Improving car fuel efficiency by 25%

Louise Smyth

Precision bearing and automotive systems supplier Schaeffler and project partner Continental, in close collaboration with Ford, unveiled the second-generation Gasoline Technology Car (GTC II), a 48-volt mild hybrid car that made its world debut at the 37th Vienna Motor Symposium in April 2016.

The first-generation Gasoline Technology Car (GTC I), which was presented to the public at the 2014 Vienna Motor Symposium, stole the show with a 17% improvement in NEDC (New European Driving Cycle) fuel efficiency compared with the Ford reference model, and CO2 emissions of less than 95 g/km. The already highly efficient Ford Focus reference model was equipped with a turbocharged 3-cylinder 1-litre gasoline engine (GTDI) and 12-volt start-stop system.

The GTC II showcases the potential of intelligent, latest-generation 48-volt hybridisation in its most advanced form. The GTC II promises a further improvement of approximately 13% on the NEDC fuel consumption compared to the GTC I. The most obvious difference between the GTC II and the GTC I is the highly efficient integration of the electric motor between the internal combustion engine and the transmission in the second-generation model (“P2 architecture”).

“The second-generation Gasoline Technology Car demonstrates the huge potential of a mild hybrid when the 48-volt electrical system, the internal combustion engine and the operating strategies are optimised holistically as a complete system,” says José Avila, Member of the Executive Board of Continental and President of the Powertrain Division.

“The GTC II, just like the GTC I, is a milestone in terms of the successful integration of highly efficient hybrid operating strategies in a manual-transmission vehicle. The GTC II’s electronic clutch supports functions such as electric launch, electric stop-go operation and energy recuperation at speeds almost down to standstill,” says Prof. Dr.-Ing. Peter Gutzmer, Member of the Schaeffler Executive Board responsible for Research & Development.

“The Ford Focus with its 1.0-litre Ecoboost engine, which has won multiple International Engine of the Year awards, provides an excellent starting point for a hybrid vehicle, showing the potential that hybridisation offers even for an engine that starts from such a high baseline. When integrating the GTC II concept, the focus was therefore on overall powertrain optimisation,” says Carsten Weber, Manager Engine & Powertrain Systems Research & Advanced Engineering, Ford Europe.

Efficiency leap – GTC II with 48 volt technology

In its general principles, the GTC II has much in common with the GTC I. Both vehicles demonstrate the potential of mild 48-volt hybridisation for cars with downsized petrol engines. And both vehicles derive their fuel economy edge over the reference model primarily from the intelligent synergies between their featured technologies. Their hybrid operating strategies are based on a holistic integration approach that is focused on delivering a whole that is greater than the sum of its parts.

However, the GTC II goes a step further than the GTC I, exploiting potential that was still out of reach for the earlier model, both with regards to the electric drive system and the internal combustion engine.

The electric motor on the GTC II is integrated in the drive train by means of a belt that runs between the internal combustion engine (ICE) and the transmission. Two clutches, one upstream and one downstream of the belt, allow the internal combustion engine to be completely decoupled when required. The electric motor can then be used independently of the ICE. As a result, the GTC II supports both constant-speed electric coasting at low load, as well as electric launch, for example in stop-start driving.

The absence of any engine braking effect in deceleration phases means that more kinetic energy is available for recuperation. Also, since overrun is avoided, cooling of the engine and aftertreatment system is reduced. This effect, which is further enhanced by the thermal management system that already proved itself on the GTC I, is a big advantage for a hybrid vehicle, where engine-off phases account for a relatively large proportion of the driving cycle. Also, thanks to systematic utilisation of Continental’s high performance, electrically heated 48-volt EMICAT® catalyst, engine-out emissions are reduced immediately, even after long engine-off phases. This strategy plays a big part in ensuring that the GTC II complies with the strict requirements of emissions standard Euro 6 c (2017/2018).

Higher thermodynamic efficiency

Measures focused on the internal combustion engine in the GTC II also included the further optimisation of the engine’s thermodynamic efficiency, with a higher compression ratio and an engine cycle with late closing of the intake valves (Atkinson cycle) resulting in reduced specific fuel consumption.

At the same time, a Continental turbocharger specially adapted to this engine and featuring a radial-axial turbine offers fast response times, particularly at low engine speeds. In combination with the electric torque assistance, this allows more flexibility when defining the operating strategy and improves driveability, which also enhances customer acceptance.