好像不是这么简单，在网上找了一段描述，好像是说用于控制档的，现在的车一般是4档，D with OD on,四档全可用。建议一般OD on,不过我也没有完全明白，又没有懂车的解释一下，我平时的OD都没有开的。
For example, the transmission selector in my car is labeled as follows:
P
R
D
2
1
And there is a separate button to enable and disable the “overdrive”.
The positions on the selector lever would be appropriate for a 3-speed automatic. If that were the case, then “D” would enable all three forward gears, “2” would lock out the third gear, allowing only the first and second gears, and “1” would allow only the first gear.
In truth, however, this is a four-speed transmission, and “D” enables all four gears, if the “overdrive” is enabled as well (which it is by default). Disabling the “overdrive” locks out the fourth gear, allowing only the first three gears. If the controls were set up in a manner that truly reflected the nature of this transmission, then there would be no “overdrive” feature; instead, there would be a “3” position between “D” and “2”, and selecting that “3” position would have the effect that — as the controls are really laid out — is produced by setting the transmission in “D” and disabling the “overdrive”.
With a more primitive three-speed automatic transmission, you would normally just leave it in “D” nearly all the time. Occasionally, there are reasons to limit it to lower gears, and that's what the “2” and “1” settings are for.
With a modern “overdrive”-equipped automatic transmission, you would normally want to leave the “overdrive” enabled for the same reason. You'd turn off the “overdrive” if you had a reason to want to limit it to third gear or lower, just as you'd use the “2” or “1” settings if you had reason to want to limit it to second or first gear respectively. But usually, you don't. |
发表于 25-1-2010 09:08:16
收藏
赞
踩
楼主
