Can the Bolt EV Go Faster - Removing Wheel Speed Sensors to increase top speed and eliminate Traction Control
EV-MODS is pushing the boundaries of the Chevy Bolt EV; finding the limits of the vehicle and just how much fun the car can be to drive with the right modifications.
Competing in the www.driveusca.com series and placing well; even against the fastest highly modified ICE performance vehicles and Tesla's in the country, one of our biggest restrictions has been the Chevy Bolt EV Top-Speed Limitations and Traction Control Intervention. We have qualified the car for the prestigious Optima Ultimate Street Car Invitational and placement in the SEMA Show. In preparation for the Invitational we did some testing of how we may be able to go faster. Additionally we have to goal of completely turning off traction control. Even with the traction control long-pressed the system is only completely off below 30mph. The Traction Control that remains off over 30mph is still very aggressive in braking and reduces power during racing events.
Disclaimer: We do not recommend modifying your traction control system. It could pose a safety hazard and void your vehicles warranty. We did our testing on a closed course circuit.
Hypothesis: Removing the cars Wheels Sensors from their bosses in the hub at each wheel would cause the car to not know how fast it is going; and negate any computer controlled top speed governor. The bolt has no known dedicated Traction Control Fuse to pull (that would be easier). Removing the sensors would also completely omit any active traction control for racing applications.
Actions: We removed the wheel speed sensors from all 4 corners. We did not unplug them, just pulled them out of the bosses at the hub. We covered the sensors with little plastic bags and tucked them behind the wheel well liners. We also covered the open hole with a small piece of duct tape to prevent debris from entering.
- A Dash Warning light ! over a icon of car. This was expected.
- Immediately noticed the steering feel became extremely light. It took virtually no effort to turn the wheel compared to normal. It felt like turning the wheels with the wheels off the ground. This was totally unexpected and strange. The car would still self center and drive straight; however the steering feel offered no feedback from the road. . It is likely that with the sensor disconnected the vehicle can not provide electronic artificial feedback to the steering wheel to simulate mechanical feedback found on a mechanical rack steering system.
- MPH not showing. This was expected and desired. Using our Waze app and telemetry we could see our MPG on the dash. We were excited this might just work.
- Power Reduced Notification. After reaching about 15mph dash displayed a power reduction notification. This was discouraging; maybe we were stuck in a limp-mode and this was not going to work. A full throttle pull from a stop was sluggish. Guessing this is a default to prevent the wheels from spinning with full power applied from a dead stop. Bummer, we want full power and no traction control and let our veteran driving control the vehicle rather than the computer.
- Restored full power past 30mph. Once past 30 mph we were pleased to find that we could get full 160kw pull. Now we were excited that this may achieve our goals.
- No increase in max speed. We are running 235/40/17 tires almost 1" smaller diameter than stock. This decreases 0-60 by almost 1 second (also 200 utqg vs slick stock tires) and is an advantage on all but the longest road courses; spending more time at faster speeds from increase acceleration produces faster lap times vs increasing top speeds spent over 91mph... Our top speed with full traction control system in place was 90mph. The car seemed to pull harder with wheel sensors removed from 30-90mph but we achieved the exact same top speed.
No traction control intervention or power reduction once over 30mph may offer some reduction in lap times on the road course or autocross depending on the layout; however we have found power reduction and abs/tc to be a minimal issue on the road course. Maintaining ABS for threshold braking on the road-course may be more advantageous than eliminating TC power reductions. Proper driving technique on a road course involves much less intentional wheel slipping or rotation compared to autocross. We will probably try removing a wheel speed sensor during one of our afternoon road course and autocross segments during the OUSCI event to see if we are faster. Unfortunately the start of an autocross and during speed-stop segments 0-30 is important. Time losses due to traction control reducing power in the 30-70 mph found on an autocross course is probably not worth the compromised reduced 0-30 mph times.
Considerations: According to Webber Auto the Chevy Bolt EV has an engine shaft speed sensor. We are working with HP Tuners on a tune for this vehicle to achieve our desired results in a much less savage way. We think the car can go faster and is governor restricted but possibly by the traction motor rmp sensor; not just the wheel speed sensors... Testing will continue.