How do AICs work?

[Daniel Houlton]

soren wrote:
> 
> Dan H. wrote:
> >It doesn't know that my AIC is injecting fuel as well, and it isn't
> watching
> >the O2 sensor to know that the mixture is going rich.  So my WOT mixture is
> >going to be way too rich and my stock injectors duty cycle is still going
> >to max out at 5000 rpm assuming of course it'll rev that high from choking
> >on all the fuel.
> 
> >So why is this apparently not a problem?  What am I missing?
> 
> 
>     Have the controller kick on under boost instead of WOT, say maybe at 6
> psi right before your factory injectors max out.  Then just wick up the
> boost until it is no longer slobbering rich.
> 
> Soren Rounds


But that doesn't do anything about preventing the stock injectors from
maxing out.  They'll still hit 100% duty cycle and stay there for the
duration of max boost.  I know realisticaly that's only going to be a
few seconds, but isn't this extremely bad for them?  I thought exceeding
the 80% duty cycle very often or for very long burns them out in a hurry.

Also, what about the ECM?  What are the chances that it freaks out when
the injectors hit 100%?  Does it not care or will it assume something has
failed and go to fail safe mode?  

I ask this because it happened last week.  I had to slow way down for a
car turning in front of me.  After I got by, I nailed it but was in a
pretty low gear.  RPMs went to redline in a hurry and boost hit I think
about 9 psi.  It happened pretty fast and I wasn't watching carefully
enough.  Immediately after, my truck started coughing and sputtering,
barely running.  The engine light started flashing.

I was paranoid I blew a head gasket or something.  I pulled over and shut
down.  After a few minutes of checking under the hood and not finding
anything obvious I tried to restart.  It started and ran fine (so did my
heart BTW).  

When I got home, I checked the codes and there were two of them, both 
indicating faulty injectors(s).  I figured out it had gone into failsafe
mode.  I tested by pulling the MAF connector to force it into failsafe
and sure enough, it coughed and sputtered and ran just like it had on the
road.

I know now that the injectors max out at 9 psi and 5K rpm and I'm sure
I exceeded that.  How likely is it that the ECM switched to failsafe
because of this?

I'm beginning to think I will have to intercept the MAF signal and alter
it no matter how I do the extra fueling.  Neither additional injectors 
or a rising rate FPR by themselves will prevent the stock injectors from
hitting 100%.  Even intercepting the signal to the injectors to prevent
it from happening won't work because the ECM will still *think* they're
at 100%.

If I need to intercept and modify the MAF signal anyways, then I'd much
rather swap to larger injectors than run the rising rate FPR or plumb in
additional injectors.  It's much cleaner I think, doesn't have any bad
sides that I can see (so long as I don't go so big it won't idle) and 
it's much more stealthy.  I'll have a much better chance of sliding this
whole thing by the smog police if I don't have a huge regulator or extra
fuel lines and injectors running everywhere.

Any insight is appreciated.  

thanks
--Dan