Replacing the Hybrid by Intelligent Driving?

Authors

Univ.-Prof. Dr. G. Hohenberg, Technische Universität Darmstadt

Year

2008

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 672

Summary

At the 27th Vienna Motor Symposium in 2006 the hybrid drive of the Lexus RX 400h was already discussed from a theoretical as well as from a practical perspective. This presentation is a follow-up, reporting on the new Lexus LS 600h L.

What has changed since 2006?

The E-CVT transmission is designed as a so-called two-mode concept, which brings down consumption to acceptable levels even at high driving speeds.

By further improving the engine, the comfort of the hybrid system could be enhanced. The start/stop behavior was even further optimized versus the very good performance in this respect of the RX 400h. As far as this feature is concerned, the Lexus LS 600h L represents the state-of-the-art.

Unfortunately, the same cannot be said about the chassis and the electric brake system, which fail to meet the standard of other premium class cars.

When comparing the Lexus LS 600h L with other premium class vehicles in terms of fuel economy, it becomes obvious that the benefits of the hybrid concept cannot be compensated, not even by an intelligent, foresighted driver. The advantage in consumption in real traffic is self-evident, not only in relation to the gasoline engine but versus diesel-powered vehicles as well. The more foresighted the driving style, the higher is the saving potential compared to the diesel engine, which is often considered to be an alternative. The CO2 benefits which can be achieved in the urban cycle by intelligent driving are close to 30%, while a dynamic driving style clearly reduces this potential for the hybrid to about 10% in urban traffic. This explains the sometimes greatly differing test results for hybrid and diesel cars reported in the media.

Of course, the hybrid is no panacea for solving the current CO2 problem. In conclusion it is shown that hybrid and/or diesel alone will not be sufficient to achieve the CO2 targets which have been set. Under the aspect of an “intelligent simplicity”, the logical consequence can only be a downsizing of vehicles.

Order Members Login