Engines offer a lot of potential savings

Despite the hypes around electric cars, diesel and gasoline engines remain the most important engines for years. However, the consumption of fuel can be greatly reduced.

By Susanne Kilimann

The whole world is talking about the electric car, the federal government has set up a "National Development Plan for Electricity" with the goal that in 2020 one million electric cars will be traveling on German roads. However, these will be only a small fraction of almost 42 million passenger cars. What is certain is that at least for the next 20 years, diesel and gasoline engines are by far the most important sources of power for a car.

However, as oil reserves become scarcer and the forerunners of climate change become more and more visible, and the number of cars worldwide continues to rise, the pressure on the car industry is growing.  The manufacturers are working on a variety of measures to improve the efficiency of their fleets. The savings potential of the diesel and petrol engines is by no means exhausted, says the autoclave companies and also the supplier Bosch, which develops injection systems for engines as well as complete drive systems for various manufacturers. 

From today's point of view, consumption is likely to drop by a third in the coming years. Three-liter cars could therefore also enter the middle-class category in the near future,

In the case of gasoline engines, the developers see a somewhat lower savings potential than in the case of the diesel engines. By 25 to 30 percent, consumption and CO2 emissions in the ottomotors can be throttled in the coming years, is their forecast. The future model will be compared with a single engine that is standard on the world's market today: four-cylinder units with a displacement of two liters and a power of 100 kW (136 hp), the standard diesel with conventional common-rail injection technology Petrol engines with intake manifold injection and an average consumption of 7.7 liters per 100 kilometers, which corresponds to CO2 emissions of 182 grams per kilometer.

"By means of direct injection and the first approaches to displacement reduction, today's gasoline generators now have 15 percent less fuel than the world's most powerful standard", explains Rolf Leonhard, development manager at Bosch. In such measures as well as turbocharging, it will continue to provide the basis for efficiency improvements.

Another field of research is the valve control of the units: modern technology is intended to improve the fresh air filling of the cylinders and thereby increase the torque. This is to compensate for the power losses of a reduced displacement. Manufacturers and suppliers are in agreement that the smaller engine of the future must be driven like a large one of today. After all, you do not want to bully customers with efficiency, which is at the expense of driving dynamics. Even today, a two-liter standard engine can be reduced to a displacement of 1.4 liters, without a too great inertia being noticeable when kicking on the pedal.

If direct injection and displacement reduction are combined with the start-stop technology, which automatically shuts down the engine during short holding phases, a petrol engine already suffers 22 percent less fuel than a comparable model in which the current technology has not yet been installed . By 2015 the developers of Bosch want to reduce the capacity of the mid-range engine to 1.1 liters, which then - compared to today's standard drive - the consumption by up to 29 percent. The pressure of the turbocharger is increased by the engineers from 1.8 to 2.4 bar at this step, so that the scaled-down unit achieves the same performance despite the reduced combustion space.

In diesel engines, the efficiency has already been improved by increasing the injection pressure and the pressure during the supply of combustion air.According to Bosch, today's technology reduces consumption by 22 percent compared to standard diesels. Next, the developers want to increase the combustion temperature in the engine, which increases the efficiency. But the thing has a catch: with the combustion temperature the amount of harmful nitrogen oxides emitted increases. A catalyst is to be provided in the waste gas tract.

If the technical problems are solved and the self-igniter can burn its fuel with more heat, the consumption will again drop by five to seven percent. If the displacement is also reduced to a modest 1.2 liters, the future medium-class diesel is 33 per cent more efficient than today's comparable diesel engine. The CO2 emissions should then be on average at 97 grams per kilometer.

As a diesel hybrid, this engine would even consume 40 percent less than the current common rail diesel. The combination of a diesel engine with a supplementary electric motor is also the targeted solution of the PSA Group, under the umbrella of the brands Peugeot and Citroën . The hybridization brings more in the self-igniter than in the gasoline, the developers at PSA. With the hybrid technology, ottomotors are only moving towards a consumption level where modern diesel engines are already economical. Consequently, it is only logical to undertake the diesel engine and to increase its efficiency by combining it with an electric unit.

In the meantime, BMW is turning to a better heat management system. An engine consumes up to ten percent more fuel during cold start than when it is warmed up. Reason for the additional demand are the internal friction and the viscous liquid of the cold engine oil. Therefore, the engineers want to avoid the cold start by storing the residual heat of the engine. For this purpose, the developers have encapsulated the engine in the BMW Research Department - the jacket keeps it warm longer after the ride. After twelve hours the temperature is still at 40 degrees Celsius. With every degree that is maintained until the next start, fuel consumption is reduced by 0.2 percent, according to BMW.

If such advances in propulsion technology are accompanied by further efficiency measures, cars can also easily reach a CO2 emission of less than 90 grams per kilometer. With light-weight components, aerodynamically improved bodyshells and tires with lower rolling resistance, cars of the lower mid-class with 70 grams of CO2 emissions could go into serial production within a few years, estimates Bosch expert Leonhard. Thus, all political objectives would be more than fulfilled.

At what point the efficiency increase in the combustion engines will reach its end point, can not be said from today's point of view at all, emphasize the experts.  Twenty years ago, no one could have predicted the possibilities of today's technology. And who knows, if the three-liter mid-range car is once standard, the two-liter car could also move into the range of standard options.