[RAV]

Many think tubo charging is the Holy Grail of increasing fuel ecomomy, but let me propose and idea why it is not. The below example is all within BMW's
present technologies.
The 3.0 N53 in Europe is rated at 272 HP and gets a fuel economy of 38.4 mpg on the EU combined cycle ( subtract 16% to get US highway equivilent ), the coversion to the US standard yields a highway milage of 32.2 MPG. Now lets add valvetronic that will increase horspower and MPG by a conservative 5%. This new engine is now 285 HP with a highway milage of 33.8. One final step would be to increase the displacement to 3.5 liters. Keeping with the 95 BHP per liter, this engine would now put out 332 HP and would most likley deliver the same gas milage ( Honda, Toyota etc. did not see a milage decline when they went from 3 to 3.5 liter V6's ) This proposed engine would now put out 335I HP ( underrated at 300 HP) and deliver 20% better fuel economy. I would also doubt that 4 Cylinder turbo would deliver this type of fuel economy.

The ? then becomes why would they not do this. Could it be space in the engine bay, I doubt this since the E46 M3 at 3.25 liters fit in the smaller body than the present 3 series. I think it is pure cost savings, much easier to slap on a turbo charger and different software to increase power. Turbos do put out a lot of torque, but it drops like a stone after 5500 RPM. The 328 at 6500has lost only 9% of its torque, whereas the 335 has lost 24%. This torque fall off greatly deminshes the High RPM smooth pull that the NA 6 will give you.

I hope I'm missing something here, I would like to be wrong. Any thoughts or comments.