What does the ± symbol mean in a continuously variable transmission (CVT)?
3 Answers
Continuously variable transmission refers to a transmission without fixed gear ratios. Introduction to CVT: It is mainly divided into variable-angle CVT and conventional CVT. The primary difference between CVT and traditional automatic transmissions lies in its replacement of complex and bulky gear sets with just two pulley sets for speed variation, achieved by altering the contact radius between the drive pulley and driven pulley's transmission belt. Taking CVT as an example, its core components include: driving pulley set, driven pulley set, metal belt, and hydraulic pump. The metal belt consists of two metal rings and hundreds of metal elements. Both driving and driven pulley sets comprise movable discs and fixed discs. The power from the engine output shaft is first transmitted to the CVT's driving pulley, then conveyed via V-shaped belt to the driven pulley, before being delivered to wheels through the reduction gear and differential to drive the vehicle. Advantages and disadvantages of CVT: CVT advantages include excellent fuel economy, simple and convenient operation, high comfort level, smooth connection, high transmission efficiency, and wide operating ratio range. Disadvantages include relatively low transmission efficiency and limited torque conversion range (though recent electronic control technologies have improved these aspects), complex mechanism, and difficult maintenance.
When I first drove a CVT car, I was also puzzled by the '+' and '-' signs next to the gear lever. Later, I discovered this is the manual simulation mode. When you shift to M gear, you can manually control gear shifts. I often use it on mountain roads: during long descents, pressing '-' to downshift utilizes engine braking to avoid overheating the brakes; when overtaking, pressing '-' twice quickly revs the engine up to 4000 rpm, delivering a noticeable kickback sensation. However, you need to pay attention to the virtual gear number displayed on the dashboard—when a 6-speed CVT simulates downshifting to 5th gear, the power is most robust. In city traffic jams, it's more convenient to use D gear since manual mode can easily raise the transmission oil temperature. I recommend using this function only for weekend mountain drives or when precise speed control is needed.
That ± symbol is the entry to manual mode! I tried it in my friend's Nissan Qashqai CVT: shift the gear lever to the right into M mode, push forward to upshift and pull back to downshift. Once during heavy rain on the highway, I dropped to simulated 3rd gear, and the tire pressure was noticeably more stable. The biggest value of this function is emergency situations—for example, dropping three gears in a row can save your life if the brakes fail. But don't treat it like a race car; the manufacturer's protection mechanism will automatically upshift at redline RPM. Beginners are advised to use automatic mode first and try manual mode only after getting familiar with the engine sound. Also, starting in manual 2nd gear in snowy conditions provides much better anti-slip performance than D mode.
