2.5 non turbo diesel

[sideshowbob]

I have a 2.5L non turbo Ford Transit that I want to fit a water injection system to. I have experemented with H2O injection in the past with a 2.0 petrol engine, gettign a small but measurable decrease in fuel consumption and very good emission readings.
The amount of water I was injecting was approx 10% fuel volume.
Does anyone have any advice? I am not looking for big power increases rather increase in economy and reduction in emmissions.