Hybrid Car Image Gallery
Hybrid Car Image Gallery

Toyota unveils the 2005 Prius, complete with new hybrid engine unit, in Tokyo. See more pictures of hybrid cars.

Yoshikazu Tsuno/AFP

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Before we can get int­o a disc­ussion about fuel mapping, you have to­ have to know a bit about electronic fuel injection (E­FI). What's that­? To put it simply, it's a computerized system that takes over where y­our old carburetor left off, regulating the mix ­of air an­d fuel in your engine to keep it running smoothly. Too much fuel, and you're wasting gas. Too little, and you could damage your engine.

For decades, fuel regulation was handled by the carburetor. In the lat­e 1950s, cars with optional electronic fuel injection came on the scene, and by the 1990s, EFI was common. Today, almost all new cars have EFI systems instead of carburetors.

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­The fu­el map is the EFI system's setting for regulating the air/fuel mix. The map has three goals:­

Optimize performance -- for better speed and acceleration

Optimize fuel economy -- to get the best gas mileage

Optimize emissions -- to eliminate as many waste particles from the tailpipe as possible

Next, we'll map out the parts that make up this intricate computerized system.