Just increase the size of the flux capacitor and you should be good to go!
A replica of the DeLorean time machine's flux capacitor
The flux capacitor, which consists of a rectangular-shaped compartment with three flashing Geissler-style tubes arranged in a "Y" configuration, is described by Doc as "what makes time travel possible." The device is the core component of the time machine.
As the time machine nears 88 mph, light coming from the flux capacitor begins pulsing more rapidly until it becomes a steady stream. Doc originally conceived the idea for the flux capacitor on November 5, 1955, when he slipped while hanging a clock in his bathroom and hit his head on the sink. A similar, but more primitive, steam-powered flux capacitor is also seen in the chimney headlamp of Doc's second time machine, the Time Train, at the end of Back to the Future Part III.
Although the films do not describe exactly how the flux capacitor works, Doc mentions at one point that the stainless steel body of the DeLorean has a direct and influential effect on the "flux dispersal", but he is interrupted before he can finish the explanation. The flux capacitor requires 1.21 gigawatts of electrical power to operate, which is roughly equivalent to the power produced by 15 regular jet engines.
The instruction manual for the AMT/ERTL DeLorean model kit says: "Because the car's stainless steel body improves the flux dispersal generated by the flux capacitor, and this in turn allows the vehicle smooth passage through the space time continuum."