what does it mean and what does it do?

I thought it originally stood for "in-line" since BMW 4 and 6 cylinder engines were configured that way. Then you get into the V8s, so I'm not sure.

injected........................................ :huh: :o :| :P maybe

Nope.

i = Injection for fuel injected motors. All diesels are "d" to differentiate them.

so why do some dont have an i or d?

here's a link from wikipedia explaining the letters

http://en.wikipedia.org/wiki/Bmw#Nomenclature

i = INCREDIBLE!! :thumbsup: Nah, actually does mean injected....the INCREDIBLE is just implied!! :cool:

and what does d mean?
dramatic maybe? :S

Nope, the "i" stands for injection like the "e" for Mercedes Benz it is just in German "einspritzt". 36 years ago when the 5 series was launched with the e12 model there were only two versions. The 520 115HP (carburetor) and the 520i 130HP (electronic fuel injection) both were 4 cylinder in line. I was a child and I remember that it was quite rare to see a car with injection at that time. Same was the MB it was the 200 and the 200E.

Attachment 69601

My guess is if "I" is for gasoline cars and "d" is for diesel, maybe "i" means internal combustion engine.