M21: FIRST BMW PRODUCTION DIESELS

M21D24

The first BMW production diesel branch is normalized as three distinct states in the Engine Master:

1. M21D24 naturally aspirated, 2443 cc, 86 — BMW 324d / 524d applications.
2. M21D24 turbo, 2443 cc, 115 — first 524td production phase.
3. M21D24 turbo + DDE, 2443 cc, 115 — electronically controlled later phase used by the 324td and carried into the E34-era 524td development.

The equal 115 headline output does not make rows 2 and 3 identical. BMW Group Classic explicitly documents the smaller turbocharger and DDE electronic diesel injection/control as a major technical revision.

Naming collision warning

BMW historical material also uses M21 as a 1971 petrol large-six period code before later M30 nomenclature. M21 (1971 petrol) and M21D24 diesel are therefore never joined by code-string similarity.

Sources

See ../../sources/source-registry-редакционная глава.md, especially P18-S003, P18-S036, P18-S037 and P18-S046.