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“Our goal was to make the hybrid system disappear into the car. We wanted to do it the way Porsche would have done it,” Vonnen CEO Chuck Moreland said about his company’s 2013 Porsche 911. The car was heavily modified to be electrified but doesn’t feel like it. It does feel pretty damn good, though.

If you were to stick an average Porsche driver behind the wheel of this custom-made hybrid, they’d never be able to tell that this wasn’t standard P-car fare. Once activated, if you’re paying close attention, you might hear the sharp high-pitched electric motor whirring away. You’d be a fool not to notice the intense electric power boost, though.

(Full Disclosure: Vonnen bought me a very nice lunch on the day of the drive. The company offered to cover travel expenses, but I organized time while I was already in the area, and told them there was no need.)

It doesn’t feel like the future. It feels pretty much like a 2013 Porsche 911. There’s no drama, it’s just freaking fast.

Porsche Didn’t Make A 911 Hybrid So Somebody Else Had To

Vonnen began as all good car ideas do, with a bit of bench racing. The electrified Porsche folks spun off from long-time Porsche suspension gurus Elephant Racing. And if you hang out in a shop full of Porsche enthusiasts all day, as the Elephant Racing guys do, you’re bound to talk about taking things to the next level.

When Porsche launched the 918 Hybrid, it got everyone in the shop thinking about adding electric performance. Where most would probably leave it at that, Moreland hired Davis, an electric propulsion engineer with experience at Tesla and in EV public transport, to see if he could spin off a new company focused on hybrid performance.

What It’s Like To Drive

It had been a while since I’ve driven a 991.1-generation 911. Basically, since they were new. Once I stepped aboard the Vonnen car, however, it all came flooding back. It’s familiar to anyone with 991 experience because the interior and exterior are essentially unchanged. You might notice the electric motor’s inverter box on the rear package shelf, or you might not. Otherwise, this car looks to be as it was from the Porsche factory.

The only new piece that is impossible to ignore is the phone on the dash. The Vonnen Shadow Drive app in the already-vintage Android phone is used as a controller for the hybrid drive system, as well as a gauge to keep the driver apprised of the system’s functionality. If you want to switch between the drive modes, there are buttons on the app for that. The big swooping dial that is the main focus of the app shows the system’s power delivery and regeneration. The bars at the bottom show system availability settings with readouts for battery and motor temperature, as well as state of charge.

While it’s fun to see the swing between power delivery and regen, I never saw the system unavailable or juice not ready for deployment. It might be easiest to just keep the phone in your pocket and leave the dash unadorned with anything that might alert your passenger that there is anything outside the ordinary under your throttle foot.

Vonnen modifies very few of the original Porsche components to install its hybrid drive system. In fact, the inverter on the back shelf and a single orange cable in the front trunk compartment are the only visual cues that this car is anything other than as the Germans in Stuttgart intended. And once installed, it’s all completely reversible. No drilling, cutting, welding. It’s all nuts and bolts.

Plopping the PDK gearbox into manual mode, I took off. I had the keys for the day, and some of the best roads in coastal California beckon just to the south and west of Vonnen’s San Jose shop. Any time you find a squiggly line on your maps app and head toward it, it’s always a good sign when you see sport bikers in oncoming lanes. This area of California is packed with two-wheelers, and the roads are equally good for sporty four-wheeled machines, too.

That’s exactly what I was looking for as I headed deep into the forested mountain spaghetti noodle roads. For the first bit of the day, I put the car into Sport mode, as that’s traditionally what you do when you find a curvy road, yes? In this case, that was totally the wrong move. Sport mode doesn’t activate until the higher end of the throttle pedal’s travel, and I quickly discovered that I was just driving a slightly heavier Carrera as the sharp corners were close enough together that I was rarely rousing the electric motor to assist.

When I did get enough of a straight to run the go pedal past its electric motor wake up call, I could tell it was packing a potent bite. With a fraction of a second between the e motor spooling up and needing to stab the brakes for the next corner, however, I soon found Sport mode’s fun a little elusive. I didn’t really figure out how potent the motor was until I clicked the button for Street mode.

Street mode moves the throttle actuation point further down the pedal’s path of travel, meaning you get a dose of electric boost earlier. Now, suddenly, the machine transforms underneath me. I’m getting a full surge of boost very early in the transition from apex to throttle. And I can keep that boost shoving me toward the apex like I just spooled a turbocharger that never taps out.

Houston, all engines running, we have lift off.

Vonnen fitted the test car with a set of sticky Michelin Pilot Sport Cup 2s, which are a far stickier tire than Porsche would have fitted to a Carrera in 2013. By virtue of stickier rubber, have the incredible ability to transition between full throttle and full brake—even mid-corner—without any fear of upsetting the 911’s balance. 991s have never been known for the unruly handling of 911s past, but this is proper supercar levels of grip and balance. Big meaty asphalt-gripping black rounders make good cars even better.

If you keep the system in Street or Sport modes, you’re not likely to run out of juice. Like, ever. The regenerative braking system works very well, and the batteries charge up during any off-throttle driving. Throw the car at a long series of tight twisty roads with a full battery, and you’ll probably come out the other end with enough charge to double back and do it again.

Similarly, I never once had an issue with overheating the electric system. This surprised me, considering the electric motor is hidden down inside the transmission bellhousing. But it is water-cooled with its own coolant circuit and air-to-water heat exchanger, as are the batteries. If you’re hitting the e juice heavy, as you might in Overboost mode, you can see the temperatures rising in the app. But if you’re just dipping into the kW pool for a second between corners, the cooling can more than keep up with your throttle foot.

I spent a few hours driving this and I wanted to go a few more. Addiction is a disease, and I’ve been infected with it by the shrill siren shriek of Vonnen’s thin electric assistant. If the Porsche flat-six is the President of engines, this hybrid drive unit is its Veep. I’ll vote for that platform every four years for the rest of my life. I’ve been indoctrinated into the party of electric performance. A Porsche in every driveway, and a hybrid drive in every bellhousing!

How It Works

The tech behind Vonnen’s so-called Shadow Drive hybrid system is fascinating. It’s astonishing that all of this advanced science is available from an independent go-fast shop today, where you would have been lucky to see anything like this from an OEM as little as a decade ago.

The company won’t let on what battery chemistry it is using but says it is “military-grade” and is already in use by an OEM EV manufacturer. It’s lithium-based and focuses on power density over energy density. “To get the same level of energy from a traditional hybrid battery, our pack would have to be four times the size,” says VP of Engineering Bill Davis. The 144-cell 400-amp battery pack is small to keep weight in check—down to just 80 pounds in the front trunk—but charge and deploy deeply and quickly.

The electric motor is only 25 mm thick—sandwiched between the engine and transmission—provides a rabid and manic 150 horsepower and 150 lb-ft of torque in assistance to the 991.1’s already-potent naturally-aspirated 3.4-liter flat-six. Road & Track ran this system on a dyno, and the results are pretty interesting if you’re into data.

The car’s hybrid system works in three different modes. Street and Sport modes provide about two-thirds of the electric motor’s boost power. With Street mode that power is doled out at about quarter-throttle. In Sport mode that power is reserved until the pedal is half-way to the metal. The former is excellent for stoplight blasts and back road mountain drives. The latter is best reserved for track use or roads with lots of big open spaces. On tighter roads, you’ll hardly ever get to half-throttle.

Because the hybrid drive works this way, it encourages those of us without reservation to push the throttle down farther and harder, which isn’t really conducive to getting good fuel economy. Sure, it’ll help a little if you don’t drive like a hooligan, but what’s the fun in that? This hybrid can be considered “green performance” in that it provides similar power to a pair of turbochargers without any fuel economy penalty, but really it’s performance first and green second.

The third mode, Overboost, isn’t really something I found all that useful. In this mode, you get the motor’s full beans at full throttle application, but you’ll blow through the battery’s juice in just a few pulls. It’s most useful for long straights to impress your friends or, one supposes, drag racing.

The History Of ‘Shadow Drive’

Photo: Bradley Brownell

Upon walking into the Vonnen shop, shared with sister company Elephant Racing, a Porsche suspension specialist, I spotted this silver pre-2001 996-generation 911 with OZ wheels and the GT3-aping Aerokit option. Because I am a 996 enthusiast, I had to ask all about it. It just so happens that this car was the first Vonnen prototype.

Once the decision was made to push this project through to fruition, the idea was always to be a consumer product when all was said and done. The goal was to use an existing Porsche architecture and to add power with hybrid-electric propulsion. The initial design used the aforementioned 996, an all-wheel drive model. The batteries and controllers were shoved into the front trunk, and the motor was fitted into the driveshaft tunnel to the transmission’s output shaft which would traditionally have connected the transmission to the front axle via the driveshaft.

Photo: Bradley Brownell

That first design was a bit lackluster, as it was on the wrong side of the transmission’s gear reduction torque multiplier. It was also totally restricted to AWD 911 applications; Carrera 4, Carrera 4S, and Turbo. It was in Vonnen’s best interest to find another route because this was a very small segment of the Porsche market, and the car would lose its AWD in the process.

Cut. Back to one. And... action.

Within three years of starting this project, Vonnen had a working prototype. This time with the current model’s sandwiched motor, which replaces the car’s flywheel in both manual and PDK applications. That 25mm plate does move the transmission forward in the chassis by the same amount. In two-wheel drive models this causes no issues. In all-wheel drive models, the driveshaft between the transaxle and the front transfer case must be shortened by the same amount.

The prototype shown here was unveiled last year at Porsche Rennsport Reunion and has been continually tweaked and revised since then. Vonnen says that there are a handful of customer cars ready for install, but the production-series electric motor unit, which is said to be 30 percent more thermodynamically efficient, is still inbound. Once that new motor unit is put through its testing paces, customers will have the full suite installed and on their driveway sometime early next year.

The Shadow Drive system is an option for any Porsche featuring a 9A1-based direct injection engine. This means all 911s from 2008 until at least 2019, and all Cayman/Boxster from 987.2 and 981 up through the current 718s. The system should function on the 992-generation 911s being delivered now, but Vonnen hasn’t had one on hand to test yet, obviously, so haven’t committed that information to stone quite yet.

What’s Great

I don’t say this lightly, but almost everything is great about this car. On the face of it, this is a 991.1 Carrera PDK with sticky Michelin Pilot Sport Cup 2 tires. That’s inarguably a great platform to start with.

The full Vonnen system weighs around 170 pounds all-in. This, of course, includes the weight lost from the removal of the extremely heavy flywheel. The Shadow Drive is like a wizard that rides as a passenger in your car and magically provides you an extra 150 horsepower boost whenever you feel like it. Unless you’re driving a stock Carrera back to back with the Vonnen Carrera, you’ll never notice the extra weight, but you’ll sure as shit notice the extra power.

Image: Bradley Brownell

A white Carrera is generally an understated car, but when you give the wheels and the engine lid wing an eye-searing shade of orange, it absolutely transforms into an attention-grabber. Why orange? It’s the color of the high-voltage cables used for the hybrid system. Obviously the company has the windshield banner and door decals to make sure everyone knows the name, but ditch those and it’s a very attractive color palette.

And finally, I asked Moreland where the Vonnen name came from. He laughed and shrugged, replying “Some say a Vonnen is an old Viking ship that used a hybrid of sails and oars... Some say we made that whole thing up.” Good to have a sense of humor about such things.

What’s Weak

In an effort to make the 991 hybrid a more daily-usable sports car, this thing is absolutely begging for an eco-mode. To take some of the stress off of the ICE flat-six, add some highway assist or some around-town assist just after the tires initially roll out. Even a few MPGs and a bit fewer emissions would be a step to help offset the cost of this electric-add-on.

Speaking of cost, it’s godawful expensive. At $75,000, this is little more than a toy for the wealthy. I mean, it is a Porsche, so you’ll have some of that anyhow, but the Shadow Drive system costs more than the 2013 Porsche 911 Carrera it’s installed in.

It’s so damn close to ready for prime time status that the little issues I found are glaring. For example, because the electric motor replaces the car’s starter, the Vonnen system has to boot up before you can start the car. If you leave the car turned off for a little while, while at lunch, for example, you are forced to wait for a second or two to boot up. This has an easy workaround, as you can simply change your startup procedure. Get in, turn key to on, put on your belt, adjust your seat and mirrors, start the motor. It’s a minor annoyance, but an annoyance all the same.

Image: Bradley Brownell

Similarly, I am torn on the Vonnen system operating from a smart phone app. For one thing, the inexpensive and already dated Android phone employed for this prototype was slow to react—press the desired mode and wait several seconds for the switch to occur kind of slow—and the user interface was bare-bones at best. Vonnen promises that the app will be updated for customer use, but this alpha prototype has been driving around for over a year, and has been tested by other outlets before, so I expected little problems like this to have been solved by now.

It is nice that all of the controls are contained within the screen of your cell phone, and can be hidden from sight when you don’t feel like looking at an electric performance gauge. But, for the incredibly high asking price, I would have expected a hard button to toggle between driving modes, perhaps replacing one of the Porsche blanking plates in the Carrera’s center console. I’m no programmer, but surely you can wire a switch straight to the controller just as easily as you can Bluetooth it.

And finally, it’s a minor gripe, but you do lose the bottom 6 inches or so of storage space in the front trunk compartment. There is still plenty of room for two overnight bags, or a single carry-on roller bag, but you do lose some storage space.

In Conclusion

From a mechanical standpoint, this power adder makes a lot of sense. Your Porsche will still pass every tailpipe emissions test with flying colors. You won’t change the car’s NVH levels appreciably, which is nice if you’re running track days at a place like Laguna Seca which has strict noise limits. This system is completely reversible, meaning you won’t hurt the long term value of some rare paint-to-sample GT3 RS or Speedster.

Vonnen says that advances in the system are coming down the pike. I was told of the virtues of using your phone’s GPS to geotarget automatic hybrid deployment down long straights at the race track. Maybe that eco-mode will make an appearance somewhere, too. I can only hope.

The short term plan is to engineer this same system to operate in G50-transmission air-cooled Porsches as well. The totally reversible aspect appeals well to folks with cars that are still appreciating rapidly. And, if you’re looking for an extra 150 horsepower in an air-cooled car, it’ll probably cost you a lot more than $75,000.

A lot of people have commented that this system has a very limited use case, myself among them. But, imagine if you can, this hybrid system being offered as an option for your new 911 Reimagined By Singer. That would seriously rip, and the folks forking out for a Singer certainly have the dosh to pony for the delightfully addicting sensation of instant-on hybrid boost.

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About the author

Bradley Brownell

Jalopnik contributor with a love for everything sketchy and eclectic.