EFI pros: calculating fuel burned per cylinder

Ameer Antar antar at attbi.com
Mon Aug 19 22:29:09 EDT 2002

Surprise, I have another crazy technical question... I'm trying to figure out how
much fuel is needed in cc/min for each cylinder. I'm coming up w/ something that
looks like it's on the same magnitude of 10, but seems a bit off.

First, I started w/ the volume of one cylinder, which would probably translate to
something like ~3psi boost and 75% V.E. Then I did my conversions, using

(.429L/cycle)*(1.2g of air/1L of air)*(1g of fuel/14.5g of air) = .0355g of fuel/cycle

how's that so far? then:

(.0355g fuel)*(1 cc fuel/.74g fuel) = .048 cc fuel/cycle

finally, considering 5000 rpm:

(.048 cc fuel/cycle)*(1 cycle/2 crank revs)*(5000 revs/min) = 119 cc/min

Why does this seem low? This isn't for WOT, but sorta near there. I guess this only
ideal and doesn't account for condensation and such, but is it that big of a
difference? So to brush up, isn't AFR based on mass, not volume? BTW, I put in
the crank to rev conversion, b/c there are to crank rev's for one full 4-stroke
cycle, and right? Thanks for the help.

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