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Posted by Uptight Motorsports Nerd on June 16, 2011
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Last year I wrote a blog explaining the differences between fuel injection and carburetion.
This year I plan to go a step farther and explain the future of fuel injection. As I had previously explained, conventional multiport fuel injection involves spraying fuel (at 60psi) into the cylinder head ports. The new technology on the market is direct fuel injection. This involves spraying fuel (at 2,200 psi) directly into the combustion chamber, completely bypassing the intake ports and manifold.
That?s not a typo, it really says 2,200 psi (that?s 151.72 bar, 154.71 kg/cm, or 15,168.466 kPa)! I assure you, it?s not dangerous, particularly when you consider that common rail diesel fuel pumps operate at 10 times that pressure. This pressure is necessary because fuel must now overcome the pressures of a combustion chamber which may already be on the compression stroke (more on that later) while staying atomized.
The great advantage at idle (or otherwise light load conditions) is that the air-fuel mixture does not have to be homogenous throughout the cylinder. This allows the engine to operate in ?ultra lean burn? mode. Fuel isn?t injected until the end of the compression stroke, just before ignition. This leaves the mixture to burn around the spark plug as a small pocket with less wasted heat leaking into the cylinder walls. As the mixture is not homogenous, the total air-to-fuel ratio can be 60:1.
At wide-open-throttle conditions, fuel is injected at the intake stroke. The mixture is homogenous throughout the cylinder. A ratio is usually slightly richer than stoichiometric (14.7:1) to prevent knocking.
If anyone wants to cheat by adding traction control, it wouldn?t be any different from cheating with multiport fuel injection. Both systems would require shutting down a specific fuel injector at a specific moment to prevent wheel spin.
Of course there are more applications for this technology than the four-stroke cycle. When applied to two-stroke cycle and Wankel rotary engines, emissions and fuel consumption (not to mention oil consumption) approach the levels of their conventional counterparts. Perhaps the four-stroke cycle will soon be rendered obsolete by direct injection two-stroke engines (of course NASCAR won?t make any such change until the last man who knows how to adjust rocker arm lash is dead).
Why is all this relevant to racing? It?s relevant because it?s a major step forward for the modern car (or motorcycle). Racing is supposed to promote either what great idea a manufacturer has in the works, or already put on the street. No major racing series ever started off as a spec series, they just became spec series after selling out their ideals.
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