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8-Speed Automatics


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If they are geared like I hear the one in the Chrysler 300 is, then I just don't see the point. Apparently 8th gear doesn't even get used until you hit speeds above 70 MPH, meaning the rest of the gears are setup pretty much like most existing 6 speeds.

 

Like how many gears do you need to get up to average speed of 45mph on most urban, surface streets? Sounds like overkill to me unless they up freeway speeds to 85mph or so which I don't think will happen in my lifetime. And with 8 speed auto or even 6 speed, probably best to have extended warranty on drivetrain if you plan on keeping vehicle long after regular warranty is over. Hate to see what it would cost to replace these super complex trans. I don't know that adding all this technology/complexity adds much value for the buck when speeds are actually going down with more and more vehicles on road every year and commute times lengthening, not shortening. One of the all new feature I see out there that makes lots of sense is auto stop since traffic jams are huge fact of life and getting worse. Maybe electric steering also as you can take the torque steer out of equation and compensate better for crown in road and adapt the steering imput to suspension settings which is another worthwhile feature.

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To the best of my knowledge can't handle much in the way of torque either.

 

I think the Lexus GS450h and LS600h with over 300hp on their eCVTs would disagree. CVTs in hybrids have to be durable since electric motors can deliver max torque at 0 rpm.

I think the eCVT in my Ford is great, it's fun to mess with your passengers by 'slamming' the tranny in to R while flying down the highway. Nothing happens! You can also drive around in L all the time if you want, makes no difference on the highway.

No tranny fluids to change either! They have proved their durability in the Escape hybrid taxi fleets.

CVTs are here to stay, just look at the trannies on the top 10 most fuel efficient vehicles in the US.

Edited by Donaldo
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I heard the exact opposite, didnt help the CVT actually got inferior mileage compared to the regular 6 speed auto....o

I'd heard the CVTs weren't popular, as well; he was correcting me on the issue. Given what he did for Ford, I kind of think he's an authoritative source, but things may have changed after he left Ford.

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Isn't Van Dyke making the new Hybrid CVT's for the '13 Fusion/MKZ/CMAX? I thought Ford was bringing that back in house to stop the production supply issues they currently have. Speaking of the C-Max when is Job 1 for the US version?

True. Van Dyke will be making the new Ford designed eCVT ! That little "e" in front of CVT makes a huge difference in the design of the transmission.

 

A "traditional" CVT, (if one can say the in regards to a CVT) uses a steel belt between to metal sheeves, similar to this picture

 

CVT%20Trans%20Side%20View%20-%20Small.jpg

 

The eCVT used in the current Fusion and Escape hybrids is made by the same company that makes them for Toyota (Aisin ?) The following is from Autoblog

 

There are actually two electric motors in the Escape Hybrid. One 70 kW traction motor and one 45 kw generator/motor both contribute to the hybrid's powertrain. How this system works is actually pretty amazing. I will try my best to relay it to you accurately. The schematic below will show you the relationship of the hybrid's components. The planetary gearset is crucial to the operation of the entire system. Its simplicity is quite elegant.

 

8278518074117163.JPG?0.6967209146838947

 

The system has three modes, Electric vehicle mode, positive split mode, and negative split mode. There is also an idle charge mode, but that does not contribute to the vehicle's direct motivation.

 

8650112790155424.JPG?0.3126689303725476

 

In electric vehicle mode, the traction motor draws energy from the batteries to propel the car without using the gasoline engine. At this point, the gasoline engine is off. When in this mode, energy is also collected when the vehicle is slowing down. This regenerative braking is done in the other modes as well. The diagram below shows how the regenerative braking torque contributes to the vehicle's deceleration effort.

 

3610517740651373.JPG?0.07934121963989293

 

In positive split mode, the gasoline engine is on and works in concert with the traction and generator motors to power the vehicle at moderate speeds or loads. In this mode, the generator is producing energy from the gasoline engine's output. This energy can be used to charge the batteries or power the traction motor. The traction motor also contributes to the Escape's motivation.

 

6289743531817276.JPG?0.08235586977518006

 

During high speed or high load situations, the system operates in negative split mode. In this mode all three power plants are contributing to the vehicle's movement in some way or another. The generator motor operates to reduce the gasoline engine speed required while the traction motor operates as a generator to provide power to the generator motor.

 

0805893924634436.JPG?0.20117619147755494

 

The electrically controlled CVT or eCVT does not have the belts and chains typically found in other CVTs. Instead the motors and planetary gear set work in harmony to operate in the most efficient manner possible. The planetary gear set allows the contribution of the gasoline and generator motor to vary depending on the situation.

 

 

I suspect the new Ford designed transmission will use a similar design.

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Very true !

 

Adding more ratios to any kind of transmission adds weight and size. It is easier to add additional ratios to a dual clutch transmission.

 

Additional ratios do not always mean additional fuel economy. Some of the gains go back into carrying around the extra weight.

 

Another problem with more ratios is customers don't like the feel of gears shifting a lot ("busy").

well theres always the 7 speed F1 transmissions, under 90lbs and can handle some serious numbers....course 1 gearbox is probably 3 or four Raptors......

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I wouldn't be too particularly worried about being late to this game. From this point forward, I think we're going to be seeing diminishing returns from adding more gears to a traditionally shifted automatic. Sure, 6 speeds are by far greater than 4, but the advantages of an 8 over a 6 just really aren't that great. Looks good in advertising...

 

You could apply the reductionist logic to 6 ratios as well... "'Oh 6th is only OD, give me five 'True" gears'" etc...

 

First 6 gears are normal whereas 7 and 8th are OD gears. The 2012 Charger, a 4000lb car, with the 8-speed auto returns 31mpg at 70mph with an engine speed of only 1500rpms. I doubt anyone here is getting that mileage at 70mph and if they are, it would be on the diminishing curve, not the positive one.

 

Imagine a V6 Mustang, which already gets 31mpg, with an 8-speed auto... That's 38mpg assuming 20% better fuel, or 40+mpg when combined with a 2.7-3.0L Ecoboost.

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Doubtful. Ford cannot amortize the cost of development with just Lincoln sales, plus Ford will need the additional mpg's across its model line, not just Lincoln.

 

Automotive News reported a few months ago that 2014 Chevy pickup would get 8 speed auto and speculated that Ford would follow with its next pickup offering. An 8 speed auto makes sense in a big, heavy pickup. Kind of like a big rig Peterbilt with its 16 gears or whatever. Overkill in a 3,500 pound car IMO. I wouldn't mind an extra overdrive gear on my 4 speed auto Taurus, but that's about it. A 5 speed auto or 5 speed manual is perfect to me.

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The whole point of more gears is to allow the engine to operate in a narrow RPM range (where it is most efficient) over a wide range of road speeds.

 

For the big trucks in the 60s and 70s, to keep the diesels of the day near their "sweet spot" (a range of about 200 rpm) you needed everything from the 13 to 18 speed Road Rangers to the old 5 + 4 arrangements (20 speeds)

 

As fuel economy bevomes more important, you want the engine to operate at the point of best efficiency with respect to fuel economy, and since road speeds easily range from 20 to 75 mph (and more) I see 8 and 9 speed units becomming more common to allow the engines to operate in a narrow RPM range.

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You could apply the reductionist logic to 6 ratios as well... "'Oh 6th is only OD, give me five 'True" gears'" etc...

 

First 6 gears are normal whereas 7 and 8th are OD gears. The 2012 Charger, a 4000lb car, with the 8-speed auto returns 31mpg at 70mph with an engine speed of only 1500rpms. I doubt anyone here is getting that mileage at 70mph and if they are, it would be on the diminishing curve, not the positive one.

 

Imagine a V6 Mustang, which already gets 31mpg, with an 8-speed auto... That's 38mpg assuming 20% better fuel, or 40+mpg when combined with a 2.7-3.0L Ecoboost.

 

In the EPA test cycle, I would be surprised if 8th gear even saw more than a couple minutes' use, so its overall impact on the Charger/300's fuel economy probably shouldn't be based on those numbers.

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I suspect the new Ford designed transmission will use a similar design.

To simplify those graphs and diagrams:

 

The eCVT looks much like a conventional automatic transmission with a planetary gearset.

 

However, the ring gear, not the planetary set, is connected to the differential/AWD box.

 

The ability of the outer ring gear to spin as well as the planetary gears and the sun gear is what makes it a CVT, relative to the output shaft.

Edited by RichardJensen
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In the EPA test cycle, I would be surprised if 8th gear even saw more than a couple minutes' use, so its overall impact on the Charger/300's fuel economy probably shouldn't be based on those numbers.

 

It takes less energy to sustain an object at that speed than it takes to get it there. I can't imagine a few minutes making a difference in fuel economy, especially considering the various control modules making thousands of adjustments at any given moment.

 

Diminishing returns doesn't have to mean there isn't any value, so when combined with other fuel saving methods, 8-10spds could pay off.

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This is what I was trying to get at in the thread about focus economy a few weeks back. Every diesel Ford superduty I've driven could benefit from another overdrive or two (or more gears spaced closer and a taller rear end gear, though the former would put less strain on the transmixer). If Ford does it it makes sense, if I suggest it in that thread and say "sweet spot" I get treated like an idiot lol... Of course it was in a diferent context mixed with my lack of knowledge on the EPA test, but the same topic anyway.

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Where did you get 20% better fuel economy for 2 more gears? That seem a bit, erm, optimistic to me...

 

Probably, maybe if you are taking a long 500 mile+ vacation which we do everyday, right? Most of the time we are going to grocery, dentist, whatever resulting in maybe a few extra miles if that at end of what gas you bought being used up. I believe Ford stated that going to 6 speed auto from 4 speed auto resulted in about 7% better fuel mileage which is about 1.5 more miles/gallaon on average. With the average new vehicle now running about $30,000, I don't know if that gives you much bang for your buck. Dang, buy yourself a used 2007 Fusion for about $13,000 and the extra $17,000 you save will buy you a lot of gas and screw the 8 speed autos. Again, if freeway speeds went up to 85mph which they won't because of too much traffic congestion which is getting worse every year, I could see the benefit of 8 speeds in a 3500 pound auto. Ford should stick to putting 8 speed auto into F-Series, Lincoln, and top of line Titanium models only for first couple years at least. Like any new technology, I assume it will filter down to more mundane models over time.

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It takes less energy to sustain an object at that speed than it takes to get it there. I can't imagine a few minutes making a difference in fuel economy, especially considering the various control modules making thousands of adjustments at any given moment.

 

Diminishing returns doesn't have to mean there isn't any value, so when combined with other fuel saving methods, 8-10spds could pay off.

 

Oh, I'm not suggesting that it won't make any difference. Just less of a difference than adding gears to a transmission has done in the past.

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If we make it a 12 speed would we get 62 mpg?

 

Ford could make a Volt's MPG look like a Mac truck with a 30-Speed trans..

 

Members of BOF have a lot of "Brain Storming" going on here... I hope Ford patents these ideas quickly...

 

Got to go and buy more Ford stock..

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