Nitrous is a boost of speed that is used in races that has been featured in most Need For Speeds. Nitrous is built up and used differently in different games.
 Need For Speed: Underground 2
Nitrous is given to you by doing near misses with other cars, air time and Drifing. Nitrous can be used at any time and you can use how much you want.
 Need For Speed: Most Wanted
Nitrous is built back up during the race automaticly. You can use any amount of it at any point in the race.
 Need For Speed: Carbon
Nitrous is built up automatically during the race, you can use nitrous at any point in the race.
 Need For Speed: Prostreet
Nitrous upgrades can be bought for your car. Cars start off with no nitrous, but you can get up to three tanks of it. Nitrous can only be used in a whole tank and not in small amounts. Nitrous is automatically recharged during the race.
Related ThreadsNitrous question - last post by @ Aug 9, 2010
Nitrous System - last post by @ Nov 9, 2006
Unique Nitrous? - last post by @ Sep 17, 2004
Its not nos, its nitrous!!!! - last post by @ Sep 4, 2007
Question about Nitrous - last post by @ Feb 28, 2006