hi all first post here, am from australia and our common large 4x4s here running a turbo diesel are the toyota landcruiser 4.2tdi or new 4.5twin turboCR or the nissan patrol 4.2tdi......... now my question is because of the size difference in capacity with a cummins 5.9 what would be a smaller compound set up on an engine with 4.2litre capacity? to help anyone help me the turbos used normally are a T3/T4 hybrid, gt2871bb, some have used gt3071r but that is getting slightly laggy down low..... all are using a .64 a/r turbine or a .63 a/r turbine. a common use is the little gt2860rs for instant boost off idle.... these engines also rev to 4500rpm fine,but i like my power/torque from idle to 3000rpm, engines have 12mm internals in VE pump....

i was thinking along the lines of a gt3583r for the larger turbo but unsure of using the .63, .82, or 1.06 a/r turbine. 1.06 is standard on this turbo and would definitly kick in higher in the rev range........... the boost i am running at the moment is 25psi which is high on these engines as the turbo is falling out of its efficiency range so ive been told. 30 to 40 psi is what im aiming for. will the larger turbo make the smaller one overspin, say a gt2871r and a gt3582r (both ball bearing)?am just tryin to get/keep instant boost and more boost up top with a larger turbo instead of a small single spinning its **** off........ i have 1 million more questions hey