mlts22 wrote:
One note about the Dodge Pentastar: As far as I saw, it is a common rail ignition system. Pretty much, turbo or no turbo, it is able to squirt the optimal mixture into the cylinder. Chevy does similar with the VVT (variable valve timing.)
This is one of the reasons why the van gets such decent MPG. Older engines have been upfitted and improved (such as the 5.4 and the Ford V-10 with cam phasors), but this is a ground-up rebuild.
The engine/transaxle engineering is also interesting. Long term, it would be great if Fiat/Dodge can get the AMT (automated manual transmission) technology shifting as well as a hydraulic transmission, because it would improve fuel economy even further.
I think you mean a common rail fuel injection system, which has been the standard for almost all EFI, port injected engines for a long time. I even have a homemade setup on our 1970 Challenger that I put on close to 20 years ago. The deal with port injection, or other fuel injection system, is that you can inject exactly the right amount of fuel, but you can't control getting exactly the same amount of air. So your mixture is not always optimal. The variance is from aiflow differences due to the different paths the air takes to get to each cylinder, and the resistance to flow variations those differences cause. The only way around it that I know of is what they do on race engines when they dyno tune. They put a wide band oxygen sensor right at the exhaust port of every cylinder to read instantaneous mixture, and have fuel injection system capable of changing the fuel put to individual cylinders at every rpm range. It is a huge tuning job a major computation in the EFI.
The newest EFI design is Direct injection for gasoline engines. It is just like a diesel in that the fuel is injected directly into the cylinder, but it is spark ignited, not compression. You get the maximum use of all the fuel energy because it always is burned with a surplus of air. Just like diesels do. You basically inject the gas into a recess in the piston, where it is very rich and concentrated, so it will ignite easily. Spark it in its rich state and it explodes out into the pure air around it, being totally burned. The engines you see that are getting much better mileage are almost all direct injection gas. It also allows turbo engines to run much higher boost and compression, as direct injection really cuts down detonation.
