Adam R wrote:
but fortunately for a diesel, the difference in mileage numbers between a 200hp engine pushing a full sized truck down the road and a 400hp engine is negligible.
I would disagree with that. I would bet that a 240 hp Ecodiesel gets considerably better fuel economy than a 370 hp Cummins does pushing the same full size truck down the road. At least 5 mpg better, but probably more.
Also, I think the argument here (TnP, please correct me if I am wrong) is the fact that people saying they want more fuel economy than the power of today diesels. Basically instead of the high powered apples we are getting, they want fuel economy oranges while keeping the same power. What should be stated is that with a diesel if you increase the engines ability to use up more of the fuel's energy giving you better fuel economy, more power is also created given that the displacement is the same. Well, unless you inject less fuel per injection event. At that point, if you want to have better fuel economy while not increasing peak power then you have to decrease displacement.
I will use the Ecodiesel again. Due to the manufacturers using technology like common rail, VG turbos, electronic injectors, and more valves the 3.0L Ecodiesel is able to have the same power output of an early 5.9L 12v Cummins while having much better fuel economy. The Ecodiesel is able to burn fuel more efficiently than the old 5.9L therefore it is getting more out of each drop of fuel.
However, if you are talking about the exact same engines using the exact same technology that only gets X% of energy out of a drop of fuel, then TnP is correct that the fuel economy will not be effected negatively if peak power output is increased.
