Quote:
Originally Posted by arcosine
CVTs rely on traction, therefore have higher resistance since the traction belt force is not modulated for load. Involute gears, on the other hand transmit force between teeth.
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Why would you think the traction belt force would not be modulated for load? I was actually surprised at how low a pressure was needed in the linked document to maintain sufficient tension on the belt. I think in one case it was 6 atmospheres or about 90 psi, not much more than some oil pumps.
The fluid Nissan uses has some unique properties that act like a bunch of microscopic rubber balls when subjected to the shear forces of the 400 segments in the push belt.
I can tell you one thing in my personal experience. When my car is on cruise control it feels like a direct mechanical connection, and the RPMs do not change when going uphill or downhill on the rather shallow grades here. Instantaneous fuel consumption can vary from 15 to over 60 MPG (gauge limit) but the RPM is rock steady and it feels like a direct connection.
The ratio range is 600%. That's the equivalent of 2000 RPM at 60 mph or 2000 rpm at 10 mph, without considering the torque converter, which under light loads locks up at 12 MPH or about 3 car lengths from a dead stop under normal acceleration.
regards
Mech