Chrysler Readies Nine-Speed Auto Transmissions to Cut Fuel Consumption
August 1, 2012 9:21 AM
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The Chrysler 300 will be a recipient of the new 9-speed automatic transmission.
A 16% improvement in fuel efficiency is expected from nine-speed transmission
Automakers are pulling out all the stops and looking to squeeze every single mile per gallon out of their automobiles by any means necessary. Automakers are looking at more
fuel-efficient engines with smaller displacements
, but they're also looking at
reducing the weight of vehicles
increasing the number of forward gears
used in car/truck transmissions.
Adding forward gears
to a transmission makes a lot of sense because the slower the engine spins, the less fuel it consumes. In years past automatic transmissions used in vehicles commonly had four or five forward gears. More recent vehicles are moving up to six-speed and in some cases even eight-speed automatic transmissions in luxury vehicles. Chrysler is eyeing even more gears inside with nine-speed gearboxes for more mainstream vehicles.
According to Mircea Gradu, vice president transmission powertrain driveline engineering, Chrysler will roll out its first nine-speed transmission by the first half of 2013. “I’m convinced that, sooner or later, others will come up with similar solutions,” Gradu said in an interview from his office in Auburn Hills, Michigan, where Chrysler is based. “Hopefully, the time will be as long as possible until they catch up with the technology.”
Chrysler CEO Sergio Marchionne believes that the automaker and its various brands will be able to meet looming fuel-efficiency standards by using technology that improves traditional gasoline engines combined with better transmissions rather than moving to plug-in hybrids and pure electric vehicles.
will reach 54.5 mpg by 2025.
Michael Omotoso, a powertrain analyst at LMC Automotive, said, "They’re [Chrysler] doing basically the bare minimum to satisfy government regulations. Their strategy is to meet the standards with minimum investment.”
reports that the nine-speed transmission Chrysler is developing could boost fuel economy of certain models by as much as 16%. Chrysler has already scored a 15% boost in the highway fuel economy of the Chrysler 300 and Dodge Charger by adding an eight-speed automatic transmission.
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I don' like 'em
8/1/2012 10:51:55 AM
Engines do not consume less fuel the slower they run. They consume te least fuel when they are operating as close as possible to the spec they are designed for.
Using more speeds yields 2 advantages :
1. you can design an engine to work in a very narrow powerband, optimizing it for that powerband.
2. you can use the 9 speeds to keep the engine in this powerband almost irrespective of the speed you are driving. The box will simply select the gear that keeps the engine in that powerband.
Now, all this is very jolly. Until you actually try it. The box is constantly shifting. So other technologies are introduced, like pre-emptive shifting. Which means whatever the computer thinks the next gear you'll want next is already selected so it's ready when you need it. But for this you need even more moving parts. Something like a DSG.
Now, things are working wonderfully well. UNTIL, that is, you want something different from what the computer has selected for you. Let's say you are slowly accelerating (fuel efficiency is importing to you. You're trying to avoid hammering the go pedal). The computer has already selected the next gear up. At which time the geriatric in front of you is looking for his pipe, and you decide you need to pass him, and you DO press the go pedal. The box has to decide what the new parameters are, unselect the higher gear, put in the new lower gear, and haul ass. The shock in the driveline is scary. I tried it wit a VW, and t was not happy.
Generally though, you won't feel a thing. Untill you're motoring along in traffic and start watching the rev counter. The thing is going up and down constantly, indicating the box is working all the time. I estimate a VW DSG box shifts 2-3 thimes more often than a regular 5 speed torque convertor box.
And this is where I get worried. It would mean you're looking at a worn out box close to 80-90K miles. Which would NOT make me a happy camper if I'd spent 50K on a new car 2.5 years ago.
RE: I don' like 'em
8/1/2012 7:17:46 PM
You have to remember than 99% of the time engines are not operating at full throttle. Even at cruise speed on the highway the demand is only in the 15-20 hp region. Max HP is only needed for high speeds, going up hills, or most importantly acceleration. Gasoline engines operating at partial load ARE more efficient at low RPMs because of the reduced friction and pumping (throttle) losses.
HP = Torque x RPM
For maximum acceleration you want a transmission that can let the engine operate at it's point of maximum HP (usually near redline) no matter what the speed of the car. This allows you to have a higher amount of usable HP available across the speed range.
This gives you a torque curve at the wheels of maximum torque at zero velocity with the torque decreasing as speed increases. This is essentially the torque curve of electric motors and why they can work so well in cars (and why Tesla can get away with a single speed transmission and still achieve 0-60mph in 3.7 seconds out of a 288 hp motor).
If you must use a transmission with only a few gears you have to use a larger motor to give you the same acceleration for those regions where the motor must operate outside it's peak hp point.
So more gears lets you use a smaller engine to achieve the same acceleration performance. Smaller engine has less friction, less throttle losses, and lower weight. All these increase fuel efficiency.
For maximum efficiency at cruise speed you want a high gear ratio that lets the engine operate at lower RPM with a higher intake manifold pressure (throttle more open). This is not as important for diesel engines because they don't have throttle losses.
Modern automatics are more expensive than manuals. However modern automatics are as efficient and in many cases more efficient than manuals, especially with the vast majority of drivers. In the old days there was considerably power wastage in the torque converter in automatics, but modern designs with such systems as lockup up torque converters and dual-clutch transmissions don't have those losses anymore.
The current trend toward dual-clutch automatics does increase costs somewhat, but the performance is much superior to manual transmissions. They can also be configured for manual paddle shifting if desired giving the driver full shifting control. Shifts can be much smoother than single clutch automatics let alone manuals and shift times are in the 100 millisecond range, way beyond the capability of any manual. The same transmission system can operate fully automatic, or manually at the drivers preference.
Also new and different does not necessarily mean less reliable. Current engines with fuel injection and engine computers etc are more complex than say an old air cooled VW, but they can also be much more reliable. Although it may be mentally convenient to make generalizations you have to periodically reevaluate them as things change.
With the electronically controlled automatics the driver can input a desired up or down shift intention to the transmission so it doesn't make a wrong shift decision. McLaren uses this feature in their MP4-12C and calls it PreCog.
Personally I have no desire to go back to gated manuals and clutch pedals, I'd prefer a DCT automatic that I can paddle shift when desired. I can understand some people want to cling to the old school stuff and sing it's praises, I prefer to embrace the advances in technology. Neither them nor I are typical of the vast majority of car buyers who I suspect don't even want to think about shifting at all.
RE: I don' like 'em
8/2/2012 3:44:19 AM
Rated you up, Excellent post and I learnt a little something about modern automatics!
Often wondered how they compare to manuals as I currently have a six speed manual V8 and am sick of fixing the clutch and rough gear changes,Wanting a new car with auto or sequential shifting or whatever they call it.I keep telling the younger guys at work that modern autos now are pretty damn good and just as quick to the average joe but they never believe me,I don't understand the tech side so I can never back up my side of the argument,This post of yours will help. ;)
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