Understanding Constant Velocity Transmission: Enhancing Your Driving Experience

In the quest for optimal vehicle performance and efficiency, the Constant Velocity Transmission, often known as continuously variable transmission (CVT), stands out as a significant innovation. Subaru’s Lineartronic® CVT is a prime example of this technology, engineered to deliver an immediate and seamless response to diverse driving conditions. By consistently optimizing engine performance within its ideal power range, Lineartronic CVTs enhance both the efficiency of the BOXER engine and the Symmetrical All-Wheel Drive system. Featuring a robust transmission case and an advanced torque converter, Lineartronic ensures a smoother driving experience while effectively minimizing mechanical noise during operation. Its adaptive control system intelligently selects the most suitable gear ratio for any driving style and road condition. Furthermore, a stepped variable control harmonizes with engine speed variations, maximizing both drivability and overall performance.

Designed for a linear and predictable driving experience, the constant velocity transmission offers more than just appropriate gear selection. A key advantage of CVT technology is its ability to allow the engine to operate at lower speeds for extended periods compared to traditional automatic transmissions. This lower engine speed translates directly to improved fuel economy. Additionally, CVTs provide a smoother ride by eliminating the gear-shifting shocks common in conventional systems, and contribute to a quieter engine operation.

Understanding Traditional Geared Transmissions

To appreciate the innovation of constant velocity transmission, it’s helpful to first understand how a conventional geared transmission operates. Think back to riding a multi-speed bicycle. The rear wheel had different sized gears; as a rider, you could only pedal so fast and with so much force. To optimize your effort, you shifted gears depending on the situation. For uphill climbs, you needed maximum power at slower speeds, so you used a wider gear. When going downhill and already moving quickly, a narrower gear allowed you to accelerate even further. Traditional vehicle transmissions function on the same principle, shifting gears to provide the most appropriate ratio for various driving scenarios. Lower gears are used for starting from a standstill, middle gears for acceleration and overtaking, and higher gears for fuel-efficient cruising at speed. Most vehicles with conventional transmissions offer four to five different speeds or gear ratios.

Constant Velocity Transmission vs. Regular Geared Transmissions: What’s the Difference?

From the driver’s seat, the controls of a vehicle with a constant velocity transmission are similar to those with a traditional automatic transmission: two pedals (accelerator and brake, no clutch) and a familiar P-R-N-D-L shift pattern. However, internally, instead of gears, the CVT employs two pulleys that can change their width, connected by a durable steel belt. By adjusting their width, these pulleys seamlessly alter the ratio between engine speed and vehicle speed. Because these pulleys can adjust their width across an infinite range, the transmission is described as “continuously variable” or “constant velocity.” Driving a car equipped with a CVT provides a unique sensation; you won’t experience the distinct shifts associated with gear changes. Instead, the system smoothly adjusts engine speed as needed, increasing RPM for rapid acceleration and lowering RPM for optimal fuel economy during steady cruising.

The Driving Feel of a Constant Velocity Transmission

Many drivers may not immediately notice the difference between a constant velocity transmission and a modern geared automatic transmission, as modern automatics are engineered for smooth gear changes. However, attentive drivers will perceive a distinct difference. With a CVT, the absence of fixed gears means you hear the engine rev as you accelerate, but you don’t feel any interruption in power delivery as the transmission ‘shifts’ because it doesn’t shift in the traditional sense. The engine quickly reaches its optimal power band, and the constant velocity transmission maintains the ideal gear ratios to keep the engine operating within this sweet spot for maximum power output and fuel efficiency.

Advantages of Constant Velocity Transmission

• Optimized Power Delivery: Engines produce peak power and torque at specific engine speeds. Constant velocity transmissions are designed to pinpoint and maintain the engine at this optimal speed, ensuring you consistently have access to the most power available.
• Enhanced Fuel Economy: For instance, when Subaru introduced CVT to the Forester model in 2014, fuel economy significantly improved. Utilizing the same engine as the previous generation, the new Forester achieved an impressive increase of five miles per gallon. The CVT optimizes fuel efficiency by keeping the engine in its most economical power band. Remarkably, the fuel economy of a CVT often surpasses even that of a manual transmission.
• Reduced Weight: By eliminating the heavy and complex gearset of a traditional transmission and its associated components, a CVT system has less mass. This reduction in weight contributes to improved fuel economy, enhanced vehicle handling, and quicker acceleration.
• Uninterrupted Acceleration: Unlike regular transmissions that must temporarily interrupt power delivery to shift gears (potentially causing damage if power isn’t interrupted), constant velocity transmissions are engineered to continuously transmit power to the wheels without any interruptions. This results in smoother and more consistent acceleration.
• Smoother Acceleration: Traditional transmissions can sometimes feel jerky, especially during hard acceleration. CVTs deliver power in a smooth, linear fashion, embodying the “Lineartronic” characteristic of Subaru’s system – linear and smooth power delivery.
• Increased Reliability: With fewer moving parts compared to a conventional geared transmission, constant velocity transmissions inherently have fewer components that could potentially fail, leading to greater long-term reliability.
• Manual Mode for Enhanced Control: For situations like towing or for drivers who enjoy a more engaging driving experience with gear selection, Subaru provides paddle shifters mounted conveniently behind the steering wheel. These allow drivers to select from six pre-programmed ‘gear’ ratios (which are simulated ratios within the CVT’s continuous range, not actual fixed gears). Note: Manual mode availability may vary by Subaru model.