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Flat-Plane Crank Q&A With Tom Lieb

Flat-Plane Crankshafts

SCAT’s founder, Tom Lieb, sat down with LSX Magazine to share his many years of knowledge on flat-plane crankshafts.

Here’s what Tom had to say:

The throw on a standard four-cylinder crank, the number one pin is up, two and three are down, and four is up. With a V8 cross-plane crank, you would start with the number one pin, pin two at 90-degrees, pin three at 180-degrees, and pin four would be at 270-degrees to the number one pin. This spaces everything equally around the centerline of the crankshaft. A flat-plane crank is equally spaced around the centerline as well, but at 180-degree spacing instead of 90-degrees.

The whole purpose of a 180-degree crankshaft is a better cylinder head breathing symmetry and exhaust scavenging. Because of the firing order on a flat-plane crank, when the exhaust comes out of the combustion chamber somewhere around 1,300-1,500 feet per second, it jump-starts the intake port to move. This jump-start makes the engine more efficient. A flat-plane crank doesn’t necessarily make more horsepower. Still, the torque curve flattens out for a more extended period because it breathes better, creating a more usable powerband. Plus, if you’re getting a more efficient fill of air in the cylinder, you will generate more horsepower with less fuel.

 

 

Read the full article on the LSX Magazine site.