When it comes to boosting efficiency in petrol engines, Mercedes is playing catch-up. Premium rival Lexus already has hybrid cars, while BMW offers regenerative braking to improve fuel economy on several models.
But the three-pointed star is working hard to regain ground – and Auto Express has driven its latest development: a CLK 500 with ISG technology.
The initials stand for Integrated Starter/Generator, and in lay terms, the set-up is a stop-start system. A disc-shaped electric motor is added between the engine and automatic transmission, while a secondary battery is charged by regenerative braking and offers a power boost during hard acceleration. The main advantage is that this layout is smaller and lighter than a hybrid transmission.
For the driver, it means fuel economy is up 10 per cent from 24.8mpg to 27.3mpg, while CO2 output is estimated to drop by a similar proportion.
The stop-start technology cuts the engine when you come to a halt, and fires it up as soon as your right boot comes off the brake. By the time you are pressing the accelerator, it’s as if the V8 has been running all the time.
The powerplant also switches off if you shift the auto box into Park mode.
At least that’s how it’s supposed to work. But in the 30-degree heat of our urban drive in Germany, it didn’t. Despite having several opportunities to cut out as we stopped at traffic lights and junctions, it failed every time.
We thought the system wasn’t working properly, but later learned it was because we had turned the CLK’s air-conditioning on. Apparently, the car prioritises driver comfort over saving the planet. On a second run with the cooling system switched off, the ISG technology worked fine.
Arguably, the Mercedes stop/start isn’t as clever as it thinks it is. Yes, it can cut the engine to save fuel, but similar devices offered by rival manufacturers switch off when they realise you are coming to a halt. That means owners get every last mile from the fuel tank by freewheeling to a standstill. What’s more, bosses won’t offer the ISG technology until 2009.
Car Review:Mercedes CLK 500 ISG
Lexus RX Getting Bigger And Seven-seat RX coming
Bigger is better at Lexus. Our exclusive picture shows that the next RX will be larger than the current model – and it could even be offered as a seven-seater for the first time.
Despite this, the Japanese firm is likely to take a conservative approach to the newcomer’s styling. It will feature swept-back headlamps and the trademark Lexus grille, while the distinctive curved roof of the existing car will also be retained. Our spy shot (below) shows that the replacement’s underpinnings are already being fine-tuned in a test mule wearing the current SUV’s body.
At first glance, it looks like any other RX, but close inspection reveals that the rear lights no longer sit flush with the bodywork. That’s because the panels have been widened to account for the new platform’s bigger dimensions. This added size could pave the way for an optional third row of seats, which would put the Lexus up against BMW’s X5 when it arrives in dealers in 2009.
The new 4x4 likely to debut at that year’s Tokyo Motor Show because, although the biggest market for the RX is the US, the model will be the first SUV in Japan to wear a Lexus badge. The current generation is called the Toyota Harrier in its home market.
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New Audi Q5 Shapes Up
Take a look at the best pictures yet of Audi’s Q5 compact SUV. The German firm’s engineers are putting the finishing touches to the model ahead of its unveiling at next year’s Geneva Motor Show.
A rival to the BMW X3, Land Rover Freelander and forthcoming Mercedes MLK, the Audi is based on the same platform as the A5 coupé and next-generation A4. These pictures reveal that the Q5 takes its styling inspiration from the bigger Q7.
Inside, there will be enough room to carry five adults in comfort, while the cabin is derived from the new A5. The Q5 will have limited off-road ability, and all models will feature a raised ride height and quattro four-wheel drive as standard. But with a chassis tuned for on-road handling, it will be sporty and fun to drive.
Under the bonnet, the Q5 will be offered with 2.0-litre turbo and 3.2-litre V6 petrol engines, plus 2.0-litre and 3.0 litre TDI diesels. There is also the chance Audi will make a high-performance 4.2-litre V8-powered model.
When the Q5 goes on sale in mid-2008, the range will start from around £30,000.
It isn’t the only new Audi SUV on the way – our spies have snapped a Q7 flagship, too. This has a 500bhp 6.0-litre V12 TDI diesel, an aggressive nose with deep air intakes and should cover the 0-60mph sprint in 5.5 seconds.
The model will be revealed at the Frankfurt show next month.
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