Engine Control Question

[Raymond C Drouillard]

>><<>When speeding up from a dead stop at WOT, the fuel injector pulse
width is
>>>around 12.2ms.  Once it goes above 3700 rpm or so, it starts to slowly
>>>decline until it hits 5200 (right before shifting).  At 5200 rpm the
pulse
>>>width is 9.8ms.  Why would this be?  Is this so the engine doesn't
melt :),
>>>or for emissions reasons.

As the engine speeds up, it's volumetric efficiency goes down.  In other
words, it is pulling in less air for each revolution.  That means it
needs less fuel for each revolution - hense, a shorter duration.

Maximum VE will be at the maximum torque part of the curve.  After that
point, torque (and VE) goes down as engine speed increases.  Power
continues to go up because power = torque * speed.  Power finally drops
off when the effect of the dropping torque overtakes the effect of the
increasing speed.


  If this stayed at 12.2ms right to the shiftpoint,
>>>would this generate more power?

Nope... it would just run rich.


Ray

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