Flat-four boxer sound

The boxer rumble is famous and misunderstood. It does not come from the horizontally opposed layout itself. It comes from unequal-length exhaust headers, which reach the collector at uneven intervals and smear the firing pulses. Fit equal-length headers to the same engine and the sound goes away.

Ten seconds from a standing start. The launch, the gearbox working up through the ratios, then the overrun as the throttle closes. Driven by the same gearbox model the simulator runs, so the shift points are the ones you would hear in the car.

The preset models that as unevenness of 34, the second highest of any car here after the muscle V8 at 38. Two firings per revolution, the same as any four-cylinder, but scattered rather than evenly spaced. That is the whole trick, and it is why a flat-four with equal-length headers loses the sound entirely.

Bass at 105 and pipe length at 135 give it the low, loose bottom end. Noise at 105 and drive at 110 keep it slightly rough. Nothing here is polished, which is right.

Brightness sits at 90, on the low side, so it stays a rumble rather than becoming a rasp. Comb feedback of 50 with that long pipe gives the loping decay between pulses.

It redlines at 6,700 and shifts at 3,200 across five ratios reaching 37 km/h per 1000 rpm. Ordinary gearing, deliberately, because the engine character is doing all the work.

Overrun pops at 20 are modest. Put it against the air-cooled flat-six, which shares a cylinder layout philosophy and sounds nothing like it, to hear how much of an engine’s identity lives in the exhaust rather than the block.

Five ratios reaching 37 km/h per 1000 rpm put 100 km/h near 2,700 rpm, where the rumble is still clearly there. Unlike the high-revving presets it does not need a back road to be worth listening to, which makes it a good everyday choice.

Specification

Every figure above is read from the preset the app actually runs, not retyped.

Drive it

Open the simulator with this engine selected, allow location, and press ignition. See how it works for what happens between GPS and sound.

Related

• Air-cooled flat-six sound
• Muscle V8 engine sound
• Three-cylinder engine sound

Every other engine

• RECORDED CARS
  • BAC Mono
  • Ferrari 458
  • BMW M1 Procar
• SUPERCARS
  • Muscle V8
  • Modern V8
  • V10
  • V12
  • Anti-lag rally car
  • Air-cooled flat-six
• NORMAL CARS
  • Three-cylinder
  • Four-cylinder
  • Turbo hot hatch
  • Inline-six
  • Diesel
• FUN SOUNDS
  • Steam locomotive
  • Radial prop plane
  • Jet turbine
  • Alien craft
  • Single-cylinder thumper

All twenty on one page, with redline and gear count for each.