Why a V10 screams and a V8 shouts
A V10 fires five times a revolution; a V8 fires four. At any given rpm that difference alone shifts the dominant frequency up by a quarter, and a V10's higher redline pushes it further still. Add how each engine handles firing unevenness and the same arithmetic explains why one screams and the other shouts.
Firings per revolution set the fundamental
Every engine here fires a set number of times per revolution. On a four-stroke that count is cylinders divided by two, which gives the reference four two pulses a revolution, the V10 five, and both the muscle V8 and the Euro V8 four. That single integer is most of what a listener responds to before anything else in the preset gets involved.
The dominant frequency an engine produces at a given rpm is pulses multiplied by rpm and divided by 60. At 6,000 rpm the V10 works out to 5 × 6,000 / 60, or 500 Hz. Either V8 at the same 6,000 rpm works out to 4 × 6,000 / 60, or 400 Hz. That is the whole of the arithmetic: one extra firing per revolution lifts the note by a quarter, before redline, gearing or anything downstream of the crank gets a say.
Rpm itself comes from GPS speed run through a virtual gearbox rather than from anything read off the car, as how it works sets out, but once rpm is known the frequency arithmetic above holds exactly for either family of engine.
Redline widens the gap
Firings per revolution only fix the ratio between the two engines. Redline decides how far each is allowed to push it. The V10 is specified to 8,500 rpm, the muscle V8 to 6,200 and the Euro V8 to 7,000, so none of the three stop at the same ceiling.
At its own redline the V10 is running 5 × 8,500 / 60, which is 708.3 Hz. The muscle V8 at its 6,200 rpm ceiling is running 4 × 6,200 / 60, or 413.3 Hz. The Euro V8, allowed 800 rpm further before its own redline, reaches 4 × 7,000 / 60, or 466.7 Hz. The quarter-higher note found at a shared rpm becomes a note nearly 300 Hz higher once each engine is taken to the top of its own range.
That is why the closer of the two V8s, the Euro car with its tighter unevenness and higher ceiling, still shouts rather than screams: reaching 467 Hz on four firings a revolution is a different event from reaching 708 Hz on five.
Unevenness decides what fills in underneath
Firings per revolution and redline set where the top note sits. Firing unevenness sets how much of the sound is that note on its own and how much is a lower growl mixed in beneath it. The V10 carries an unevenness of 6, the lowest of the three. The muscle V8 carries 38, the highest, and the Euro V8 sits at 24 in between.
Firing unevenness produces half-order growl: energy at half the fundamental, alongside it rather than instead of it. A V10 with unevenness at 6 keeps almost all its output at the five-per-rev fundamental, which is why the note stays clean as it climbs. A muscle V8 at 38 fills the space below its four-per-rev fundamental with a strong half-order component, the mechanism behind the lope this preset is named for.
Brightness compounds the effect at the top end. The V10's brightness, the level of orders above the first, is set to 150; the muscle V8's is 85 and the Euro V8's 105. A high fundamental with strong upper orders on top of it is what a scream sounds like. A lower fundamental with a growl underneath it is what a shout sounds like, and the two V8 presets sit at different points along that same description rather than outside it.
The gearbox decides how long each spends there
None of this holds an engine at one rpm for long. The presets shift on the way up at 4,600 rpm for the V10, 2,900 for the muscle V8 and 3,400 for the Euro V8, and each has its own set of gears translating road speed into that rpm.
The V10's seven gears run from 8 km/h per 1,000 rpm in first to 44 in top; the muscle V8's four gears run from 9.5 to 36; the Euro V8's eight run from 9 to 51. A car that shifts at 4,600 rpm and revs to 8,500 spends more of its range above the point where its fundamental has already passed 400 Hz than a car that shifts at 2,900 and stops at 6,200. The scream is a higher note, reached earlier in the rev range and held for longer before the gearbox asks for another one.
Two numbers do most of the work here. Firings per revolution set where the fundamental sits at any rpm, and firing unevenness decides how much lower growl accompanies it. Redline and gearing decide how far up that fundamental is allowed to travel before the next gear resets it. Everything else in a preset, brightness, drive, exhaust resonance, is finishing work on a difference the crank has already decided.