I think I heard a RUMOR that the PRV V6 was unable to reach the 88 mph so they dropped in another engine, possibly a Porsche engine (remember this was just a rumor that I heard on the internet; therefore, it could be false). The top speed I think was supposively just barely over 100mph on stardard DMC-12s, considering all the extra junk they had to add to that DMC-12 in the movies and considering how much older electronics weighed and the drag of the external parts they added like say Mr. Fusion (even though that was first introduced at the end of the first movie), it is definitely logical to assume they had to at least modify it to reach that speed.

For the sake of discussion, if you were the company that was going to build these new Deloreans, what engine would you use? Let's assume that only a V6 would work. I would order 3800s from GM and add direct-injection and twin-turbocharge them for the base level then top it off with a twin-turbocharged 3.6L Porsche engine from the new 911. That way 88.8 mpg is achieved in second gear so then the Doc doesn't have worry about his authoritus (forgive my spelling).