Excessive technical effort

Excessive technical effort

Motor vehicle economy:Mr. Indra, almost four years ago in the Automotive Industry Interview you described the full hybrid drive as a violation of physics. Nevertheless, more and more manufacturers are offering this drive solution. Have you changed your mind since then?

Fritz Indra: No way, I'll stick with it. The combination of electric motor and combustion engine is extremely complex and must be made as simple as possible. A mild hybrid is enough and offers the possibility of producing large quantities in terms of cost. It is not for nothing that Audi has withdrawn its A6 Hybrid model from the market. Not only was it heavier and more expensive than the equally powerful diesel model, it also consumed slightly more fuel and had higher CO2 emissions.

Why is it that the electric motor cannot exploit its high efficiency in a full hybrid?

The problem is very clear in Formula 1, which has now made hybrid drive a mandatory drive in the regulations. The conclusion is that, despite the completely exaggerated technical effort, the cars are up to four seconds slower than they used to be with pure combustion engines. In addition, the batteries have to deliver their full power in a fraction of a second every time they accelerate and therefore only last for two races. Then you can only throw away the electricity storage devices, which cost around 60,000 euros.

You were head of all advance development at Opel in the 1990s. Has the development of the internal combustion engine already reached its ceiling?

The 1990s were actually a golden time for Opel; many young engineers applied to us back then. It was a duel between Opel and VW for the best engine, and I can proudly say that with our GSI engine we were always ahead of Volkswagen's GTI. Today, as a consultant to several development companies, I am involved in making the combustion engine even more economical and powerful.

What measures can be achieved that are justifiable in terms of costs?

The trick is to make things as simple as possible and not more complicated. For example, when there is a low load requirement, one or two cylinders of a four-cylinder engine or three or four cylinders of a six-cylinder engine can be switched off. This works relatively simply by closing the valves and saves fuel by 7 to 8 percent. Furthermore, diesel engines with steel pistons can save weight compared to aluminum pistons, and the friction losses in the engine can be reduced with low manufacturing tolerances. Further improvements can also be achieved with demand-controlled oil and water pumps. You can also turn the compression a bit, down on the diesel engine and up on the petrol engine. And last but not least, modern multi-stage gearboxes always set the operating point of the motors to the best level of efficiency.

What are the physical limits to the efficiency of combustion engines?

That depends entirely on the design and operation. The most efficient diesel engines today are large engines for ships that have over 50 percent efficiency. Gasoline engines are around ten percent lower. This distance will not change significantly in the future. There is still a lot of development potential in both engine types.

ABOUT THE PERSON: Fritz Indra, born in Vienna in 1940, studied mechanical engineering at the Vienna University of Technology and worked at BMW-Alpina from 1971 to 1979 as head of development and from 1979 to 1985 as head of engine design at Audi. From 1985 to 1998 he was head of engine development at Opel and director of advance development. Indra designed and developed the first Ecotec engines, including the C20XE, which at the time was considered the gasoline engine with the highest efficiency at 37 percent. From 1997 to 2005, Indra was executive director of advanced engineering at General Motors Powertrain in Detroit. In addition to his teaching position at the Vienna University of Technology, he now works as a consultant for AVL List, Thyssen Krupp Technology and Fritz Winter Eisengiesserei.