I did not see how the PCM could make up for the extra fuel without some sort of closed loop feedback sensor. Since there is no AFM or O2 sensor on a diesel, then it would make sense that the PCM is using a fixed timing and fuel map to regulate the fuel injected. There are only two ways to get more fuel into the engine on an injected motor. Either raise the rail pressure to increase the amount of fuel squirted through the same size hole, or increase the size of the hole. If there was a way to put a variable fuel pressure regulator on that could sense vacuum and boost, then it would be possible to use the "stock" fuel flow at low demand, and then let the boost pressure to the variable raise the rail pressure as boost increases. This was a popular way to get more fuel into gassers when installing an aftermarket turbo kit. The problem was that it did not regulate well enough. You would probably have to have Quad, TTS, Juice, or some company that has visibility to the maps in the PCM program the fuel maps to take advantage of the higher rates of fuel flow and adjust the injectors for a 20 % lower duty cycle at times of less demand and off boost running. It really is not just as simple as sticking in bigger injectors without adjusting the timing and fuel maps to compensate for the larger fuel flow. It will smoke more and run richer all of the time and hurt fuel economy and off boost response unless to you can get into the maps and recurve them to take advantage of the larger injectors both on boost and off boost. Someday very soon someone will come up with a program and interface that allows visibility to the stock fuel and timing maps. Then you will be able to see what the aftermarket programmers are doing to the maps. Until someone either makes a read only program that can do this, or one of the aftermarket tuners comes out with a program or box that will let us program our own timing and fuel maps, we are just guessing at best. The only ones that really know what the maps are doing are the programmers like Quad, Edge and Diablo. It would be very very interesting to know what they use to get access to the maps and how they decide on what to change. I for one am used to the gassers that allow full access and visibility to the maps. Then you are not just taking someones word for whether or not the programming is "right". It would be very easy to compare the fuel and timing maps from one programmer to the other, say the Predator to the Juice, and see why one runs hotter and the other does not. It is still just a matter of more or less timing vs more or less fuel at certain vacuum and boost conditions. There is not any rocket science, other than no ignition parts to worry about. More timing and more fuel mean more power. The "art" is knowing when to apply and how to apply to get the most power at the safest levels without creating any drivability issues.
Jess
