5 Fuel-Saving Technologies
In the long run, the internal combustion engine (ICE) is on the way out and electric motors are on the way in, but ICEs have been around for so loooong that we should be careful about announcing their demise. They're going to stick around a while longer, and so it's very important to make them as efficient and clean as possible.
Car and Driver looks at 5 fuel-saving technologies that are keeping the ICE relevant (if far from ideal). As they say, they still work on basically the same principle as they ever did, but old 4-cylinder engines produced about 20 horsepower while modern ones can generate up to 250 hp while being cleaner and burning less gas. Read on for more details on the 5 fuel-saving technologies: Clean diesel, direct injection, cylinder deactivation, turbochargers, and variable valve timing and lift.Clean Diesel
Various advances such as the availability of ultra low sulfur diesel fuel, better catalysts and particulate matter traps, better control over combustion are making diesel engines cleaner, so you can expect a new wave of diesel passenger vehicles to come to the US in the next few years.
Diesel engines are certainly far from perfect, but they have inherently better thermal efficiency than gasoline engines, and they are usually more durable (if also more expensive and heavier). Another benefit is that they can run on biodiesel, which if you can find fuel made from waste cooking oil or (in the next few years) from algae can be very green.
Before direct injection, the fuel was mixed with air in the car's intake manifold. Now, with direct injection, the fuel is mixed with air inside the cylinder, allowing for better control over the amount of fuel used, and variations depending on demand (acceleration vs. cruising). This makes the engine more fuel efficient.
The name says it all. ICEs with this feature can simply deactivate some cylinders when less power is required, temporarily reducing the total volume of the engine cylinders and so burning less fuel. This feature is found on V6 and V8 engines.
Turbochargers increase the pressure inside cylinders, cramming more air and allowing combustion to generate more power. This doesn't make the engine more economical in itself, but since a smaller displacement engine can generate more peak power, you can more easily downsize and save there.
Variable Valve Timing and Lift
Valves open and close to allow air and fuel to enter cylinders and for the products of combustion to exit. Different valve timings produce different results (more power, better fuel economy). Traditionally, you couldn't vary that timing, so the choice had to be made once when the engine was designed. But many modern engines can vary valve timing, allowing for example the default low RPM range of the engine to have more economical timing, and the higher RPM range to go for max power. This allows a smaller displacement engine to produce more peak power, so it allows for downsizing and fuel savings.
One Big Problem With All of This
The problem is that most of the gains from these technological breakthroughs have been used to increase power instead of reducing fuel consumption. At best, fuel economy stayed the same while power increased.
Now that environmental awareness is increasing, that global warming is on everybody's mind and that oil is very expensive, we can hope that carmakers will end the horsepower arms race and finally use these technologies to truly make more efficient cars.
A Second Life for the Internal Combustion Engine
All the technologies listed above (and more, like Homogeneous Charge Compression Ignition) could be useful for longer than we think. If series plug-in hybrids like the GM Volt become popular and battery-only electric cars (or hypercapacitors) take a while to mature fully and come down in price, many cars could still have an ICE as a range-extending generator that only kicks in when the batteries are low. The more efficient and clean these are, the better.
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