Daihatsu KF / EF (Kei three-cylinder)

Daihatsu's 660 cc three-cylinder — in the Mira, Ayla and the Kei-class cars, and, as the 1KR-VE, in a great many small Toyotas.

⚑ The 1KR is the connection worth making. Daihatsu is Toyota's small-car subsidiary, and the 1KR-VE three-cylinder it designed appears in the Toyota Aygo, Yaris and Peugeot 107 and Citroën C1 — so a very common European city-car engine is a Daihatsu design, and neither the badge nor most of the literature says so.

660 cc is a legal ceiling rather than an engineering choice, and these engines are built to make the most of a fixed limit — which is why they rev freely and why a turbocharged one works hard.

The recurring item across the family is the timing chain and its tensioner, giving a rattle on a cold start. On a three-cylinder that noise is easy to dismiss as the engine's inherent imbalance and it should not be.

Oil consumption on high-mileage examples is the other common complaint, and on an engine this small the consequence of running it low arrives quickly.