Nick
06-03-2008, 08:03 PM
The Bac brought a point that I think deserves more discussion in the rail pressure vs. cylinder pressure thread (http://dmaxcentral.com/forum/showthread.php?t=95).
Is there any merit to running weaker than average timing and unleashing the compressor on it. This would be all at the same overall per/stroke fuel volume of course. I think it's generally agreed that once you've started main injection, it's best to atomize as much fuel as possible as quickly as possible.
Higher rail pressure moves to this cause, but it also raises peak cylinder pressure as verified. With that said, I think we'll run out of technology before we're able to inject at a pressure substantial enough to affect cylinder pressure more than main injection timing (at stock nozzle size). Injection timing seams to rule peak cylinder at this stage, although- that doesn't necessarily rule the Torque factor. Look at these two graphs, the first one is high timing, the second one is lower timing. They're the same fuel quantity and make the same torque factor, but one has a significantly higher peak cylinder pressure.
http://i105.photobucket.com/albums/m201/vortecfcar/CPT_60_2575RPM.jpg
http://i105.photobucket.com/albums/m201/vortecfcar/CPT_20_2535RPM.jpg
When I first saw this I was surprised that they made the same torque. I wondered if timing really was that important. ?
But then I noticed that I was running clean. The truck had very little smoke on a WOT run. I was certainly not overfueled by traditional gearhead standards.
My question is, do you think it's reasonable to spray fuel that late in the power stroke for the intent of making power and keeping the engine alive. And if so, is it cost effective to run 55 lbs of boost on a stock longblock to make the same horsepower, as reliably as built engine would make said horsepower at 42lbs?
Nick
Is there any merit to running weaker than average timing and unleashing the compressor on it. This would be all at the same overall per/stroke fuel volume of course. I think it's generally agreed that once you've started main injection, it's best to atomize as much fuel as possible as quickly as possible.
Higher rail pressure moves to this cause, but it also raises peak cylinder pressure as verified. With that said, I think we'll run out of technology before we're able to inject at a pressure substantial enough to affect cylinder pressure more than main injection timing (at stock nozzle size). Injection timing seams to rule peak cylinder at this stage, although- that doesn't necessarily rule the Torque factor. Look at these two graphs, the first one is high timing, the second one is lower timing. They're the same fuel quantity and make the same torque factor, but one has a significantly higher peak cylinder pressure.
http://i105.photobucket.com/albums/m201/vortecfcar/CPT_60_2575RPM.jpg
http://i105.photobucket.com/albums/m201/vortecfcar/CPT_20_2535RPM.jpg
When I first saw this I was surprised that they made the same torque. I wondered if timing really was that important. ?
But then I noticed that I was running clean. The truck had very little smoke on a WOT run. I was certainly not overfueled by traditional gearhead standards.
My question is, do you think it's reasonable to spray fuel that late in the power stroke for the intent of making power and keeping the engine alive. And if so, is it cost effective to run 55 lbs of boost on a stock longblock to make the same horsepower, as reliably as built engine would make said horsepower at 42lbs?
Nick