > 
> > In the following run, the 3rd gear pull uses the long-term learns (152,
> > I know, I know) and fattens things up big-time.  Injector pulsewidths jump
> > way up as do the O2 sensor voltages.
> 
> Do you really think your PW is that high?  15 mSec isn't really
> that bad unless you are trying to spin 7000 rpm.  My PW goes up
> to 26.xx mSec around 5400.  I haven't done the math yet, but I
> think I'm more than exceeding the capacity of the stock 24#
> injectors.  My O2s stay mid 900s all the way up to 6000 rpm and I
> don't see any knock retard.  I am working on an intercooler
> project right now and will be looking for some 36# injectors soon
> to get rid of the FMU. >:(

I think the max at a given rpm is 60000/rpm and is in ms.  For 5400
rpm this comes out to be 11ms, now this is on a batch fire car (93 and
below LT1) on a 94+ LT1 you double that number and get 22 for 5400rpm,
so you are well past 90% duty cycle, and if I am reading things right
your injectors are probably never closing at WOT at those RPM's, so
the fuel is probably pretty hard to control at WOT.   What sort of
injector times were you seeing stock?   GM seems to push the injectors
pretty close to the 90% duty cycle point just on a stock motor.   

The 60000 conversion is 60 seconds per minute and 1000ms per second.
At 6000 rpm it comes to 10 (20) ms, and at 7000 it comes to 8.6 (17).


				Roger

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