SUVs, or SAVs for those that want to stick to the BMW nomenclature, are undisputed for their utility by drivers everywhere. In addition to the ability to haul and tow large loads, drivers enjoy the higher seating position and spacious interiors. The trade off of course comes in fuel economy; driving around a 5,000lbs box is less then optimal for fuel efficiency.
Environmental responsibility, or cost at the pump, have been valid reasons for buyers to shy away from SAVs. This presents an opportunity for BMW. How do you make a more fuel efficient X5? The obvious first solution is to put a smaller, lighter, and more fuel efficient engine in it. The BMW N20 TwinPower turbo 4 cylinder fits the bill and makes a respectable 245hp and 255lbs-ft of torque. The motor has been well received in the 3, 4 and 5 series and moves them along nicely. In the X5, with an additional 800lbs, BMW needs to add something more exotic to retain the driving experience.
Enter eDrive. This is BMW's term for stealing tech from the BMW i8 and adding it to a series vehicle. The i8's speed, 0-62mph in 4.4, comes from combining a 3 cylinder gasoline engine and an electric motor. The X5 eDrive benefits from the same combination. Take the award winning 4 cylinder N20 for fuel economy, add a BMW i electric motor (eMotor) and you have a fuel efficient, green SAV that drives like a BMW.
The BMW X5 eDrive alternates between the gasoline engine and the electric motor giving you the best of both worlds. The default mode is AUTO eDrive, meaning the computer decides how to best use the two power sources. From a standstill the eMotor moves you off the line with 185ft-lbs of torque available from zero RPM pulling away you have more torque available then the X5 M5. The eMotor spins out 95 horsepower, which doesn't sound like much but does a surprising job of moving around the 5300-ish pounds the X eDrive weight in at. Continue to push the go pedal, a very suitable name in this case, and you'll cue the computer to fire up the 4 cylinder and feed in the power. With the gasoline engine running, the eMotor takes a secondary roll 'torque filling'. Basically this means it adds power to the drivetrain as needed. As the turbo spools up, the eMotor's instant torque on demand makes a big difference. BMW did not simply bolt two motors together to get the sum of the outputs; they use each to complement the other for a driving experience greater then the sum of the individual parts.
How does this mechanically all work? The N20 4 cylinder sits under the hood where you would expect. Behind the TwinPower engine is an electronically actuated clutch. The clutch is similar to what you'd find in a manual transmission car. The clutch allows the computer to couple and decouple the engine from the drivetrain, meaning in eMode the internal combustion engine is 100% out of the loop. Behind the clutch is the eMotor, taking the place of the torque converter in the transmission. Interestingly the eMotor also replaces the alternator keeping the eDrive battery and the standard 12v car battery charged. Behind the eMotor is the same ZF 8 speed found in the X5 and coupled to that is the standard X5 xDrive system. It was critical to BMW that eDrive not take away any capability from the X5, including xDrive. Having all four wheels connected back to the eMotor also means the regenerative braking can be more aggressive as regenerative braking force can be balanced across the front and rear axle.
BMW X5 Drivetrain Highlights
- Combined output of 270+ horsepower and 300+lb-ft of torque
- N20 4 cylinder TwinPower gasoline engine makes 245hp, 255lb-ft
- eMotor is BMW designed, ZF built and puts out 95hp and 185lb-ft
- eMotor alone can power the X5 15-20 miles
- Battery pack tucked safely under rear trunk floor
- Electronics borrowed from BMW i and applied to X5
- Estimated US miles per gallon of 62 MPG puts total range of 1388 miles
- Electronically actuated clutch can completely decouple engine from drivetrain
- 8 speed ZF transmission and xDrive retained, no impact on X5 capabilities
How does all this technology actually drive down the road? Setting off in the X5 eDrive is very similar to the BMW i3 or i8. The car is 'on' but the engine isn't running and that takes getting use to. Put it into drive as you would normally and you pull away silently under eMotor power. Driving around the computer seamlessly adds gasoline power as needed; the switch over is almost imperceivable. Once you get use to the silent pull away and stop referencing the tachometer as a measure of speed, the driving is no different from the X5 xDrive35i model. With a conservative combined power output of 270+ horses and 300lb-ft of turning force, the power output is on par with the 35i N55 numbers. BMW designed the AUTO eDrive, and set it as the default, so in your daily drive you forget you're driving a hybrid. Amazingly it works, driving the X5 eDrive is unobtrusive, gives you the power of the 35i when you need it and the fuel economy of the 4 cylinder when you don't.
This is the third generation of BMW's hybrid electronic drive system and from the driving experience the 10+ years of R&D have paid off. It is a highly tuned system that gives you the best of both worlds, a giant utility vehicle with seating for 7 and the fuel economy of a sedan.
Sound too good to be true? Having driven the BMW eDrive I can tell you it works and it works well. It is a hybrid green car for someone who doesn't want to schedule their life around a vehicle's recharging schedule. It is a range topping SUV that sips fuel giving you a theoretical 1350 miles between fill ups. The question remains when will it comes to market, and what it will cost. BMW says it won't come to market in the 2015 model year. Stay tuned for production details and pricing which may be the determining factor on whether this model will be successful.
Official BMW X5 eDrive Concept Press Release
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