The slowest firing rate in the library
Two presets in EV·ENGINE share the lowest firing rate in the library: the big single and the steam locomotive both produce one firing every two revolutions. Below a certain rate the ear stops hearing a pitch and starts counting bangs, and both machines spend most of their working range in that lower zone.
One firing, two revolutions
EV·ENGINE describes each preset's pulses value as firings per revolution, and on a four-stroke engine it comes straight from cylinder count: cylinders divided by two. A single-cylinder four-stroke completes only one power stroke across a full intake, compression, power and exhaust cycle, a cycle that spans two turns of the crank, so its pulses value sits at 0.5, the lowest a real four-stroke engine can produce. The big single preset carries that exact figure, and nothing else in the library shares it by physics alone.
The steam locomotive preset carries the same 0.5, but nothing about a steam engine's own cylinder arithmetic forces that number. A locomotive's driving wheels turn on pistons following a completely different cycle, with no four-stroke to divide by two, so the figure here is a choice: whoever built the preset matched its firing spacing to the big single's, giving both the same slow, spaced-out cadence, one because a single cylinder demands it and the other because someone decided it should sound that way.
Compare that against the site's own reference point, the four-cylinder 2.0, which fires twice every revolution: four times the rate of these two. Firings per revolution set an engine's fundamental note, as covered in the piece on why a V10 screams and a V8 shouts, and a fourfold difference in that number works out to two octaves. Before either machine's rpm has moved at all, the big single and the steam locomotive start two octaves below the reference engine at the same engine speed.
At idle, both read as bangs
Multiply pulses by revolutions per second and you get firings per second. The big single idles at 600 rpm, which is ten revolutions a second, and at 0.5 pulses that comes to five firings a second. Five events a second is slow enough to count on your fingers, and that is exactly what it sounds like at a standstill: five separate bangs, not a hum.
The steam locomotive idles lower still, at 430 rpm, a little over seven revolutions a second, which at the same 0.5 pulses works out to roughly three and a half chuffs a second. That is slower than the big single's idle by nearly a third, and the gap is audible: the locomotive's chuffs sit further apart than the single's bangs, even though both engines are, on paper, firing at the same rate per revolution.
Redline changes the picture more than idle does. The big single revs to 5,500 rpm, which at 0.5 pulses is about 46 firings a second, comfortably inside the range where separate events blur into a continuous note. The steam locomotive's redline is only 2,600 rpm, giving around 22 firings a second, barely enough to blur into a tone. Run both up towards their own redlines and the single builds into something closer to a snarl, while the locomotive keeps sounding like a fast, insistent set of chuffs.
Same rate, different weight
Sharing a pulse rate does not make two presets sound alike, because everything downstream of that number is set separately. The big single carries a noise level of 110, while the steam locomotive sits at 200, nearly double, so its chuffs ride under a wash of intake and exhaust hiss the single never gets.
Low end differs the same way. Bass is 112 on the big single and 155 on the steam locomotive, with sub-oscillator level following the same pattern at 65 against 120, so the locomotive starts out heavier underneath. But that weight lasts a different length of time: the single's bass fades above 2,600 rpm, close to its 2,800 rpm shift point, carrying that low end through almost its whole working range. The locomotive's bass fades above 900 rpm, well before its own 1,400 rpm shift point, so most of its range runs on noise and chuff alone.
Exhaust length adds another layer. The big single's pipe figure is 175 decimillimetres, giving a first comb delay of 17.5 milliseconds, against 220 decimillimetres and 22 milliseconds for the locomotive, as covered in the piece on the exhaust is a comb filter. Comb feedback is higher on the single, at 42 against 30, and firing unevenness is higher too, at 55 against 45, the highest figure in the library. Between the two, the single ends up harder and more clearly pitched, while the locomotive stays softer, longer and less defined.
One gear against five
Gearing is the last piece, and here the two could not differ more. The big single runs five gears, from 4 km/h per 1,000 rpm in first up to 18 km/h per 1,000 rpm in fifth, shifting up at 2,800 rpm. The steam locomotive runs one gear only, at 42 km/h per 1,000 rpm, as covered in the piece on a jet turbine has one gear, which groups it with the jet turbine and the radial prop plane as machines that never shift at all.
That difference changes how firing rate tracks road speed. Each time the big single shifts, rpm drops back toward its 2,800 rpm shift point and the firing rate drops with it, so the bang-per-second count resets in a series of short climbs rather than rising smoothly as the car picks up speed. The locomotive has nothing to reset: with one ratio covering its whole range, rpm and firing rate climb in a single, unbroken line from idle to redline.
The result is two different shapes for the same underlying number. The big single's 0.5 pulses per revolution get chopped into five repeating climbs and drops as the gearbox works through its ratios. The locomotive's 0.5 pulses get stretched across one long, continuous rise from 430 rpm to 2,600 rpm, with nothing to break it. Same firing rate, same spacing between events, almost nothing else in common by the time either reaches the top of its range.
Both machines start from the same number, the lowest firing rate in the library, and both spend real time in the zone where the ear counts events rather than hears a pitch. Everything after that number is a separate decision: how much noise rides under the firings, how long the bass lasts, how long the exhaust rings, and how the gearbox spaces the climb from idle to redline. A shared pulses value is a starting point, not a description of what either engine sounds like.
Hear it
Ten seconds each: an acceleration run through the gears, then the overrun. The same presets the numbers above come from.
- BIG SINGLE1-cyl thumper · bang
- STEAM LOCOMOTIVEpiston chuff · steam