hone eagle wrote:
Isn't that what DI prevents -detonation- because they can have the injection event after top dead centre?
after all these compression ratios are in the 10/1 range,well into detonation territory?
DI injects a mist of fuel during the exhaust stroke to cool the cylinder which "reduces" detonation, but does not eliminate it.
I was referring to detonation from having too high of fuel pressure squirting too fine of a mist that it detonates before it is suppose to. This is the reason why you cannot have the 25-30k psi fuel pressures that a diesel has on a GDI engine. DI creates a lot of particulate matter because the fuel being injected does not have enough time to fully mix with the air and burn which produces particulate matter.
The port injection on the Ecoboost is always running and accounts for 5-10% of the engine's fuel delivery from what I have read, but the DI only kicks in at mid to high loads. When the DI is not working you have wore fuel economy, but once it does kick in then you have higher PM.
