Why auto-transmission cars return less mileage?


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A manual transmission is inherently better equipped to prove better fuel economy. The manual transmission couples the engine to the transmission with a rigid clutch instead of an automatic transmission's torque converter, which bleeds off power. The automatic transmission wastes engine power to drive the high pressure hydraulic pumps required for its operation.
 
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@ ilango is it true?? i have heard that mileage also is less compared to a manual one!![shock]
 
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Now a days even AT gives good mileage, almost same as Manual.
Earlier the difference was more as there was only 3 stage transmission, now AT has upto 7 stage.
 
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A quick overview on Automatics.
Planetary gear systems- remember the zen auto, or even humble 800 auto??
More recentely, the santro auto? All had planetary gear trains. 3 gears.
PRNDL.[ Parking,Reverse,Neutral,Drive,Low]. Used Energy sappping torque converters.Low mileage.

Robotised Manuals- Neccesarily manual transmissions, robotised using hydraulics and computer controls. Fast, less energy sapping, but bulky. Sonata H matic, Recentely The scorpio.

Cvt- Almost like the variators used in scoterrets, sunny, activa and the lyks.
Came later in cars, due to engineering constraints. It Primarily uses a belt sliding on cone shaped pulleys. The torque rating of cars being higher, the belt construction was dificult.Proggamble for paddle shifting. Used in city,Civic.

Sequential Gearboxes- Next generation robotised manuals.Very quick. Audi A4, A6, Bmw 3 series, 5 series.
DSG- Dual clucth sequentials. Lightning fast. Twin Clutch. 100 Milisecond gear changes. Ferrari california, A8 W12.

Still Somebody in the notion of automatics being slow, bulky energy sapping systems??
[thumbswink]
 
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Hmm kk thanks. That's the reason i asked compared to normal auto tranny.[:)]

Have some more questions. Will put them up soon.
 
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@ racerdabba.. the explanation is cool. i never till now thought about the foreign AT cars!! sure they are faster!![lol!]
 
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