HomeMediaElectric-hybrid retrofit adds up to 150 horsepower to Porsche 911

Electric-hybrid retrofit adds up to 150 horsepower to Porsche 911

Manufacturer collaborates with Kelly-Moss racing team to produce 991 turbo show car with safari treatment


Want to add a quick, clean 150 horsepower to your Porsche 911? 

Vonnen, a California electric-hybrid manufacturer, has developed a plug-in kit that provides added power without losing fuel economy or effecting engine emissions.

Called Shadow Drive, it’s a retrofit electric kit for Porsche 911, Boxster and Cayman that replaces the engine flywheel with a slim electric motor/generator powered by a battery pack mounted up front. 

A control unit monitors driving conditions to add as much as 150 horsepower and 150 pound-feet of torque on top of the flat-six-cylinder gas engine’s existing power, including the already strong output of turbocharged models.  The hybrid drive also provides the instantaneous torque of an electric motor.

“Shadow Drive represents a novel approach to hybridization that is capable of fitting into vehicles with space constraints, while keeping weight impact to a minimum,” according to a Vonnen news release.

Kelly-Moss built the Porsche 911 Turbo safari car with the Vonnen hybrid system

Vonnen and Kelly-Moss Road and Race of Madison, Wisconsin, recently collaborated on a 2014 Porsche 911 Turbo S that’s not only boosted by Shadow Drive but designed with a rally-style safari treatment, for which Kelly-Moss is known.

The custom 991-series Porsche marks the start of KMR as a certified reseller installer of Vonnen’s performance hybrid system, according to a Vonnen news release.

“KMR is the caliber of partner that will serve customers well in the Midwest region,” Chuck Moreland, founder and chief executive of Vonnen, said in the release.  “They are highly respected in the Porsche community with a well-earned reputation for competence and quality earned through their rich racing heritage and popular safari cars.”

The motor flywheel adds power as well as regenerating electricity for the battery pack | Vonnen

Andy Kilcoyne, KMR director of operations, said the electric hybrid system will add a new level of excitement to its custom Porsche products.

“The experience Shadow Drive provides is both impressive and addictive, and we can’t wait to offer this unique tuning solution to our customers,” Kilcoyne said. “The ability to boost power without trading off fuel economy, emissions, and drivability really sets it apart from traditional power adders.

“It’s like adding the instant torque of a Tesla to the raw driving excitement of a Porsche – the best of both worlds. We are confident that our customers will find it a welcome addition to both stock and modified cars alike.”

The Shadow Drive system is a pricey addition, which Vonnen says costs $75,000 to have installed on a customer’s car.  The system can be uninstalled with relative ease if a customer wants to return the car to stock for resale or other reasons.

The KMR safari 911 includes other engine-performance mods besides Shadow Drive, including Xona rotor turbos, Tial wastegates, CSF intercoolers, fresh-air intake, Boost Logic headers and titanium exhaust.

KMR also added Braid Winrace T wheels with Yokohama Advan V601 tires, Motion Control Suspension adjustable coil-over shocks with a 2-inch lift, Baja Designs LED lights and a custom wrap.

The KMR custom 991 will be on the show circuit in the coming year, appearing at such venues as the Amelia Island Concours week, Das Renn Treffen and Caffeine and Octane in Atlanta, the company says.

Bob Golfen
Bob Golfen
Bob Golfen is a longtime automotive writer and editor, focusing on new vehicles, collector cars, car culture and the automotive lifestyle. He is the former automotive writer and editor for The Arizona Republic and SPEED.com, the website for the SPEED motorsports channel. He has written free-lance articles for a number of publications, including Autoweek, The New York Times and Barrett-Jackson auction catalogs. A collector car enthusiast with a wide range of knowledge about the old cars that we all love and desire, Bob enjoys tinkering with archaic machinery. His current obsession is a 1962 Porsche 356 Super coupe.


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