某人最近吃春药了，发骚了。。。绝对够骚。。（绝对无码）
- 主题发起人 LOVE_UU
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.....
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4-banger 有硬伤的。。
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HEMI EATS ALL THE CAR ON THE ROAD....6.1L 430HP+
0-60MPH 4.8sec
and it's a 4200 lbs car...
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直四活塞上下运动的时候会产生无法克服的纵向颤波
通常直四都有一个或者两个counter mechanism。不过都无法完全去除。
浪费一定的动力而且不太平衡
The straight-4 engine is much smoother than one, two, and three cylinder engines, and this has resulted in it becoming the engine of choice for most economy cars, although it can be found in some sports cars as well. However, the straight-4 is not a fully balanced configuration.
While an even-firing straight-4 engine is in primary balance because one pair of pistons is always moving up at the same time as the other pair is moving down, piston speed—as with all internal combustion engines—is higher through the top 180° of the crankshaft rotation than the bottom 180°. Therefore, across the 4 cylinders two pistons are always accelerating faster in one direction while two others are accelerating slower in the other, which leads to a secondary dynamic imbalance—an up-and-down vibration at twice the crankshaft's speed. This imbalance is tolerable in a small, low-displacement, low-power configuration, but the vibrations get worse with increasing size and power.[2]
The reason for the piston's higher speed during the 180° rotation from mid-stroke through top-dead-center and back to mid-stroke is that the minor contribution to the piston's up/down movement from the connecting rod's change of angle here has the same direction as the major contribution to the piston's up/down movement from the up/down movement of the crank pin. By contrast, during the 180° rotation from mid-stroke through bottom-dead-center and back to mid-stroke the minor contribution to the piston's up/down movement from the connecting rod's change of angle has the opposite direction of the major contribution to the piston's up/down movement from the up/down movement of the crank pin.
Most straight-4 engines below 2.0 L in displacement rely on the damping effect of their engine mounts to reduce the vibrations to acceptable levels. Above 2.0 L, most modern straight-4 engines now use balance shafts to eliminate the second-order harmonic vibrations. In a system invented by Dr. Frederick W. Lanchester in 1911 and popularized by Mitsubishi Motors in the 1970s, a straight-4 engine uses two balance shafts, rotating in opposite directions at twice the crankshaft's speed, to offset the differences in piston speed.[3] However, in the past there were numerous examples of larger straight-4s without balance shafts, such as the Citroën DS 23 2347 cc engine that was a derivative of the Traction Avant engine, the 1948 Austin 2660 cc engine used in the Austin-Healey 100 and Austin Atlantic, the 3.3 L flathead engine used in the Ford Model A (1927), and the 2.5 L GM Iron Duke engine used in a number of American cars and trucks. Soviet/Russian GAZ Volga cars and UAZ SUVs, vans and light trucks used aluminium big-bore straight-4 engines (2.5 L or later 2.9 L) with no balance shafts in 1950s-1990s. These engines were generally the result of a long incremental evolution process and their power was kept relatively low compared to their capacity. However, the forces increase with the square of the engine speed—that is, doubling the speed makes the vibration four times worse—so modern high-speed straight-4s have more need to use balance shafts to offset the vibrations.[4]
Four cylinder engines also have a smoothness problem in that the power strokes of the pistons do not overlap. With four cylinders and four cycles to complete, each piston must complete its power stroke and come to a complete stop before the next piston can start a new power stroke, resulting in a pause between each power stroke and a pulsating delivery of power. In engines with more cylinders, the power strokes overlap, which gives them a smoother delivery of power and less vibration than a four can achieve. As a result, six and eight cylinder engines (and sometimes five) are generally used in more luxurious and expensive cars.
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我记得LS3的0-60数据是4.9sec~还是5.1sec, LS7大概4.5 sec的样子
不过不要忘了camaro的curb weight要轻了challenger 400lbs.....
dodge viper 0-60 3.6sec.... even faster than gt-r
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V6 V8 H4 H6 都是perfectly balanced
你丫得騷到何年何月啊?
