Just to provide a baseline for comparison, i thought to include a link to the best VW engine database for weights that i have found on the web:
VW Engine Database (auto scrolls to 3-cyl TDI)
Unfortunately 4-cyl data is hard to find, however the automotive 4-stroke turbodiesel is as follows (using the best figures):
3-cyl: 0.52kW/kg
V6: 0.77kW/kg
V8: 0.9kW/kg
V12: ~2.4kW/kg - this is the engine used in the R10 LeMans racer!
A realistic figure for 4-cyl 4-stroke engine is probably about 0.6kW/kg. Interestingly VW are now looking along the lines of higher boost in smaller engines.
Mart