05 VONNEN CARRERA 3.4

Electrifying an atmo 991 911 into supercar leagues

BY KYLE FORTUNE

SILICON VALLEY, California. There are Teslas everywhere, the US electric upstart is evident in the traffic here. Elephant Racing, a Porsche specialist, is taking its traditional expertise and applying some new thinking - thatís how the idea of hybridising the existing 911 platform came about.

Doing so has seen the creation of Vonnen. The company has built a kit to make hybrid 911s using an electric motor to supplement the performance of the original engine. The hybrid system is called Shadow Drive and it works by pushing drive through the gearbox, but without having to talk to the flat six.

This is a hybrid thatís been created for performance. What Vonnen has done is sandwich an axial flux electric motor between the gearbox and the engine. To do so itís removed the flywheel and also thrown out the starter motor. Thereís been modifications to the structure ahead of the gearbox to make it all fit.

The e-machine requires some batteries, situated under the floor in the luggage area up front, while thereís an inverter and additional cooling circuits for the different elements of the system.

Shadow Drive adds a maximum of 200Nm of torque and 110kW to the 3.4-litre 991 Carreraís stock engine power of 257kW and 390Nm. Those peaks need to be qualified, as not all the e-motorís performance is used in the various driving modes. There are three; Street, Sport and Overboost. Street adds 125Nm of torque from 40-60 per cent throttle, Sport adds 110Nm from 65-95 per cent throttle and Overboost adds the full 200Nm with the same accelerator application as Sport.

There isnít any ability to run on the Shadow Drive alone and the system is entirely self-charging. The flat-six doesnít know the electric motor is there. The PDK gearbox has had a re-flash of its software, but otherwise itís stock.

Starting up the Vonnen-equipped 991.1 3.4 Carrera is no different from any other. In Street thereís no real change in character apart from masses of torque. Escape the CBD and the Shadow Driveís assistance is more obvious. Sport mode seems appropriate, even if it dials back a touch of total output torque. Push past 65 per cent and Shadow Drive adds 110Nm, the e-motorís operation is signalled by a not unwelcome electrical sound accompanying the familiar flat six.

The e-motorís assistance is so well integrated that thereís no obvious kick, just more performance, more of the time. Overboost does as it says, giving the Carrera the sort of startling off-theline performance that will impress.

Itís only when you switch Shadow Drive off that you realise how much help itís been giving, the Carreraís performance feeling a little inadequate.

Yes, itís quick, but at around $108,000 fitted (you supply the 911), itís a difficult improvement to rationalise, even if itís a no-compromise fit that adds power, while retaining driveability/character. As proof that a hybrid 911 is something that works, itís convincing. Thatís Silicon Valley, one, Stuttgart nil, then.