Techsplanations: Direct Injection – Autoblog

Gasoline direct injection is one of those technologies that make you think, «Why the heck didn’t they figure this out sooner?» It’s a simple fix to the regular old combustion engine, and it saves a lot of fuel. Instead of mixing air and gasoline outside the combustion chamber, the system sprays gasoline directly into the chamber. The result is literally more bang for your buck. (Don’t worry, we’ll explain this all in detail in a little bit).

Actually, engineers in the auto industry did think about it earlier.
Mercedes-Benz used it in their 300Sl Gullwing in the 1950s. It’s been primarily used in
diesel engines ever since. But most U.S. drivers are not familiar with diesel passengers cars.

How does it work?

The combustion engine works by mixing air and gasoline and shooting it into the combustion chamber. Gasoline needs air, otherwise it won’t explode. And you need a series of controlled explosions to get the pistons on the engine moving, which is what ultimately moves your car.

Direct injection sprays gasoline directly into the combustion chamber, while air comes in through a valve nearby. That results in what engineering geeks call a «leaner» burning process. In other words, the engine needs less gas to make the same powerful bang that pushes the pistons.

And because the gas doesn’t have to travel as far to get inside the combustion chamber, it’s cooler. And cooler gas can be compressed tighter to create more power. Think of it as kind of a Jack-in-the-box: If you push that guy down in the box harder, when you let go, he’ll bounce back harder and higher than normal.

Why would I want it?

Because it gives you
fuel economy and power at the same time. When
GM introduced the
Cadillac CTS in 2008, it offered one 3.6-liter V6 engine with direct injection, and one with standard fuel injection. The direct injection engine got 304 horsepower and the standard got 263 horsepower. But both engines got the same 26 miles per gallon fuel economy. That’s as easy a real-world explanation of the value of direct injection as we can think of.

Is there any downside?

It costs a couple hundred dollars more to put it under your hood, because it’s a little more complex to manufacture and uses some more expensive parts. It also needs a more sophisticated computer system to manage the engine and flow of fuel, further adding to the cost.

Automakers probably won’t pass that cost on to consumers, because they’re under a lot of pressure to meet higher fuel economy standards in the next few years. But the engines could be more expensive to
repair if anything goes wrong.

What vehicles offer it?

Audi and
Buick offer it on their full lineup.
Volkswagen markets its models with direct injection engines with the initials «TSI.»
Ford calls its direct injection engines «EcoBoost», and luxury models like
Mercedes and
Porsche offer it on most of their models.
Ferrari offers the technology on the $230,000
458 Italia if you can afford that.

Bottom line

Direct injection is a true win-win for the internal combustion engine, offering both greater power and improved fuel economy.

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