I checked Jeff Fisher's blog tonight and found this post, containing a 2001 Ford press release on Direct Injection for Gasoline engines. Now, I'm not a mecahnic or an engineer, but this seemed interesting, but also left me with some questions. According to Jeff's post, Direct Injection, which is more common in Diesels, can increase fuel economy in gasoline engines by almost 20%. But it seems that this lean burn is ideal at low rpm and allows higher compression. It also seems to work best on Four Valve engines.
So here are my questions, if today's multivalve engines are designed to perform at high revs with lower combustion ratios, and the lean burn of direct injection can actually be harmful to these engines at high rpm, what is the answer to the lean condition, auxilary injectors? And what do you do about the higher compression ratios and detonation/knock?
I'm sure these are the questions that industry engineers are working on right now, but if anyone has an explination that the average Joe might understand, please comment here.
Here is a Wikipedia entry on Direct Injection; http://en.wikipedia.org/wiki/Gasoline_direct_injection