Ottix

Meet Ottix, an engine cylinder who wastes less fuel the harder he squeezes it first.

Most petrol engines follow the Otto cycle, named after Nikolaus Otto, who built one in 1876. The piston squeezes a mixture of air and fuel, a spark ignites it, the hot gas pushes the piston down, and the exhaust is pushed out.

For an ideal Otto cycle the efficiency depends only on the compression ratio r, the cylinder volume before squeezing divided by the volume after, and on γ, the ratio of the heat capacities of the gas. For air γ ≈ 1.4, so η = 1 − 1/r^0.4.

A compression ratio of 10 gives an ideal efficiency of about 60 percent. Real engines lose heat and friction and reach roughly 30 to 40 percent.

Higher compression would help, but squeezing too hard makes the mixture explode on its own before the spark, a damaging knock. Diesel engines avoid the spark altogether, using compression ratios near 20 so the air gets hot enough to ignite the fuel.