CHILD'S PLAY

Nicolas Fremau built a Lego model with his kids one Christmas. Then he and his Renault colleagues scaled it up into the radical E-Tech Hybrid system. Steve Cropley hears the story

- Steve Cropley

About 10 years ago, while playing with his kids and their Lego toys one Christmas holiday, a clever young Renault engineer called Nicolas Fremau came up with an idea for a new, super-efficient form of hybrid gearbox - exactly the thing he knew his company would need for the rapidly approaching electrification age.

Back then, Toyota was the only company building hybrids in large numbers, notably the Prius. But Fremau's idea was simpler, it was potentially cheaper and he knew the mechanical parts would fit models originally engineered for conventional transverse front-drive ICE powertrains.

In particular, the new gearbox would utilise several innovative ways of dramatically cutting friction, an efficiency killer in any powertrain. One ruse was to eliminate any need for a conventional start-up clutch in favour of an electric drive motor that would always set the car in motion, with the petrol motor chiming in later.

Another was to replace conventional, power-sapping gearbox synchromesh with a system of more efficient dog clutches - using torque from a second electric starter-generator to match the gear speeds and mesh the gears.

The benefits were spectacular. Here was a powertrain with the potential to be fully 20% more efficient than the conventional drive systems it would replace - in other words, every bit as efficient as out-of-favour diesels. Here, also, was a system that, because of its EV-like driving characteristics, could easily introduce new Renault owners to their future of electric car driving.