Chapter 35, Problem 1RQ

How many degrees of crankshaft rotation are there between cylinder firings on an inline four-cylinder engine, an inline six-cylinder engine, and a V-8 engine?

To determine

Identify the crank rotation degrees between cylinder firings in the given engines.

Explanation of Solution

Inline four cylinder engine:

In a 4-cylinder engine where all the cylinders are mounted in a single line, the piston moves in pairs. The pistons of cylinders 1 and 4 move together and the pistons of cylinders 2 and 3 form a pair. With this arrangement, the engine will fire each cylinder after $180°$ rotation of the crankshaft.

Inline six cylinder engine:

An inline six cylinder engine is a perfectly balanced engine. The crankshafts ride on 4 or 7 main bearings and use six crank throws in three planes at 120 degrees apart. With this arrangement, the engine will fire each cylinder after $120°$ rotation of the crankshaft.

V-8 engine:

The V-8 engine crankshaft has two planes and one throw every 90 degrees resulting in a total of four throws. The engine operates smoothly with firing at each $90°$ rotation of the crankshaft.