PDA

View Full Version : Semi auto transmission for fuel economy?


[ GTR ]
11-10-2011, 06:19 AM
An automatic car with the option of clutchless shifting - will it save money on how much petrol is consumed compared to the standard automatic transmission?

ollinger
11-10-2011, 06:58 AM
In recent years, for most cars, automatics have surpassed manual in fuel economy. This is due to more gears (some high end cars like Lexus and even some Chryslers now have automatics with as many as 8 speeds), more efficient and direct gear coupling, and better computers in the cars programmed to shift at lower RPM to save fuel. Of course, automatics typically add about a thousand dollars cost and are more likely to need repair, and much more expensive to fix when they do break, so money saved on fuel may be lost elsewhere.

chrischris
11-10-2011, 07:05 AM
Have you guys seen the movie 'Fuel'?




How to drive your current gas car way cheaper without gas altogether.

http://www.youtube.com/watch?v=upTCSSkxlxE


http://www.youtube.com/watch?v=-0qIjghiko0&feature=related

Bhagi Katbamna
11-10-2011, 08:34 AM
There's no benefit to manual transmissions in most high-end cars anymore. Even in Porsche's the double clutch auto cars are usually a hair faster than the manual cars with the same test driver driving them.

LeeD
11-10-2011, 04:01 PM
Most drivers don't have the skills to drive a manual shift car efficiently, so an auto works better for them.
Auto and select is the fastest on the racetrack.
But in the real world, going down a 11 mile hill, a standard can save you lots of gas if you know when to clutch it or go to neutral without killing everyone in front of you.
Some modern cars have 8 speed autos, so they work really efficiently.
But some people don't buy the newest cars.

A Very New Stringer
11-11-2011, 03:46 AM
Automatic cars with sport shift is the same thing as auto. I've driven many of these vehicles and they'll shift for you when the rpms get too high or too low. If I coast whenever I can, I can squeeze out 31 mpg on my car EPA rated 24/29

autumn_leaf
11-11-2011, 05:45 PM
I drive a Nissan Altima with a CVT engine. It's been rated with better speed and mileage in its automatic mode than its manual.

LeeD
11-11-2011, 05:51 PM
As usual, you cannot believe everything you read.
Car manufacturer's rate their autos against what they consider the AVERAGE driver of a manual. If you are AVERAGE, you may believe the stats.
However, not everyone is NORMAL, or AVERAGE, when it comes to the skills of driving a stick shift. Some people cannot drive stickshifts. They are included in the poll. Some kill the engine with every start...they are included.
Some can barely drive a stickshift. They are also included.
That askewers the results.l
Everyone can drive an auto pretty decently.

BreakPoint
11-11-2011, 07:03 PM
Automatic cars with sport shift is the same thing as auto. I've driven many of these vehicles and they'll shift for you when the rpms get too high or too low. If I coast whenever I can, I can squeeze out 31 mpg on my car EPA rated 24/29
However, most cars with the shift for yourself automatic transmissions will get worse gas mileage than the same car with just a standard automatic transmission. I know this is the case with some cars like the Ford Fusion with the SelectShift transmission. I think this is because most people who shift for themselves will delay the shift to higher gears at higher RPM's to get more performance, whereas, the standard auto transmissions are programmed to shift automatically at lower RPM's.

BreakPoint
11-11-2011, 07:05 PM
I drive a Nissan Altima with a CVT engine. It's been rated with better speed and mileage in its automatic mode than its manual.
How can a CVT transmission have a manual mode when they don't have distinct gears? :confused: What are you shifting up and down to?

Mick
11-11-2011, 07:29 PM
There's no benefit to manual transmissions in most high-end cars anymore. Even in Porsche's the double clutch auto cars are usually a hair faster than the manual cars with the same test driver driving them.

except there are some people (like me) who enjoy driving a manual transmission car over an automatic transmission car. to me, driving a manual trans car is like playing tennis and driving an auto transmission car is like watching someone else playing tennis since the car performs all the shifting functions and there's nothing for me to do.

mikeler
11-11-2011, 07:48 PM
except there are some people (like me) who enjoy driving a manual transmission car over an automatic transmission car. to me, driving a manual trans car is like playing tennis and driving an auto transmission car is like watching someone else playing tennis since the car performs all the shifting functions and there's nothing for me to do.


Have you ever played tennis in rush hour traffic? You can get leg cramps from pushing the clutch in some locales. :(

Mick
11-11-2011, 07:56 PM
Have you ever played tennis in rush hour traffic? You can get leg cramps from pushing the clutch in some locales. :(

i think i am used to it so it doesn't bother me. i drive a 370z nismo and everything on that car is heavy (steering, gearshift, clutch) and driving it in rush hour traffic doesn't bother me.
i know i am in the minority. people nowadays prefer driving an automatic over a manual.

ollinger
11-11-2011, 09:11 PM
Manuals won't be available much longer. The percentage sold is getting so low that it barely pays to produce them. And as noted high performance cars are forsaking them -- Ferrari no longer imports cars to the USA with manual transmissions.

mikeler
11-12-2011, 05:49 AM
i think i am used to it so it doesn't bother me. i drive a 370z nismo and everything on that car is heavy (steering, gearshift, clutch) and driving it in rush hour traffic doesn't bother me.
i know i am in the minority. people nowadays prefer driving an automatic over a manual.


I enjoyed stick shift in my younger days living in rural communities.

bad_call
11-12-2011, 06:54 AM
I enjoyed stick shift in my younger days living in rural communities.

haven't had an automatic since high school. pushing in the clutch doesn't bother the legs much since the 4 bangers today don't require as much pressure.

know someone getting one of these higher end cars and it's stick (only i think).

http://www.porsche.com/usa/models/cayman/cayman-r/

A Very New Stringer
11-12-2011, 11:33 AM
How can a CVT transmission have a manual mode when they don't have distinct gears? :confused: What are you shifting up and down to?

I think he's referring to the automatic vs manual version. Also, I don't think they're going to be doing away with manual anytime soon. Many cars are only offered in manual and they seem to be doing pretty well e.g civic si, WRXs, STIs. I see these cars a lot on the road, especially the SI

ollinger
11-12-2011, 11:43 AM
^^ though in theory CVT spools have an infinite number of positions, in practice the belts are pulled to a limited number of distinct positions corresponding to gear ratios, so manual shifting is possible. I've noticed that while CVT seems appealing, absolutely no high-end manufacturers have adopted the technology, so I wonder how desirable it is compared to, say, a conventional automatic with 8 forward speeds. Whining noise is also a frequent complaint about some CVT.

Steve Huff
11-12-2011, 09:40 PM
Breakpoint--even cars with CVTs can have a "manual" mode. Seems pointless, but Nissan builds it into their CVTs. Find a road test in Car & Driver, Road & Track or Motor Trend. I've read it there and thought the same thing that you did.

BreakPoint
11-12-2011, 10:55 PM
Breakpoint--even cars with CVTs can have a "manual" mode. Seems pointless, but Nissan builds it into their CVTs. Find a road test in Car & Driver, Road & Track or Motor Trend. I've read it there and thought the same thing that you did.
Thanks Steve. Yeah, that's very strange. I thought with a CVT the transmission is always supposed to be in the optimum "position", so what would be the point of manually shifting it?

ollinger
11-13-2011, 10:37 AM
^^ because there is no single "optimum." At any given time what is optimum for mpg may not be optimum for climbing a hill. So sometimes one wants to shift for a particular need.

BreakPoint
11-13-2011, 11:16 AM
^^ because there is no single "optimum." At any given time what is optimum for mpg may not be optimum for climbing a hill. So sometimes one wants to shift for a particular need.
Then there is no point to a CVT, is there? You might as well just have a regular automatic transmission with 6 or 8 speeds.

ollinger
11-13-2011, 12:28 PM
^^ there is a point....the CVT is cheaper. This is why the first ones were seen in low end cars like the Subaru Justy. The Justy was famously an inexpensive piece of crap, yet it showcased this relatively new technology. Hmmmmm. And why no high end cars have them -- 8 speeds accomplish essentially the same goals with less noise and probably more durability.

Steve Huff
11-13-2011, 01:46 PM
I think the top-of-the-line Nissan Maxima uses a CVT. I think the CVT is available in all Nissan cars now (not trucks). Nissan seems to be banking on it as a selling point. But, you notice they did not put it in their Infinity line.

baek57
11-13-2011, 01:59 PM
i think i am used to it so it doesn't bother me. i drive a 370z nismo and everything on that car is heavy (steering, gearshift, clutch) and driving it in rush hour traffic doesn't bother me.
i know i am in the minority. people nowadays prefer driving an automatic over a manual.

I'm with you. I can't stand driving an automatic. It's so boring! My daily commute is 2+ hours in rush hour traffic, and as much as 3 hours when it's really bad. I still prefer driving manual. Besides, I'm more likely to fall asleep driving an automatic out of the sheer boredom.