Required CFM per HP
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TECH Enthusiast
Joined: Apr 2010
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From: North Carolina
Required CFM per HP Peak_HP = Flow_CFM x .257 x Number_of_Cylinders
This is the estimated potential Peak HP to expect.
You multiply .87 percent times cam's theoretical max lift , round off to nearest .050" in Flow Test, then see what CFM is at 28 inches
example : .700" Lift cam
.700 Lift times .87 percent = .609" Lift
Flow head at .600" Lift , then take CFM at 28 inches and calculate HP potential with above formula
.257 Factor = for beginning engine builders and engines near 10.0:1 Comp Ratio
.285 Factor = would be for Professional engine builders with wet sump pans, lightweight rotating assemblies, low tension great sealing rings, deep oil pans, etc. Excellent use of inertia/wave tuning with 9.5 to 11.5:1 Comp Ratios or 11.5 to 13.0:1 CR ranges without fully utilizing inertia/wave tuning effects.
.300 to .310 Factor = Current Pro Stock Technology with dry sump, unlimited carburetion, Hi Comp Ratio, ultra lightweight rotating assembly, etc, max use of inertia/wave tuning, etc, 14:1 to 17:1 Comp Ratios (usually no better than .3200 efficiency or no worse than .2980 eff %).
This is the estimated potential Peak HP to expect.
You multiply .87 percent times cam's theoretical max lift , round off to nearest .050" in Flow Test, then see what CFM is at 28 inches
example : .700" Lift cam
.700 Lift times .87 percent = .609" Lift
Flow head at .600" Lift , then take CFM at 28 inches and calculate HP potential with above formula
.257 Factor = for beginning engine builders and engines near 10.0:1 Comp Ratio
.285 Factor = would be for Professional engine builders with wet sump pans, lightweight rotating assemblies, low tension great sealing rings, deep oil pans, etc. Excellent use of inertia/wave tuning with 9.5 to 11.5:1 Comp Ratios or 11.5 to 13.0:1 CR ranges without fully utilizing inertia/wave tuning effects.
.300 to .310 Factor = Current Pro Stock Technology with dry sump, unlimited carburetion, Hi Comp Ratio, ultra lightweight rotating assembly, etc, max use of inertia/wave tuning, etc, 14:1 to 17:1 Comp Ratios (usually no better than .3200 efficiency or no worse than .2980 eff %).
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