More Efficient Transmissions

[shovel]

If our engines were external combustion instead of internal combustion, they wouldn't care what fuel they burn and they wouldn't need a transmission at all.

[gone-ot]

Battery-powered vehicles made a comeback, why not steam (tell that to Bill Lear)???

[user removed]

In their 2006 research paper the EPA predicted an 80% increase in fuel mileage through powertrain improvements alone. Combining all other predicted improvements the total gain in mileage was 120%, with the powertrain still responsible for 80 of that 120%.

regards
Mech

[tjts1]

When I swapped a manual transmission into my 300D, a 30mpg car became a 40mpg car. One more gear and no torque converter loss makes quite a difference.

[gone-ot]

EPA pedicted improvements: Theory routinely achieves 100% efficiency, reality never achieves 100% efficiency.

[user removed]

Kind of like the predictions of battery technology improvements from 7 years ago.

regards
Mech

[jeff88]

So as a recap and to make sure I have this right:

1. The big hog isn't the transmission as much as it is the torque converter. After you guys mentioned the TC, I've been watching some videos about torque converters (thank heaven for Youtube!). Basically, the less "slippage" the TC has the more efficient (albeit w/ minor driver discomfort).

2. Highly generic and oversimplified order of efficiency: manual (good driver)> dual clutch auto (driver can manually switch gears if need be)> centrifugal clutch CVT> torque converter CVT (if that's a thing)> locking torque converter auto > old automatics (with lots of slip)
[and somewhere in there would be the inefficiencies of lower amount of gears vs. higher amount of gears (i.e. 2, 3, 4 gears vs. 5, 6, 7, 8 & 9 gears)]

Q's:

• Can a manual swap really produce an increase of 10MPG?!
• Many of the videos I watched mentioned the TC will increase the torque put out by the engine. Can someone explain how that works exactly and is there a way to increase the amount it increases it by (i.e. an electric motor which forces more fluid through faster, or something)?
• Does the ATF in the TC ever leave the TC and back into the trans. pan or is it just revolving back and forth between the pump and turbine?
• In an automatic, is there a such thing as too many gears? I guess if you were planning on having a lot, then a CVT would be better?
• According to Wikipedia, the dual clutch is an automatic, but the driver has the ability to manually shift (with automatic shifting, no clutch) I've seen these before, with the gear shifter having extra gear options, but did not know what gave it that ability. So a DCT is sorta like a manumatic?

Thanks as always for the help!

[niky]

A DCT is a clutch-type transmission. It's more properly termed as a robotic clutch transmission (like BMW's SMG), only there's two clutches and two separate sets of gears... so while one gearset is coming out of gear, the other one is already in gear, and all you need to do is to release one clutch and activate another for a near-instantaneous shift.

[justme1969]

If we all drove pencil shaped cars and were not spoiled by sitting inside Giant caverns then engine displacement overall would / will drop.
Smaller compartments = less storage so economy would/ will rise and cars could get solar chaser type economy... some day...
And then Ill be living on the moon.

[RobertISaar]

i know GM made at least one CVT with a torque converter(think it was a joint venture with toyota?).... i want to say it was continuously locked above ~10MPH.

a torque converter can multiply torque... it's kind of strange to think about though. in any case, when it's multiplying torque, it's also slipping to the point of stall, which is not what anybody interested in efficiency would be interested in. see: Torque converter - Wikipedia, the free encyclopedia

ATF in the torque converter moves around quite a bit. if it didn't, whenever the torque converter clutch locked, small amounts of clutch material would shed off every time. if it never got pushed out and filtered, it would build up and cause issues.

too many gears? depends on who you ask. if you like constant shifting to keep at BSFC peak, you can never have enough gears. anything above 6 feels excessive to me, even then, calibration dependant. there are both good and bad 6 speed autos.

dual clutch = a more complicated manual transmission that has the PCM/TCM controlling the clutch and shifter. so, to the driver, it's an automatic. ability to command shifts is not DCT specific, nor a requirement.