Transverse and longitudinal engine layouts organize the engine in the engine compartment. Cars with transverse engines have parallel engines and front axles. The transverse engine’s crankshaft, transmission input and output shafts, and axle are all parallel, so if it’s a front-drive car, the power transmission distance is short and the direction is the same, so transmission efficiency is higher; longitudinal engine refers to the engine’s perpendicularity to the front axle, and longitudinal engine allows the transmission to be extended as far as possible to the rear.
Cars with transverse engines have engines parallel to the front axle. This means that if you stand in front of the car and look at the engine horizontally, it is transverse.
Front-drive compacts, mid-size sedans, and some premium sedans have transverse engines.
Transverse engines have parallel crankshafts, input and output shafts, and axles, so power is transmitted over a short distance and in the same direction if front-drive, making the transmission more efficient.
Transverse engines take up less longitudinal space, so they can shorten the engine compartment in exchange for a larger driving space, especially for the front passenger’s leg room. Compact sedans with limited dimensions need this.
The transverse engine’s biggest flaw is the front and rear weight distribution imbalance. The engine crankshaft transmission input shaft are connected in parallel, so they can be arranged in the engine before the front axle, but the weight of these heaviest car parts is concentrated in the front, making the front axle load too high and prone to understeer. The head-heavy front and rear axle weight distribution will also reduce rear wheel pressure when cornering at high speeds. Some transverse-engine sedans with irrational axle loads have even reached 70% of the front and 30% of the rear, which is possible.
The transverse engine transmission mounting position is too biased to one side, so its drive shaft is too long and too short. When the huge driving force in the unequal length of the drive shaft causes the car’s two front wheels to have a rotational speed difference, which leads to rapid acceleration when the front end of the car oscillates left and right.
A longitudinal engine
The engine is longitudinal if it is vertically in front of your eyes and perpendicular to the car’s front axle.
Rear-wheel drive cars usually have longitudinal engines because power must be transferred to the rear axle and transmission distance cannot be shortened to minimize conversion power. If transverse is used, the crankshaft and driveshaft are perpendicular to each other, so the direction must be converted once to transmit power through the driveshaft. However, the driveshaft and rear axle are also perpendicular, so the rear axle must be converted again, which reduces transmission system efficiency. Longitudinal engines can parallelize the crankshaft and drive shaft, reducing transmission conversion direction and energy loss.
However, the longitudinal engine allows the transmission to be placed as far back as possible, placing the powertrain’s center of gravity behind the front axle and distributing weight more evenly between the body’s front and rear.
Audi’s longitudinal engine front-wheel drive is unusual. Audi uses the longitudinal engine for quattro, but its front-wheel drive engine layout can also improve front-to-rear weight ratio. This arrangement can be longitudinally arranged in the engine before the front axle of the car, and the engine is directly connected to the transmission will be limited by engine compartment space, to be arranged in the front axle after the transmission input shaft and engine crankshaft rotate around the same axis, for the weight of the engine and transmission bearing the front axle:
The engine and transmission are distributed on both sides of the front axle, so the weight is more evenly distributed, the center of gravity is more reasonable, and there will still be a front-drive car to push the head phenomenon, but the weight ratio is much better than ordinary transverse engine models, such as front-wheel-drive Audi A4 before and after the weight ratio of the more perfect.
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