CVT / Fuel economy discussion

Non-Suzuki related topics. Anything can go here.
bdleonard
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SamirD wrote:
Stodge wrote:Weight?
Almost the exact same--4400 gvwr. In fact, I think the Altima was a bit heavier, almost to 4500.
The GVWR is the maximum load including passengers + cargo. So it is not appropriate to use to compare the weights of the vehicles themselves. Curb weight is the more appropriate metric.

My 1999 Altima GLE: Curb Weight ~3020 lbs
My 2013 Kizashi SE AWD: Curb Weight ~3480 lbs

The previous gen Altima was a very similar design to my 1999 (many shared chassis parts), so the weigh should be similar. The FWD Kizashi is shown as about 150 lbs lighter, relative to the AWD. So, the Kizashi is at least 10% heavier, perhaps as much as 15% depending on your trim level.
SamirD
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bdleonard wrote:The GVWR is the maximum load including passengers + cargo. So it is not appropriate to use to compare the weights of the vehicles themselves. Curb weight is the more appropriate metric.

My 1999 Altima GLE: Curb Weight ~3020 lbs
My 2013 Kizashi SE AWD: Curb Weight ~3480 lbs

The previous gen Altima was a very similar design to my 1999 (many shared chassis parts), so the weigh should be similar. The FWD Kizashi is shown as about 150 lbs lighter, relative to the AWD. So, the Kizashi is at least 10% heavier, perhaps as much as 15% depending on your trim level.
The 2nd gen Altima 98-01 was lighter than the previous generation by a decent bit (couple of hundred lbs). It was a cheaper quality and lighter car while the engine, tranny, and basic chassis stayed the same.

I wish I had my FSM to look up the weights. It's in the first 10 pages. :(

Even if their weights are this different, that's a 10% difference. So a 10% difference in fuel economy would basically net them as being very similar. And that's my point--no real 20-30% gains in efficiency, so why bother with CVTs?
bootymac
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Anecdotal experience isn't reliable for this comparison due to the number of variables. It's best to use standardized measurements.

Combined EPA fuel economy for an automatic 1997 Altima (2980lbs) is 21mpg using the most current method of testing. A CVT Kizashi FWD (3330lbs) gets 26mpg and the AWD (3485lbs) gets 25mpg.

So fuel economy has improved despite the increased power output (30hp) and increased weight of vehicles.

Also of note is that the 155lb difference in weight and drive train inefficiencies between the FWD and AWD models yielded a 1 mpg difference

CVT isn't the only reason for the improvement but it's a step in the right direction in vehicles for the masses.

Edit: I figured I'd mention that the above mpg figures might not be accurate in reality, but they are consistent with each other which makes them suitable for comparing
SamirD
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But a lot of real-world mpg ratings from Kizashi drivers doesn't match the stanardized results. So while those are more comparable results due to the testing environments, they don't really mean much in the real world.

I know I'm getting close to 20mpg city in the Kizashi. I know the Altima would regularly do better than this. Once I bring one up here to match the environments, I'll see if that still holds true. Even if it doesn't, the CVT doesn't really impress me. I'd never want to trade reliability for namesake of efficiency.
bdleonard
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SamirD wrote:Even if their weights are this different, that's a 10% difference. So a 10% difference in fuel economy would basically net them as being very similar. And that's my point--no real 20-30% gains in efficiency, so why bother with CVTs?
As far as the fuel economy is concerned, I'm driving an AWD Kizashi that is 15% heavier, has 20% more power, handles much better, and is as economical or slightly better than the Altima I came from. I'm happy with that, but that was basically what I was expecting when I bought the Kizashi.

I've been keeping track of my Kizashi on Fuelly, and once I get to 7500 miles the transfer case and rear diff are getting Redline 75w-85 (the lightest weight allowed in the owners manual) and I'm going to see how that impacts economy. I may try a high quality synthetic 0w-20 or 5w-20 oil, though I recognized the Kizashi manual recommends 5w-30. The J24B engine in other countries and vehicle applications lists 0w-20, and I'm familiar enough with oil specs to feel comfortable trying that. I would expect all of that may net me about 1 more MPG.

Losses due to pumping and to agitation of the CVT fluid are one of the biggest reasons that generation of Jatco CVT transmissions don't show fuel economy much better than a good 4 or 5 speed automatic with a reasonable overdrive. The newer Jatco CTV7 / CVT8 transmissions improve that significantly, and provide a wider ratio spread as well. Those improvements increase vehicle mileage about 10% from the CVT design used in the previous generation Jatco CVT found in the Kizashi.

http://www.jatco.co.jp/ENGLISH/products/cvt/cvt8.html
SamirD
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bdleonard wrote:Losses due to pumping and to agitation of the CVT fluid are one of the biggest reasons that generation of Jatco CVT transmissions don't show fuel economy much better than a good 4 or 5 speed automatic with a reasonable overdrive. The newer Jatco CTV7 / CVT8 transmissions improve that significantly, and provide a wider ratio spread as well. Those improvements increase vehicle mileage about 10% from the CVT design used in the previous generation Jatco CVT found in the Kizashi.

http://www.jatco.co.jp/ENGLISH/products/cvt/cvt8.html
Great info! I guess just like many other things, you can't judge the whole concept from one example. 8-) I should have remembered that so thank you for reminding me. ;)
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Woodie
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SamirD wrote:I'd never want to trade reliability for namesake of efficiency.
If that were the case then you would never get any type of automatic, they all compromise reliability, efficiency, performance, and control.
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SamirD
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Woodie wrote:
SamirD wrote:I'd never want to trade reliability for namesake of efficiency.
If that were the case then you would never get any type of automatic, they all compromise reliability, efficiency, performance, and control.
True, but going to a manual introduces a host of other issues not related to reliability but usability.
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KuroNekko
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SamirD wrote:
Woodie wrote:
SamirD wrote:I'd never want to trade reliability for namesake of efficiency.
If that were the case then you would never get any type of automatic, they all compromise reliability, efficiency, performance, and control.
True, but going to a manual introduces a host of other issues not related to reliability but usability.
True, automatics are easier to deal with, especially in stop and go traffic. However, manuals are hard to beat when it comes to reliability and longevity. The part that takes most of the abuse is the clutch which is a wear item much like brake pads. Unless you are a horrible driver and/or often dump the clutch, your gears will last the life of the car. The only thing you'd have to do is replace the clutch at every 100,000+ miles and change the fluid. Automatic transmissions simply wear out over time due to the intricacies and heat that they generate. The cost of replacing an automatic transmission will usually offset the value of the car so that's why most people will junk them at very high mileage. Nearly all that cars that are still running with over 300,000 miles have manual transmissions for this reason. By that time, most automatic transmissions would have needed a replacement.
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Stodge
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What do you mean by "dump the clutch"?
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