Yesterday I have done a Mercedes G class with OM606 engine tuned with VNT turbo a big Dieselmeken EDC fuel pump controlled by a Baldur DSL1 ECU.
Mercedes OM606 is a legend among small diesel engines able to make easy over 500Hp power on stock engine and yes bigger fuelpump in combination with S200 or S300SX-E turbo still able to use it as a daily drive with a lot of oumpff if needed.
.
Did take my time and fine-tune the start and idle fuel so that the engine runs just as smoothly with the larger fuel pump as if it were a standard engine.
What I wasn't too happy with is the VNT turbo that my client got pressed into his hands. This one does what you need, we put a bigger compressor wheel in it, now it easily makes 2.5Bar turbo pressure and 350HP. If our turbo experts only opened their eyes then you know that the compressor wheels have improved in recent years with air mass displacement etc but have not gotten bigger in recent years. Another thing is that most VNT turbo designs are quite recent, so go ahead and improve on that! OK but what is the effect of putting a bigger compressor wheel on an existing VNT turbo??? Very simply the turbine has to deliver more torque to be able to turn the larger compressor wheel and for that you need more exhaust pressure to generate torque and with a VNT turbo this is also possible because there are adjustable vanes in the exhaust housing of the turbo that allow you to so the exhaust gas flow can squeeze causing it to blow harder on the blades of the turbine. The VNT mechanism is controlled via an electronic activator by the DSL1 ECU and you have quite a few options in this ECU to get turbo and exhaust pressure under control. Run make data log and view and adjust parameters in the DSL1 etc.
The OM606 is a hi revving engine, which means that they are quite sensitive to exhaust pressure. Too little turbo pressure and you have smoke, too much turbo pressure and with this pimped turbo also too high exhaust pressure and you also have smoke because the engine simply does not want to breathe. The advantage with an electronic activator for the VNT system is that you can see in which position it is, see picture (boostpw) where it is roughly open at 41%, 10% is fully closed and 90% is fully open to get an idea . The normal picture with a VNT turbo is more boost, more fuel and then you see that the activator opens the VNT vanes more because more fuel also gives more exhaust gas volume and therefore the balance between turbo and exhaust gas pressure remains fairly equal with only a peak in the exhaust gas pressure while spooling up the turbo that you close the VNT vanes for a little extra if you know how to hit the accelerator pedal well and therefore the turbo pressure flies up.
VNT turbo, they perform well are compact but little more complicated than conventional turbo so often some more control is needed to get the max out of your set-up so we mainly use a good aftermarket ECU systems to handle this and if possible a electronic activator as for good VNT position feedback and compact easy install.