Ar-Rehman: September 2025

Why V8 engine Sound Different Than V6 engine?

For all, it's a matter of honour 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. The engine is the beating heart of a vehicle. The sensations we gearheads receive from the combustion process activate feelings deep within our psyche. Like the goosebumps which come during the climax of your favourite song, the sounds from an engine can elicit that same unconscious flood of adrenaline. It is a complex subject but we will review the physics which give an engine its unique sound signature, and the effect of headers and exhausts, intake noise and more. 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 which 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. At the end, you will have a deeper appreciation for how these complicated assemblies of metal and plastic gain a soul through their vibro-acoustic expression.

Before we get started, First we must know that our goal is to measure the sound of the test object to the highest levels of accuracy. Not only could there be any number of exhaust setups which would greatly influence the sound, but the location and type of recording device would be different for each. 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. Trying to get a clean and true A to B comparison that you could draw conclusions from would be like finding two needles in a haystack in the middle of a tornado. For example, the engine parts you see whirling around in the display aren’t just some cool, preloaded animation. It is a live rigid body simulation that is figuring out the physics in real time, and the physics gets deep. This thing is doing fluid dynamics computations, flame propagation, inertia, friction and airflow calculations. All that these equations are calculating is the resulting pressure wave sent through the exhaust system (the 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. In the end, the beautiful songs our beloved engines make all boil down to cold, hard physics. 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. Luckily for us, the frequencies of the rotating components in an engine or transmission are easily calculated and tracked with something called “order analysis.” Let’s pretend we have a gear with 10 teeth. Every time that gear rotates, there will be 10 regular, evenly spaced “events,” or impacts, per rotation that will generate noise and vibration, basically each time a gear tooth rolls in and out of mesh with the tooth of another gear. If that gear is spinning at 600 RPM, or 10 rotations a second with 10 events per rotation, it would create a noise at 100 Hz. Since Hz measures oscillations per second, you need to convert your rotations per minute to rotations per second, so divide by 60:-

600 RPM / 60 = 10 rotations per second

Since there are 10 gear teeth ie. 10 “events” per rotation, you multiply the number of “events” per rotation times the number of rotations per second to get the frequency:-

10 events per rotation * 10 rotations per second = 100 Hz sound and/or vibration.

The RPMs of our typical test subjects are constantly changing, whether they are engines, transmissions, axles, or electric motors. When these parts get more complicated with multiple gear sets, bearings, shafts spinning at different speeds due to different gear ratios, tracing a frequency to its source gets a lot more difficult.

It may surprise some of you, but the baritone roar of your favourite car isn’t the sound of the explosions going off inside its V8. The ignition of the fuel and air mixture in the cylinder creates combustion noise, which is totally different from exhaust noise. In fact it sounds pretty annoying. Compared to exhaust and intake noise, the combustion noise is much quieter when you stand next to your car. This makes sense, as it’s happening inside a heavy, tightly sealed hunk of metal. You can hear it when you stick your head under the hood, it’s a high frequency roar, almost like white or static noise. While exhaust noise is made up of relatively low frequency tones (mostly under 1500 Hz) that change with RPM, the combustion noise you hear is higher frequency (between 1000 and 4000 Hz), Combustion noise occurs in the explodey part of the engine cycle. The piston compresses the air/fuel mixture inside the cylinder, where that mixture is ignited by the spark plug. This explosion dramatically increases the pressure inside the cylinder, creating a sudden, high-level dynamic load on the piston and the walls of the combustion chamber. The pressure waves ricochet around the cylinder with aluminium foil. This pressure increase pushes the piston downwards, putting forces into motion. Before that happens, the vibration from the pressure waves are absorbed by the various parts of your engine. This sound is caused by vibration, and everything vibrates at natural frequencies. Your engine block, pistons and crankshaft are necessarily very stiff, so their natural frequencies are quite high. Because of this, the low and mid frequency combustion vibrations are absorbed while the high frequency vibrations radiate as noise off the surface of the engine. This is your combustion noise.

With that out of the way, let’s get to the good stuff: exhaust noise. A musical chord you’d play on the guitar or piano starts with the “root note,” which is the foundational note the rest of the notes in the chord are built off of. It's configuration of your engine which creates its own unique chord that you can identify from a mile away. And to reiterate, the headers and exhaust have a transformative effect on the noise an engine makes, but they all start with a base set of frequencies created by their exhaust pulses. Our first example will be comparing two-stroke and four-stroke, single cylinder engines. By reviewing a single-cylinder engine, it eliminates some variables and we can extrapolate this process to multi-cylinder engines. Almost all car engines are four-stroke, meaning the combustion cycle (intake, compression, combustion, exhaust) happens over two rotations of the crankshaft. Each stroke is an upward or downward movement of the piston. So in a four stroke cycle the piston is going down for the intake stroke, up for the compression stroke, down for the combustion stroke, and up again for the exhaust stroke. A two stroke engine takes care of all of this business in one engine crankshaft rotation, with the intake and exhaust events happening in the same stroke of the piston.

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. 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. A one cylinder, two stroke engine, is going to have one exhaust pulse per rotation of the crankshaft, so the primary noise from this engine will be first order (1 pulse / 1 RPM). A one cylinder, four stroke motor will have one exhaust pulse every two engine rotations, so the primary order will be 0.5th order (1 pulse / 2 RPM). As the RPMs change, the frequency of these explosions will change with it, but it will always have this physical, mathematical, 0.5th order link to the RPM. The exhaust sound you hear is the exhaust pulse, not the combustion, but the relative timing is the same for this purpose. The two stroke has one event per RPM, while the four stroke has one every two RPM. You may have noticed that these single cylinder engines don’t sound great, almost like a vintage square wave synth. The reason for that are the harmonics, which really give each engine type its unique character.

If you put a V6, an inline 6 and a flat 6 on a dyno with no headers they will basically sound the same. As long as those exhaust pulses are coming out of the heads at the same frequency, and those pulses are taking the same path to your ears, you won’t be able to tell them apart. However, in the real world, the exhaust pulses from each cylinder aren’t taking the same path to your ear, they have to go through a manifold and then through the exhaust. Due to cost and packaging constraints, different engine configurations have certain exhaust manifold styles, which have a huge effect on the resulting sound. The world is a messy place when it comes to math and physics. The sound of a violin is created by a taut bow of horsehair being dragged across a steel string, which will vibrate with a number of modes based on the length between the bridge and the player’s finger. The frequencies created by these modes vibrate the neck and the wooden body of the violin, which have their own resonances including the resonance of the cavity of air inside the violin body. The construction and tuning of violins has been perfected into an art over hundreds of years, making a distinctive sound. When you add headers and an exhaust, those pressure pulses change. Each pulse is taking a different path to your ear through the tubes in your exhaust manifold, and some of those paths are longer than others. As the evenness of the pulses gets scrambled by different header lengths, different harmonics will appear. Then the exhaust and any mufflers will change the sound further. But it all starts with the base set of frequencies, or the chord, that your engine creates.

After exiting the headers, these pressure pulses pass through an exhaust system before reaching your ears. Mufflers are a critical component and do what their name says, muffle the sound. Now, we all love the idea of straight pipe exhausts, in theory. But in practice it leads to angry neighbours and your own sanity rattling apart as your brain gets constantly blasted by violently loud pressure waves. If we didn’t have mufflers, automakers would fail their standardized noise testing and no-one could get any sleep. The mufflers in your exhaust can reduce the overall volume, or can eliminate certain frequency bands, or both depending on the design.