Injector sizing

[Tlsalt at aol.com]

Greg Hermann wrote:

the .55 bsfc does it. Try looking at the HP AT the torque peak to figure
out the pw (and duty cycle) you will need at the torque peak. HP is work
per unit time, and injector flow rate is a part of the determination of
fuel flow per unit time. They are consistent units. Torque has no time
factor in it.

Hello Greg:

    I am still puzzled how a 20% increase in BSFC can account for a 50% 
increase in torque.  If torque is proportional to the mass of air consumed 
doesn't the amount of fuel increase proportionally for a given air fuel 
ratio.  Is there a thermal efficiency difference between NA and supercharged 
to explain it ?  The pulsewidth at peak torque is higher than at peak 
horsepower, so I don't see how horsepower at peak torque is used to calculate 
peak torque pulsewidth.  Do you have a formula ?  I used the VE based formula 
to calculate the mass of air at peak torque and then a 13:1 AFR to calculate 
the injector puslewidth as a base setting for the Haltech fuel curve. Since 
the puslewidth is relate to a single event and the amount of air inhaled per 
event is greatest at peak torque, pulsewidth at peak torque should be the 
longest in the fuel curve ? Do you agree ?  I understand the time bit and the 
maximum flow rate, duty cycle etc. for the ultimate fuel delivery in lbs/hr 
and the highest duty cycle I've seen in a data log was 84% at WOT at redline 
rpm.  I am having a hard time with this partially because the original torque 
curve of this engine was a peak at 1500 rpm and a flat line to 4500 rpm.  The 
problem my be entirely in my head.

Paul

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