How does it work? The new belt-driven integrated starter-generator (in techie circles it is known as a BISG) operates both as an alternator and as an electric motor. As a generator, it recovers energy normally lost during braking and coasting which is stored in a lithium-ion battery. As a motor, it obviously starts the engine but then, using stored energy from that lithium battery, also spins the crank with a dose of extra torque. This torque is used both to allow the petrol motor to work less hard – hence the efficiency advantage – and to give a performance kick when you need it.
Neither the electric motor nor the battery is man enough to drive the Fiesta on electricity alone, but then there is nothing to plug in, either. It’s the same system that was introduced in the Puma small SUV in 2019.
The BISG has allowed Ford to tweak its petrol motor (lower compression ratio and bigger turbocharger) to make it more efficient and responsive, as well as make the automatic stop-start system more effective. That now cuts in at speeds up to 15mph when coasting to stop. Forty-eight volt electrics also means new systems can be introduced to the Fiesta such as cylinder deactivation – when you don’t need all four cylinders, the engine works as a three-cylinder – adaptive cruise control with speed sign recognition, and parking assist.
“Adding EcoBoost Hybrid technology to Fiesta’s best-in-class driving dynamics means customers can have even more power and still go further on a tank of fuel,” says Ford marketing chief Roelant de Waard.
If you’re a fan of the Fiesta, might we point you towards our review of the tuned Fiesta ST Mountune?