[Updated at 2:55 p.m. PDT March 25: "Investigators determined the cause of the fatal solo-vehicle collision was unsafe speed for the roadway conditions," said Cmdr. Mike Parker of the Los Angeles County Sheriff's Department.]
Investigators also determined that a pair of 9-year-old tires contributed to the crash, not a mechanical failure. There was no evidence of any car system failures, such as the brakes, according to the report.
Rodas was a veteran race car driver, but the speed into a tight curve proved too much, investigators with the sheriff's department and California Highway Patrol found.
An earlier L.A. County coroner's report had pegged the speed as being more than 100 mph, but the traffic analysis in the recent report determined it was a bit slower.
Walker and Rodas were killed almost instantly, succumbing to multiple traumatic injuries and a fire that quickly consumed the car.
Walker died of "severe blunt head, neck and chest trauma," sustaining a broken arm, wrist, jaw and ribs, according to the coroner's report. The fire burned his body beyond recognition.
Rodas suffered similar injuries and a fractured skull.
Investigators spent months examining the videos, interviewing potential witnesses and working with experts from Porsche in Germany and tire manufacturer Michelin to determine the cause of the deadly crash.
After reviewing numerous security videos from cameras around the business park, investigators found no evidence that the pair was racing against any other vehicle, according to the report. The four-lane road is part of a business park loop in Rye Canyon near a car company that was owned by Rodas and Walker.
Skid marks and video revealed that the car spun out of control and hit the sidewalk, sending it smashing into a tree and a light post with tremendous force.
Rodas' and Walker's bodies were found braced for impact in a "pugilistic" stance, the report said.
Since the 2001 debut of "The Fast and the Furious," Walker had become the face of the Southern California car culture. While the movie became a billion-dollar movie franchise, Walker kept his street credibility by driving a Nissan Skyline GT-R, appearing at real tuner events and investing in a super-car business.
The 2005 Porsche Carrera GT has a history of being difficult to control. The sports car is capable of reaching 100 mph in less than seven seconds. But it was built without the stability management system with which most Porsche models are equipped. The data the carmaker helped to retrieve allowed investigators to determine RPMs and throttle and airbag deployment at the time of the crash.