@devilsadv
i am glad u asked
d4d is just a name for comman rail high pressure diesel engines made by toyota,new generation diesel engines like u see from BMW's mercedes VW with different names etc.really good engines for both performance & economy
D4D used Variable Geometry Turbos that constantly work unlike conventional turbos that kick in at higher RPM's
also D4D's produces lots more torque than conventional engines
e.g
1kz-te(conventional) 3.0L 120BHP
1kd-ftv(D4D) 3.0L 170BHP
get the point or should i explain more?