Difference between two four cylinder motors

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Why does an inline four cylinder motorcycle make a different sound than a V4? They’re both four cylinders but an inline four makes a deeper, louder grunt than a V4

In: Engineering

Anonymous 0 Comments

Different cylinder bank angles have a different firing pattern.

A 4-stroke engine has a duty cycle of 720° (2*360, one for intake and compression, one for expansion and exhaustion)

In a straight row of four cylinders, lets call it R4, the angle between the individual ignitions is equidstant in order to reduce first- and second order vibrations and accompanying energy losses. 720°/4 = 180°. Thus every 180° turn of the crankshaft one of the cylinders is adding torque during ignition.

With a V4 design of the engine we still want the ignitions to be equidistant because vibrations cause wear and friction losses. But due to the different shape of the cylinder banks, we also need a different shape of the crankshaft. Due to the altered shape of this lever, torque isn’t applied from the same angle on the shaft anymore, such that the we have to alter the ignition pattern into a 2*360° rather than a 4*180° one. It’s basically two out of phase, synchronous R2 engines working on the same crankshaft. Thus it also sounds differently.