firing stroke

Between any two consecutive firing strokes, the engine turned through 80 degrees.

This helps to reduce pulsations from individual firing strokes.

Every cylinder added beyond five increases the overlap of firing strokes and makes for less primary order vibration.

Also, the residual gases displace room for fresh air/fuel mixture and will thus reduce the power potential of each firing stroke.

This temporarily boosts the compression ratio for the first 2-6 firing strokes, the effect dropping down quickly as the oil is burnt off.

It has no crankshaft, and the pistons are returned after each firing stroke by compression and expansion of air in a separate cylinder.

Large engines are usually multicylinder to reduce pulsations from individual firing strokes, with more than one piston attached to a complex crankshaft.

Bigger capacity engines produce more torque as more fuel is burnt per firing stroke, giving a bigger push to the piston.

Thus long-stroke engines were traditionally high-torque engines, but modern short-stroke turbocharged units can produce as much torque (and usually more) by giving the piston a bigger shove on each firing stroke.