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Monday, May 25, 2009

Fisker Karma Vs Chevy Volt

The Fisker Karma and Chevy Volt are both Extended Range Electric Vehicles (E-REV) or more commonly referred to as series Hybrids we thought a thorough comparison of their specifications was over due.

In an E-REV or series hybrid there is no mechanical connection between the combustion engine and the wheels as in a conventional car. The wheels are driven by an electric motor at all times with power supplied by a battery that can be plugged into any electrical outlet to be charged. To keep to size of the battery pack small a petrol engine is used to charge the battery pack for extended journeys where plug in charging is not convenient.

The Karma will be using a GM sourced 4 cylinder engine as it's Internal Combustion Engine (ICE) generator. The Ecotec 2.0L uses direct injection, variable valve timing and an intercooled twin scroll turbocharger and puts out 260 hp (190 Kw) as standard. The ICE generator in the Chevy Volt is also a 4 cylinder but is 1.4 liter normally aspirated with 72 hp (53 Kw)

Both the Karma and Volt will be equipped with Lithium ion battery packs, the Volts capacity of 16 kWh giving it a 40 mile (64 km) EV mode range while the Karma carries a 22.6 kWh pack giving it a 50 mile (80 km) EV only range. While GM have signed a battery supply deal with South Korean firm LG, the Karma will use batteries supplied by Indianapolis based EnerDel who have also been supplying Norwegian EV company Th!nk. The larger battery pack and ICE in the Fisker help contribute to a substantial weigh difference between the two vehicles as the 4650 lb (2109 kg) of the Karma is 1510 lbs (684 kg) heavier than the 3140 lb (1424 kg) of the Volt.

Where the Volt is Front Wheel Drive like the conventional Delta II platform it is based on, the Karma is Rear Wheel Drive as is more traditional for luxury saloons. The GM Volt has a 150hp (111 Kw) EV motor with an impressive 273 ft/lb (370 Nm) of torque from zero rpm, the Karma easily blows that away by running 2 x 200 hp (150 kw) EV motors that deliver a combined total of 403 hp (300kw) and a mind blowing 959 ft/lb (1300 Nm) at the differential input shaft.

1300 Nm of torque

To put that torque number into perspective, that's actually 30% more torque than the most over-the-top Mercedes motor currently on the market, the 612 hp (450 Kw) 6.0 liter V12 twin turbo normally found in the $492,000 SL 65 AMG. The V12 BITURBO has ONLY 1000 Nm of transmission breaking torque compared to 1300 Nm for the Karma. Add to that the standard electric motor characteristic of 100% torque from zero rpm and we're sure the 5.8 seconds 0-60 mph (100 kph) is a conservative estimate of the Karma's performance potential as the SL 65 does 4.4 sec. (the Volt does 8.5 sec)

The Volt has a range of 640 miles (1025 km) with a full tank of fuel while the estimated range of the Karma is closer to 300 miles (480 km) although this all comes down to the size of the fuel tank in each not through any difference in energy efficiency. The Karma takes energy efficiency a step further than the Volt and comes with 80 PV solar cells in the roof. These are arranges in 4 modules of 20 cells each and have a total output of 130 watts. When parked in unobstructed sunlight they will provide 0.5 kWh per day, enough to power auxillary systems such as vehicle ventilation or to top off the battery.

So why is the Karma twice the price of the Volt? The bottom line is, Fisker CEO Henrik Fisker designed the Aston Martin V8 Vantage and BMW Z8 amongst other and with the extruded aluminum chassis being produced by the same company that makes the Lotus / Tesla chassis Norsk Hydro, the Karma will be assembled by the same company who currently make the Porsche Boxter and Cayman, Valmet Automtive in limited production of 15,000 cars per year. With over 400 hp and more torque than a 6.0 liter V12 twin turbo, the Karma is the first of a new breed of EV sports tourer while the Volt is a series hybrid family compact car that GM expect to make in the 100s of thousands.

As both cars are 4 door series hybrids both with GM manufactured 4 cyl ICEs there might be a temptation to think they are very similar, but as we have hopefully pointed out, they are in different leagues. With the first Karma's due for delivery in November 2009, we can't wait to read the first road tests.

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1 comment:

Anonymous said...

Ps,a MB 65 Amg engine produces 1320Nm as standard,
when put in a car it is mapped to 1000Nm from ca 2000 RPM, this beacause they dont have transmission for full load. This is common knowledge.

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