Why auto-transmission cars return less mileage?


raj_5004

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DSG in skoda means dual sequential gearbox. basic principle is that it has two clutches- one for the odd gears (1,3,5) & one for the even gears (2,4,6). so if one clutch is engaged, the other clutch becomes ready to engage thereby saving on shift timings.
for example, if the car is in 2nd gear, the clutch used for even gears is engaged whereas the other clutch (meant for odd gears) is ready to shift to 3rd, which is turn saves a lot of time usually taken in shifting.
 
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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]
DSG in skoda means dual sequential gearbox. basic principle is that it has two clutches- one for the odd gears (1,3,5) & one for the even gears (2,4,6). so if one clutch is engaged, the other clutch becomes ready to engage thereby saving on shift timings.
for example, if the car is in 2nd gear, the clutch used for even gears is engaged whereas the other clutch (meant for odd gears) is ready to shift to 3rd, which is turn saves a lot of time usually taken in shifting.
Great explanation guys. You cleared my doubts even before asking [lol]

Ok now one of my friend was driving someones Civic AT. Now in the S mode (paddle Shift mode) he said he was shifting in low RPM's but whenever he braked he forgot to downshift the car automatically downshifted.He said while braking the car used to automatically downshift after a certain RPM.

So i asked him if the same happened while upshifting,like did the car automatically upshift after a certain RPM or it used to redline untill you upshift using the paddles.But he dint knew the answer because he said he was shifting at lower RPM's.

So do the cars having CVT tranny in paddle shift mode automatically Up-shift & down-shift if the driver does not in a certain RPM limit ?

Is it the same case of automatic up-shift & down-shift (in paddle shift mode) in cars with DSG trannys ?
 
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Great explanation guys. You cleared my doubts even before asking [lol]

Ok now one of my friend was driving someones Civic AT. Now in the S mode (paddle Shift mode) he said he was shifting in low RPM's but whenever he braked he forgot to downshift the car automatically downshifted.He said while braking the car used to automatically downshift after a certain RPM.

So i asked him if the same happened while upshifting,like did the car automatically upshift after a certain RPM or it used to redline untill you upshift using the paddles.But he dint knew the answer because he said he was shifting at lower RPM's.

So do the cars having CVT tranny in paddle shift mode automatically Up-shift & down-shift if the driver does not in a certain RPM limit ?

Is it the same case of automatic up-shift & down-shift (in paddle shift mode) in cars with DSG trannys ?
Kickdown works in S mode yo.

When it doesn't work is after you've activated paddle shifting.

There is a distinct difference here. The Civic A/T has three modes of operation:

D - Drive mode. Sedate. Your average A/T box.
S - Sport. Different shift points, better throttle response. Lotsa fun in this mode.

Now, press a paddle in S mode and the box goes to Manual mode. Here, there is no kickdown and no auto upshift. Revs hold till redline. You cannot upshift at an RPM which will stall the engine. You cannot downshift at a speed which will blow up the drivetrain. Automatic downshift when you are too slow for a give gear.

The gearbox does learn your driving patterns. The accelerator pedal has a lot of subtle control built into it. Takes a bit of time to learn all the nuances.

Hope Its clear. Thats the CVT. Fun, Practical and Safe.[cheers]
 

Arun

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Interesting.This thing is better than my physics text book.I never knew automatic transmission was so varied.
Racerdabba, when we say "your average A/T box"we mean auto-up shifts and down-shifts in accordance to speed and rpm right?

The Skoda thing was well explained. Thank you Rajeev!
 
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ilango[speed thirst];7558 said:
so in paddle shift the upshifting is mannual for performance , down shifting is automatic?

hope i got right from your post
Yes in paddle shift the downshift is automatic if you are too slow in speed for a given gear.
Like say 30km/h in 5th gear,then it will automatically downshift.
 
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Yes in paddle shift the downshift is automatic if you are too slow in speed for a given gear.
Like say 30km/h in 5th gear,then it will automatically downshift.
Manual mode, Everything manual. Upshifts as well as downshifts.
But The 'box has brains.
Too slow for a gear-downshift.
Trying to downshift while redlining-no shift
Thus, no damage to transmission.
But u can hold on to a gear as long as u want, and redline to your hearts content.[lol]
 
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Automatic Transmission

What are Automatic Transmission cars? Do they not have gears and the clutch? Whats their comparison to the Manual Transmission ones including all their advantages and disadvantages? Which is the best Automatic Transmission car in India at the moment?
 
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