By on June 29, 2011

When asked by if he preferred to drive his McLaren F1 or Mclaren-Mercedes SLR to work everyday, the man who designed both legendary hypercars, Gordon Murray demurs:

I wouldn’t say the SLR is quite an everyday car but I certainly like to drive it to work. But for me, despite all those cars and my single-seater Rocket [a car he privately designed], it’s the [eight year-old Smart Roadster] I’m most taken with. For one, it’s a great-looking car. It has a power roof, heated seats and air con, and it all weighs just 830kg. In fact, it’s got all you’d want from a car. It nips around corners and it’s fun to drive.

So, other than proving that Murray has exquisite taste (I’d kill you all for a Brabus Smart Roadster Coupe), what’s the point? That, having been there and done that in the world of high performance, Murray’s taking on a less obviously sexy but ultimately significant project that first occurred to him in a traffic jam back in 1993: the T.25 and T.27 city cars. We’ve written about Murray’s T.25 before, but the real news today is the release of specs for the T.27, an all-electric version of the tiny three-seater. And yes, it weighs 1,500 lbs on the nose (including batteries), and ekes 100 miles of range out of just 12 kWh. That beats the efficiency of competitors like the Smart EV (by 29%), the Mitsubishi iMiEV (by 36%) and MINI E (by 86%). So, how does it do it?

The lightweight body is just one part of the equation, allowing not only high efficiency, but also a radically low-energy, low-capital assembly technique called iStream, which does away with the steel stamping-based manufacturing process that has dominated automaking since Henry Ford. Murray explains the process in the video above, clarifying that his firm is not interested in actually manufacturing these vehicles, but that they are talking to other firms who might be interested in licensing the iStream process and building the T.25 and T.27.

But one of the most fascinating developments that keeps the T.27 so light and efficient is its drivetrain, which was developed by a British firm called Zytek. GreenCarCongress explains some of the most salient features:

Minimizing the torque requirement of the motor (to allow it to be smaller, lighter and more efficient) while maintaining vehicle performance, requires a high motor speed. Zytek analyzed a wide variety of motor topologies and designs using 2D and 3D simulation tools, leading to a reliable maximum motor speed of 14,500 rpm. This high operating speed allowed motor torque to be reduced to 64 N·m (47 lb-ft) while maintaining vehicle based performance targets.

The peak motor power of 25 kW (available for 30 seconds) means vehicle performance is maintained in all expected usage conditions.

The second major powertrain component is the three-phase inverter. Zytek concluded that the inverter should also combine battery charging and high-voltage switching capabilities. This has the added benefit of reducing the weight of high-current copper cable and also avoiding any reliability issues associated with use of high voltage connectors.

The total weight of the motor, inverter and gearbox is less than 50 kg (110 lbs), approximately 45% of that of a comparative, current production, water-cooled drivetrain with its associated radiator, cooling fluid, pumps etc. This light weight contributes to the low overall vehicle weight while the highly compact size means that luggage space can be increased compared to the regular internal combustion engined vehicle.

Gordon Murray has long compared his T.25 project with his other great accomplishment, the McLaren F1, arguing that building this kind of tiny, efficient and affordable (estimated cost: $9k for the gas-powered T.25 and about double that for the electric T.27) car requires the same kind of innovative thinking, only the task is made even more challenging by the absence of unlimited budgets and the need for creature comfort. With the T.27’s tiny powerplant, it’s radical front-hinging door, unique manufacturing process (said to require 10% of the startup capital of a typical auto plant), and all-round funky uniqueness, the Murray City Car is proof that the coolest cars need not be limited to the insanely wealthy. An argument, in fact, that the Smart Roadster once made in a slightly less convincing manner. Now the question seems to be: who’s going to build this thing?

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5 Comments on “What’s Wrong With This Picture: McLaren F1 Meets Smart Roadster Edition...”

  • avatar
    bumpy ii

    “100 miles of range out of just 12 kWh”

    At what speed? Range figures for electric cars are worthless without an average velocity, since aero resistance is exponential. The air-cooled motor-controller package and fancy body shell are nice, but to get a 3-seat minicar down to 120 watt-hours per mile at highway speeds requires skinny LLR tires and very aggressive streamlining.

    As for the smart roadster, there is a good argument that Penske imported the wrong smart. The roadster was at the end of its product cycle and had some reliability issues, so he didn’t really have a choice. Still a fun weekend/commuter car, though.

    • 0 avatar

      Since the car is being positioned as a city car, likely the economy is quoted at somewhere around 35-45 mph.

      25 kw peak probably means 0-60 times of around 15-20s. It’s a step up from a NEV, and likely will be fine for city traffic, but is likely neither safe enough for nor capable of 70 mph freeway travel.

      This car sounds very much like a modern Mini – which had an optimistic top speed around 70 mph as well.


      EPA claims 390wh/mi (at the wall), likely 340wh/mi at the pack for the Smart ED. Daimler originally claimed 200wh/mi – which is still higher than “beats the efficiency of competitors like the Smart EV (by 29%)” indicates.

      Let’s list the EPA numbers (at the wall), combined usage:

      Tesla Roadster 300 wh/mi
      Nissan Leaf 340 wh/mi
      Chevy Volt 360 wh/mi
      Smart ED 390wh/mi

      Mitsubishi i MiEV is claimed 213 wh/mi (assuming at the pack to 100% DOD) in the US driving cycle, which is no doubt ridiculously optimistic.

      120 wh/mile may be the targeted UK rating, but the EPA tests will likely result in somewhat higher consumption. Still.. if the EPA only tests city driving, 1500 lb curb weight should help significantly.

  • avatar

    This is a city car and the range claim might be for congested low speed city traffic. Not a lot of aero drag at jogging/running speed.

    How would the US safety agencies handle this? Would it meet any standards? And would it be worse than a motorcycle’s safety? Here is a green solution for moderate expense and its downright cheap for the gas version.

  • avatar

    My questions (even as an observer from the outside) for the designer:

    1. Reliability? the new light weight technology stuff is nice, but will it last? Can it be repaired easily? How much abuse can it take?

    2.Can it handle weather, like the weather England had last winter, or that many places in the US have every winter? What about 4WD or AWD?

    3. How can a car so light be survivable in even a minor accident? I could see getting bumped at 3 mph at a stop light doing enough damage the car can’t be repaired, or is so expensive to repair it’s not viable for most families to own?

    It seems like so many of these new high tech ideas to combat oil usage/global warming/problem of the month you want are very expensive, have no economy of scale in production so it can be cheap for everyone to drive, and is nice for people in urban crowded European/Asian/US East or West coast environments. Not everyone in the world is in that situation.

    I hope his ideas work out for the betterment of all, not just a small sliver of rich humanity, but maybe it’s a beginning.

  • avatar

    Conceptually there is something inherently attractive about how this car was developed; low-cost by a small talented team. Everybody likes the independent underdog.

    That said, I’m having difficulty conceiving a market for this car. Its small, its slow (65mph top speed, 0-62 in 15s), and isn’t particularly cheap ($9-18k).

    The gas version is a mere stones throw away in price from cars with much more utility. Its not Tata Nano in price. There is no enthusiast element that would appeal to more boutique tastes.

    But there is future in this ‘iStream’ development methodology, and they deserve a shot at production by a daring manufacturer.

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