eli5: Why does a CVT transmission still “shift” if it can be in any position and move seamlessly as they say?
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Interesting question. I’m interested as well. As a qualifier I would add under 100% throttle. Everything under 100% is a give/take in efficiency.
You mean like an “overdrive” when you try to floor it? That’s it, I assume, just rapidly changing to a new gear ratio, and it can’t do it smooth enough so instead it jumps to that ratio (in math speak the graph of the ratio has a discontinuity jump).
Subaru CVTs will step the position under hard acceleration to mimic the shifting of a traditional automatic. It’s purely done for preference as people tend to hate CVTs.
Many of them do this artificially because drivers are used to gears and don’t expect CVT-like behavior like the engine sitting at the same RPM all the time for maximum efficiency or power output. The transmission acts like a traditional one to make drivers more comfortable with the different technology.
User experience. There’s no mechanical reason for the CVT to jump between fixed ratios other than that’s how transmissions have worked for decades.
It’s also feedback to the user to let them know that the transmission is doing something/give the feeling of acceleration.
During acceleration traditional CVTs will generally run the engine at peak torque (Constant rpm) and decrease the gear ratio to go faster, this may be faster than shifting but it also feels/subs very different than people are use to.
Yeah my Ford CMax’s CVT doesn’t shift and that’s one of the things I love about it. The car is an awful piece of shit in many respects, but that hybrid power train delivers smooth and impressive acceleration.
My 2012 Subaru Legacy didn’t have shift detents on the CVT unless you put it in “manual” paddle shift mode (which was stupid and useless IMHO). The first experience was weird under hard acceleration. It felt like there were rubber bands stretching and releasing as you accelerated. Normal driving was just smooth as butter and really nice. When it was time for a new car (192k+ miles and the crank seal failed how many more weird problems were going to start) I was told that Subaru added the fake gear changes because customers had heard horror stories about the Nissan CVTs always breaking and associated those with all CVTs.
People got used to the feeling of gear changes. It’s better for the transmission to not have gears but it’s very monotonous so they added the changes.
There are situations like motorsports where paddle shifting the CVT might be better than just letting it go, but at the end of the day a manual transmission is preferred. (Inb4 porch has a really good automatic, that’s a totally different discussion and I don’t like them)
Because companies found that when the CVT doesn’t feel like it’s shifting people call and complain that their transmission is broken.
Because people resisted the change early on and companies made it “simulate” gear shifts to placate consumers who avoided cars.with cvt
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