CVT transmissions: My thoughts


The culprit
So today at work I had to deliver a Nissan Sentra which was equipped with a CVT transmission before I go any further I should explain this would be my first time I drove a CVT equipped vehicle. The only other time I've driven is just moving them around in a parking lot which doesn't really let you get a good feel of how it works. Before I give my opinion I will explain the benefits and what the big difference between CVT's and conventional automatics are.


CVT transmissions can work a number of different ways but the most basic method is having a set of pulleys and belts that shift up and down on a shaft to alter the angle at which the belt is sitting on the pulleys. This changes the ratio from input to output based on how the pulleys move on the shaft, it is important to note that this doesn't affect the distance or length of the belts in anyway. The big difference between the two is CVT transmissions allow constantly variable ratios meaning they have no fixed gears like a traditional transmission. This allows them to increase fuel efficiency by keeping the engine at it's sweet spot all the time. This also means in theory the car would also accelerate fast due to the engine remaining in peak power all the time. A traditional automatic works based on fixed ratios and has a set number (5 speed for example) this means when the transmission changes gears there is a drop (or increase) in engine revolutions which could take it out of peak power or put it in to peak power.

Nissan's CVT
Now back to my delivery. When I got in the Sentra it of course looks like any vehicle inside the typical labels were on the shifter (P R N D L) however when put into "D" the car drives much different. When you start to accelerate the engine revs up quickly and stays there as your speed increases. I knew this would happen, but what I didn't know was how bad the sound would be. It sounded like an angry weed whacker. It did end of course quiet down when the vehicle got up to speed where the engine dropped to 1100 RPM, so you go from loud to near silence. While I liked how quiet it was cruising a long at the speed limit, getting there is very annoying. This is how the transmission is so fuel efficient because while cruising along it revs low down and upon acceleration it only revs up for a short period of time. However the noise when accelerating is not pleasant at all, I dreaded every stop light just because of that. The other thing I found was the transmission didn't react that great to speeding up or making a pass, it would let the engine rev up but there was always a fair delay between that and actually increasing in speed. This became annoying in city traffic while having to change lanes and quickly pick up speed.

In actual practice the CVT isn't as great as I had thought, the fuel efficiency would be nice but getting it isn't worth the sacrifice in my mind. I think I now know why luxury manufacturer's like Nissan's Infiniti use 7 speed autos instead of the CVT, it's very loud and seems very unrefined as a result. I wonder if soundproofing could solve this issue and a large displacement engine would allow the car to rev lower during acceleration and thus create less noise. I'm guessing it would help to a certain degree but not enough otherwise we would see Infiniti's with CVTs.


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