Can anyone explain what the purpose of the “pre-cup” cylinder head design is vs. direct injection? Like why was the pre-cup design originally used? History?
Thank you. P

Some good reading, courtesy of Google.

http://www.cms.daimlerchrysler.com/emb_classic/0,,0-195-78768-1-84721-1-0-0-0-0-0-434-78641-0-0-0-0-0-0-0,00.html

http://www.oldengine.org/members/culp/lister_diesel_miscellany.html

http://en.wikipedia.org/wiki/Diesel_engines

OilBurner,
By pre-cup do you mean "pre-combustion chamber"? If so, I believe the original purpose was for a quieter operating diesel. Though charge burn patterns also make it a lot easier on pistons and rods as you get a slower burn initiating from multiple sites thereby avoiding high-speed detonation. I think this is still direct injection as non-direct injection is port injection. Though I might be too picky on definitions and do understand you're defining direct injection as having no pre-combustion chamber. Then again, I apologize if "pre-cup" means something other than having a pre-combustion chamber.