Paul Walker Crash -- Cops Summon Porsche Experts From Germany

The Paul Walker death investigation has taken a new turn -- mechanical experts who work at Porsche in Germany are flying out to L.A. in an attempt to get to the bottom of what caused the fatal crash ... TMZ has learned.

Law enforcement sources tell us ... they want a full analysis of the Carrera GT, including brakes, engine and body. They also want the experts to help determine speed at the time of impact. Our sources say they're also interested in the tires, and at least one is available for analysis because it was not completely destroyed in the fire.

TMZ broke the story, the L.A. County Coroner determined Walker died from a combination of impact and flames.

The Porsche experts will be working with Sheriff investigators to make an attempt to determine a clear cause of the crash.