eCVT

Baja SAE Electronically-Controlled Continuously Variable Transmission

Problem statement

The continuously variable transmission (CVT) critically affects drivetrain efficiency and performance in sport vehicles such as bikes, snowmobiles, Baja competition vehicles, and more. Conventional CVTs are purely mechanical, relying on fixed ramp geometries, centrifugal forces, and passive sheave mechanics. While robust, these systems require extensive trial-and-error tuning over narrow operating conditions [1]. A paper from Autozine Technical School suggests that mechanical CVTs are 10% less efficient than regular transmissions [2]. These constraints establish a clear need for active transmission control in UW-Madison’s Baja SAE vehicle. An eCVT enables closed-loop, real-time ratio adjustment based on engine and vehicle state, enhancing transient response, reducing manual tuning, and improving consistency. For example, closed-loop ratio control allows the transmission to command optimal torque multiplication at launch, during hill climbs, and throughout acceleration events. Although added complexity, weight, and belt efficiency are considerations, preliminary analyses indicate that a compact, competition-compliant actuator can be integrated while retaining the belt-and-sheave architecture and fail-safe operation. The proposed eCVT demonstrates a scalable approach to active ratio control in compact belt-driven transmissions, offering insight for small off-road and powersports applications where packaging, cost, and robustness constraints limit traditional transmission solutions.

Team members

Arnav Mehta – facilitator
Matthew David – communicator
Nathaniel Reiff – accountant
Nicholas Adler – admin
Shane Prahl – communicator

Client