Re:This is not news, or a discovery. (Score 1)

That aside, the problem with this is that a turbocharged engine at full output is very inefficient. A larger naturally aspirated engine will always be more efficient than the small turbocharged engine of the same maximum output. That's because a lot of energy is wasted compressing the intake charge, more than can be made up for with the displacement decrease, even with the newest fanciest garrett turbos. The only merit efficiency-wise of turbo engines is engine efficiency at low loads (when the engine is not under boost) relative to the maximum output. There is obviously a balance to be struck here, and that's why 18 wheelers have big v8's with turbo chargers, rather than even bigger engines or smaller engines running under high pressure. Designing a motor vehicle is always a balancing act, and in most cases a turbo is not helpful because of the cost, reliability and other shortcomings versus the benefits.

This isn't really correct. The turbo does increase efficiency because the engine is always dumping a lot of heat into the exhaust that just goes out the tailpipe. The turbo uses this heat energy to compress the intake charge. This isn't wasting energy, but using energy that would otherwise be wasted. Tht is why heavy duty trucks use turbos - that lets the engine use more of the fuel energy for moving the vehicle and less for heating up the air. They also use big inline 6 engines, never V8s, and they use very high pressure - at least twice atmospheric pressure.

That efficiency gain may be fairly small on a gasoline engine, which is more due to how the turbo system is set up than anything (full boost comes at much less than full engine power, for drivability - that means that too much boost would come at full power so the system frequently dumps compressed air to the outside before it reaches the engine, which limits any effiicency gain). A semi engine will have a turbo system designed to come on full at maximum power, which is pretty close to where the engine operates when the truck is going down the road. That lets the entire intake and exhaust system be optimized for where the engine runs most often and that gives efficiency.