The Nissan Sentra is totally redesigned for 1991. Edges are smoothed out and corners are rounded, giving the '91 Sentra a more substantial feel. A racy SE-R is introduced with an outstanding little 140-horsepower engine. All other Sentras get a 110-horsepower engine that is about average for this class. A four-speed automatic transmission is available on all Sentras but the SE-R.