Mechanical & Aerospace
Thermo Cycle Lab
The four strokes of a petrol engine, drawn as one loop. Squeeze the charge (1→2), burn at constant volume (2→3), let it push the piston (3→4) and exhaust (4→1) — the area enclosed is the net work, and the efficiency η = 1 − r^(1−γ) climbs with the compression ratio. Drag r and the heat input and watch the loop fatten; the readout compares the Otto cycle against Diesel and Brayton at the same compression, so you can see why each engine type has a different efficiency ceiling.
56.5 %
Otto efficiency
8 : 1
Compression r
46
Peak P / P₁
At r = 8: Otto 56% · Diesel (cutoff 2) 49% · Brayton 56% — same compression, different cycle, different ceiling.
The Otto cycle (your car's petrol engine): squeeze the gas (1→2), burn fuel at constant volume (2→3), let it push the piston (3→4), exhaust (4→1). The loop's area is the net work; efficiency η = 1 − r^(1−γ) rises with compression — which is why high compression engines knock and need higher-octane fuel.
How to use this simulation
The four strokes of a petrol engine, drawn as one loop. Squeeze the charge (1→2), burn at constant volume (2→3), let it push the piston (3→4) and exhaust (4→1) — the area enclosed is the net work, and the efficiency η = 1 − r^(1−γ) climbs with the compression ratio. Drag r and the heat input and watch the loop fatten; the readout compares the Otto cycle against Diesel and Brayton at the same compression, so you can see why each engine type has a different efficiency ceiling.
Everything runs in your browser — no sign-up, no download. Change a value and the result updates instantly, so you can build a feel for how each input shapes the outcome. It pairs with Crameleon's practice exams and step sheets when you want to go from intuition to working the problems.