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How Good is the CVT Transmission??

191K views 161 replies 73 participants last post by  KSKarl 
#1 ·
My first time posting to this forum, but I have a fundamental transmission question for the members. I plan to be a Subaru owner in the very near future, probably an Outback, or possibly a 2014 Forester. For handling mountain grades, with extended downhill sections, can the CVT be shifted down to retard the vehicle so you don't have to ride the brakes so hard? The 2.5 models come with the CVT, whereas the 3.6's come with a conventional 5 speed auto w/ paddle shifters. My concerns are tending me to go for the 3.6 just to get away from the CVT. I see where the mileage seems to be better with the CVT, but I worry about slippage and ineffective downshift control. I plan to do some light trailer hauling (1600 lbs) in addition to general highway and errand running use. Do these CVT's do a decent job? My Ford Superduty has the Tow/Haul mode which really works great, so this is kind of setting my expectation.

Thanks for any info and experience you may offer.

Infidel
 
#46 ·
Subaru is about to install a 3rd CVT transmission in my 2012 Outback with just 17k on the clock. I love everything else about the car, but I got a lemon. Your luck would surely be better. At least Subaru backs their products. To their credit, they're replacing it on their dime.
 
#47 ·
no matter what car you buy, there are lemons like that one. my rallycross times would probably increase dramatically if i had the 2.5l engine with a normal slushbox. i think after 2014 all subaru ATs will be CVT. i believe a large portion of the auto industry will go in this direction...
 
#48 ·
My friend has a 2012 Outback 2.5L CVT. I've noticed when it is in auto mode and I floor it from a stop, the engine won't reach 5000RPM until 40MPH! Perhaps if I switch it to manual 1st gear it would reach peak HP RPM at much lower speeds. But in automatic mode there is a lack of power until you get around 30-40MPH, I'm not sure why they programmed the transmission to behave like this. Flooring mean I need to accelerate fast.
It's probably just programming, not a hardware limitation.
 
#50 ·
Does your friend know that your treating his car like a tool?

Just so you know the Auto mode with the CVT uses lots of various logic to decide how much RPM its going to run up before adjusting the gear ratios also anything beyond about 4500rpm with the new engine is flat anyway meaning if what you want to be doing is moving the vehicle faster its good to be in the torque band too. BTW its even different when I tow my trailer the CVT runs the car with higher rpms at lower speeds. Empty car in AT mode its not a sports car and the focus is being fuel efficient so makes sense the car would be set up this way. Also its easy for people to forget that the car only has 175hp
 
#53 ·
The engine was hot, why would it care if I did a few 0-40MPH runs? Figured the wear would be nonexistant. It's not like I'm revving it up in neutral and slamming it into drive or anything like that.
If it is just a software issue then I wonder why they programmed it the way they did, having a "long" first "gear". It would be pretty quick if it reached 4500-5000RPM by 15MPH or so and kept it in the sweet spot, which it might be able to do in manual mode.
If it's for fuel economy, I'm not sure why they would favor fuel economy over performance if the pedal is all the way down (what if it's an emergency).
 
#54 ·
If it's an emergency then you obviously need to plan for such circumstances. Anyone who buys a 4 cylinder with a CVT and expect responsiveness with performance car numbers obviously doesn't have any idea what car to buy or how to drive. :rolleyes:

In whch case, as I've already said, that person should have bought a 2014 Subaru Forester XT or a Subaru Outback 3.6R. :D
 
#55 ·
A CVT with the right ratio abilities and the right software can give as good of acceleration as a manual transmission. Yes the CVT has a clutch or even a torque converter to get it going from a stop but then it should lock and it should be as efficient as a manual. This means you can get full power from the engine. If the CVT has the ratio abilities and software it can bring the engine RPM to peak HP starting at low MPH and hold it there. There doesn't have to be a performance penalty with driving a CVT versus a conventional automatic or a manual. If the CVT were perfect it would be quicker at low speeds, and once again it may just be software.

, 4K at ~23MPH, 4.5K @~31MPH, 5K@~43MPH. Peak HP is at 5600RPM, I'm not sure what the curve is exactly but somewhere around 4500RPM is when output gets to 80%+.
 
#56 ·
A CVT with the right ratio abilities and the right software can give as good of acceleration as a manual transmission. Yes the CVT has a clutch or even a torque converter to get it going from a stop but then it should lock and it should be as efficient as a manual. This means you can get full power from the engine. If the CVT has the ratio abilities and software it can bring the engine RPM to peak HP starting at low MPH and hold it there. There doesn't have to be a performance penalty with driving a CVT versus a conventional automatic or a manual. If the CVT were perfect it would be quicker at low speeds, and once again it may just be software.

2012 subaru outback 2.5 cvt 0-60 - YouTube , 4K at ~23MPH, 4.5K @~31MPH, 5K@~43MPH. Peak HP is at 5600RPM, I'm not sure what the curve is exactly but somewhere around 4500RPM is when output gets to 80%+.
There's a reason why the CVT on the Forester XT is completely different from the one found on the 2.5i Outback. That's because the CVT on the Forester XT is made to handle the higher torque and higher HP of the engine and abrupt demand for acceleration. It's hardware and software.
 
#63 ·
Peak torque is where the most power is.
Uhhh, no. Amazingly, peak power is where the most power is.

BTW, acceleration depends entirely on power, NOT torque -- so
5600 rpm at WOT yields maximum acceleration. Not 4000-ish.

Lemme guess: not a physicist?

…or a language major, :rolleyes:

Looby
 
#60 ·
Thanks! This makes it seem like pegging the rpm's at peak torque for full throttle acceleration is making the best use of the power curve. It is a little engine and a big car....(mine has climbed Pike's Peak, Beartooth Pass, and many other climbs with no issues. We do not pull a trailer or use a rooftop carrier, but for our use the power has been adequate, and the cvt allows keeping the engine in it's sweet spot.)
 
#64 ·
“You know, a lot of people buy horsepower, when what they really want is torque,” Hubbard told me. “Torque is what gets you to the speed you want quickly; horsepower is what keeps you there.”
The concept of horsepower as a measurement of work was identified in the 1800s by steam engine pioneer James Watt, who ponied up the term based on his observation of horses working in a mill. It’s an arcane concept that has stuck with us to this day.
Torque, on the other hand, is the twisting, rotational force generated by an engine; this force is transferred through the drive system into the wheels. Torque is what pushes you back in the seat when you step on the accelerator." Looby, you are correct, I am neither. Perhaps you can tell me what rpm the engine is capable of without tire spin at launch and through, say, 30 mph. The cvt does not have an infinite ratio available to it, thus it can't reach peak torque or HP until the available ratios allow those rpm points to be made. Although you are correct the fastest acceleration would be to peg the rpm at peak HP and hold it there and allow the cvt to change its ratios to keep it there. A street car with other expectations than fastest acceleration is a whole bunch of compromises. So, Looby, is peak HP even available at low speeds? Or is an engine built to achieve good torque down low a better compromise than an engine that has to be wrung out to achieve decent acceleration for a street car? I do have to admit you got me with the language major jab....
 
#65 ·
“You know, a lot of people buy horsepower, when what they really want is torque,” Hubbard told me. “Torque is what gets you to the speed you want quickly; horsepower is what keeps you there.”
The concept of horsepower as a measurement of work was identified in the 1800s by steam engine pioneer James Watt, who ponied up the term based on his observation of horses working in a mill. It’s an arcane concept that has stuck with us to this day.
Torque, on the other hand, is the twisting, rotational force generated by an engine; this force is transferred through the drive system into the wheels. Torque is what pushes you back in the seat when you step on the accelerator." Looby, you are correct, I am neither. Perhaps you can tell me what rpm the engine is capable of without tire spin at launch and through, say, 30 mph. The cvt does not have an infinite ratio available to it, thus it can't reach peak torque or HP until the available ratios allow those rpm points to be made. Although you are correct the fastest acceleration would be to peg the rpm at peak HP and hold it there and allow the cvt to change its ratios to keep it there. A street car with other expectations than fastest acceleration is a whole bunch of compromises. So, Looby, is peak HP even available at low speeds? Or is an engine built to achieve good torque down low a better compromise than an engine that has to be wrung out to achieve decent acceleration for a street car? I do have to admit you got me with the language major jab....
Torque quantifies pressure available to do a task.......Horsepower adds the dimension of time, quantifying the amount of actual work that can be accomplished.

Say a 300lb man can lift and carry 150lbs, and take 30 seconds to move it 20'. A 150lb man can only lift 75lbs, but he can make the 20' trip in 15 seconds. Big man is twice the torque, but exactly the same horsepower.
 
#70 ·
So Looby buys huge cars with small engines so he can drive them at max rpm. If I want to accelerate quickly from a dead stop I'm going with torque because you can't rev an engine to peak hp in an automatic car with a street tranny and rearend ratios at 0 mph, or until about 30mph in the Outback. I didn't realize we were talking race cars here, or the hp vs torque issue. In the case of acceleration from a dead stop even the cvt can't keep the engine in it's sweet spot of peak HP from the get-go. Looby, when you mention sweet spot at any rpm or load level, what does peak HP do for you at cruising speeds of 30 or 55 mph? Would the sweet spot be the lowest rpm that sustains that speed for the sake of economy and longevity? How is it you are attaining peak HP at launch with the cvt in an Outback? Seems pretty basic that a larger engine can produce more HP and torque, but in true performance street cars bigger is usually better, in part because the low end torque gets the car rolling. Of course if you are talking concourse racing weight and other considerations come into play. The discussion was acceleration from a dead stop.
 
#73 ·
So Looby buys huge cars with small engines so he can drive them at max rpm.
Sounds like you've talkin' to Mr. Hubbard again ...or maybe Mr. Jameson?

- YOU said: "Peak torque is where the most power is."

- YOU said: "This makes it seem like pegging the rpm's at peak torque for full
- YOU said: .throttle acceleration is making the best use of the power curve."

- YOU cut n' pasted: “Torque is what gets you to the speed you want quickly;
- YOU cut n' pasted: .horsepower is what keeps you there.”

I have simply pointed out that you are wrong on all counts -- DEAD WRONG.
This is not a matter of opinion, it's a matter of simple high school physics.

If I want to accelerate quickly from a dead stop I'm going with torque because
you can't rev an engine to peak hp in an automatic car with a street tranny
and rearend ratios at 0 mph, or until about 30mph in the Outback.
Oh? But you apparently believe that you can "rev an engine to peak torque
in an automatic car with a street tranny and rearend ratios at 0 mph …?"

……please proceed,

Looby
 
#71 ·
Torque does a lot more to help you maintain speed without having to downshift. Horsepower gives you acceleration.

Trust me... I come from a diesel background. My Golf put down over 200 pounds of torque at just 950 RPMs... but it still took 12 seconds to get to 60 MPH. That's because it only had about 105 horsepower.

There are NO internal combustion engines that put down max horsepower immediately. You ALWAYS have to rev up to max power (horsepower) to get max acceleration. It's just a matter of gearing that determines WHEN that happens. Yes, it may happen at a little lower speed in some cars than others... but the Outback is not unusual on the way it revs up. The BENEFIt of CVT is that once you rev up to max HP, you can STAY there instead of having to upshift and wait again until you get to max HP.
 
#72 ·
Green, I don't think Looby said anything about driving at max HP all the time. Where did that come from? For maximin acceleration, you need to be at max HP. CVTs have the benefit of being able to hold max HP from the lowest speed that hearing allows, all the way up until you let off the pedal. No other auto or manual trans can do that.

You seem to mention acceleration when it benefits your argument, then you switch to maintaining speed when that is in your favor. More HP gives quicker acceleration. More torque helps hold speed without needing to downshift. That's all the is to it. It seems like the only thing you have a problem with is that the bottom gearing isn't low enough for you. You want max HP to come on sooner. As mentioned, even some sporty cars have had issues with this... Including the 450SL I once owned. Imagine waiting 12 seconds (up to about 55 MPH) before reaching max RPMs in first gear!

Yes, a bigger, more powerful engine would be faster. Is anyone arguing that? Is the Outback so slow that it is unsafe. No. Believe it or not, the Outback is one of the quickest cars I've owned, and I have owned about 15 cars.
 
#74 ·
Torque vs horsepower discussions always bring up interesting and often false assumptions, generally because of the misunderstanding of how the two directly relate to each other. Torque is the ability to do (actual or potential) work, period. With a stallable power source such as an electric motor you can be producing torque, yet zero horsepower if you prevent the shaft from turning.

You can convert torque directly to horsepower and vice versa. If you look at the formula for calculating horsepower from torque here:

Horsepower - Wikipedia, the free encyclopedia

You will see that the torque mutiplied by the rpm is then divided by a constant, 5252. This should tell you one thing right away: At 5252 rpm, both torque (ft/lbf and horsepower numbers will be exactly the same, for any engine! Internal combustion engines for various reasons produce varying power at different rpms. If you graph the horsepower produced at a range of rpms, you get a power curve. If the engine produced a constant torque at all rpms, then more rpm = more horsepower. But the mechanical nature of the engine with all its inertial parts, rate at which fuel actually burns, rate at which you can draw in air and fuel and also expel the burnt mixture, etc usually ends up producing a power curve where maximum horsepower occurs at a specific rpm, and diminishes gradually on either side of that specific rpm. For the FB25 in our beloved Outback, the power curve reaches a maximum of 173 hp at 5600 rpm. This is the most power you'll get out of it.

If horsepower is the ultimate measure of available power, then why does torque matter at all? Well one reason is that we're talking about a car here, which starts and stops, and accelerates and slows down. For various reasons it is often not the best thing (and not the quietest...) to accelerate from a standing start with the engine revving at 5600 rpm. Reaching a higher torque output at lower rpms (as the FB25's design did in relation to the EJ25) does mean that more power is available sooner as the engine revvs up. Also, maximum power does not necessarily mean maximum fuel efficiency. Higher torque also gives you the ability to get a larger mass moving at all or accelerating for a given gear ratio. Any engine can move any mass with enough low gearing, but it is not always practical to design a vehicle that way. Generally speaking, an engine with higher torque is best for accelerating from zero or low speed, or for getting a large mass moving. An engine with higher horsepower will be best for accelerating at high speed such as for passing a truck on the highway.

There are mechanical limitations with how you can smoothly accelerate from a standing start to a good speed with a constant rpm for maximum power (but if you could, that would give you the best acceleration times). This is where the CVT makes for such a compelling case, because now you can do just that: accelerate in a linear fashion at a relatively constant rpm. The engine computer "knows" at which rpms you get the most power, and at which you get the most fuel efficiency. If you're willing to trade off some acceleration performance for better fuel efficiency, you can "tell" it that by gently pressing down on the gas pedal. Mash it down quickly and the computer will say "hey, fuel be damned...the boss wants horsepower now!".
 
#77 ·
This should tell you one thing right away: At 5252 rpm, both torque (ft/lbf and horsepower numbers will be exactly the same, for any engine! Internal combustion engines for various reasons produce varying power at different rpms.
Maybe not. Over the road diesel truck engines have a hp rating and a torque rating, but they are governed to 2100 rpm. 5252 rpm would blow them up.
A popular make of ocean going transport ship diesels are governed to about 127 rpm. Even 200 rpm would blow them up, as they have a stroke of about 3 feet.
Formula still works, but conclusion above regarding 5252 rpm is faulty somehow.
 
#75 ·
Looby, I did not say you can achieve peak torque at 0 mph. But with a well matched torque convertor and good low end torque you can get a car moving more quickly. An engine built to favor max hp at the expense of torque down low generally is less desirable in street applications. A peaky high HP engine is not as practical in a street vehicle as an engine with a wide torque curve. Most people rarely run their engines to peak HP, but torque available at rpms suitable to city speed limits is used frequently. I did misstate peak power is = to peak torque. Still, even with a cvt available ratios are limited and more available low end torque will get you going quicker and result in a more satisfying street car. Looby, as you point out you can achieve more peak torque than a combustion engine can with extra leverage. Obviously a combustion engine can create zero torque at zero rpm so I am not sure how that comparison is valid in any way when dealing with the ability to move an object with a combustion engine.
 
#82 ·
As it happens, I have a Mercedes in the shop getting some transmission work. I asked the technician if he saw many Subaru CVT's. He said no, because there are few spare parts available for it. He also told me to avoid shock loads if I wanted the transmission to last...specifically, to make sure the car was stopped dead before shifting into gear. To sum up, the transmission still works great for me at 50K miles, but if it ever breaks, it's a dealer-only issue.
 
#84 ·
Not sure if it was mentioned previously but I have heard the subaru cvt has a built in ramp mechanism that protect the chain and cones from shock loads such as spinning wheels on ice suddenly hitting pavement. These are real situations that the engineers have designed for.
 
#85 ·
Honda's CVT in the Accord is pretty darn good,(I had one) but I have to say I like Subarus HD CVT in the FXT(have one) and the 15 WRX better. Totally seamless power without very much of the rubber band feel. My 10 OB feels unrefined compared to the Honda and especially the FXT.
 
#93 ·
A lot of transmissions don't last the life of the car. Honda has been havng a lot of transmission problems recently.

But what it means, if I may speak for Subiesailor, is that you should get a lot of miles out of the CVT if it is maintained properly, just like any other transmission. Random transmission problems will happen to every brand, from Kia to Mercedes. However, when buying a new car, we all assume the transmission will last a good long time.

An important question is: what do YOU mean by "life of the car"? Is the car "dead" when the wheels fall off? When the body rusts away? When it is 15 years and 200,000 miles old and the transmission fails? My father is a Mercedes mechanic who has many customers with cars well beyond 400,000 miles. Blue book may be less than $1,000, but they continue to spend thousands every year to keep them on the road. Countless others have gone to junk yards because they needed $1,500 in repairs. "Lifetime" of the car means something different to each of us.
 
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