10-01-2014, 01:56 PM
Well, Indirect injection is better at being able to use power throughout the stroke, since there's heat in the precups throughout the combustion stroke - cetane is directly comparable to the ignition delay meaning that the pressure rise from the diesel starting to burn happens quicker (great in a direct injection engine) and means the fuel completes it's burn faster and sooner throughout the stroke - but Indirects take advantage of the fact that they can exert the maximum amount of effort on the piston later into the cycle, where it's most effective.
DIs you can only inject fuel when there's heat there, otherwise you won't have enough heat to keep burning the fuel - soon as the piston starts dropping past TDC, the heat from compression is only ever going away.
Imagine being on a bicycle and only being able to apply force in first about 30* of crank motion past TDC - you'd not get very far. That's like what a DI does, they're getting better these days as more complex CFD can help keep heat in the cylinder for longer.
IDI can provide effort throughout the stroke MUCH better, since you can carry on injecting the fuel much later into the stroke, just when you get to the most effective point...
DIs you can only inject fuel when there's heat there, otherwise you won't have enough heat to keep burning the fuel - soon as the piston starts dropping past TDC, the heat from compression is only ever going away.
Imagine being on a bicycle and only being able to apply force in first about 30* of crank motion past TDC - you'd not get very far. That's like what a DI does, they're getting better these days as more complex CFD can help keep heat in the cylinder for longer.
IDI can provide effort throughout the stroke MUCH better, since you can carry on injecting the fuel much later into the stroke, just when you get to the most effective point...
