teamlseep13 wrote:I am sure you know this, but the main reason GM did the variable cam phasing on the V8's was to help pass emissions standards while making more power than the earlier engines, as well as help interface with the DoD system.
I would agree that playing with the phasing to change the DCR would be fun though. It would be cake too, the whole system is so simple most 5 year olds could understand how to work it.
Do have to remember though that even if the MAP is low, on a really hot engine, detonation may rear its ugly head anyway from a heat soaked combustion chamber despite the fact that load and TP angle is low. Sure dumping a bunch of EGR could help combat that but thats just a bandaid.
I understand GM's after emissions and power. I'm after thermal efficiency, pure and simple. In fact, it may be MORE difficult to get the engine I outlined above to pass emissions because the high chamber pressures and temps are more likely to produce oxides of N and other weird things.
Obviously there would have to be temp compensation for the compression, just like there's temp compensation for spark timing, cold start modifiers for fuel, etc.
If we can cool it appropriately, a LOT of EGR might not be a bad idea. Diesels have the efficiency they do partly because of high compression ratio, but also partly because they don't have pumping losses the way a gasoline engine does.
EGR reduces pumping losses by increasing manifold pressure. If the exhaust is almost completely recirculated at idle, the gasoline engine could run like a diesel. Getting rid of the exhaust heat is the tough part, though.
The FWD Northstars cool the EGR gasses by running them through the water manifold on the back of the engine. The volume of gas that this would require would be MUCH greater, however.
