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How it works

Technology improving even the worst gas guzzlers Add to ...

Remember when gas-guzzling large SUVs were the scourge of the market, burning fossil fuel at a frightening rate and polluting the atmosphere with frightening amounts cancerous stuff? At least that’s the reputation in the minds of some consumers.

Despite this, SUV sales have remained strong, especially at the upper end of the size and price ranges. Let’s face it; there is a strong market for these vehicles. People who can afford them, want and use them.

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What you might not have noticed in recent years is how much these vehicles have improved, not only in terms of ride, handling, comfort, convenience and features – but in fuel mileage and emissions.

The latest large SUVs are meeting the strictest emission standards and returning fuel mileage that would be the envy of an economy car only a few years ago.

Case in point: the 2012 Mercedes ML. This is a 2,200-kg vehicle, stretching more than 4,800 mm from bumper to bumper. It can be equipped with engines producing as much as 306 horsepower or 457 lb-ft of torque and is rated to tow 3,500 kg. It will accelerate from rest to 100 km/h in less than 7.5 seconds and reach a top speed of 224 km/h. That’s big, powerful and fast by any measure.

Yet, this big Mercedes is rated at 6.8 litres/100 km when equipped with a new-generation diesel engine and 8.5 with the company’s newest gasoline engine. Those are improvements of 24 per cent for the diesel and 25 per cent for the gasoline engine respectively. In an age when engineers spend millions of hours and dollars looking for single-digit improvements, these are remarkable achievements.

And you can dismiss any notion of noisy, smelly, dirty diesel engines. These new V-6 BlueTec diesels are equipped with enough cleansing technology to pass tough new European emission regulations slated for introduction in 2014. They have the same power and performance as the 4.5-litre V-8 engine previously offered in this vehicle, yet use 36 per cent less fuel.

To put those numbers into perspective, the only other vehicles on the Canadian market with lower fuel consumption are much smaller four-cylinder economy cars. The competition for the ML in the luxury SUV class – Acura MDX (9.5), Audi Q5 (9.0) and BMW X5 diesel (7.5). The gasoline engine is also the most efficient in the class.

How did they do it? A little bit here, a little but there and when all the steps are added up they make for a pretty amazing total.

Let’s look at some of the technology and science used to create these numbers.

Diesel engine

BlueTec and AdBlue are patented Mercedes technologies used in its diesel engines to reduce emissions, especially nitrogen oxides, by 80 per cent. An aqueous solution is injected into the exhaust stream where it converts the nitrogen oxides into harmless nitrogen and water.

Gasoline engine

The brand-new, 3.5-litre BlueDirect engine appearing in the 2012 ML and SLK sports car has the same displacement as an existing engine used elsewhere in the company lineup – but it is an entirely new design bristling with technology. Where the older engine is a 90-degree V-6, the new cylinder banks of the new V are 60 degrees apart.

At the heart of the BlueDirect system is a third-generation “spray-guided” direct injection system with piezo injectors operating under more than 2,900 PSI and multi-spark ignition. The first injection of fuel into each individual combustion chamber is done on the intake stroke and a second during the compression stroke before ignition. With the multi-spark setup, there is an initial spark followed by a brief combustion period and then one or more additional sparks. The ignition system is capable of up to four sparks within one millisecond. The result is incredibly complete combustion and use of available fuel.

This engine also boasts completely new intake and exhaust manifolds to optimize air flow into and out of the engine dependent on throttle position and demand. With the same displacement as the old engine, this one produces 12.5 per cent more horsepower and 5.7 per cent more torque while using 25 per cent less fuel

Aerodynamics

Again, best in class with a drag coefficient of 0.32. In addition to the sleek design, which optimizes wind flow around the front end, windshield and rear window, there are seals around the radiator section and between the hood and headlights. There are spoilers for the front wheels and rear window. Air outlets in the wheel wells, special wheels and under floor panelling all add to the cause.

This modern SUV can hold its head high as it passes gas (or diesel) stations thanks to a whopping amount of technology.

globedrive@globeandmail.com

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