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Drives: Z4 M40i
Join Date: Jan 2019
Location: South Florida
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Lucy: BMW's 720 HP Three Motor Electric Prototype
Lucy Footage at about 2:27-3:04:
https://jalopnik.com/i-rode-in-bmws-...opm-1835820250
Quote:
I Rode in BMW's Absurd 710 HP Electric 5 Series Development Car; Here's How It Works
BMW calls it “Lucy.” It’s 710 horsepower, 848 lb-ft, triple-electric-motor, one-off sedan that the automaker says can do 0-62 mph in 2.8 seconds. Lucy’s being used to develop future electric vehicles, and after getting a ride in this modified 5 Series, I can tell you that the thing is an absolute monster.
(Full Disclosure: BMW flew me business class to Munich, and put me up in a fine hotel just to show me cool car things.)
On Monday, BMW took a few journalists to the BMW and Mini Driving Academy in Maisach near Munich, Germany. There, the self-proclaimed purveyor of ultimate driving machines gave us a chance to ride in a G30 BMW 5 Series which had its floor modified to fit a 45 kWh battery, and its internal combustion engine replaced by three electric motors—one in front and two out back. Here’s a look at the development vehicle’s basic layout:
BMW said in a press release that modifying a standard 5 Series to create Lucy—which also goes by the name “Power BEV”—was a “serious technical undertaking,” particularly when you consider that the resulting trial car’s interior looks no different than a 5 Series’. There are no strange bulges or electronics boxes to speak of. Inside, it all looks pretty normal.
That’s one of the first things I noticed upon stepping in, but it’s definitely not the main thing I took away from the test ride that the BMW engineer gave me—no, what I remember most was absurd acceleration in every horizontal direction.
The video below won’t do the drive justice, in part, because it’s all just so quiet. But don’t let the relatively tame clip fool you, as inside my gut, violent turmoil was brewing. According to project manager Matthias Stangl, it’s this duality—this quiet nature and tame, standard 5 Series interior coupled with absolutely brutal acceleration—that got the Power BEV its nickname. It’s called Lucy, like Lucifer, a name that elicits thoughts of evil, but which actually means “bearer of light.”
The car’s three motors—rated at a combined 885 lb-ft of torque and 710 battery-limited horsepower according to BMW—helped the car defy its approximately 5,300 pound curb weight, accelerating out of the hole like a fighter jet off an aircraft carrier. When Torsten, the engineer at the helm, first smashed the pedal, the cell phone I was using to record nearly slapped me right in the face.
What’s just as impressive as the “longitudinal dynamics” (as BMW nerdily puts it) are what Germans called “Querdynamik,” or lateral behavior, and on that front, the Power BEV test vehicle was so impressive that I legitimately nearly vomited as Torsten chucked the Heavy-As-A-Full-Size-Truck sedan through a slalom and into a chicane. I almost regretted eating a delicious Butterbrezn immediately prior to the test drive. Almost.
This photo doesn’t show it, but upon exiting the cabin of the 710 horsepower EV beast, I was feeling woozy, as my internal organs attempted to shift back into their proper places.
It was in the turns that BMW was getting the most out of this test vehicle, as the company’s engineers use Lucy to really dial in and play with torque vectoring—which can be manipulated far more precisely than on a normal limited slip differential-containing road car, since Lucy contains two independent rear motors. It’s this lightning-quick torque vectoring that BMW says allows the vehicle to rotate so gracefully through the turns despite its heft. Per BMW’s press release:
Key to its dynamic attributes is that the two electric motors at the rear axle are controlled separately. This brings e-torque vectoring into play, which enables maximum drive power to be translated into forward propulsion even in extremely dynamic driving manoeuvres.
The result is more effective and precise than with a limited slip differential, because actively targeted inputs are possible in any driving situation. By contrast, a limited slip differential always reacts to a difference in rotation speed between the driven wheels.
I was curious to learn how BMW managed to fit the motors into the 5 Series, so Stangl, the project manager, drew the diagram above (I added the “Wheel,” “GB,” and “motor” designations). As shown here, the rear motors do not lie on the axle centerline and do not use a planetary gear reduction like you might see on other EVs like the Jaguar I-Pace. (Incidentally, BMW’s CTO Klaus Froehlich later told me that Jaguar is having a hell of a time making those planetary gearboxes work—I haven’t confirmed if this is true).
Instead, each gearbox output in the rear of Lucy is offset with its corresponding motor input, and the two motors are placed such that one sits further back and sends power forward, while the forward motor ultimately sends power rearward to its drive wheel. To fit this setup into the car, BMW engineers had to use up trunk space, mounting the drive units such that the 250 kW motors sit high, and send power down through the single-seed gearbox towards the wheels. Also taking up trunk space is some sort of box in the for the inverters for each of the two motors (based on my conversations with engineers, this did not seem to be integrated into the drive units).
Up front, though, the power electronics are integrated into a roughly 220-pound (100 kilogram) cast aluminum case that houses a motor and gearbox in what BMW dubs its “fifth-generation drive unit,” also called “HEAT.” I asked BMW engineers what that meant, and though they admitted that it was a bit of a backronym, they did say it meant “hoch integrierte elektronische Antriebstopologie,” which basically means “highly integrated electric powertrain.”
Cooling the 200 kW HEAT up front—a drive unit design also found on the upcoming iX3 crossover—is both water and oil, and BMW claims the setup has a maintenance-free target of over 186,000 miles (300,000 kilometers).
To clear up space for this drive unit up front, BMW says it used a modified suspension from a G12 7 Series, and the suspension out back is also similar to that of a standard steel coil spring-equipped 7.
As for the aforementioned small 45 kWh battery, BMW says it can do 10 laps around the track I rode on before needing a recharge. The company’s engineers say they’re not concerned about the small pack because the car is just being used for development, and is not meant to be sold to customers. Also, the 200 kW quick-charging capability makes it viable for BMW’s development tasks.
From the side, you can see the pack hanging below the rocker panels. The battery appears to be rather slim.
BMW wouldn’t discuss a whole lot about the pack, but did emphasize that the company had worked with a supplier to ensure very limited degradation of performance as the state of charge dropped. Mentioning the Tesla Model S’s alleged issues during track driving, a BMW engineer said: “[Our] focus was that this car stays on the same performance level over every state of charge.”
The Bavarian automaker says that this ridiculously quick 5 Series-based development tool, designed and built over a period of about 18 months, allows engineers to emulate the behavior of many different future BMW EVs with just a single demonstrator.
Stangl told me that his team can simulate the dynamic response of a heavier, taller car by simply making adjustments to the torque vectoring system. “You can make this car feel like it would be 500 kilos heavier,” he said. In addition, it’s simple enough to vary the car’s power level so that it provides insights into the performance of cars with different motor capabilities.
So basically, Lucy is a test bed for BMW’s EV development, allowing BMW to assess a number of vehicle functions. For example, engineers can use the car to look at different ways of seamlessly switching on a front motor during driving, they can understand the behavior caused by various levels of brake energy recuperation, they can determine the effects of different motor output ramp-up strategies, they can—per one BMW engineer—figure out “how a driver can control this much power without being scared,” and most importantly, they can play with the two rear motors to design a torque vectoring system that yields the best handling.
So even though it seems like a 710 horsepower jackhammer, Lucy is actually meant to facilitate official engineering work. Or at least, that’s what BMW tells me. I’m still not convinced they didn’t just build it for fun.
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Last edited by BMWGirlFL; 11-29-2020 at 05:32 AM..
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