Engine Sim
An iPhone sound simulator that synthesizes engine sound in real time — not looped recordings.
An iPhone sound simulator that synthesizes engine sound in real time — not looped recordings.
Most engine sound apps ship a folder of recordings and cross-fade between them as you move a slider. Engine Sim does not have that folder. Every sample you hear is computed on the phone, one cylinder event at a time: the ignition pulse of each cylinder, the occasional misfire on overrun, the uneven spacing between the exhaust pulses of the two banks, and the resonance of the pipe the gas leaves through.
Because it is a model rather than a playlist, the sound follows what you do instead of jumping between clips. Throttle position, the H-pattern shifter (or paddles, or full automatic), the brake and the blip between downshifts all move the revs continuously, and the note moves with them — including the parts that are hard to record cleanly, like the load change at part throttle or a long overrun down through the gears.
Twenty-one configurations are included, chosen so that the differences between them are audible rather than cosmetic: a 450 cc single, parallel twins and a boxer twin, inline-fours with both crank layouts, an inline-six, V6s, crossplane and flatplane V8s, a V10, a V12, a W16, and a racing V10 that pulls to 19,000 rpm. Each one has its own firing order, bank angle, redline and exhaust geometry, which is why they sound like different engines instead of the same engine at different pitches.
Distance driven becomes “miles”, and miles unlock engines and parts through an unlock tree. Exhausts, intakes, headers, forced induction, camshafts and ECUs each change both the numbers (0–100 km/h, top speed) and the sound. Game Center leaderboards rank top speed and acceleration times.
Every engine and part can be unlocked by driving; the in-app purchases only shorten that, or remove the full-screen ads. There are no subscriptions.
Building the synthesizer meant working out, in some detail, where each part of an engine’s character comes from. These are the write-ups of that — the physics behind the noises enthusiasts argue about, without the hand-waving.
Two engines, same cylinder count, same displacement, completely different noise. The whole answer is in the crankshaft — and in an exhaust pulse that arrives at the wrong moment.
Why a V8 at 3,000 rpm and an inline-four at 6,000 rpm hum at the same pitch, and why the firing order decides everything else about the sound.
More cylinders raise the firing frequency and smooth the pulse train. That single fact explains the burble, the howl and the turbine-like V12.
Unequal-length headers, a boxer firing order, and the exact reason equal-length manifolds turned the burble into an ordinary four-cylinder buzz.
At those revs the firing frequency lands in the middle of the human ear’s most sensitive band. The pitch was not an accident of tuning.
From crank angle to loudspeaker: firing events, pulse shaping, waveguide exhaust resonance and the constraints of a 5 ms audio buffer on a phone.
Questions, feature requests and bug reports go to [email protected]. For a bug report, please include your device model, your iOS version and the app version shown at the bottom of the Settings screen. The Japanese support page, with the full in-app purchase breakdown, is at /apps/enjine-sim/, and the privacy policy is here.