Direct Injection & Large Injector, Late Port Injection Similarities?

[NewbVetteGuy]

I remember reading a thread on Direct Injection that essentially stated that with direct injection all of the cooling benefit of the fuel evaporation goes into the cylinder WHERE and WHEN it's most needed and that it's taking out heat right when pre-ignition and detonation is most likely to happen and that this is a major contributing factor to WHY DI can tolerate such high DCRs. (Less cooling of the air in the intake tract, more cooling of combustion.)

-If this IS one of the factors that allows DI to run higher compression vs. carbureted, throttle body injected or port injected NA engine, then wouldn't a "large injector, fast and late injected" port injection strategy also bring with it some of the same benefits, or not in any significant way because with port injection the intake valve is closed so far before the spark event that it just doesn't matter by that point?

(If you're cooling the intake air charge less and the cylinder more with a large, fast, and late injector strategy, does this give you any addition margin of detonation resistance or ability to push DCR slightly further?)



Adam

[NewbVetteGuy]

And just to better understand and mentally visualize what's happening with DI injection, roughly how far before the spark event and TDC is fuel starting to be injected with DI?

(I'm curious how that timing compares to when pre-ignition and detonation normally occurs and whether DI engines simply "not having fuel in the mixture" at the time that pre-ignition normally occurs is actually a significant factor or if that's just urban legend that gets repeated often..)

The injection timing changes with RPM and throttle position, or how are the ECU's doing this? -I assume at high RPM and throttle positions they're not spraying 100% of the time like they end up doing with traditional port injected motors, just to keep up, right?


Adam