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发帖数: 10009 | 1 看看就知道了。
http://auto.howstuffworks.com/question399.htm
Diesel engines have never really caught on in passenger cars. During the
late 1970's, diesel engines in passenger cars did see a surge in sales
because of the OPEC oil embargo (over half a million were sold in the U.S.),
but that is the only significant penetration that diesel engines have made
in the marketplace. Even though they are more efficient, there are eight
historical problems that have held diesel engines back:
1.Diesel engines, because they have much higher compression ratios (20:1 for
a typical diesel vs. 8:1 for a typical gasoline engine), tend to be heavier
than an equivalent gasoline engine.
2.Diesel engines also tend to be more expensive.
3.Diesel engines, because of the weight and compression ratio, tend to have
lower maximum RPM ranges than gasoline engines (see Question 381 for details
). This makes diesel engines high torque rather than high horsepower, and
that tends to make diesel cars slow in terms of acceleration.
4.Diesel engines must be fuel injected, and in the past fuel injection was
expensive and less reliable.
5.Diesel engines tend to produce more smoke and "smell funny."
6.Diesel engines are harder to start in cold weather, and if they contain
glow plugs, diesel engines can require you to wait before starting the
engine so the glow plugs can heat up.
7.Diesel engines are much noisier and tend to vibrate.
8.Diesel fuel is less readily available than gasoline.
One or two of these disadvantages would be OK, but a group of disadvantages
this large is a big deterrent for lots of people.
The two things working in favor of diesel engines are better fuel economy
and longer engine life. Both of these advantages mean that, over the life of
the engine, you will tend to save money with a diesel. However, you also
have to take the initial high cost of the engine into account. You have to
own and operate a diesel engine for a fairly long time before the fuel
economy overcomes the increased purchase price of the engine. The equation
works great in a big diesel tractor-trailer rig that is running 400 miles
every day, but it is not nearly so beneficial in a passenger car.
As mentioned, the list above contains historical disadvantages for diesel
engines. Many of the new diesel engine designs using advanced computer
control are eliminating many of these disadvantages -- smoke, noise,
vibration and cost are all declining. In the future, we are likely to see
many more diesel engines on the road. |
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