Vonnen's Shadow Drive system adds an electric motor—and a whole lot of power—to the venerable sports car.
Having finally fought my way out of the congestion choking the San Jose suburbs, I take the 2013 Porsche 911 Carrera climbing up Skyline Boulevard. The 911 is an ideal match for the hills of Northern California, a lovely mix of balance and power. But Bill Davis, riding shotgun, isn’t here to sell me on a six-year-old car. “Floor it,” he says. Once my foot’s all the way down, he taps the smartphone mounted on the dashboard to engage the Vonnen Shadow Drive system. He’s part of the team that added an electric motor to the Porsche’s powertrain, making it a hybrid. And not the kind that’s going to save the planet.
Instantly, that motor kicks in, boosting the native engine’s horsepower and torque by roughly 50 percent and giving me an idea of how Popeye feels after gulping spinach. Instead of punching a gang of no-goodniks out of the frame, though, I’m tearing through the hills of Northern California. “Oooooohhhhhhhhh,” I say, before getting on the brake and heading into a corner.
That oooooohhhhhhhhh is what Davis and his colleagues at Vonnen have spent the last three years developing. For $75,000, their Shadow Drive system will turn a wide range of Porsche 911s into high-performance hybrids, using a motor and a small battery to add 150 horsepower and pound-feet of torque to an already impressive powertrain. In an age where electric cars are finally getting recognized for their performance, it’s a way to offer those benefits to the folks who cling to their older machines. Over the coming years, Vonnen will work to make its system compatible with older generations of the 911, and then they hope to bring it to other makes and types of vehicles. They could even target pickup truck drivers. “It’s all about torque,” says Vonnen boss Chuck Moreland.
Vonnen's custom-designed motor takes the place of the car’s native flywheel, between the engine and the transaxle.
Vonnen is a new branch of Elephant Racing, a shop Moreland opened about 20 years ago, after fleeing the tech industry during the dot-com bubble crash. (He had been working on what we now call cloud computing.) Based in Santa Clara, the shop modifies and maintains Porsches; many of its clients are weekend racers who want beefed-up suspensions to take to the track. The notion of hybridizing the cars came up over lunch one day. Ferrari and McLaren had combined electric and engine power to make newly potent supercars. So had Porsche itself, with the 918 Spyder. So why not find a way to bring the trend to older sports cars? “It was one of those crazy ideas that wouldn’t go away,” according to Moreland.
The 911 was a good candidate for the experimental operation. First, Moreland and his crew know the car well. Porsche owners tend not to be overly price-sensitive. While many are purists (typically deriding whatever change Porsche made to the car that followed theirs), the enduring success of mod shops like Singer, Guntherwerks, and Magnus Walkerson shows there’s plenty of appetite for alterations. Plus, the rear-engine, rear-wheel-drive layout would work well for the setup they had in mind when they started the project.
That first attempt involved putting an off-the-shelf motor outside of the engine, in front of the passenger compartment. “It was a bit crude,” Moreland says. It felt tacked on (or rather, jammed in). It wouldn’t translate well to other kinds of cars. Most importantly, it only delivered serious power in the upper gears—meaning once the car was already moving at speed. Moreland wanted to do better, with a solution that was as elegant as the 911 itself.
The team—just three full-time employees, with the odd contractor pitching in—found another way. Their custom-designed motor takes the place of the car’s native flywheel, between the engine and the transaxle. (The motor doubles as a flywheel, so the car still gets the rotational inertia that smooths out the vibration of the combustion engine.) The motor is about the size of a small pizza, and fits nicely into the bell housing, the bit of the transmission that covers the flywheel and the clutch.
For the 911 we took into the hills, the Vonnen team had to move the transmission forward about an inch, requiring some new brackets near the front of the car to support it properly. That’s a relatively minor change. The whole idea, Moreland says, was to devise a system that can make hybrids out of cars whose designers thought only of gasoline. And this solution put the motor in a place where it adds power to every gear, including the low ones where drivers looking to accelerate off the line or around a bend most appreciate the extra torque. Because it connects directly to the engine, the motor can’t be run by itself, meaning the car can’t drive on electricity alone. But that’s not the point of this system, anyway.
The 1-kWh battery fits into the bottom of the trunk and is designed to release a lot of power very quickly. “It’s like a small fuel tank with a fat hose,” says Vonnen engineering chief Bill Davis.
The point is the extra strength, especially the torque. At just 2,000 rpm, the hybrid setup boosts the 2013 911’s pulling power by 61 percent. According to Road & Track testing, the system cuts the car’s 0 to 60 mph time from 5.0 seconds to 3.6. Instead of taking 6.4 seconds to go from 50 to 70 mph, it takes 3.9. That power kicks in seamlessly, earning the “Shadow Drive” name. You don’t have to wait for a turbocharger to spin up; you don’t have to redline the engine to feel the boost. It’s like driving the car downhill, or having Hafþór Júlíus Björnsson help you out in an arm-wrestling match. Whatever the metaphor, it makes the car potent, without compromising the balanced nature of the 911.
The battery is good for a single kilowatt-hour (a Chevy Bolt offers 60), and fits into the bottom of the trunk (which in the 911 is up front). Moreland declined to name the “major manufacturer” that provides the pack, but says his team selected it for its ability to deliver lots of power, real quick. “It’s like a small fuel tank with a fat hose,” says Davis, Vonnen’s engineering chief. The inverter, which translates the AC power made from regenerative braking to the DC sort the battery can use, sits in a silver box on the 911’s “parcel shelf,” behind the seats and over the engine. Gleaming silver and the size of two stacked VCRs, it’s the only visible bit of the Shadow Drive setup.
Right now, Vonnen can build its system into any 911 built between 2012 and 2019 (the seventh, or 991, generation of the car). Installation takes about a week in its Santa Clara shop, but Moreland and Davis expect to get more efficient, and they want to strike deals with other shops around the world to reach customers who don’t feel like sending their cars to Northern California. They offer a one-year warranty and are considering going longer. That’s a good thing, since Porsche itself notes it has the right to deny warranty coverage for “unapproved modifications.”
Vonnen’s next step will be making the tweaks necessary to fit Shadow Drive into older generations of the car. It’s only fair, it seems, to give folks driving decades-old cars a taste of what a new kind of powertrain can do. “A 1970s 911, by modern standards, is not a fast car,” Moreland says. Indeed, the 1973 edition 914 he bought when he was 20 years old offered about 100 pound-feet of torque. The Vonnen system would more than double its output.
Altogether, the system adds about 170 pounds to the car, counting the weight lost from the ditching of the original flywheel and downsizing the 12-volt battery the car no longer needs. That’s not much more than the difference between a full and empty gas tank, or the person you’re likely to have riding along and enjoying the fun.
And considering how fun it is, you’ll definitely want to bring a friend along, if only to see them have their own oooooohhhhhhhhh moment.
Corrected, 6-10-19, 8:55pm ET: An earlier version of this story misstated the types of power created by regenerative braking and the type of power the battery can use. It also implied that the typical 12-volt battery had been eliminated; it has been downsized but not eliminated.
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