Fuel goes in and the crankshaft turns. How does the energy in the fuel become motion, and where does the rest go?

intake camvalve springintake portair and fuel inintake valvecooling waterpiston and ringsconnecting rodcounterweightcrankshaftoilexhaust camcylinder headspark plugexhaust portburned gas outexhaust valvegas in the cylindercylinder blockintakecompresspowerexhaustone cycle= 2 crank turns= 1 cam turnthis cycle's energy (fuel: 317 J)fuelhot gasmotionheat outlent by the crank100 mm
crank · cam
0° (turn 1 of 2) · cam 0°
stroke
Intake
engine speed
15 rpm (idle slowed 53 times)
piston
0.0 mm below top · 0.00 m/s
gas
55.5 cm³ · 100 kPa
valves
intake open 0.2 mm · exhaust open 0.2 mm
energy
fuel 0 J · hot gas 0 J · motion 0 J (0%) · heat out 0 J
each second at idle
fuel 2.11 kJ → motion 0.63 kJ

Press the steps in order, or press Auto. Steps 1 to 4 play one cycle in slow motion. Step 5 runs at real idle speed. Watch the energy bar.

Four strokes, spark and valves: LibreTexts College Physics (OpenStax) 15.3 Heat Engines and their Efficiency; Purdue ME 200 notes 3.8.4 (two crank turns per cycle, compression ratio 8 to 10); NASA Glenn, Engine Parts and Otto Cycle. Gas: pV^γ constant, γ = 1.40 (University Physics II 3.7). Fuel energy 1.2 × 10^8 J per gallon and 30% gasoline engine efficiency: College Physics 7.6. 1 gallon = 3.785 L: NIST. Example values: 86 mm bore and stroke, 145 mm rod, 10:1 compression, 0.010 mL fuel per cycle, valve timing, spark timing, 800 rpm idle and housing sizes. Drawn to scale in millimeters with the Anatomy kit (MIT license).