Eight steps to a more economical car

(Source: Bosch Media)

February marks the start of car buying season – and cost-effective drive systems are an ever more prominent factor in their choices. Modern powertrain technology can cut fuel bills by several hundred euros. Examples include Bosch’s expanded start/ stop function and adaptive cruise control (ACC), which by keeping speeds as constant as possible makes journeys more economical. “Many Bosch innovations help drivers to save fuel – and money – with every mile they drive,” says Stefan Seiberth, president of the Gasoline Systems division of Robert Bosch GmbH. But fuel-efficient functions need not always cost a lot; some technologies – among them the start/stop system – are now standard equipment in many models, while others are popular extras. Let us take the example of automatic transmission: for a long time it was a rule of thumb that automatic transmission increases fuel consumption in real traffic conditions by around a litre per hundred kilometres. But this is not true of Bosch continuously variable transmission (CVT), which actually saves fuel by constantly optimizing engine speed. Here we take a more detailed look at each of the stepping stones to fuel efficiency:

Direct injection – reduces consumption by at least twelve percent
Modern common-rail diesel systems have relied on direct injection for many years. In 2000, this technology revolutionized the image of diesel cars, making them not only economical but also fun to drive. These days, every second new car sold is a diesel. Gasoline direct injection, meanwhile, works with downsizing and turbocharging to reduce fuel consumption and hence CO2 emissions by around twelve percent. At the same time, gasoline cars with direct injection are more powerful and hence also more fun to drive.

Continuously variable transmission – reduces consumption by up to seven percent
Driving up a winding mountain road can be a tiresome task. None of the gears seems to be right. Automatic transmissions make this task much easier, taking over the task of shifting and gear selection. Advanced versions already offer up to nine gears for more efficient mobility. Continuously variable transmissions (CVT) even work without any fixed shifting point. The result is a smooth drive at constant traction and engine speed. CVT especially comes into its own in urban stop-and-go traffic. It can reduce fuel consumption by as much as seven percent, since the engine is constantly kept at its most efficient operating point.

Start/ stop – fuel is no longer used at a red light, reducing consumption by at least five percent
Already, every second new vehicle produced in western Europe is equipped with a start/ stop system. In many models – from low-cost compact cars to high-performance premium sedans – this function comes as standard at no extra charge. In the new European driving cycle (NEDC), start/ stop systems reduce fuel consumption, and thus CO2 emissions, by up to five percent. In the NEDC urban cycle, the saving is as much as eight percent. On congested city streets, especially at peak times, the real savings potential is even higher.

Alternative powertrains – CNG cars can pay off from 7,000 km upwards
Compressed natural gas (CNG) powertrains are now a real alternative even in series-produced vehicles. In Germany, they pay off in passenger cars as soon as annual mileage exceeds 7,000 kilometres. This is also because CNG is as much as 50 percent less expensive than gasoline. Compared with a conventional gasoline engine, generating the same power causes 25 percent less CO2 to be emitted. This is due to the chemical properties of this fuel source. The Bosch system can start in CNG mode even when it is cold, which means that customers can practically always drive on more cheaply priced natural gas. Other systems have to use expensive gasoline to warm up in the starting phase.

Electrification – reduces consumption by up to 60 percent
With the strong-hybrid systems currently made by Bosch, drivers can reduce their fuel consumption in the NEDC by 15 to 25 percent. These days, many automakers offer this kind of hybrid vehicle with just a moderate mark-up; in fact sometimes a hybrid costs the same amount as a comparable diesel car. This means hybrids can pay off even in the midsize “Golf” class. Plug-in hybrids currently cost substantially more. But these can reduce energy costs by up to 90 percent, provided users always remember to charge up at the socket. These hybrids are especially suitable in the midsize segment, as electric SUVs, and as sports cars.

Coasting function – stopping the engine while driving reduces consumption by ten percent
Bosch start/ stop coasting lets even vehicles with an internal-combustion engine travel long distances without generating emissions or noise and with little resistance. This innovative technology stops the engine while driving, which means it consumes no fuel. The low-cost coasting function saves up to ten percent of fuel in real driving conditions. The engine is stopped without the driver noticing whenever the vehicle is able to keep its speed up simply by coasting – for instance on a gentle downhill slope. As soon as the driver depresses the accelerator or the brake, the engine starts up again.

Predictive navigation – deliberate coasting on the approach to built-up areas
Bosch predictive navigation ties map data in with the vehicle’s powertrain, allowing drivers to save up to 15 percent of fuel. The engine management system uses the route preview both in its dynamic calculations of how much power the powertrain needs and in its predictive control of the internal-combustion engine or electric motor. For example, when the navigation software sees that the current two-kilometre downhill stretch of road leads to a built-up area, it can tell the vehicle to enter fuel-efficient coasting mode or to generate more power for the electric drive.

Adaptive cruise control – driving at a constant speed reduces consumption by up to five percent
Adaptive cruise control (ACC) makes drivers’ lives easier by keeping to the specified speed, taking account of vehicles in front, and maintaining a safe distance from them. Radar sensors monitor traffic and adjust the speed accordingly. ACC is now available as an extra even in many compact cars.

By maintaining a constant speed and ensuring the engine always operates at the most efficient speed for every situation, the system is able to save up to five percent of fuel in real driving conditions.

The potential fuel savings outlined above relate in each case to the system described. A total saving of over 100 percent is physically impossible.

Gasoline direct injection

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