Review: Subaru's Gearless Transmission
|Regular Transmission||Lineartronic CVT|
This is what your bicycle looks like:
distinct gear. A regular transmission
uses the same principle, switching
between fixed gears.
Subaru's continuously variable
transmission uses a steel chain connecting
pulleys that vary in width, with no
Regular transmission cutaway--
See the fixed gears?
Lineartronic CVT cutaway--
just pulleys that vary their width.
First of all, how does a regular transmission with gears work?
Remember the ten-speed bicycle you rode as a teen? On the back wheel, there were different size gears. A human can only pedal so fast, and with so much power, so to make the most of your effort you used different gears for different speeds. Uphill, when you needed all your power at a slow speed, you used the wide gear. Downhill, when you were already cruising fast, you needed the narrow gear to go even faster. Traditional transmissions in vehicles employ the same principle. The transmission shifts gears to
provide the most appropriate ratio for a given situation: lowest gears
for starting out, middle gears for acceleration and passing, and higher
gears for fuel-efficient cruising. Most vehicles with conventional gears have four or five different speeds.
How does the CVT compare to a regular geared transmission?
The controls are the same inside the car: two pedals (no clutch) and a P-R-N-D-L-style shift pattern. But instead of gears, the CVT has two pulleys that can vary in width, and a steel belt that connects them. By getting narrower or fatter, these pulleys change the relationship of engine speed to car speed. And because these pulleys can vary their width infinitely, they are "continuously variable." When driving a car with a CVT, you never hear or feel the transmission shift -- it simply raises and lowers the engine speed as needed, calling up higher engine speeds (or RPM) for better acceleration and lower RPM for better fuel economy while cruising.
What does a CVT feel like when driving?Many people don't notice the difference. Modern cars with regular transmissions shift so smoothly that you don't really feel the gears changing. You may notice a difference if you pay close attention. With a CVT, there are no gears, period, so you hear the engine rev when you press the accelerator but you never feel any power interruption as the gears change. The engine finds its power band, and the transmission keeps the gear ratios married to that sweet spot for maximum power and fuel efficiency.
What does it do for me?
- Power. Engines do not develop constant power at all speeds; they have specific speeds where torque (pulling power) and horsepower (speed power) are at their highest levels. The CVT finds that exact spot and stays right there.
- Fuel economy. For example, for the 2014 Forester, Subaru introduced a CVT. With the same engine as the previous generation, the new Forester gets FIVE (!) more mile per gallon. The CVT finds the most fuel efficient point in the engine power band and keeps it there. The fuel economy is so impressive with a CVT that it beats the manual transmission!
- Less weight. Without that heavy gearset and all those extra parts, a CVT has less mass, which helps fuel economy, handling, and acceleration.
- Acceleration speed. A regular transmission can't continue to apply power while the transmission is shifting because it would damage it. The CVT is designed to send power to the wheels without any interruption.
- Smoother acceleration. A regular transmission can feel jerky, especially under full throttle. The CVT builds power in a smooth, linear manner, hence the trademark, "Lineartronic."
- Greater reliability. The CVT has fewer parts to break.
- Manual mode when you need it. If you're towing, or you just want the thrill of changing gears, Subaru gives you paddle shifters mounted right behind the steering wheel so you can choose from six preset "gears" (which are not really gears but just programmed set points along the continuum). Excludes Forester.
Side view, kneeling outside the car. You
pull the silver "paddle" with your fingers to
Looking through the steering wheel.
This is the "minus side." On the right is
the "plus side" to goup a gear.