ensim4 is a real-time inline combustion engine test-bed simulator that uses isentropic flow equations and one dimensional computational fluid dynamics to simulate exhaust gas pipe dynamics.

ensim4 generates audio, so crank up your headphones!

For an audio sample:

https://www.youtube.com/watch?v=fq1WPNeVXrI

Requires a C23 compatible compiler.

Dependencies:

pacman -S sdl3

Compile one of either built in engines:

make ENGINE=ENGINE_3_CYL
./ensim4

or

make ENGINE=ENGINE_8_CYL
./ensim4

Then, to start your engine:

1. Hold space to engage your starter
2. Tap d while holding space to ignite your spark plugs
3. Manage your throttle with h, j, k, l

Engine nodes (volumes) can be toggled with the cursor.

Otherwise, via the keyboard:

    p: Selects all piston nodes
    i: Selects all intake nodes
    e: Selects all exhaust nodes
    c: Clears selection
    n: Selects the next node(s) of the currently (only) selected node

The effects of 1D-CFD on audio can be enabled and disabled with the y key.

Performance tuning is done via perf-stat. Logs to perf.txt, runs for a number of cycles.

make perf

Ange Yaghi for inspiration and impulse convolution (https://github.com/ange-yaghi/engine-sim).