Back to the Future is over 30 years old, but you wouldn't know it based on how well Steven Spielberg remembers it. Steven Spielberg was a producer of Back to the Future back in the 80s but he also directed Ready Player One, which meant he was in the perfect position to make sure the digital recreation of the famous Delorean was as close to the real thing as possible. Supervising Sound Designer Gary Rydstrom explains in one of the special features attached to the new Ready Player One Blu-ray that Spielberg even remembered exactly how the time machine's exhaust was created on the set back then, which meant they could recreate it by using the proper sound. According to Rydstrom...
Steven even remembered, when the Delorean first appears in the movie, the big exhaust vents in the back shoot out this steam. And we were doing it and he said, 'oh we just used a CO2, you know a fire extinguisher for that.' So we went to the [sound] library, cut a fire extinguisher. He remembered what they used for Back to the Future.
The Delorean in Back to the Future was a real car and digital effects just weren't that advanced in 1985. As such, the desire to have your exhaust expel a lot of steam meant doing it practically. Ready Player One didn't need to do that, but since the film still wanted to create all of the 80s nostalgia as perfectly as possible, they still wanted to create all of the vehicles sounds properly, so that the version inside the OASIS sounded like the real thing. Most of the time, that involves research in order to figure out how a particular sound was originally created. However, in the case of this one particular sound, no research was needed, because Steven Spielberg somehow remembered.
It would be one thing if Speilberg had directed Back to the Future and had thus been overseeing the entire production. However, Steven Spielberg was actually the producer. While clearly involved in the production, you wouldn't expect him to necessarily remember a lot of the details. Producers tend me more "big picture" guys, and yet, somehow he knew this random bit of trivia.
It sounds like Steven Spielberg remembered most of the other details about how sounds were created for Back to the Future as well. Since the vehicle did different things in Ready Player One than it did in Back to the Future, simply using the same sounds wasn't going to work, but knowing how those sounds were created means being able to use the same methods to create the sounds you need.
Ready Player One is available now on Digital and Blu-ray.