Stock Toyota Prius Streets of Willow Hot(ish) Lap

Jun 17

Jun 17 Stock Toyota Prius Streets of Willow Hot(ish) Lap

Surprisingly tolerant of track day driving abuse, there is a trick to making a Toyota Prius go around a race track.

After fixing most of the things that were wrong with my cheap Toyota Prius Track Taxi, track time was inevitable, so on a particularly blustery day it was time for a shake down at the Streets of Willow Springs.

The usual and somewhat unusual pre-flight checks checked (is there oil in the engine, do the tires have air in them) it was time for lapping and, surprisingly, the Prius proved to be very tolerant of hard driving, until the safety systems intervened.

Toyota Prius Track Taxi build DriveBreakFixRepeat Jake Stumph Racing

The third-gen Prius has extremely invasive traction and stability control systems, but no button to turn off either. Google searches yielded little practical results other than Prius web forums where the consensus was “why would you want to turn off the traction control?” As you can imagine, the people who inhabit a Prius web forum, and the topics they discuss, are truly riveting.

Eventually, I decided to start pulling fuses to see what would happen, an while there are no dedicated traction or stability control fuses on a 2013 Prius, the big ABS fuse seemed appealing (it’s all tied to the ABS system after all, right?), so out it came. The Prius’ dashboard lit up like a Christmas tree upon start-up, surefire evidence that progress had been made.

Success! No ABS, no traction control, no stability control, no…hybrid battery system. The Prius regenerative braking system, the main means of charging the hybrid battery, is linked to the ABS, and went out the window with the fuse pulled. The brake pedal also firmed up and now offered more feedback, so pros and cons.

With the electrical interference out of the way, the Prius gamified driving on track, because with regen braking out the window, the only way to charge the battery up (which accounts for about 30% of the Prius accelerative abilities) was to take prolonged cool down laps and coast all the downhill stretches of the track to charge the battery up and line the car up for a hot lap.

After working around the Prius’ shortcomings, the lap times dropped tenth by tenth as the day went on. The best lap of day eventually worked out to a 1:50.4, which would be considered a blisteringly fast lap time, if you had ridden a bicycle around the track.

Oh well, the Prius did it! It survived an entire track day, no overheated engine, no fried brakes. Surprisingly, it was completely unbothered by a day of lapping, which is more than can be said for many cars. Now, it’s time to start modifying it to unlock the raw speed it’s capable of.

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