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Originally Posted by keithmac
I think you may have your calcs wrong? I run 15psi though a 1.8l engine on a 0.8 or 1.0 jet to give approx 300cc/min, think I originally worked for a 20% water to fuel ratio.
You need to work out you injector duty cycle, fuel used an go from there.
My 300cc`s come in at 2000 rpm and don`t bog the engine at all.
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Here are my calculations, it would be nice to have somebody else look them over:
First I calculate my cfm
CID * Pressure * RPM * VE / 3464
For 5200rpms (my redline), I expect to be making .3 bar boost. This is a 235 cubic inch engine, with about an 80% VE.
235*1.3*5200*.8/3464 = 366.88CFM
For 2000rpms I'll be making a touch more boost .34 bar
235*1.34*2000*.8/3464 = 145.45CFM
Convert CFM to lbs of air per hour:
CFM * lbs of air per cubic foot * 60
366.88 * .080645 * 60 = 1775.23 lbs of air per hour
145.45 * .080645 * 60 = 703.79 lbs of air per hour
My A/F on my current tune sits at about 12.8 at WOT, so to calculate the amount of fuel to burn the air:
lbs of air per hour / 12.8
1775.23 /12.8 = 138.69 lbs of fuel per hour
703.79 /12.8 = 54.98 lbs of fuel per hour
Using 1.74 gallons of 60% water/40%methanol per hour (2.3GPH nozzle on a 65psi pump) in lbs:
gallons of water * weight of a gallon of water + gallons of methanol * weight of gallons of methanol = lbs of water/methanol
(1.74*.6) * 8.33 + (1.74*.4)*6.63 = 13.31lbs per hour
Water to fuel percentage by mass:
lbs of water per hour/lbs of fuel per hour
13.31/138.69= .096
13.31/54.98= .0200
Based on those calculations 9.6% at redline and 20% at 2000rpms.