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Discussion Starter · #1 ·
I'm sure most on here can normally identify the number of cylinders an engine has by the sound (at least I can)
Question is , is it just "a particular sound or is there a musical definition (is it to do with the rhythm, beat or what?)
 

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My name is Martin
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Yes. Before I looked in to this, I had it in my head that a V8 would simply fire each bank in turn. e.g. L, R, L, R, L, R , L, R, for every 90 deg of the crank turning.

Now that may be true for some V8's but most (nearly all) US of A V8's have cross plane, not flat plane cranks. This results for each bank, that there are two fires occuring on the same bank and then 360 degs later the same occurs on the other bank.

Therefore, the firing is L,R,R,L,R,L,L,R or it may read easier as R,R,L,R,L,L,R, L

So if you were to listen to each bank, in stereo (you could use a music app to try this out), the left would sound as Boom... Boom.......Boom................Boom

Or, Boom, (90 degs later), Boom, (180 degs later), Boom, (270 degs later), Boom (final 180 degs)

The other bank will be doing the same firing, but it's 360 degs out of phase. Since the firing pattern per bank has a situation where the overlapping firing varies and then with the other bank out of phase too, it simply creates a magical sound. Fucking love a V8.
 

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Therefore, the firing is L,R,R,L,R,L,L,R or it may read easier as R,R,L,R,L,L,R, L
That might explain why a yank V8 with headers and an 'X' pipe perhaps 'divides-up' or splits-up the sound impulses even further and tends to sound like its revving significantly higher than the rev counter would indicate?
 

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Not all American V8's sound quite the same though - firing order on late model stuff differs (and sounds a bit 'bland') an early small block Chevy or big block Pontiac can have a very different sound to a Ford............
 

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Discussion Starter · #7 ·
I get the bit about the paradiddle (that is really apparent if you listen to a Ford DOHC V8 on open headers!) but it doesnt explain the difference in sound between a four or six cylinder engine.
I have a few friends who are "propper musicians" and they cant explain it (but neither can tell how many cylinders an engine is)
 

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My name is Martin
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Difference between a 4, 6 or an 8 is the amount of overlap between firing strokes. Not accounting for valve timing etc, a firing stroke is 180 degrees of the crank. With a 4 stroke, these complete in 2 turns of the crank ie 720 degs.

So for a 4 pot, 4 strokes are neatly 180 degs of power from one cylinder then, the next will follow after. So the exhaust pulses all follow one after the other.

Now think about 8 cylinders with a 90 degs V. When one cylinder is half way through (90 degs) in to its power stroke, another cylinder will fire. So the exhaust pulses will overlap. 180-(720/8)= 90 degs of overlap

Take a V6, these typically have 60 degs (except some like the VR6 with 15 degs). So 180-(720/6)= 60. So for a firing stroke, the overlap will occur on the first 1/3rd of the stroke, there will then be another 1/3rd of the power stroke however with no other cylinder also firing. At 2/3rds of the stroke, another cylinder will begin its power stroke.

If you take a 3 cylinder engine. There are 540 degs of power strokes to fill 720 degs of crank turn. So in between each cylinder firing there is a 60 deg moment of no power stroke and complete silence.
 
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