At BMW, hybrid powertrains have gotten off to a slow start, but they’re about to pick up steam. The company rolled out a mild hybrid version of the 7-series and a full-hybrid X6 in 2009. The X6, however, was quietly dropped at the end of last year, and the ActiveHybrid 7 hasn’t exactly been a big seller. This year, however, sees the debut of the hybrid 5-series, out this spring, followed this fall by a hybrid version of the new 3-series sedan.
From 8 to 6
Whereas the company’s first two hybrids used a turbocharged V-8, the hybrid powertrain debuting on the ActiveHybrid 5 -- and in the upcoming 3-series -- is based on the N55 turbocharged straight six.
The 300-hp twin-scroll turbo six, which powers the 535i and 335i (among others), is here supplemented by a 54-hp electric motor fed by a lithium-ion battery. That electric motor is located in the bell housing of the 8-speed automatic transmission, and it takes the place of a torque converter. Because this is a full hybrid, the electric motor can power the car on its own, at speeds up to 37 mph. Like the Porsche Cayenne hybrid, the ActiveHybrid 5 also can coast with the engine off, at speeds up to 100 mph; and of course, it can shut down its engine at a stop.
Endorsement: It doesn’t drive like a hybrid
Despite all this, the ActiveHybrid 5 drives exactly like a 535i. The added oomph from the electric drive system -- which bolsters total power output from 300 to 335 hp, and torque from 300 pound feet to 332 -- negates the roughly 300-pound weight penalty of the hybrid. BMW’s 0-60 figure of 5.7 seconds for this car exactly matches that of the 535i. Interestingly, that 0-to-60 time and total horsepower figure are also near matches for those of the new Lexus GS hybrid (338 hp and 5.6 seconds to 60). However, unlike the GS450h, which uses a CVT, the ActiveHybrid 5’s 8-speed automatic (or, optionally, 8-speed sport automatic, which features quicker shift times and paddle shifters) which means there’s not the elastic throttle response and strange rev characteristics you get with a CVT.
Additionally, brake pedal feel is totally normal and the electrically assisted power steering (which is in traditional 5-series as well) is very nicely weighted. The powertrain is absolutely seamless. There is no whirring from the electric motor and no shudder when the gasoline engine fires up or cuts out. Unless you’re gazing at the powertrain schematic on the standard split-screen LCD, you’re likely only to be aware of what the engine is doing or not doing if you happen to notice the tach needle drop to zero or bounce back up again.
The degree to which the car takes advantage of the electric drive system is somewhat customizable. As in many BMWs, there’s a driving dynamics mode selector, with Sport-plus, Sport, Comfort, Comfort-plus, and Eco Pro modes -- Comfort-plus with the optional adaptive dampers only. Besides damping, the modes affect transmission and throttle mapping. Additionally, Eco Pro uses the climate control more efficiently and electric drive more aggressively. Eco Pro is also in non-hybrid BMWs -- other 5-series models and the new 328i sedan -- and while we hated its lazy throttle mapping in the 328i, here it’s much better; it’s quite livable, particularly around town.
All this is not to say that the hybrid is totally free of drawbacks. The most notable is reduced trunk space. The battery pack is located behind the back seat and as a result, cargo volume drops by roughly one third. Also, the hybrid cannot be had with all-wheel drive. Oh, and there’s the price penalty. At $61,845, the hybrid is a cool $8500 more expensive than the 535i, although it does come with more standard equipment (such as navigation). Depending on your point of view, the fact that the hybrid looks little different from the 535i also might be a negative; besides the badging, its visual distinctions are its “streamline” 18-inch wheels and, on our test car, the bluewater blue paint -- both hybrid exclusives.
What about fuel economy!?
Ah, yes. This is a hybrid, so some mention of fuel economy is probably in order. Well, EPA figures are not yet available, but BMW expects the hybrid 5 to better the fuel economy of the 535i by 12 to 13 percent. That would mean a city estimate of 24 mpg and a highway figure of 35 mpg -- those are a hair better than the four-cylinder 528i, which gets 23/34 mpg. The Lexus GS hybrid, by comparison, is rated at 29/34 mpg.
Philosophically, one wonders why BMW didn’t use its most fuel-miserly 5-series engine -- the 528i’s 2.0-liter turbo four -- for the ActiveHybrid 5. Christian Schulte, project manager for the ActiveHybrid 5, gave three reasons.
First, because of the price demanded by the hybrid, the feeling was that customers spending that kind of money would want very dynamic performance, more than what you would get using the turbo four. (Although one can option up a 528i past $60,000 pretty easily.)
Second, the hybrid’s fuel-economy advantage over the non-hybrid version of the same engine would not have been as great with the four-cylinder as it is with the six, and thus it would be harder to justify the hybrid upcharge.
Finally, he characterized the 535i customers as buyers who are very interested in having the latest technology.
This thinking is also why the upcoming ActiveHybrid 3 will use the turbo six as well.
Evidently, BMW sees a hybrid powertrain not as a way to achieve headline-making MPG numbers, but as a way to deliver both high performance and very good fuel economy. The thing is, hybrid buyers really prize fuel economy; that’s why they buy a hybrid. And with BMW’s direct-injected turbo four already offering good performance in the 528i (and the 328i), it seems that BMW would better meet the expectations of hybrid buyers by using that engine to create the hybrid iteration with the best possible mileage. As it stands now, however, what buyers of the ActiveHybrid 5 instead get for their extra money is the performance of a turbo six with the economy of a four-cylinder. They get it in a car with very few compromises, and no dilution of driving pleasure. Maybe that will be enough.