From E30 Zone Wiki
This is a basic run-down of other BMW models that have some relevance to the E30. Some provide parts, some provide history; all are part of the big BMW family.
Models are categorised by E-number. E stands for Entwicklung, German for "design". In that way, the E-numbers form a chronological history of BMW development.
Cars with Z-numbers mean Zukunft, or "future". They were conceived as radical redesigns of existing platforms, usually as roadster form. While they start with Z1, their order is illogical, with the current sequence being Z1-Z3-Z5-Z4, and Z2 planned for 2014.
If a BMW model is not listed here, and you think it deserves an article in the Wiki, get in touch with Grrrmachine.