CVT
CVT
(OP)
I`m considering purchasing a Nissan Murano w/ a continuously variable transmission. I realize that cvt technology is as old as the light bulb, but most automotive applications until recently have been w/ fairly low horsepower applications. What should the consumer expect in the way of long-term reliability from the Murano cvt, which is hooked up to a fairly potent 3.5 liter V6?





RE: CVT
What is wrong with the usual trans? And, having owned Nissans, Toyotas and Hondas, my opinion is that Toy. and Hon. are well ahead of Nis. in engr., etc.
RE: CVT
RE: CVT
RE: CVT
Get coverage for somewhat longer than you intend to have the car!
Jay Maechtlen
RE: CVT
We do own one working one which we are driving and it is a really neat thing to drive! Much nicer than a normal auto!
Ken
RE: CVT
I expect a conventional automatic to do much better than 100k miles!
it's funny- at low speeds, a conventional (lazy american) automatic looks a bit like a cvt, due to the torque converter. Cruise in town, maybe turn 1500-1800 rpm.
Gas it a bit, goes to 2500-3000 immediately, without downshift!
(Buick Regal, 3.8, 4-speed auto.)
Jay Maechtlen
RE: CVT
surely they last longer than that!
RE: CVT
RE: CVT
60k miles is about half what I expect as a reasonable minimum lifetime.
regards
Jay Maechtlen
RE: CVT
"Xtronic CVT transfers power through two variable pulleys and a high-strength steel belt."
RE: CVT
RE: CVT
RE: CVT
Jatco's CVT strategy is quite simple. Half toroidal IVT for RWD and belt drive CVT for FWD.
Belt drive CVTs are currently limited to about 500 Nm, see http://www.luk.de/english/Bibliothek/Download/k7/luk_k7_chap07.pdf
so they would be not useful for anything like a 2000 horsepower 2025 Nm Walley Larson Groundfighter, but should be fine for a housewife driving kids from school to the supermarket in her SUV.
RE: CVT
My usual confidence in Nissan tells me that surely they tested this thing in the desert under load. After all, wouldn`t heat be the biggest concern for the belt/
RE: CVT
I keep meaning to go test-drive one of these when I have the patience to endure the sales pitch. They seem to be selling well in my area. Anyone have any driving impressions of this powertrain? Nissan reportedly wasn't planning to promote the CVT feature of the Murano, so I wonder if it's evident to the driver or not. Some CVTs even have shift-points synthezized in their ECUs to give the customer what they're expecting-
RE: CVT
RE: CVT
The transmission generates a shudder when starting off from a standstill when the engine is relatively cool. This disappears when the vehicle is driven for about 15 minutes. Fluid change eliminated the problem, but the shudder is back after 2,000 km. I am using Honda Transmission fluid. Is there a special CVT fluid (which is not available with the local distributer) which I should have used? Can someone help?
RE: CVT
We had 330,000 km on our manual transmission model before it threw a rod so that is our comparison to the CVT model.
Ken
RE: CVT
There is definitly no general CVT- Fluid like an AT-Fluid out there. Every make and eaven model has their own fluid.
I hardly recommend if you think about flushing:
1) Do it in yours contractors shop
2) Use only this one from the OEM recommended.
Berblinger
RE: CVT
They showed me under the hood - you don't do anything at all with the transmission fluid. The access tube where the dipstick would go is semi-sealed, you're not even intended to check it. I read another place the fluid has rubber molecules that help the belt plates and pulleys grab together.
Let the dealer change the fluid and if it shows any problems, only keep it as long as the warranty covers it. That's MHO.
RE: CVT
There were also questions raised about improving the performance of the mini by replacing the air filter with a performance air filter, or other more drastic modifications. I think the official BMW/ZF position is that the engine and CVT are pretty much a matched pair and are nicht-zu-finger-poken!
RE: CVT
RE: CVT
RE: CVT
RE: CVT
Inefficiency in conventional AT setups is concentrated in the torque converter. The Murano CVT employs a TC for low speed operation. Nevertheless, Nissan has claimed the setup adds approximately 2 mpg to the vehicle's (modest) 20/25 mpg efficiency. Many preproduction CVT designs use wet start clutches instead to improve their efficiency. Such designs are reported to rival manual transmissions in fuel economy.
RE: CVT
Mart
RE: CVT
FORD
VOLKSWAGEN
HONDA
DAIMLER
PEUGEOT
HYUNDAI
... kinda makes you wonder why we have manuals ...
The distinction between manuals and automatics is eroded away by drive-by-wire. To refer to a transmission as one or the other is becoming a sign that its an old car.
RE: CVT
The cost difference is what?
From what I've seen, the manual is still a lot cheaper than an automatic!
I suspect that a good CVT may get similar economy to a manual with mediocre driver, though.
Jay Maechtlen
RE: CVT
Reason is that it can hold the optimum speed for a given demand power, as a continuous function.
I'll pick my favourite example - Toyota Prius. During the standard fuel consumption cycle you'd have to be changing gear every second or so to get close to what it manages, even without a battery.
Cheers
Greg Locock
RE: CVT
anyone know horespower losses on average of a cvt compared to a traditional automatic?
BMW Mini CVT.
http://www.honestjohn.co.uk/road_tests?id=46
PERFORMANCE, FUEL CONSUMPTION
AND CO2 EMISSIONS
MINI One: 1,598cc manual: 0-60: 10.6 seconds; top speed: 115mph; combined mpg 43.5; CO2 emissions 158g/km; Emissions Class EU4; Insurance Group 5
MINI One: 1,598cc CVT auto: 0-60: 12.4 seconds; top speed: 106mph; combined mpg 36.7; CO2 emissions 187g/km; Emissions Class EU4; Insurance Group 5
===============================
115/106=1.08490566037735849056603773584906
1.17702029191883232467070131719473
(Or using the mini cooper figures)
125/115=1.08695652173913043478260869565217
1.1814744801512287334593572778828
Wind resistance governing top speed is a square law, so I've squared the top speed effects to determine the percentage horsepower losses resulting from having a CVT.
==================
The CVT doesn't add 2 seconds to the acceleration time.
The CVT doesn't knock 10 mph off the top speed.
The CVT doesn't knock 7 mpg off the fuel economy.
And the CVT doesn't add 30g/Km to the CO2 emmissions.
But nearly!
===========
Your question was how things compare to an automatic, but a manual might as well be the benchmark for everything nowadays. Automated manuals should have similar efficiency to manuals and are effectively automatic. Drive-by-wire makes the manual/automatic distinction meaningless.
I'd be glad to look at the figures for a better CVT if anybody has a weblink.
RE: CVT
Perhaps the manual/automatic distinction still has meaning in terms of the clutch operation rather than gear selection.
RE: CVT
Here is more than enough text to answer your question, but there is plenty more on the website if your interested.
http://www.mini2.com/forum/showthread.php?t=41926
When you get a CVT MC you have three transmission selection options. (It is recommended that your MINI be past its brake in mileage (1,250 miles or 2,000 km) before trying this because it is very easy to exceed the maximum recommend engine rpm of 4,500 or 95 mph or 150km/hr.)
“D” This is the fuel economy / normal driving mode. Hold the gas pedal at any position less than the detent (hard spot - feel for it when you drive) and *with an eye on the road* watch the tachometer. It will stay at a fairly constant rpm while the MINI gains speed; never "shifting" in the conventional sense. Stomp the pedal down to the floor and the CVT will run up to the peak 6,000 rpm and then "shift" down, and run the rpm up to 6,000 again as the car accelerates, (until you draw the attention of the police and have to stop.) The CVT will do this as long as the pedal is held to or near the floor (past the detent).
“SD” This is the sport drive mode. The engine rpm will be approximately 800 rpm higher than D mode. To get there, move the shift lever to the right from D mode. The CVT behavior will be similar to D mode. There will be more engine braking in SD mode. It may be used it like a passing gear. Put it into SD when preparing to pass another vehicle to increase the engine rpm toward maximum power.
“+/-” This is manual shifting mode. From SD move the shift lever forward two times and 1 will be displayed in the speedometer where D or SD were. Step on the gas and when you want to "shift", tap the shifter back one time for each "gear". Here's the tricky part: keep your foot on the gas. Do not lift off like a conventional stick shift. If you do, you could find yourself nominated for the dork of the week award. You will have 6 "gears" to choose from in +/- mode. The engine management computer will not let you select a gear and engine rpm combination that is likely to damage the vehicle. e.g., you cannot shift into 6th gear at 25 mph or into 1 at 50 mph. It will also automatically "downshift" if you slow too much and upshift if the rpms go too high. You can downshift just like a stick, but without need for your foot on the gas and clutch work. Also, whilst in a higher gear such as 5 in +/- mode, if the car is going slow enough, pressing the accelerator past the detent will cause the CVT to shift to a lower gear. If you were on a long downhill grade, you could put the CVT into +/- and choose a lower gear for engine braking.
Here's something to experiment with. Put the CVT into 1 (steptronic) and just leave it there as you accelerate. The MINI is programmed to protect itself from "inappropriate" CVT and engine RPM combinations. So if you leave it in 1, it will go to redline and shift itself to 2, 3, etc. You can get similar results keeping the gas pedal floored, but doing this in +/- mode works in less than full throttle positions too.
Even in SD mode, if you let up on the gas, the CVT will go to higher gear ratios. But maybe you don't want it to go to higher ratios... If you use the +/- mode, it will not up-shift when you lift off the gas. It keeps the RPM up and everything running in the power band. You only need to downshift manually to keep the RPM up as you slow. Seems like this would be the best mode for racing with a CVT.
RE: CVT
Mart
RE: CVT
lately.
http://www.lasercannon.com/cvt.htm
Im heading up there for my next duty station.
If any one could help me find out the who what wheres of a CVT that can withdstand high rpms and torque (besides the Audi model), it would be much appreciated.
RE: CVT
Hoorah Grease Monkey