The dev already confirm there's no issues with DVD9,

http://www.bizarrecreations.com/article.php?article_id=5257

On July 27, a Bizarre Creations staffer posted on their forums that the upcoming Project Gotham Racing 4 won't have day and night versions of their tracks in the game because "Whilst this wasn't a problem for our dev team, it was a problem fitting all this data onto a single DVD. So we've worked around the problem by providing different lighting models per city."

Seems pretty straight forward, right? But when people sorta went quasi-ape-shit pointing out, rightfully so, that perhaps the medium (DVD) is holding back the game, Bizarre Creations cranked up their spin machine and issued a response under the befuddling headline "Wrong end of stick been grasped?"

In it they seem to blame "fanboys" for the spin on their story, instead of the person in their company who actually said the DVD didn't have enough space.

But the DVD has plenty of space, they say now: "DVD size is absolutely not a factor that we consider when designing our games... and PGR4 is no exception. DVD9 gives us more than we need to create a fabulous experience for you guys."

Notice the word "designing", does that mean that it is a factor when they actually get down to creating them? Because it certainly seems so. BC goes on to write that the issue of no night and day was one caused by developer time and resources, which directly contradicts what was posted in their forums. They had to pick and choose what they wanted to spend development time on and they went with dynamic weather rather than time of day.

The question now is who do we believe: Bizarre Creations or Bizarre Creations?