Originally Posted by swamp2
Well there is a reason if the questions are still unanswered. Do you expect me (or anyone) to believe that Audi added a fairly complex DI system for fun or for marketing as apposed to for efficiency and performance benefits? Highly doubtful. This is a system in a very confined space that required the modification of the head and combustion chamber - absolutely not small things. The car is producing a very good torque/l and I suspect DI has something to do with that. If the M3 had the tq/l of the RS4 it would have 307 ft lb, a full 4% better than it has now.
If you can not prove the Audi system is not good or only offers marginal benefit you shouldn't claim so.
I guess you know what FSI technology means to Audi, it's almost like what the inline 6 means to BMW. So the question "if marketing alone would be reason enough to implement FSI" isn't that obviously to answer with NO.
We had exactly this discussion already some time ago here: http://www.m3post.com/forums/showthread.php?p=1222664
, and that's what I want you to refer to. It's a very interesting discussion with an RS4 owner who himself said that the benefits over a conventional (manifold injection) engine are "small."
Autobild had a comparison between M3 and S5, the S5 did need more gas than the M3.
Best regards, south
EDIT: The M5 has a better tq/l ratio than the RS4...