what does continuous variable transmission mean?
It means the transmission "gear" ratios are continuously changing to keep the engine at it's most efficient operating level. CVT transmissions don't have gears as such. These transmissions have been very troublesome on some vehicles and it is about an $8000 repair if you are out of warranty and the CVT fails. Do some reading at the link below or "google" CVT transmission.
It means you had better take good care of it as a new one can run $8,000. Change the fluid regularly even if Subaru says it is "lifetime". Life can be short and expensive.
Hi Debbie. In Subaru's iteration a woven metal belt fits between two conical cylinders; positioned as load, speed, and power require. You can picture it as trying to spin an hourglass with a string wound around its center: the closer the string sits to the skinny center, the faster the spin...but the harder you have to twist. CVT's have been used in industriy (like textile factories) for many decades. Advantages include having fewer parts, high efficiency, and if programmed well can be reasonably satisfying to drive. Given that they still use auxiliary internal components like torque converters, seals, valves, etc, their reliability is not inherently better nor worse than conventional multi-gear "automatics". Worrisome failure rates have resulted in a burgeoning salvage market in the $1.5-$2k range. Replacing one is annoying, indeed, but not necessarily fatal to the host chariot. Notwithstanding Subaru's failure rates, I like the mating of its CVT with the 2.5i motor (Leg/OB). The weaker 2.0i struggles more, resulting in anemic, much louder operation. It's important to note that Subie's CVT's are built in "clean rooms", and are thus nearly impossible to rebuild. We're learning to drain and refill (pump in) fresh fluid every few years as proper prophylaxis. When fuel prices recover to environmental fairness the efficiency of the system will be its reward.
Guru - I have extensively driven both 6 speed and CVT Foresters over identical routes and the CVT actually works quite well. My gripe with it is the high cost and potentially short life. The 6 speed gets the exact same gas mileage on the roads I normally drive. On the highway the CVT does get a mile or so per gallon better mileage but that is due to the higher final "gear" ratio. I don't see that CVT's are more efficient, if the 6 speed had a little wider gear spread the highway efficiency should be the same as the CVT.
Hi FOR. Theoretically it's possible to keep the discrete-gear (6 sp) tranny at a most efficient engine speed to approach the efficiency of the CVT under light acceleration, as the direct drive efficiency offsets the torque-converter slop; but the great majority of folks exercise greater throttle dynamic range, wherein the CVT, if programmed well, will be more efficient. It's simply about trying to integrate a power/efficiency curve, where a continuous curve is automatically (pi!) better than a stepped (6 sp) function. In practice it's pretty easy for the CVT to pull greater efficiency from the 2.5i than the EAT...and a bit better than the manual 6 sp. With the 2.0i the CVT has to work pretty hard to offset load mass, so that its efficiency is barely better than the 5sp stick, for example. An interesting example is with my '06 Miata, wherein the 6sp Aisin autobox is geared 37% (!!) taller than either the 5 or 6 sp sticks, resulting in the same eco, as the gearing offsets the sluch-box slop. Plus the 6AT is faster in hole shots, and immeasurably quieter above 75mph.
With the flat torque curve of most modern engines I suspect that gear steps in the 6 speed are not terribly significant in highway driving fuel efficiency. They are more fun anyway. Maybe someday the CVT will be "perfected" but in the meantime the development will be funded by the victims of these transmissions.
I do find it interesting that Subaru charges so much for new CVT's. If these transmissions really cost that much the cars should be priced a lot higher. You can buy a new Forester CVT for around 22k and a new CVT installed is around 1/3 of that. I do realize there is a labor cost to factor in.
I have been told Subaru wants to go 100% CVT including their performance cars. If they are gouging on CVT replacement costs word will eventually get out and this could cost them sales if people realize these cars are not financially worth fixing due to transmission issues with the only option being installing a used CVT. I know I would never buy a CVT car unless I can afford to dump it before it hits 100k miles. Is the supply of used CVT's sufficient to keep up with demand?
Subie's first few years with their 1989 debut 4EAT were problematic also, but after the late 90's they became pretty bulletproof, unless abused via unequal rolling radii at the corners. Since the failures of the 2010 debut CVT are related to its auxiliary components, and not the actual primary drive mechanism I'd hope that improving the durability of these components will extend mean time between failure and lower the idiosyncratic failures of late. I'm still cherry-picking 2013-14 OBs and 2011-14 Legs, hoping for long lifespans, but just checked out an otherwise-nice '13 OB Ltd yesterday with a grinding CVT. Damn...! In the meantime I suggest folks avoid the 2010 year because of all the new-model teething pains. For that matter, the new 2015 seems to replicate this cycle. Subie hasn't redesigned their old manual tranny, so going to all- CVT rather than buying another manual box is an interesting path. So I wonder why they chose the Aisin 6AT (as Mazda has for a decade) for the BRZ? It's not like its meager motor is too torquey for the CVT. Maybe it has to do with spatial requirements in a RWD layout? That doesn't quite seem right, though....
You relalize that if we keep this up we'll have to deal with Grasshopper soon....
Wax on, Wax off.
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