Submitted by Daftworks t3_11ce6mt in explainlikeimfive
Some American muscle cars and Italian supercars will both have a V8 but they make wildly different noises. Same goes for Harley Davidsons vs regular motorbikes. Why is that?
Comments
hems86 t1_ja3ac5g wrote
A great example of this contrast is the Corvette. Look up a video of the new 2023 C8 Z06 and then compare the sound it makes with any other corvette ever made. The C8 Z06 has a flat plane crank V8 for the first time ever and it sounds like a Ferrari.
Alternative-Sock-444 t1_ja4p719 wrote
That's 90% of the sound difference. The rest comes down to cylinder head design, camshaft lobe shape/timing, and the obvious one, exhaust. Which is why two different flat plane engines, with the same displacement, even with identical exhausts, will still sound very different. But cross vs flat plane is definitely the biggest defining factor.
Any_Werewolf_3691 t1_ja6mr89 wrote
Oddly enough not all 4 cylinders fire evenly. There were some Yamaha race bikes that used a 13-24-0-0 firing order. Increased low end torque to assist acceleration out of corners. I wonder what they sounded like.
bal00 t1_ja72xr8 wrote
Yamaha also used a cross-plane crank, so it was basically half a cross-plane V8 and they also sounded somewhat similar.
Madrugada_Eterna t1_ja36ggs wrote
It is partly due to the internal design of the engine. The cylinder firing order has an effect. A lot of the sound is down to the design of the exhaust system.
Vehicle manufacturers will tune the exhaust system to get the sound they want. The sound from the exhaust system is affected by the length of the pipes and the amount and design of the silencers (mufflers).
American muscle cars don't rev as highly as European supercars which also has an effect on the sound. Lower revs results in a lower pitched sound.
im_the_real_dad t1_ja3jup8 wrote
>Same goes for Harley Davidsons vs regular motorbikes.
With Harley-Davidson motorcycles, the V-Twin cylinders are 45° apart. With most other V-Twin makes the cylinders are 90° apart. The cylinders fire at slightly different times relative to the other cylinder and produces a different sound.
And, of course, a V-Twin will sound different than other engine configurations like an inline four or a triple.
A Boss Hoss sounds like a small block Chevy because it has a small block Chevy engine in it. For example, https://bosshoss.com/motorbike/standard-bike/
bal00 t1_ja2qlbn wrote
Ferrari V8s fire their cylinder like this:
O-O-O-O
Most American V8s fire their cylinders like this:
OO-O--O
Longer explanation:
There are two different types of V8, one with a cross-plane crankshaft and one with a flat-plane crankshaft. This refers to how the crankshaft of the engine would look when viewed head on: + vs. |.
Flat-plane V8s are basically two inline-4 engines glued together, and that's why they sound a bit like a 4-cylinder. That's the type you'd find in most Ferraris or McLarens for example. They're lighter, can rev higher, but they vibrate more.
What determines the sound of the engine are the gaps between firing events of the cylinders of one bank (one side). In a flat-plane V8, if you only look at say the driver side bank of the engine, one cylinder fires every 180°.
With a cross-plane crankshaft, these gaps are uneven, specifically 90-180-270-180. Sometimes two cylinders fire in quick succession, sometimes there's a longer pause, so you get the characteristic rumble.