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Do you like the Murano's CVT?

  • yes

    Votes: 24 77.4%
  • no

    Votes: 4 12.9%
  • the jury's still out

    Votes: 3 9.7%

  • Total voters
    31
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any comments on this??

CVT RIP?

17 March 2005
By Bob Elton


The Ford Five Hundred features a CTV transmission. Why?

I can't figure out the appeal of the Continuously Variable Transmission (CVT). Currently featured in the new Ford 500 sedan, the transmission system consists of a pair of cones and a steel drive belt to transfer power. The CVT offers a continuous ratio change (similar to changing gear with a standard manual or automatic) by varying the diameter of the cones, without a step in ratios like a conventional automatic transmission. While conceptually simple, the actual hardware is tremendously complex and expensive. What’s more, supporters’ claim that the CVT increases economy and performance simply doesn’t bear close scrutiny.

Proponents claim that the CVT offers superior mileage by providing a higher overdrive ratio than other transmissions. (Overdrive is another way of saying that the engine turns slower than the driveshaft, which is typical of all modern automatic transmissions.) In the case of the Ford 500’s Ford/ZF unit, the overdrive ratio is .41:1. In other words, the engine turns 4/10s of a revolution for every turn of the driveshaft. That’s considerably greater than the .69 overdrive ratio of the conventional automatic transmission on offer.

In theory. In practice, the Ford CVT’s ratio is 5.41:1; which is a much lower final drive ratio compared to the same car with a conventional automatic. The result is an overall ratio of 2.2:1 in the CVT car vs. 2.3:1 in a car with an autobox. The overall relationship of engine speed to wheel speed is nearly identical.

At 70 mph, the tach needle would point to the same number, no matter which transmission was installed. When cruising down the expressway, the engines in both cars would be going the same speed, doing the same amount of work, and thus getting the same mileage. The comparison remains valid at any cruising speed over about 30, where the automatic transmission is in overdrive.

It's a similar situation for off-the-line acceleration. The CVT has much less torque multiplication, but a lower-geared final drive. The Ford uses a torque converter between the engine and the gearbox to further increase torque multiplication at launch. Since Ford uses torque converters with the same torque multiplication (effectively the same as a gear reduction), the overall ratio between the engine and the wheels is the same. With the same gear ratios, the cars will have the same acceleration, no more and no less.

The CVT’s main claim to fame is that it keeps the engine at a constant speed, either the most efficient or the most powerful, while accelerating. In the days when engines had narrow power bands and peaked torque curves, this may have been more than a theoretical advantage. But today's engines have torque curves as flat as Kansas, and power curves to match. And today's automatic transmissions have five or six geared speeds, usually with only about 18-25% ratio differences between ratios. In other words, modern engines have essentially the same amount of power or torque over a relatively wide RPM range, and today's automatic transmissions have a narrow enough ratio spread between their gears to use all of the torque and power that the engine produces.

Every transmission suffers internal power losses, but internal losses in the CVT's hydraulic control system are higher than that of a conventional automatic transmission. The hydraulic control systems have to operate at higher pressures or flows, to squeeze the steel cones on steel belts, diverting more energy from the engine and leaving less to move the car. Since the CVT's torque converter is similar to the conventional transmission, internal efficiency of the CVT is lower. This hurts the CVT's ability to deliver the promised higher mileage.

The CVT also requires special, expensive fluid to withstand the heat and pressure demands, and scheduled oil changes. In fact, all things being equal, the CVT has no performance, economy or reliability advantages over a more conventional system. But this equation doesn’t include ergonomic factors, which put the CVT at a distinct disadvantage.

It’s clear that people aren’t comfortable driving a car without transmission shift "feel”; they like to know when their transmission is in “low gear” or "high gear". Obviously, a seamless CVT transmission doesn’t transmit this kind of information. As a result of customer feedback, Audi felt compelled to programmed their CVT to have steps, just like a conventional automatic transmission. This made drivers feel better, but defeated the CVT’s original purpose.

Of course, I’m not the only one who fails to see the rationale for a CVT. After having invested millions in new technology and a new plant, rumor has it that Ford is about to discontinue the CVT option from the 500, writing off their investment before the model year has properly begun. The move would be a hugely expensive about-face, but it’s the right thing to do.
 

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Geez... this guy sure does have a problem with CVTs.

I don't know what world HE lives in, but I've never seen a car dyno with a torque or power curve "as flat as kansas". Why does every Road and Track article I read still tell me I have to get the motor to 4800rpm (for example) for peak torque, or 5500rpm for peak horsepower? That doesn't sound "flat as kansas" to me.

Also, most of today's automatic transmissions are "multiple ratio" or "dynamic ratio", in that for every major gear that are minor multiple ratio variances. For instance, in my 2001 Pontiac, while cruising if I hit the accelerator moderately, the tranny will kick down a "half-step" to a different ratio but in the same primary gear. If I mash the pedal hard, it will drop a full gear or maybe even two in some cases.

Saying that the CVT is a simple design but incredibly complex internally -- I'm not sure I buy that argument. I'm no mechanical engineer or gear-head, but I've seen the diagrams for CVTs vs. regular transmissions. A regular automatic transmission is incredibly complicated. So what if the CVT uses a few expensive components? If the overall design is simpler, requiring far fewer moving parts and thus reducing wear and friction on interacting parts, it would seem to me it's going to be more reliable in the long run -- not to mention the major cause of wear on automatic trannys, the "shift shock" factor when it changes gears hard and fast during hard acceleration.

I do agree with the torque loss issue in the CVT... but as the technology progresses I'm sure in future revisions we'll see things like torque loss and overall strength improved... so that perhaps tomorrow's MOs can tap into the power of thier motors instead of being limited by the capabilities of the CVT.

He's quick to point out all of what he considers to be shortcomings and faults of the CVT, but he never really addresses thier core advantages. Smooth ride? No shift shock? Quiter drive under normal circumstances since the motor isn't revving into higher and louder RPM ranges often? Gee, the 500 is supposed to be a luxury sedan, who would want a smooth, quiet ride?

Obviously this guy's never drivin a MO.

He also probably doesn't like them newfangled gadgets like color TVs.
 

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The CVT is being used by the Toyota Prius, Lexus rx400 hybrid, Ford 500, and Audi among others. Nissan plans to use the CVT in more products in the near future. The CVT is conceptually simple like the wankel rotary engine in the Mazda, but takes some good engineering to make it viable.
 

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It is obvious that this writer doesn't like change for better tech or perhaps that FORD instead embracing JATCO CVT tech is trying to reinvent the wheel and has not got the CVT bugs worked out of it's design.

Having done a lot of research on the CVT before I bought the MO with the CVT, I am in love on how well it performs and delivers on most of it's claims.:29: :29: :29:
 

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I subscribe to the theory that he's just an idiot.

Next!:32:
 

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I've driven the 500.
1- the CVT is as smooth as glass, just like ours.
2- That car is crying for more power.

Homer
 

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I'll risk being listed among the idiots that blaspheme against the hallowed CVT, and suggest that if the 500 (or the MO) had a normal transmission it might not FEEL like it needs more power.

A CVT feels unique and it certainly is smooth, and a given vehicle might actually be faster with a CVT (I doubt it), but it sure FEELS sluggish. I drove an Altima as a loner. It FELT much much faster and more responsive than the MO. Sure, there is a weight difference, but I don't think that accounts for the major difference in perceived acceleration. After an initial period of curiousity, the CVT actually diminishes the FUN factor.

The MO is fun to drive, but it feels like you have to wait for it to spool up a bit before the feeling of acceleration starts to build. It takes too much time for the converter to unlock and the pulleys and belt to adjust the ratio after you hit the GO pedal. The Altima, or just about any other car, gives you a major kick in the rear practically before the pedal hits the floor.

Up to this point, when people have asked about the CVT I've rationalized by saying that it is real smooth, but after only 3000 miles I'm really ready to vote for a normal trans. I'd give up some smooth for some responsiveness. Even if I were to concede that the CVT is faster (I don't), I'd still rather have the more responsive feel of a normal trans. I'm not going to do much drag racing in the MO, so I don't care if the CVT helps it go a 10th faster than a Camry, I'd rather feel the kick.

In short, I'm surprised that anyone is thrilled with the CVT after the initial curiosity wears off. Like my Nissan mechanic told me, the CVT is fine for a snowmobile, but there is no real advantage to putting it in a car other than the fact that it is unique, and that fact helps move units off the showroom floor.

And then there is the issue of the CVT being programmed for too much overdrive in an effort to maximize MPG, and as a result creating drivetrain vibration....


JeffC
 

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The Murano's engine is held back, from a stop, so high torque conditions aren't applied to the CVT. It's one thing to burn rubber, it's another to do it to your transmission.

I find it's well designed, as it's not too far off the tires traction ability. Gas it into a corner from a stop, and the tires are slipping slightly, go straight and you're getting most of the power to the ground that you could apply, anyway.

The CVT "feels" slower, because the transmission is not jerking you around with shifts that are out of the peak of the power band. But all those vehicles in your rear view mirror, back at the stop light, are a pretty good indicator that it's performing well.

Conventional autos can't touch the CVT for roll on performance, especially if you drop it into S.

It's highly unlikely I'll get another vehicle without a CVT.
 

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After experiencing a cvt car, ...

the regular auto transmission on the rental vehicles my company gave to me during my business trips are POS :moon: ...I'd opt for the manual transmission instead of the regular auto.
At least I can have the fun shifting through gears.

I dont care what the author of the article think, this is a free country rite? He can say whatever he wants..
 

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I think all of the 3.5 series and tranny's perform admirable in their own respect within the Nissan family. An 03 Altima can do 0-60 in 6.25 secs and the 03 MO does it in 7.44? That's only according to 1 website (I couldn't find that info on the 05's yet). The curb weight on the 05 Altima is 3274 lbs and on the 05 MO, 3981 lbs, 707 lbs lighter than the MO. It's still a big heavy SUV, but I think the performance specs are pretty damn good. I'd like to see what an Altima could do with a CVT, now that would be impressive... I bet 0-60s would be in the 5s.

I'm completely happy with the CVT and I'm 'not' experiencing all the things I didn't like about a 4 speed automatic.
 

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The Altima is often ignored by people with the budget for Maximas or G35's, but when you think you can take an Altima with the 3.5 in it, supercharge it and it looks like the same 2.5 litre version gramps is driving, it's a great sleeper...

I think the Altima's a sharp looking car, especially now they've upgraded the interior. Unlike the one I drove in the late 80's that made me feel like I was stuck in a Coke can, with a bee.

Of course, many G35 drivers don't want to hear that their engine is the same one. They'll come up with reasons, (different bolt here, different washer there) to say it's not the same fine engine.

Yeah, for an "SUV" the Murano's a lot a fun and not slow.
 

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Human factors on the sluggishness...

Here's my 2 cents....

I've found that as I let others drive my MO, they are hesitant to push the gas pedal down when starting from a dead stop. My theory is that we are so used to pushing a little and waiting for the Tranny to shift before putting more gas down. If you do this in a MO you get 'slugginsh feel' in my opinion. However if you want a responsive acceleration all you have to do is push down more on the gas and it will come without any hesitation.

When I drive someone else's car without a CVT, I think that their car is sluggish becuase I am pushing the gas down wanting more accel and it does not come because the transmission is waiting to shift and then I get jerked by it when it comes.

This all comes back to being trained to drive a certain type of vehicle a certain way and getting used to it. You just hav eto condition yourself that it's OK to keep pushing the gas if you want more speed and that you do not have to wait for the transmission to shift before you get it.

This is my perception.
 

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I just realized something...:rolleyes: I have '2' CVT's in my yard, my MO and my "White Outdoor's" Ride on lawnmower, 16 horsepower, and CVT tranny. I love that tranny too...:2:
 

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That guy who wrote that article is probably one of those "All American" collector car, garage mechanic, narrow-minded, gear-heads! The "Patriotic" types with the bumper stickers and flags in their front yard... without really understanding what it takes to be patriotic... the type who buy GM because it's "American"...

The types that snicker at any indication that the automotive industry is fast moving away from smoggy, greasy, dirty, old steel clunkers.

The CVT gives the MO more accelleration and torque transfer than any powertrain on any other SUV in it's class. SIMPLE. It's an elegant car... designed for current times. The CVT just makes more sense. I specifically bought an MO because of it's CVT.

I come from a very technical background and I am frankly tired of the plain and inefficient powertrains in today's cars. They have not changed in decades and are soon to be ancient relics.

If there was a Hybrid Murano with CVT, I would buy it in a heartbeat! I just might trade mine in for a Lexus RX Hybrid.

I support inovative auto technology anyday!
 

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Actually the opposite is true. Ford is building more CVTs, and phasing out the 6-spd automatic on the Five Hundred.

Ford increases CVT production
 
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I disagree with several things that guy said...

One of the biggest things that ate away at me, and caused me to quit reading it and just make this post, is where he said "torque curves are flat as Kansas, and power curves to match it"........

What is he talking about? I'd like him to post his dyno print outs from every car he's driven and lets take a good long look at those perfectly flat torque curves. I know that the two cars I drive day in and day out do NOT have a flat curve.... one is domestic, one is japenese so it's not apples to apples. Silly guy.

:1pat:
 

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First look at the poll results, right now 23-yes 0-no 1- not sure.
I think the writer's brother owns an AAMCO transmission shop.

The Altima is often ignored by people with the budget for Maximas or G35's, but when you think you can take an Altima with the 3.5 in it

Since I own both the MO and the 3.5 Altima I can speak with confidence. Yes the Altima is fast.......real fast. I had a 77 Vette and the Altima could blow that off the line. On my test drive (without the salesman) I put the hammer down on a back road. I was thrown back im my seat as the Altima flew down the road. I was all grins and bought it that day.
I knew the MO had the same engine and I knew what to expect from the CVT. I did not expect the same thing. Two differ cars with differ functions and purpose. I know this may sound strange but one of my favorite features on the 3.5 is the timing chain.
No steenkin $600.00 belt to change! I am very pleased with the MO's CVT and the MO is preforming exactly as I expected. :4:

Bob1
 
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