Diff between theory and practice

[Mazda Ebrahimi]

jon hanson wrote:
> 
>  [snip]
> >The engine IS most efficient at peak torque, but that is not why he needs
> more fuel at
> >higher RPMs.  If he needed more FUEL PER HORSEPOWER produced, then you are
> right.  But
> >what he is indicating is that he is maintaining constant air fuel ratio
> (constant CO),
> >and is using more fuel at 6000 RPM.  This simply means he is flowing more
> air which
> >means that:
> >
> >       (vol eff @ 6000)* 3000 * disp > (vol eff @4800) * 2400 *disp
> >
> > [snip]
> 
> Thanks to all who replied.
> The fuel no I talked about is a no between 0 and 255 which this particular
> system translates into an injector open time in ms. the larger the no the
> more fuel per injection event.
> 
> The above explanation still confuses me as it is based around the rate at which
> fuel is being used. As I understand it (and this not neccesarily correct)
> at Peak VE each intake stroke draws in the greatest mass of air into the
> cylinder
> compared to any other rpm which is off peak torque rpm. To maintain the
> desired A/F
> ratio (in my case 3.5% CO) I then need the greatest mass of fuel per
> injection event.
> Note i see the whole thing very much as a per
> induction/compression/power/exhaust
> event and the particular revs of the engine dont come into it.
> Rpm comes into it when you are interested in the rate at which you are using
> fuel.
> ie the more induction/power strokes you make per second the more fuel per
> second you use.
> But a fuel no of 150 represents an injector open time in ms for each single
> injection.
> my figures suggest that each induction stroke at 6000 rpm is drawing in a
> geater mass of
> air than each induction stroke at 4800 rpm and I know the torque peak is
> quoted as 4800rpm
> I live at 5,500 ft altitude could this affect the breathing characteristics
> of the engine?
> If I'm being thick please dont hesitate to bash some sense into my head.
> 
> Regards
> Jon Hanson
> Johannesburg
> South Africa


Now we are talking about a problem.  Since you clarified that your 
numbers are injector duty cycles, as opposed to fuel flow rate, non of 
the explanations so far are correct.  You have mentioned the CO numbers 
stay fairly constant.  How about the hydrocarbons?  CO is only produced 
when your fuel is burnt.  Maybe at 6000 RPM you have higher hydrocarbons 
which indicate some of your fuel input is comming out of the tail pipe 
without reacting.  If that is the case, you should adjust your spark 
timing for minimum advance for best torque at each RPM, and then 
re-compare your CO readings to adjust fuel flow.

Good luck