The dogbox, a key choice for Renault E-Tech full hybrid powertrains
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Without the dogbox, Renault would probably not be the international car manufacturer it is today. In 1898, it was a dogbox that took the Renault type A voiturette up the rue Lepic in Paris. Invented by Louis Renault, this major innovation contributed to the renown of Renault over the decades. Today, E-Tech hybrid technology has made the dogbox revolutionary once again, pairing it with Renault’s E-Tech full hybrid powertrains. The dogbox gives Rafale, Austral, Espace and Symbioz outstanding levels of efficiency and driveability. Read on for a more detailed explanation.
The dogbox is exceptionally efficient
The mechanical gears are engaged by means of large teeth (dogs) through a non-progressive action. Lightweight and compact, this technology is exceptionally efficient (98.5% efficiency per gear mesh).
These properties explain the long-standing popularity of the dogbox in motorsports, particularly in Formula 1 and rallying, which is all about performance.
In passenger cars, however, comfort is more important than efficiency. This has led manufacturers to prefer synchronised, automatic gearboxes over the harsher shifting of the dogbox. . A “mini clutch” makes gear changes more comfortable, but also leads to continuous friction, resulting in a loss of efficiency.
The return to favour of the automatic dogbox with hybrid technology
Unlike ICE and hybrid cars, all-electric cars such as Renault 5 have no gearbox. Without the talent of Renault engineers, dogbox technology might have fallen into obscurity. They realised that hybrid powertrains offered a way to eliminate the major shortcoming of dogboxes by assigning gearshift control to the electric system and to smart technology.
Ultra high-tech and innovative, the dogbox coupled with the E-Tech full hybrid powertrains has no clutch or synchromesh. On E-Tech hybrid powertrains, it is the HSG or high-voltage starter generator – one of the two electric motors – that manages vehicle start-up and synchronises the six-speed dogbox. The all-electric start-up and gear control are particularly smooth, contributing to the exceptional driveability of Renault E-Tech full hybrid models such as Rafale hyper hybrid E-Tech 4x4 300 ch. A master stroke.
An intelligent, multi-mode gearbox
The HSG electric motor manages vehicle start-up, gear shifting and battery regeneration. The main electric motor drives the vehicle as shown by a series-parallel diagram. The hybrid technology deployed on E-Tech engines combines the advantages of series hybrids (where only the electric motor drives the wheels and the ICE charges the battery) with those of parallel hybrids (where the two types of motor can operate alone or simultaneously).
Managing this complexity, the dogbox and HSG motor act as the pilot and brain of the E-Tech hybrid system.
This smart system manages the activation of the two electric motors and ICE engine, along with their independent or simultaneous operation.
This multimode dogbox includes two electric speeds and five ICE speeds to constantly optimise driving pleasure, fuel consumption and CO2 emissions.
Fifteen operating combinations are possible. In short, the dogbox operates in the five modes below:
- All-electric (only the electric motor drives the wheels). This mode is activated at low speeds in cities and during manoeuvres.
- Dynamic hybrid (the combustion engine and electric motor drive the wheels together). The full potential of torque and power is available for overtaking or climbing a hill, for example.
- E-drive (the electric motor drives the wheels, while the ICE charges the battery) This mode can be activated manually, but also engages automatically at steady speeds, on the motorway, for example.
- ICE (the petrol engine drives the wheels and/or charges the battery). This mode is activated when the battery is empty.
- Energy recovery (the wheels drive the electric motor that charges the battery). This mode kicks in during braking or deceleration, and can considerably increase battery life while reducing wear and tear on the brakes.
Under the bonnet of Renault Rafale, Renault Espace and Renault Austral, the 200 hp E-Tech full hybrid powertrain offers standard fuel consumption of just 4.6 litres per 100 km, for 104 grammes of CO2 per km. This performance enables a range of up to 1,100 kilometres without charging.
E-Tech powertrains are unique on the market for their performance/efficiency ratio, based on the combined innovations of E-Tech full hybrid technology and the dogbox. This combination brings Renault Group customers the best of both worlds, delivering efficiency, performance and comfort.
