Hi

I´m rather new to diesel tuning at a software level, but the thought of tweaking the mpg´s a little do tempt me :)
I know the basics of economy tuning in regards to gasoline engines, but I´m not that familiar with the diesel principles in the area.

Most people I understand got their main focus on increasing the power and/or torque, but I really want to focus on improving the cruising mpg´s in my project - and if I can gain additonal power and torque as a biproduct that off course is just fine by me :)

The engine at speak is a 1.9 TDI PD (100 bhp) controlled by an EDC15 ECU.
But what maps should I, in particular, look for when tweaking for max. mpg´s, and does this aim require another approach when modifying the map values?

Lower your boost in cruising places. Advance your soi. Thats the base for diesel.

What eeds35 said, but change your n75 maps to open vanes aswell or the PID control will still allow it to boost higher than requested. Tuning soi takes a bit of getting right for economy. Really you need to use a dyno, set torque limiter to 10mg then dyno, advance soi then run again until you start to loose power, then set it to minimum required to make highest power. Repeat for all axis values in soi table. Or buy a cylinder pressure measuring tool in relation to crank degrees (£££), and tune so peak pressure is ~13degrees atdc.

What about EGR? My initial thought was, that an increase in available 02 (reducing the EGR) would mean, that the turbo needs to produce less to boost for the same power output, meaning less parasitic loss.
But I´ve also read that reducing the 02 (by increasing the EGR) and avancing SOI even more would let the engine reach a higher fuel conversion effiency:

http://ecomodder.com/forum/showthread.p ... 055-3.html

I think I would try by avancing the SOI by 3 degrees, and then reduce boost and trim the n75 maps accordingly at first.

This is a very low cost project, so I will have to settle with VCDS logs, records of tank-to-tank fuel economy and my butt dyno :D

I wouldn't just advance the soi by 3 degrees. I would change the whole column by a %, if you are just guessing. The only reason to change n75 maps is because the PID will allow a little bit of overboost before it ccontrols it.

And just turn the EGR off.

People say you need to tune for turning it off but I never have. You can also play with pre injection but you are really just guessing without dyno'd and stuff. Remember there is a margin, the oems tune for economy first, then have to tune for emissions sacraficing economy.

In TDI PDs example the hint is not only in SOI and lower boost but also playing with duration of course not at full load...