GM: Don't forget about the transmission's role in overall efficiency
Click above to watch the video after the break
We often tend to focus on alternatives to the internal combustion engine when discussing the future of transportation. While it's true that electric motors, batteries and hydrogen fuel cells are likely to play an increasingly large role in the future, there's little doubt that fossil-fuel-burning engines will remain the dominant technology powering our automobiles for at least the next few years.
This being the case, it's extremely important to continue finding new ways to improve the efficiency of the internal combustion engine and the transmission it's hooked up to. A few short decades ago, it was common to see automatic transmissions with as few as three forward gear ratios. Today, that figure is often doubled. Why does it matter? According to Jeff Lux, Transmissions Global Chief Engineer at GM:
Six-speeds provide the best of both worlds, delivering both improved fuel economy and performance. On average, a six-speed transmission will provide up to four percent improved fuel economy compared to a four-speed automatic transmission. In addition, a six-speed provides up to a seven percent improvement in 0-60 performance... Because six-speeds have a wider range of gear ratios to choose from, the engine speed can be optimized for the driving condition. The result is lower engine speeds for many conditions and better overall vehicle noise quality.There you have it. Click here to read more interesting tidbits about GM's future plans for the automatic transmission and click past the break for a video explaining how these modern transmissions work.
[Source: GM FastLane]
Video:
Reader Comments (Page 1 of 2)
Matt 5:12PM (5/13/2009)
And if you don't believe that, just look at the mileage improvements VW/Audi made with their DSG transmissions.
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paulwesterberg 5:44PM (5/13/2009)
An efficient transmission is just a band aid on the gaping wound of inefficiency that is the internal combustion engine. Using controlled explosions to produce motion will always waste 75% of the energy as heat. The prius already uses a continuously variable transmission to optimize engine output.
A whopping 7% improvement might help the malibu improve to 28mpg(combined), I bet it costs 7% more also.
MikeW 10:40PM (5/13/2009)
Don't forget the biggest gain.
A bigger transmission allows for a smaller engine.
Joe Bonaparte 5:36PM (5/13/2009)
how about using that liquid crystal lubricant in motor, transmission, bearings? that oughta help everything.
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required 6:11PM (5/13/2009)
Popular Science had an article in the 1990's that listed a plethora of simple inexpensive things the automotive industry could do to improve fuel efficiency. In other words I have no reason to trust GM in regards to them caring one iota about efficiency.
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win39 6:12PM (5/13/2009)
Sad really. Still building inefficient torque converter transmissions when even VW is building automatic dual clutch operated geared transmissions. This is kind of like all those ads for SUVs and trucks because they are just sitting around. Buy our outmoded transmission. It is the wave of the future. Humph.
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downtoearth 8:41PM (5/13/2009)
win39 6:12PM (5/13/2009):
> Sad really. Still building inefficient torque converter transmissions
Sorry, but your post is misleading and completely outdated.
Torque converter based automatic transmissions use torque converter lockup clutches since maybe 60ies or 50ies. Back then only overdrive gears were locked after shifting was done, now virtually everyone expect 1st or 2nd is.
The only parasitic loss in automatic transmissions is a power sucking oil pump since pressure needs to be kept all the time. This is a very minor problem and in some cases even this has been fixed. Examples:
1. 6-speed automatic Lexus IS 250 gets a better EPA rating than its 6-speed manual version: http://www.fueleconomy.gov/feg/compx2008f.jsp?year=2009&make=Lexus&model=IS%20250&hiddenField=Findacar
2. 5-speed automatic Mazda 6 beats its 6-speed manual version: http://www.fueleconomy.gov/feg/compx2008f.jsp?year=2009&make=Mazda&model=6&hiddenField=Findacar
> when even VW is building automatic dual clutch operated geared transmissions
Double clutch gearboxes present mostly disadvantages when compared with modern torque converter automatics with lockup.
- both types offer imperceptible shifts
- both are as efficient as manual gearboxes
- both provide smooth uninterrupted power delivery
Meanwhile you do not need to replace clutches in torque converter automatics.
Gordio 9:47PM (5/13/2009)
For some reason EPA rates highway automatics higher. But if you look at real data from real consumers, automatics often get worse mileage than their manual counterparts. Even on highway.
9394 10:40PM (5/13/2009)
At highway speeds (65+mph), most MT are not as fuel efficient as AT because the MT rpm is higher. I have a Mazda6 5sp. The rpm is around 3100 at 65mph. I think the rpm is about 2600 for an AT Mazda6.
win39 10:49PM (5/13/2009)
And yet, if I take my foot off the brake a car with a torque converter will run into the car in front of me.
What Gordio says is true. The fallacy with the automatic vs. manual transmission EPA mileage is that virtually all manufacturers put in different final drive ratios for the two drive systems. It is easy check in the manufacturer specs and it can be observed in road tests that give engine RPM for a specific road speed. And just for a little marketing logic. Build a car with an automatic transmission that gets better fuel economy on the sticker(it's acceleration figures are not there) and then you can sell a car with an automatic for extra money and you can manufacture it with greater economies of scale.
I could not find any real world mileage for the cars you mentioned because few people buy them with manual transmissions, but looking at a Honda Civic which has lots of contributions to fueleconomy.com, the automatic gets 25/36 from EPA while the manual gets 26/34. Real world mileage is 31.6 average for 82 automatic drivers and 34.4 for 31 manual drivers. Honda cons the system too with different final drive ratios and two overdrive transmission ratios in the automatic and only one in the manual. I own the manual model and have driven the automatic. There is a performance difference and the manual does get significantly better mileage for me than the automatic.
MikeW 1:06PM (5/14/2009)
The Honda civic automatic absolutely beats the manual in terms of highway mileage.
5th gear of the manual (where is the 6th Honda) equals 4th gear of the 5 speed automatic.
I have seen 44mpg with E10 regular gasoline. (and I wasn't going slow)
win39 2:29PM (5/14/2009)
Being a fanboy is OK, but to ignore the experience of the over a hundred other Civic drivers I mentioned and pointed you to means that it passes into irrationality and people snigger behind your back. You must be a very good driver to get such amazing mileage out of the automatic. Imagine what you could do with the manual.
MikeW 5:08PM (5/15/2009)
I'd get worse mileage.
I looked in to how Honda's i-vtec works on the R18 engine.
You need to stay under 3500rpm, so you can go 100mph and still be in vtec.
With the manual transmission, 80mph=3500
Here is the progression of what happens when you tip into the throttle:
eEGR turns off, torque converter unlocks, i-vtec turns off, transmission downshifts, and if you rev high enough-short runners open at 5200-6700
So with experience you learn how much throttle you can give it and still keep the torque converter locked up.
vfx 6:25PM (5/13/2009)
I'd rather have the the solution that has the fewest parts to break down.
Hint,
It's not a 6 gear transmission with automatic, 5 gears with paddle shifting, 4 gears on a stick, 3 on the tree, or even 2 gears (nice try, Tesla).
The best solution is an Electric Motor with a no-shift, no-reverse simple reduction gearbox.
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kballs 9:21PM (5/13/2009)
Even better would be direct drive, no differentials, an electric motor for each wheel (could still connect to wheels with CV axles if unsprung weight or jarring over bumps are issues). It would also allow you to do maximum regenerative breaking, and torque vectoring.
UH2L 6:39PM (5/13/2009)
Yes, so lets not improve efficiency by 7% where we can. What idiotic comments some of you make. These aren't outdated transmissions. Dual clutch ones are expensive for the main stream. How can anybody criticize doing this. And what about other companies not doing these simple fixes to improve efficiency? Why shouldn't we trust them either?
Have people considered that consumers don't want to pay extra for some of these features or wouldn't like them for other reasons? I've driven automated manual transmission vehicles and I think they're fantastic transmissions, but our American butts generally don't like the feel of the jerkiness and relatively slow shifts compared to traditional torque converter automatics. CVT's are a great way to go, but consumers like simulated discrete gear ratios because they don't like the rubberband effect they feel with a CVT. It's sad, but not everybody wants green over comfort. Car companies have to sell what sells and try to make money.
And to the person that criticizes torque converters, do you realize that torque converters multiply torque meaning that a car doesn't need to downshift as often like a manual to pass? Torque converters can save fuel in these cases. Look at the numbers. Automatic tranny vehicles often rev more slowly than their manual transmission counterparts at highway speeds and first gear doesn't need as extreme of a ratio to get the vehicle moving. This is all thanks to the torque converter. And by the way, GM was one of the pioneers of the partially locking torque converter. Hopefully you understand that torque converters lock up and what that means.
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downtoearth 8:56PM (5/13/2009)
Torque multiplication action always come at a price of some losses (heat from torque converter slipping and warming up its fluid). The key to classic automatic gearboxes efficiency are lockup clutches that simply do not allow any skid (thus losses) of torque converter plates and are engaged moments after shifting was done.
Gordio 7:01PM (5/13/2009)
How bout...we drive a manual transmission and get a 10% fuel economy increase...
I"m so glad I got my fit in manual tranny--I almost got it in automatic until a lot of my car enthusiast friends peer pressured me into getting a manual. At the time, i'd drive my dad's truck every now and then, and I was very intimidated. I"ll never drive an automatic every again (unless CVT technology improves to the point it's superior to a MT)
I used to moderate a fuel economy forum on a Fit site, and most of the people who complained their ~27 mpg mileages (and not the 35 mpg as in the EPA rating) were drivers of automatics. A stick shift car can easily achieve the EPA estimate.
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UH2L 7:20PM (5/13/2009)
Automatics often get better fuel economy on the highway (for some of the reasons I mentioned above including having to rev higher to reduce the need for downshifting). In the city, because of engine braking deceleration with fuel cut-off, manuals often get better fuel economy. At idle, on an automatic, the engine has to keep spinning the torque converter whereas the manual can keep the engine free-spinning. That hurts automatic city fuel economy.
Matt 9:21PM (5/13/2009)
The key to getting better mpg in a manual on the highway is driving at the correct speed. While a CVT can adjust the ratio if the engine is not at it's most efficient rpm, the manual is in a fixed gear ratio. If you drive at the optimum speed, the manual will achieve better mileage every time. There are simply fewer losses in a manual transmission, and that leads to better efficiency, all other factors (engine speed) aside.