Maximum Fuel Economy Tuning

Dear HPA, I am excited to have just joined your community. I have the Alientech Kess V2 with the ECM Titanium as my tuning equipment. I am wanting to do fuel economy tuning for turbo diesels here in California. I can already hear Andrew saying, "The fundamentals are the same across all platforms and engines." My question is, what should I tune for maximum fuel economy? What maps and what areas in those maps and by what amount should I be changing? I know this might be irrelevant but just to make sure, tuning for economy is the same for a turbo diesel as it would be for a Naturally Aspirated Gasoline engine, correct? Assuming both are automatic transmission.

First up I need to be clear that the concepts of diesel and gasoline tuning are very different so a turbo diesel and a gasoline engine can't be compared. With a diesel engine it's all about finding the amount of engine torque required for steady state operation and then achieving that amount of torque with a minimal fuel volume. There's a limited number of parameters we have at our disposal here but one that can provide an improvement in economy is injection timing. The OE tuning strategy often uses retarded injection timing in order to limit NOx production and sometimes we can advance the timing and gain economy at the expense of NOx. What you can achieve will depend on your engine and ECU though as modern diesel engines include NOx sensors that will likely produce a fault code if you exceed predefined limits.