If you’ve ever driven in Japan you can easily understand why Japan’s automakers were first off the mark with hybrid-drive cars in production. Their traffic is dense. The concept of hybrid propulsion, combining both a petrol engine and electric drive with batteries and a control system that decides which to use when, pays off best in slow stop-and-start driving like that in Japan. It’s of little value on the highway, writes Karl Ludvigsen.
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That this would be so is not exactly news. A 1981 investigation by Volkswagen and General Electric concluded (slightly edited) as follows:
‘It is clear that the attractiveness of the hybrid vehicle is a strong function of daily driving distances. For daily ranges of 25 miles or less, the use of the hybrid would result in saving a large fraction of the fuel use by an internal-combustion (IC) car of the same passenger-carrying capacity. For much longer daily urban ranges and highway driving, the hybrid is much less attractive.’
Last April, after the passage of 25 years, researcher and author Jamie Lincoln Kitman highlighted the same shortcoming of the hybrid in remarks in the International Herald Tribune:
‘As consumers and governments at every level climb onto the hybrid bandwagon, there is the very real danger of elevating the technology at the expense of the intended outcome — saving gas. Just because a car has so-called hybrid technology doesn’t mean it’s doing more to help the environment or to reduce the country’s dependence on imported oil any more than a non-hybrid car. The car that started the hybrid craze, the Toyota Prius, is lauded for squeezing 40 or more miles out of a gallon of gas, and it really can. But only when it’s being driven around town.’
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By GlobalDataThe Prius, added Kitman, spends ‘most of its highway time running on gasoline because at higher speeds the batteries quickly get exhausted.’ He’s rightly concerned that people will be buying hybrids just because it’s the new buzzword, not because they’ve actually considered the real-world fuel economy they’ll be getting.
Insufficient attention is being given to the engines that are used in hybrid vehicles. In 1975 a University of Wisconsin study reached the following conclusions:
‘The hybrid vehicle is complex, expensive, difficult to maintain, heavy and ill-suited to highway driving. A hybrid vehicle with an IC engine small enough to obtain significantly higher mileage than present-day cars will be unable, because of that small engine, to cruise for long periods of time at highway driving speeds; and a hybrid vehicle with an IC engine large enough for continuous highway driving will not be able to achieve significant improvements in mileage. A worthwhile hybrid vehicle may be possible but only with a heat engine different from those now commonly employed.’
Since that was written the small-engined hybrid has been helped significantly by improved car aerodynamics and higher-performance engine design. But the fundamental point remains valid: no hybrid can be better than its base IC engine. This is what designers and buyers should be assessing in weighing the merits of a hybrid vehicle.
This point was made forcefully by a senior BMW engineer at a recent technical exposition in Munich. He was frankly dismissive of the engines in Toyota’s hybrids. ‘As a basis,’ he said, ‘you need a good engine and a gearbox with mechanical gears. Then you can use electricity for the recovery of energy and the accessories. With that, in a hybrid you can get a 10 percent economy improvement if you use small higher-revving electric motors that are less heavy.’
BMW recently announced that it was partnering with General Motors and DaimlerChrysler in the application to its products of GM’s so-called two-mode hybrid drive. It will be well suited to BMW’s bigger products. But the Munich firm will take a different approach in the drive’s application, the engineer said. ‘Toyota has a 100-kilogram battery pack with a 40-kilowatt capacity,’ he said. ‘But with 100 kilograms of capacitors you have 400 kilowatts! For BMW it has to be light and powerful!’
Emphasising what they call ‘Efficient Dynamics’, the BMW engineers showed the results of some of their latest researches into engines that are fuel-sipping without losing their zip and zing. ‘High performance at reasonable fuel consumption is an important objective for us when developing engines and vehicles for the BMW Group,’ said Prof. Burkhard Göschel, management board member for technology. ‘Mobility as we understand it means continuing to offer the sporting flair, safety, convenience and driving pleasure people are used to.’
Impressively, BMW has been working through the entire vehicle power train to find fuel savings and performance enhancements. Added to its unique Valvetronic induction system is an impressive use of high-precision fuel injection close to the spark plug that achieves charge stratification, allowing extremely lean part-load fuel/air ratios. The result has been a dramatic 10 per cent reduction of fuel use on the EU’s test cycle. Consumption in relaxed driving on normal roads is niggardly, easily in excess of 200 miles per gallon. ‘We have never seen fuel economy like that on the road before,’ said BMW’s Klaus Borgmann. ‘We expect real advantages against the competition.’
BMW’s energy-saving measures include electric power steering, electric drive for the water pump and an ingenious alternator control that heightens the battery charge when braking and cuts out electricity generation when accelerating. Other important savings come from lighter vehicle construction and better aerodynamics, thanks to underbody cladding. Improvements to its 6-speed automatics will deliver a 3 per cent economy improvement with gasoline engines and an impressive 6 per cent with diesels on the EU driving cycle.
BMW has already shown a system that stops the engine when the car stops, starting it again when the driver takes his foot off the brake. Offering important fuel savings, this will come to the market in 2007 in Europe. In combination with the alternator control, said Klaus Borgmann, this gives ‘about an 8 percent fuel-economy improvement, depending on the driving cycle. That’s about half the value of a hybrid system. We will introduce this in Europe on a broad range of cars because it’s not so expensive.’
So…are hybrids the answer? That depends on the question, but in general the answer is no. For decades researchers have been telling us that a hybrid system is no better than its IC engine. BMW’s findings confirm that the venerable piston engine can still deliver impressive results without hybrid band-aids. What we need now are new fuel-consumption testing regimes that will better represent real-world experience. With their help, customers will be able to make intelligent choices of the cars whose fuel economy best suits their driving needs.
– Karl Ludvigsen
Karl Ludvigsen is an award-winning author, historian and consultant who has worked in senior positions for GM, Fiat and Ford. In the 1980s and 1990s he ran the London-based motor-industry management consultancy, Ludvigsen Associates. He is currently an independent consultant and the author of more than three dozen books about cars and the motor industry, including Creating the Customer-Driven Car Company.
