Historic Information - Identifying Model Years
The differences between model years is very slight, and I usually differentiate them by their "bonnet" (hood). The early 81s have the fuel filler flap, while the later 81s have no filler flap but still have the "crease" that runs longways down the bonnet on either side. The 82s have a totally flat hood as do the 83s. Many 83s have the "DeLorean" lettering on the bonnet. I think the angled tailpipes are primarily on the 83s. These hard/fast rules do not always apply as in practice it is apparent that some intermixing of features has occurred.
Most of the updates were made during production of the cars and not "aligned" on model year boundaries. It is therefore difficult to distinguish model years in the traditional "Detroit" sense. You can either think of the car as having a single model year (produced for 2 years) with numerous production fixes, or you can take note of the updates made up to a particular model year.
Minimizing model year changes was one of the aspects involved in producing the "ethical" sports car. John Z. felt that a lot of the model year changes were introduced not as genuine improvements to a car, but as styling changes intended to make previous models obsolete.
The production changes to the car are documented in the Technical Bulletins publication available through most DeLorean specialty shops as well as the part number changes in the Parts Catalog.