CVT

[Arkaign]

I am *NOT* an expert, or even all that well versed in CVT technology and so forth, hence this thread.

From what I've heard, CVT's are a good idea for a lot of reasons, but there seem to be an awful lot of complaints about them, notably from owners of Nissans.

My questions are a bit open on this, but in general :

(1)- Are the complaints about the Nissan CVT's something that apply to CVT's in general?

(2)- Are the issues things than can or will likely be overcome?

(3)- Will CVT's ever have any performance-oriented benefits? (ie; use in Vettes, Z-cars, etc?)

(4)- What are the general Pro v. Con of CVTs?

(5)- Any good examples of effective implementation of this technology?

Thanks!!

 

[Zenmervolt]

Originally posted by: Arkaign
(1)- Are the complaints about the Nissan CVT's something that apply to CVT's in general?

Nissan uses a toroidal CVT, which is different from the traditional pulley-based CVT. Complaints about Nissan's CVT may be unique to toroidal types, or they may be unique to Nissan's implementation, or they may be inherent to any CVT. It's hard to tell. CVTs do have a different feel than traditional transmissions which can lead to complaints just because it's "different".

(2)- Are the issues things than can or will likely be overcome?

That all depends on what is causing them.

(3)- Will CVT's ever have any performance-oriented benefits? (ie; use in Vettes, Z-cars, etc?)

It's possible. Early "normal" transmissions had limited ability to handle torque, and I think that with advances in engineering and metallurgy there will eventually be high-performance applications of CVTs. Whether those applications will be accepted or not is an open question because of how important "feel" is in high-performance cars.

(4)- What are the general Pro v. Con of CVTs?

Pro: Ability to optimize gear ratios (within a range) to suit any driving condition.

Con: Limited ability to handle torque (this will pass as engineering gets better), and a limited range between the lowest ratio and the highest (while CVTs have an infinite range between the minimum and maximum, there are limitations on how far apart the minimum and maximum can be).

(5)- Any good examples of effective implementation of this technology?

Honestly, Nissan's implementation is regarded as one of the best in the industry, and Audi has done a good job with their metal belt CVTs. The biggest benefits really seem come with smaller engines though since larger engine with more torque can handle a limited gearing range more easily.

ZV

 

[Arkaign]

Very cool summary, thanks!

 

[Aikouka]

I don't really have any complaints about my CVT. But I went back and read some reviews on the '07 Altima (mainly to see if they had some of the complaints that I have) and one thing I noticed was that authors typically said that the CVT was nice on the 3.5 but horrible on the 2.5. I don't recall seeing why though.

The only annoyance about my CVT is the engage lag that it has sometimes. This being, when the clutch pedals (or whatever system the CVT uses for that mechanical purpose) disengage, sometimes the CVT isn't very quick about reengaging them. For a second, it almost feels like the car is in neutral and if you aren't very aware of this and push down too hard, your car will jolt forward (similar to what happens if you're revving too high in a manual and you release the clutch). I've never really done it as I notice when it fails to engage quickly. It's not a huge deal unless you're trying to get going quickly.

The manumatic mode also works fairly well, but another interesting thing I read in some reviews is that they said the CVTs normal automatic mode is faster than the manumatic mode.

Oh, another annoyance with the CVT is how sometimes it doesn't like to shift out of "passing gear". It's where sometimes when you rev a bit high and then let off and push onto the gas again, the car won't shift up. It's like the computer still thinks you want to push the car hard but you don't.

EDIT:

One other thing you also really have to get used to is how the car feels a lot more like a manual in regard to coasting. You can engine brake quite easily with a CVT (or at least with Nissan's), which is not something I ever recall being able to do with an automatic. It's usually decent enough that I've had to use the accelerator to keep a decent speed going down a hill.

 

[LTC8K6]

Automatics engine brake very well. Why wouldn't they?

 

[Aikouka]

Originally posted by: LTC8K6
Automatics engine brake very well. Why wouldn't they?

The nature of the torque converter is why an automatic car doesn't engine brake in the same manner as a manual. Technically, there's not much of a "connection" between the transmission and the engine (the turning parts I mean) in an automatic as the fluids being rotated by the rotation of the flywheel turning the turbine is what makes the transmission spin.

You can see some of that here: http://auto.howstuffworks.com/.../torque-converter2.htm

But in a manual, the direct connection between the two when the clutch pedal is not depressed causes a drop in RPMs in the engine to directly affect the rotation in the transmission at a much faster rate than you'd see in an automatic.

This is why I say that before in automatics, I could just kind of let my foot off the gas when going down certain hills in said car. But when I switched to my Nissan (which has a CVT), I could not do this and actually had to use the gas or my car would begin to slow down... much like when I used to drive my old Talon TSi AWD.

 

[Demon-Xanth]

If the power handling and efficiency (and weight can be kept in check) concerns can be worked around, I could actually see CVTs enter racing as they would allow a peaky engine to stay at that peak much more. But CVT's biggest complaint is the different feel. There's no rising revs, jerky shifts, etc. so it feels slow even though it isn't.

 

[Zenmervolt]

Originally posted by: Aikouka

Originally posted by: LTC8K6
Automatics engine brake very well. Why wouldn't they?

The nature of the torque converter is why an automatic car doesn't engine brake in the same manner as a manual. Technically, there's not much of a "connection" between the transmission and the engine (the turning parts I mean) in an automatic as the fluids being rotated by the rotation of the flywheel turning the turbine is what makes the transmission spin.

You can see some of that here: http://auto.howstuffworks.com/.../torque-converter2.htm

But in a manual, the direct connection between the two when the clutch pedal is not depressed causes a drop in RPMs in the engine to directly affect the rotation in the transmission at a much faster rate than you'd see in an automatic.

This is why I say that before in automatics, I could just kind of let my foot off the gas when going down certain hills in said car. But when I switched to my Nissan (which has a CVT), I could not do this and actually had to use the gas or my car would begin to slow down... much like when I used to drive my old Talon TSi AWD.

Yup, you've got it. The reason is that automatics tend to be programmed to coast in the highest gear and to disengage the lockup clutch when coasting.

If the automatics kept the lockup clutch engaged they would engine-brake nicely as well as a manual.

ZV

 

[joutlaw]

I rented a Ford Five Hundred back in 2006 and it had a CVT. It was a strange feeling, but to me it felt as if the car was always able to give it 100% power going 30mph or up. If you floored it would stay at redline until you let off. It was smooth in operation too.

I could see it more beneficial in the luxury market, but some automatic transmissions can be pretty close in smoothness.... albeit by intentional slipping between gear changes.

 

[Eli]

Originally posted by: LTC8K6
Automatics engine brake very well. Why wouldn't they?

They engine brake well to an extent. If you can force a downshift, you can get good engine braking.

If you just leave it in Drive, they suck compared to a manual.

It's a good portion of my hate for automatics. I'm constantly rev matching and downshifting in a manual.

Saves brakes. And yes, transmissions and clutches are more expensive than brakes - hence the rev matching.

 

[Matilda]

the honda civic hybrid has a CVT tranny and from what I've heard, it's helped a lot with acceleration since the car has such a weak engine. I'm all about manual transmissions, but if I were to get a weak car that has the CVT transmission as an option, I'd have to pick CVT.

 

[CrimsonWolf]

I've been very happy with the CVT in my 2007 Nissan Versa.

I guess my only complaint is that it feels slow. It's not that the car is really any slower than it would be with the manual or auto, but there's no shock shift or anything like that and it just kind of rolls right off to a start. Not really material, but it is a different sensation. I guess also the revs can be a little jumpy on the highway. I've found that unless I tap the gas oh-so-lightly, the engine will rev way up immediately. It can be noisy, but the upside is that the motor is instantly at peak power for passing. That's probably more important. So, to me, I haven't noticed anything major to complain about.

On the other hand, it is incredibly responsive. If I need power immediately, the motor instantly revs to it's peak RPM. It doesn't lag, hunt for gears, need to increase the revs gradually, etc. It just goes. Also, another voucher for it's excellent engine braking. I was pleasantly surprised the first time I drove it in the mountains. When I was going down a hill, the moment I tapped the brakes (not sure if it was just coincidence) the CVT "dropped" a gear immediately and maintained my coasting speed very well.

Overall, it was a very different sensation going from a 5-speed manual to a CVT, but I've been very happy with it. I wouldn't hesitate to get a CVT again if it were offered. I also like it much more than the 4-speed auto I used to drive.

 

[Arkaign]

^^^ Cool feedback. I guess CVTs take a bit of adjustment as they must feel notably different than conventional automatics or manuals.

 

[angry hampster]

Originally posted by: Arkaign


(5)- Any good examples of effective implementation of this technology?

Thanks!!

Mopeds. Damn near all of them use a CVT. Polaris has also been using CVTs in their ATVs for about 20 years. All (I believe) snowmobiles use CVTs.

 

[lurk3r]

I recently got the altima hybrid with the CVT, and being a confessed automatic hater I have to say, I was quite impressed with the CVT. The only complaint I had was the initial startup seemed a bit funkey. I'm sure it's just related to starting in electric mode and will just involve a learning curve.

 

[Zenmervolt]

Originally posted by: angry hampster

Originally posted by: Arkaign


(5)- Any good examples of effective implementation of this technology?

Thanks!!

Mopeds. Damn near all of them use a CVT. Polaris has also been using CVTs in their ATVs for about 20 years. All (I believe) snowmobiles use CVTs.

Is this only recently? I used to have a moped and I remembered all of the ones I looked at having a two-speed transmission that was controlled by centrifugal clutches.

ZV

 

[angry hampster]

Originally posted by: Zenmervolt


Is this only recently? I used to have a moped and I remembered all of the ones I looked at having a two-speed transmission that was controlled by centrifugal clutches.

ZV

All the Japanese ones have since the 80s. Not sure if Vespa still uses straight transmissions.

 

[Zenmervolt]

Originally posted by: angry hampster

Originally posted by: Zenmervolt


Is this only recently? I used to have a moped and I remembered all of the ones I looked at having a two-speed transmission that was controlled by centrifugal clutches.

ZV

All the Japanese ones have since the 80s. Not sure if Vespa still uses straight transmissions.

That would explain it. I was looking at European models. Ended up with a Tomos. From that experience I learned never to buy anything electrical from Slovenia. Engine was great, but I think just about every electrical piece (including the coil) failed during the two years I had it. Still, it got me everywhere for two years before I could get my driver's license (age 14 to 16) and I learned a good bit about wrenching from it.

ZV

 

[TraumaRN]

I've read good things about the CVT on the 2010 Fusion Hybrid. And to that end I love the CVT on my polaris ATV.

 

[SonicIce]

Man, when are they going to put CVT's on a bicycle? That would be totally kick-ass.

 

[LordMorpheus]

I remember when I was 12 or so I was pricing out building a go-kart (never did it, didn't have the money for what I wanted, wasn't willing to settle for what I could afford), and rubber-belt CVT's were the norm for higher-end applications.

 

[LTC8K6]

Well yeah, I meant when you downshift.

I'm well aware of the differences, but I thought you wanted engine braking, in which case, you'd downshift the auto.

Which for most modern autos, is a very small movement of a hand or a finger.

 

[MadScientist]

I also like the feel of the my '07 Nissan Versa CVT. No complaints, except a bit of noise when passing, but very responsive and smooth.

My son though has a '07 400cc Suzuki Burgman scooter with a CVT that has been nothing but problems, broken belts, bad clutch, squeal, and slipping. He finally installed an aftermarket clutch and Kevlar belt.

 

[aleckz]

I cruise the Versa forums on NICOclub and there are only a few threads on complaints about the CVT and usually it pertains to a burning smell or ways to make it more efficient. Overall I think they are great, from the two cars I've driven with the CVT (both Nissan), they were smoother than normal autos and were more efficient at cruising speeds. I wish my manual Versa would put out the numbers that the CVT gets on the highway doing 70+ mph. While I see 27-29mpg, they are getting 32-37 depending on the style of driving.

I think the CVT is a good thing, there are some kinks that need to be worked out.

 

[avash]

There will always be complaints and praises for the Nissan CVT depending on who it's coming from. The praises typically come from the people that understand the CVT, know what to expect, how to use it, etc. The complaints come from the opposite. That said ...

1) I've driven a lot of CVT-equipped vehicles from the one in the Ford Five Hundred / Taurus, the Dodge Caliber to a lot of the Nissans. Not all CVTs are alike. Also, CVTs will yield different experiences depending on the engine that they are paired with.

2) Most/all CVTs now use metal bands instead of rubber, so the "elastic" feel akin to a rubber band on gears isn't really there anymore.

3) Performance oriented benefits typically require high torque applications. CVT's have come a long way, take Nissan for example that pairs the CVT with their VQ35 engines which is a very capable motor. Driving say an '09 Versa with a CVT vs an '09 Maxima is like night and day. With today's technology, performance has its limitations when it comes to CVTs but I'm sure that will improve over time. True performance enthusiasts will expect a proper manual (for control, high torque, etc) or a clutchless manual, or an automatic with twin clutches and REALLY good shift logic and response time.

4) Pros: Fuel efficiency, optimum and virtually infinite gearing. Cons: Not for high torque (including towing) applications, different driving characteristics compared to conventional automatics.

5. Nissans. They have been adopting CVTs for over a decade, and each generation has improved over the past.

I think that most complaints about CVTs are:
a) Lack of understanding on how a CVT operates. For example, in conventional automatics, people expect that when accelerating to merge on a highway, you will shift from gear to gear with your RPMs rarely going peaking out. With a CVT, when you merge, the RPM stays constant (because it is under load) at say 5k. People perceive this as a bad thing and automatically hate the CVT, referring to it as loud or slow or weak. The ability of a vehicle to get up to speed depends on the engine that it is paired with. A CVT on a 1.6L engine will sound "strained" and be in the peak RPM range a lot longer than one on a powerful V6 which will sound "sporty" and be in the peak RPM range for a shorter time, because it can get from 0 - 70 in a 3rd the time it takes for a small motor.

b) Expectation of gear shift points that can be felt. You do NOT feel that in a CVT unless you engage a "manual" mode where it uses pre-determined shift points to simulate a conventional automatic. If you're cruising on the highway at 70mph through PA where there's constant hills, a conventional automatic will constantly downshift and you will feel it. In a CVT, it's great because with infinite gearing, it will adjust (your only indication would be a change in the RPM).

c) Knowing when to let go. In a CVT, you have to let off the pedal once you've reached proper speed. That requires you to keep an eye on your speedometer and adjust your driving. A lot of people don't like how a CVT will also peak the engine when accelerating, so they will prematurely let off the gas pedal because they associate engine noise with straining. If the engine is not near the redline, it is NOT straining. So they will back off the pedal to drop the RPMs, effectively going against the working principles of the CVT.

d) Engine braking ... the idea you have to push down on the gas pedal when going downhill. You're not wasting more gas doing so, you're just regulating speed.

Once you learn to use a CVT properly, it will probably be the best automatic you can get to go from point A to point B. When you expect a CVT to perform like a sports car, then you're expecting apples from oranges.