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Sedans Nissan Altima Nissan Altima CVT
85 messages, Last post on Nov 29, 2009 at 7:45 PM
You are in the Nissan Altima Forum. Your Hosts are pat & karens
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One thing to keep in mind about the road noise, is that the OEM tires on pretty much any car made today are garbage. I threw Turanza LS-Vs on my Maxima, and it was night and day. The "Turanzas" that come from the factory on our cars are in no way, shape or form related to the store tires. They last a LOT longer, are quieter, and handle better in bad weather. I've only had my Altima 850 miles, and I am already looking forward to putting LS-Vs on it to see what the car can really do. 
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I just want to say I love the CVT. My car is the Xterra and my wife has the Altima. Going from a traditional transmission to the cvt on the weekend, when I get to drive it, is like driving a new car every week. It is so smooth, and my favorite thing about it is the acceleration when you depress the pedal about half-way, maybe get the rpm's around 4,000 and stay there. It's such a smooth acceleration and I leave people in the dust without looking like I am flooring it. Weird thing with the Altima is you can feel like you are flooring it, but if you push a little harder it feels like the pedal clicks a little further and you get more power. I am only sad I didn't get the 3.5 when I floor it, so I mainly stick to my half-way flooring it and get the smooth quick take-off. CVT gets 2 thumbs up from me.
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Replying to: karpediem (Mar 24, 2008 8:32 pm) Couple of observations: 1) The motor has excellent bottom end torque. The CVT still has a torque converter to get the car moving and to engage neutral or reverse. The lowest gear ration allws the car to crawl up fairly steep grades in gear (no torque converter slip) as low as 5-6mph. 2) For economy, the CVT attempt to operate the engine as low as 1300- 1500RPM until it reaches it's highest ratio (at around 35mph). thsi does cause some "booming" due ot the low RPM's. I think Nissan could add soem active engine mounts of noise cancellation to help this (Honda NEEDS this when running on 3 or 4 cylinders on it's V6 for hte same reason). 3) EVERY automatic I've ever drien at times uses too low of a gear causing the "booming" sound. They only did it at a couple of speed sranges and as soon as you hit the gas the torque converter unloocked. On the CVT with the torquey 2.5, it can hold 1500RPM from 5mph-35mph. My '04 Honda Accord 5 speed automatic always got into 5th gear really early (35mph) and made a booming sound. 4) The best atribute of the CVT is that it's incredibly responsive, there's no waiting for a downshift. 5) My Honda Accord also used to have the RPM's jump and hte engien braking change as it downshifted while slowing down. At 10mph, my braking force would change dramatically. I haven't noticed this with the Altima, but I don't drive it aggressively in traffic. I suspect that when accleratign and braking hard in stop and go traffic, this could happen. I'll find out this Fall when my wfie and I drive back to my parents in Detroit, MI. I always forget how aggressive and fast they drive out there. 6) You do need to retrain you foot and learn to drive smoothly to get the most out of the transmission. Don't get me wrong, the Accord has an excellent automatic trnsmission. Very responsive, but when I want to pass on a 2 lane road, I get instant power with the Altima. On the Honda and my wife's previous Altima, you have to anticipate your move sicne the transmission needed a 1/2 second to get in the right gear and provides no accelration at that moment. On the Altima accelration start immediately and increases as hte gear ratio drops as needed. Form a engineering standpoint. What's ideal about the CVT is that the throttle positon causes an increse in RPM linerarly. Therefore horesepower increases almost directly porportionally to throttle position since the 2.5 motor has a very flat torque curve and HP is constant since you are at a constant RPM. Very similar to thrust from a jet turbine. IN a conventional automatic the RPM's change and therefore the HP varies between the shifts. The only downside of the CVT is that hydralic force is needed to hold the gear ratio. So there are some losses with the hydralic pump. Thsi might explain why the RPM's jump around at low RPM's as the car is transitioning possibly form the torque converter to the CVT and the hydalic pump suddenly puts a load on the engine at the same time the torque converter locks up. Here's how that works. The CVT's lowest ratio would allow for lets say 4000RPM at 15mph. If you acclerate hard, the torque converter must "slip" all the way until it can lock up when it reaches the same speed at the lowest gear range in the CVT. To make the car feel responsive and not bog down when you hit the gas, it takes some fancy "footwork" between the torque converter, throttle and CVT to make them all match up under 20mph. Above 20-25mph, you're pretty much locked up 100% on the CVT and it behaves in many ways more like a manual transmission with an fly by wire throttle except that the gear ratios are infinitly vairable between the max and mimimum ranges. |
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That "booming" that you hear is normal. You can't honestly expect a car to be perfect for under $30k. I've felt this in my car, and it doesn't bother you if you don't think about it. An easy way to cure this is to either shift to manual mode, or give the engine a little more throttle. This car is a great car. The CVT is very responsive, the interior is nice on the S and wonderful on the SL, the ride is very sporty, responsive, and comfortable, and the car gets great gas mileage for the power it puts out. People need to stop complaining. Either enjoy the car or trade it for something else. I love my 2.5 SL, and I have no intention of trading it just because of the CVT has a couple drawbacks. The advantages more than make up for its shortcomings. |
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Replying to: altimaowner2 (Feb 16, 2008 10:28 pm) However, I experience an annoying slow pulsation in "cruise" when going downhill. It is certainly tolerable, but noticeable. I assume it's the combination o CVT and throttle being confused.............. No biggie. .......... |
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Replying to: sal1948 (Jun 23, 2008 1:31 pm) The engine spins about 2000rpm at 60mph in 6th, yet when you need to accelerate more, it simply & instantly gathers speed, drama-free, like there's a giant, torque-monster Cummins diesel under the hood. By the same token, the motor & soundproofing are good enough that I've accidentally left it in 4th gear for a few 60mph freeway miles, and only a glance at the tach revealed my error. In 9000 miles, I've yet to feel the need for revving past 4000rpm (except to pass a long tractor-trailer on a 2-lane road). BTW -our last tank got us 31.5 mpg (calculated by hand) in mixed city/fwy driving. Very happy. |
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Replying to: sal1948 (Jun 23, 2008 1:31 pm)
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Replying to: dbarrett2 (Jun 26, 2008 9:42 am) |
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Replying to: dbarrett2 (Jun 26, 2008 9:42 am) But apparently we're all crazy and should just be quiet and enjoy the jerkiness.
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Replying to: ripper82 (Jun 26, 2008 1:04 pm) You have a choice: 1. Go get a car with a regular automatic that has several larger shifts that are dictated by gear placement. -or- 2. Enjoy the Altima and ignore its slight quirkiness at lower speeds. Even with these micro-jerks, it's still the smoothest transmission on the market. |
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