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April 11, 2019

WILLOWS , Calif. — Faraz Khan’s all-electric Kia Soul is his workaday car, but on a drizzly weekend last month, he and his teammate, Jose Rojas, were hoping it would drive them to a racing milestone.

So they squeezed on safety helmets, booted up their laptops and inched toward the west track of Thunderhill Raceway in rural Willows. Poised behind the wheel at the starting line, Mr. Khan stared into a laptop balanced on his partner’s knees. “In theory, this should work,” he said. “Although it might be an embarrassment.” The two men laughed off their nerves as Mr. Rojas initiated the car’s homegrown autonomous controls.

Mr. Khan and Mr. Rojas, both software engineers, have been using evenings and weekends since last fall to hack the Kia. They are among a loose-knit community of perhaps 50 independent hobbyist-engineers who — for fun and the sake of learning — rip open vehicle dashboards and splice essential wires to turn cars into robots.

“The bar is high. You need to get a car, and then you need to really mess with it,” Mr. Khan said with another laugh. “Most people aren’t comfortable with that.”