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cr45 · 01-17-2017, 03:22 PM

This equation can be used to calculate the ratio of piston crown and cylinder head surface area for one engine compared to another.

n - number of cylinders
V - engine capacity
e - bore to stroke ratio

Surface Area Ratio = (n2 / n1)^0.3333 + (V2 / V1)^0.6666 + (e2 / e1)^0.6666

If comparing 2 engines that have the same capacity and bore/stroke ratio then the equation simplifies to (n2 / n1)^0.3333

Using this equation to compare the piston crown surface area of a 4 cylinder vs a 3 cylinder engine we get

ratio = (4 / 3)^0.3333

ratio = 1.1006

Hence a 4 cylinder engine has 10% more piston crown and cylinder head surface area compared to a like sized 3 cylinder engine. This gives the 3 cylinder engine a nice head start in the fuel economy stakes.

01-17-2017, 03:22 PM	#53 (permalink)
cr45 EcoModding Apprentice Join Date: Oct 2010 Location: ireland Posts: 102 Thanks: 8 Thanked 52 Times in 34 Posts	surface area ratio This equation can be used to calculate the ratio of piston crown and cylinder head surface area for one engine compared to another. n - number of cylinders V - engine capacity e - bore to stroke ratio Surface Area Ratio = (n2 / n1)^0.3333 + (V2 / V1)^0.6666 + (e2 / e1)^0.6666 If comparing 2 engines that have the same capacity and bore/stroke ratio then the equation simplifies to (n2 / n1)^0.3333 Using this equation to compare the piston crown surface area of a 4 cylinder vs a 3 cylinder engine we get ratio = (4 / 3)^0.3333 ratio = 1.1006 Hence a 4 cylinder engine has 10% more piston crown and cylinder head surface area compared to a like sized 3 cylinder engine. This gives the 3 cylinder engine a nice head start in the fuel economy stakes.