AutoBlog Green tested the Tesla Roadster

Even at 90 percent efficiency, a motor still produces some heat. In this case, the heat is in the rotor. The current motor being used in the Roadster is air-cooled. To prevent damage, when the rotor temperature gets too high the current flow is reduced, limiting power. In the course of doing development on the drivetrain for the WhiteStar sedan project, a more powerful motor was needed for the larger and heavier car. In order to achieve this, the team developed a larger diameter motor with a liquid-cooled rotor.

This liquid-cooled unit forms the basis of what’s being done for Roadster DriveTrain 1.5. The current air-cooled motor will be replaced by a unit the same size with liquid cooling. This will allow it to run at higher sustained power levels without overheating. Upgraded power electronics will feed more juice to the motor when needed for acceleration. A higher torque rated single-speed reduction gear transmission will handle sending power to the rear wheels.

For the moment, though, the Roadster still has DriveTrain 1.0 and that’s what I got to exercise. The first thing you notice with the Roadster is relatively heavy steering as you initially pull away. That’s because the Roadster inherits the Elise’s non-boosted steering system. Like most other things in the Roadster interior, the steering wheel is tiny. However, even with the minimal mechanical advantage, the steering weight isn’t overly oppressive.