How Renault's Lego gearbox changed the hybrid game

Nicolas Fremau built a Lego model at Christmas - then Renault scaled it up into the radical E-Tech Hybrid system

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.

Fremau's good idea soon thrived in the fertile environment of the Renault Group's mighty Technocentre at Guyancourt, west of Paris, where he worked. Experiments rapidly grew into a fully blown engineering programme.

After a decade of development, Renault now offers a unique, clutchless hybrid powertrain family sold under the E-Tech Hybrid name, launched in 2020 and already in its second generation, that combines two electric motors with a staple petrol engine.

The bigger electric machine is mounted where a transverse engine's conventional clutch would be. The second is a meaty, gear-driven starter-generator that as well as starting the petrol engine and regenerating power for the hybrid battery can also help propel the car when needed, even to speeds above 70mph.

Delve deeper and the complexity underpinning E-Tech Hybrid goes further. The traction motor is linked to a two-speed gearbox (this allows for a more compact motor) and the petrol engine a four-speed.

But clever combinations of E-Tech Hybrid's three 'torque sources' mean the system can function in a total of 15 different drive modes, including electric-only and engine-only cruising. In future iterations, if it makes sense, engineers say there may be even more.

The first-generation E-Tech Hybrid system, making 144bhp in total and linked to a normally aspirated 1.6-litre Alliance petrol engine with a 200V 1.2kWh battery, was launched three years ago in Renault's smaller cars and remains current. You can find it today in the Clio, Captur, Arkana and Dacia Jogger.

The second-gen system, which makes 198bhp in total, is based around a purpose-designed 1.2-litre three-cylinder engine feeding a 400V 2.0kWh battery. This later, more advanced system is used in the recently launched Austral, will come soon in the larger Rafale, and you might also find it in the new Espace SUV, if Renault UK were ever to reverse a decision not to sell the model here.

Fremau is proud of his pivotal role in E-Tech Hybrid's discovery, though quick to acknowledge the huge, complex team effort that brought it to reality. "Friction is my obsession," he says cheerfully, "and I was very happy to see a way of reducing it in a hybrid application - especially since it would use dog-clutch technology that both goes back to Louis Renault's first machines and is used today in our F1 cars."

Fremau, who cites his most creative time of day as breakfast time, says the early E-Tech Hybrid development team first made a series of simple proving models. One key supporter was Eric Peccoud, Renault's global powertrain engineering project director - and both he and Fremau were on hand when Autocar visited the 6000-strong Guyancourt Technocentre to view the original E-Tech Hybrid Lego models and hear how it had all developed.

"For Renault, the ultimate direction is towards EVs, no question," explains Peccoud. "But we believe the right hybrid vehicles can provide an ideal first step to EVs. We are Renault; we wanted this to be a typically Renault project. So it had to be simple to use, and though it used the latest technology, it had to be affordable.

The affordable, customer-accessible potential of E-Tech Hybrid was initially seen as particularly applicable to future Dacia models, so early testing was done on a Sandero prototype.

Results were instantly very promising, but as work proceeded, a wider potential for the system became obvious: E-Tech Hybrid was also included in a futuristic 2014 Paris show concept car called the Eolab. Fremau's original innovation team involving three people was soon employing hundreds.

"Innovation never comes from one just person," he says, "especially when it's as complex as a hybrid system.'

A plethora of innovations in gear design, gearchange actuation and software design have followed - and are continuing. Renault wants to press its advantage. The E-Tech Hybrid project has already picked up 150 patents, and Peccoud and Fremau believe their technology isn't something that rivals will be able to match in the short term.

After a couple of hours' talking, I was offered a short drive in a Clio with a first-gen E-Tech Hybrid gearbox. Others from Autocar have driven this car and my findings confirm theirs.

Over a short, varied route, the car completely fulfilled the claims made for it: smoothness, quietness, easy step-off, long legs and (according to the trip computer) excellent fuel economy.

Renault says in normal use, E-Tech Hybrid cars use electric power 80% of the time. This also seemed to be proven on our short test.

What of E-Tech Hybrid's future? Renault's engineers acknowledge that hybrid powertrains may eventually become time-expired, overtaken by pure EVs, but they believe they have at least 12 years to run in Europe and maybe double that in other regions.

They believe E-Tech Hybrid and efficiency will be comfortable bedfellows for many years to come.