The 07 Civic (R18A) engine opens the throttle butterfly completely under low load conditions and pumps some air back out during the compression stroke (effectively making it a 1.5L instead of 1.8).
The system is so fine tuned that I can't even guess the theoretical best engine speed/load combination. In theory in low revs and heavy load it shifts to the performance cam, thus negating the "low-load" efficiency.
Has anybody seen a BSFC chart for the R18A engine? Or anybody know a Honda engineer who has the keys to the company vault?
