I understand that firing order effects the sound, but I'm specifically talking about even firing (screamer) engines.

I noticed that 4/8 cylinders sound very clean and monotone, but it seems like V10 and V12 aren't like this.

The V10 seems to have the same scream of the 4/8, but with an extra lower pitched sound. Same idea for the V12, but sounds even more complex with maybe three sounds.

Common sense tells me that with even firing, a 10,000 rpm V8 and an 8,000 rpm V10 should sound the same. This doesn't seem to be the case and I'm wondering why.

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    This question is very subjective. What sounds like what to you will sound different to me. Maybe you can re-ask your question in a way which has more objectivity? – Pᴀᴜʟsᴛᴇʀ2 Feb 10 '17 at 10:58
  • Maintenance or repair? – cory Feb 10 '17 at 13:56
  • By different I mean 4/8 sounds monotone and the others mentioned have their own multitone sounds. By the way, 10,000 rpm V8 and 8000rpm v10 are both 40,000 combustions per minute. – Guest Feb 10 '17 at 14:24
  • sorry, misread your statement (as 10,000 rpm v8 and a 10,000 rpm v10) – Hobbes Feb 10 '17 at 14:59

Exhaust sound is influenced by several factors besides the firing order. The exhaust construction is a big influence: which cylinders are combined into one pipe, separate exhausts per bank or combined or separate with a balance pipe, material (mild steel vs stainless) etc.

A 4 cylinder has no overlapping power strokes, so back pressure is minimal. A 5- or 6-cylinder engine has overlapping power strokes, so each exhaust stroke vents into a pipe that's still pressurized by the previous exhaust stroke, so there's more backpressure.

A V8 with an independent exhaust per bank sounds a bit similar to 2 4-cylinders side-by-side (more so if the V8 uses a flat-plane crank), unless you install a balance pipe.

  • Ah I see, so basically overlapping power strokes sharing an exhaust path are the cause. So anything more than 4 cylinders sharing the same exhaust will have multiple sound waves or back pressure or whatever, causing that multitone effect I was referring to with V10/V12. So I guess an even firing V6 would pretty similar to a 4/8 with a similar design (plus identical combinations per minute). Since with 2 exhaust routes, it would also have no overlapping power strokes to cause a non-monotone sound, but would sound a little different due exhaust as you mentioned (2 sets of 3 vs 2 sets of 2). – Guest Feb 10 '17 at 15:28

It has been well known that even harmonics sound pleasing to the ear .The second harmonic is like playing an octave on the piano.This is why old valve Amplifiers sound good .This is why 4 and 8 cylinder engines sound good.Odd harmonics sound bad to the ear .This is why the Audi 5 cylinder sounds terrible.The V10 Dodge Viper dont sound too good either . The higher the order of the odd harmonic the worse it sounds .7 cylinder radial engines sound horrible too .If the engine is not even firing the higher order odd harmonics are more prevalent .This is why some V6 cars sound like hair dryers.The V12 always sounds good because it is like 2 straight 6 cylinder engines .Normal street V8 engines have a dual plane crank for smoothness .This means that each bank actually odd fires but with lots of even order subharmonic .This is why a V8 sounds better than a straight 8 .The same cylinder bank reasoning gives the Boxer engine its pleasing sound .All of this Even harmonic theory should mean that a 90 degree V twin sounds good .

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    How does a 5-cylinder produce more odd harmonics than a 4-cylinder? – Hobbes Feb 13 '17 at 11:17

The fundamental frequency of exhaust is simply the number of firing cycles per second. Harmonics are integer multiples of the fundamental frequency. There is no difference between how the fundamental frequency is calculated no matter how many cylinders the engine has. The harmonic frequencies resulting are completely determined by the acoustic properties of the exhaust system from the point of exit past the exhaust valve to the output of the tailpipes(s)

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