What Makes V6 Engines Sound So Different From V8s?

For budding car enthusiasts, it’s a badge of honor to correctly identify the number of cylinders in an engine just by its exhaust note. The number of cylinders plays a vital role in how an engine sounds. On the same note, even the cylinder configuration makes a difference to the exhaust note. An inline six-cylinder engine sounds different from a V6 motor. The primary exhaust noise you hear isn’t combustion noise; It’s the exhaust pulses.

Several factors determine how your car’s engine sounds and why a V6 sounds different from a V8. Factors like the number of cylinders, engine configuration, cylinder firing order, crankshaft configuration, engine balance, and even exhaust tuning. In the same vein, there are a lot of factors that come together to create an exhaust note that’s unique to each engine. An engine’s sound is a symphony of combustion explosions, exhaust pulses, vibrations inside the engine, the mechanical tap of a cam follower, and even the induction noise as air is sucked into the engine. Nothing sounds more heavenly than a twin-turbo Hayabusa V8, though. 

Consider a single-cylinder four-stroke engine. In a four-stroke engine cycle, there is one combustion explosion every two revolutions of a crankshaft. Let’s consider these explosion beats or pulses. So, with the engine spinning at 1,000 revolutions per minute (RPM), you have 500 pulses every minute. At 1,000rpm, a twin-cylinder engine will have 1,000 pulses per minute due to two cylinders firing every two revolutions of the crankshaft. A four-cylinder engine will have 4,000 pulses per minute. The more cylinders there are, the more pulses produced, which, together, offer a consistent, smooth engine sound. The number of pulses also influences the way a V6 and a V8 engine sound.

An inline six-cylinder engine and a V12 engine are inherently balanced due to two cylinders always working in pairs, in the intake and compression cycle, and one in the combustion and exhaust cycle (a 1-5-3-6-2-4 or 1-4-2-6-3-5 firing order for an inline-six). These actions cancel out the horizontal and vertical action, ensuring a pure sound and minimal vibrations.

A V6 or V8 engine has two cylinder banks consisting of three or four cylinders per bank, placed in a V configuration. In a V6, the cylinder in each bank fires alternatively, i.e., R-L-R-L-R-L. However, with three cylinders per bank, a V6 is not that well balanced due to its different firing order (1-5-3-6-2-4 for a 60-degree V6). Despite this, some V6 engines can put the LS1V8 to shame. To balance out these vibrations, engineers add a balancer shaft, which influences the mechanical sound. Compared to V8 engines, the exhaust pulses in a V6 are more evenly spaced, leading to a high-pitched wail at high revs.

In comparison, a V8 emits an uneven burbling exhaust note at low revs, and a deep, bassy rumble at high revs. Its higher cylinder count and resulting higher firing order result in a richer sound. Think of a drummer playing six drums compared with a drummer playing eight drums. The latter will have a larger variance when it comes to sound notes. A traditional V8 employs a crossplane crankshaft, which looks like a cross when viewed from the side and with the crankpins sitting at a 90-degree offset. Due to this configuration, the engine has two cylinders moving up at any given time, with one cylinder heading for the power stroke. For example, a small block V8 has a firing interval of 1-8-4-3-6-5-7-2. So instead of a cylinder in each bank firing alternatively, you have two cylinders in one bank firing simultaneously, preceded by a cylinder in each bank firing alternatively, i.e., L-R-R-L-R-L-L-R. This gives the V8 its distinctive rumble. It’s a good reason Mercedes-AMG is returning to V8s from turbo fours.

Modern, exotic V8s employ a flat plane crankshaft where all the crankpins are on a single flat plane, like that of an inline four engine, i.e., the firing order is L-R-L-R-L-R-L-R. This allows each cylinder bank to fire in an 180-degree cycle, allowing for equally spaced exhaust pulses. A flat plane V8 revs faster and emits a high-pitched whine. Unlike a traditional V8 muscle car, a flat crank V8 sounds very different. Its Most American muscle cars use crossplane V8s, while most European exotics prefer flat-plane V8s.