Gas mileage-enhancing features became a popular target for automotive research and development when the price of gas made driving a car more expensive than just owning a car. Gas-guzzlers like the Hummer H3 began to sat idle on sales lots just months after large SUVs were a preeminent status symbol.
Engines had been improving every year for some time, but any automaker that wasn’t targeting drastic increases in fuel efficiency across its entire product line quickly altered the design strategy to reflect the new consumer demands. Here are some of the smarter mileage-enhancing features that automakers have brought to the table recently.
Direct Injection
Gasoline direct injection is a variant of fuel injection in which the gas is delivered through a common rail fuel line directly into the combustion chamber of each cylinder. Conventional engines used the more common multi-point fuel injection, which injected fuel into the cylinder ports or intake manifold. Direct injection can improve the air-to-fuel ratio it takes to fire each piston, reducing overall consumption considerably.
These “lean burn” mixtures can be as high as a 65:1 air-to-fuel ratio. The precise control over the amount of fuel and injection timing is important, as the load conditions or driving patterns change. Emission levels are cut, fuel economy is improved, and power output is increased. General motors introduced three direct inject engines in 2004 which appear in several models, including the Saturn Sky (2.2 L Ecotec), 2010 Chevrolet Camaro (3.6L V-6), and Cadillac CTS (3.6 L LLT). Ford’s EcoBoost series was introduced in 2007, and was designed for vehicles across the company’s product line.
Turbochargers
This feature is a little confusing when it comes to fuel savings. If you have two vehicles with the same engine size, the one with a turbocharger will in fact get less gas mileage. To find out how a turbocharger can save gas, you first you have to know how they work. Turbochargers use your car’s own exhaust gases, which are still super-heated, to spin a turbine that compresses are and injects it into your intake. This forced air increases horsepower when you need it, but a turbo remains dormant during normal driving.
The extra power allows automakers to install smaller engines in any given model without sacrificing overall power. The smaller engine generally uses less gas, and has the added benefit of weight savings. So if you had two cars rated for the same power output, the one with a turbocharger would have a smaller engine, weigh less, and get a pretty distinct advantage on fuel economy when everything is considered. BMW, GM and Ford have all started using turbochargers, and it is projected that all automakers will have turbocharged engines that are smaller for most models within a few years.
Engine Conservation Systems
Ford announced that it plans to implement an Auto Start-Stop system that shuts off the engine while a vehicle is stopped. The feature is already on Ford’s hybrid models, but will be available for conventional gas engines by 2012. Ford said last year that the feature will provide 4 percent – 10 percent fuel savings, and will eliminate all emissions while a vehicle is stopped. The feature is expected to be added to all conventional, crossover and SUV models.
A similar system used by GM called Active Fuel Management turns off half of a vehicle’s cylinders when under light-load conditions for better fuel economy. EPA tests have shown a 5.5 percent to 7.5 percent improvement on fuel economy. Chevrolet’s 2010 Camaro SS is the latest model to include the technology, which allows the vehicle to get better gas mileage under normal conditions but have all the power of a normal V8 when needed. Honda’s Variable Cylinder Management and Chrysler’s Multi-Displacement System have both followed GM’s lead with automobile variable displacement systems.