A Quick Look at a Direct-Injected Gas Engine, Courtesy of General Motors
By John O'Dell March 10, 2009We've written a bunch about direct-injected gasoline engines and run a few pictures, but wished and wished and wished we could find a good video or animation that helps explain it.
Well, General Motors Corp. has posted this direct injection video on its Fastlane blog and while not exactly the step-by-step instructional we'd like, it may help a bit if, like us, you find that a visual helps increase understanding.
The video is 1-minute, 44-seconds long and you can tune out after the first 40 seconds because the rest is pretty much a GM commercial (although it does provide a list of GM vehicles that have direct injected engines, or, like the upcoming 2010 Chevrolet Camaro, will have once they are on the market).
For those who like words along with the pictures, here's a brief boil-down of the technology:
In a direct-injected engine, the fuel is sprayed under high pressure directly into each combustion chamber, rather than first being mixed with air in the intake manifold.
By being introduced directly and in a very fine spay (or atomization), the fuel mixes more thoroughly with the air, which still enters the cylinders via the intake manifold.
The unmixed fuel also can be metered and its introduction into the cylinders timed more precisely by the fuel management computer.
Because the end result is a mixture of air and fuel spread very precisely throughout the combustion chamber rather than aggregated near the top of the cylinder, combustion of the mixture is more complete than in a conventional fuel-injected engine.
The result is that less gasoline is needed while the evenly distributed fuel-air mixture produces a more powerful combustion event, or explosion, in the cylinder, delivering more power to drive the crankshaft.
As a result of saving fuel, or delivering better fuel economy, a direct-injected engine reduces hydrocarbon emissions relative to the power it delivers.
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