Bosch has bundled enabling powertrain technologies for gasoline and diesel engines into various packages, to further increase the internal-combustion engine’s fuel economy. At the recent Frankfurt Motor Show, Dr. Rolf Leonhard, Executive Vice President of Development for diesel systems, explained his company's roadmap.
“Compared to a four-cylinder port-injection gasoline engine with 100 kW power and 200 N·m torque, installed in a reference car with a curb weight of 1.4 t, our first gasoline technology package can offer up to 22% better fuel economy at Euro 6 emissions level,” Leonhard said.
To achieve this improvement, direct injection and turbocharging at 1.8 bar (26 psi) level are used to enable downsizing the engine displacement from 2.0 L to 1.4 L without compromising power or torque.
“Turbocharging is absolutely essential to make sure that downsizing does not mean downgrading,” Leonhard noted. This technology "package" also includes the control function for variable valve timing on the intake and exhaust sides to improve low-rpm torque via cylinder scavenging. The package is completed by improved thermal management and a start-stop system.
The second technology package developed by the supplier is based on a more aggressive downsizing approach. This reduces the number of cylinders to three, brings down displacement to 1.1 L, increases the charge pressure to 2.4 bar (35 psi) and adds valve lift control. As a result, fuel economy can improve by up to 30% on a port-injection engine.
“If both packages are combined, the vehicle manufacturer harvests up to 30% better fuel economy, which brings down the CO2 emissions from 182 g/km to 130 g/km for 1000 euros added cost (per vehicle) in 2015,” Leonhard explained. “If you consider the expected European CO2 penalty of around 95 euros per gram of CO2, this is an absolute bargain.”
Adding Bosch's hybrid technology package, a 25-kW electric engine and 1-kWh battery, could give the 1.1-L gasoline engine hybrid nearly 40% better fuel economy than that of port injection technology.
Working the trade-off between NOx and consumption
The company's diesel technology packages are very similar, with the exception that direct injection is standard in modern diesel engines. Typical diesels offer 30% better fuel economy than today’s standard port-injection gasoline engines anyway.
The first diesel package includes downsizing of a four-cylinder 2.0-L engine to 1.6 L capacity. Improving combustion plays a key role in this package, which is tailored to increase fuel efficiency by up to 22% compared to basic contemporary diesel technology.
Diesel package number two offers a remarkable strategy to improve fuel consumption by up to 28%: “Normally we will not need DeNOx technology to meet Euro 6 legislation in smaller diesel passenger cars,” Leonhard said. “However, DeNOx technology such as SCR or a NOx storage catalyst can help to increase fuel efficiency by another 5-7%.”
For that purpose, Leonhard suggests to accept a higher engine-out NOx level and to add a DeNOx system with 50% conversion rate. “This is efficient to meet Euro 6 NOx levels. At the same time, it makes a further reduction of the diesel engine’s fuel consumption possible.”
More aggressive downsizing of the diesel engine to 1.2 L and just three cylinders is at the core of diesel package number three, which aims at up to 33% better fuel efficiency. By adding a hybrid option of the same size as the one in the third gasoline technology package, the diesel could ultimately achieve up to 40% better fuel efficiency.
To supply lithium-ion batteries as part of a hybrid drive, Bosch founded the SB LiMotive joint venture with Korea's Samsung SDI in September 2008. Series production of lithium-ion cells is planned to commence in 2011; BMW will be the first customer. The automaker will use the cells for its Megacity electric vehicle.