The stock oil pressure sender unit is removed and an oil take-off hose is installed in its place at the rear of the engine block. This hose is routed and connected to the turbocharger oil control anti-drain-back solenoid situated at the rear of the LHS cylinder head. From there the oil flows through the oil distribution block and onto each turbocharger. The stock oil pressure sender unit is physically mounted on the oil distribution block and it now senses the oil pressure inside the oil distribution block rather than the oil pressure in the stock position.

The benefit of installing the stock oil pressure on the oil distribution block is that in the event of failure of any hose/connection/component in the oil supply circuit to the turbocharger distribution block, an engine oil pressure error condition will be activated and the operator can then take appropriate action to avoid damage to the turbocharger assemblies.

The oil take-off hose has specific dimensions and is a critical part in the flow tuned turbocharger oil supply system. This introduces a difference in the oil pressure reading inside the oil distribution block when compared to the dead-head oil pressure at the stock location at the rear of the engine block. The net result is a lower pressure registered by the stock oil pressure sender unit and a more damped reading at engine start-up. This phenomenon however has no impact upon the actual before/after engine oil operating pressures inside the various critical points inside the engine.

In other words, there is no change to the engine's actual operating oil pressure - just a lower and slower reading by the stock oil pressure sender.

Subnote:
If one was to experience actual reduction in effective oil pressure after the installation of the twin turbo system, this would be because of the stock oil pump's inability to supply adequate volumetric oil flow rate to compensate for the small oil flow used through the turbocharger bearing assemblies.

A stock LS1/LS2 oil pump system that is in healthy condition and operating with turbocharger grade gasoline engine oil, will result no change to the effective engine's operating oil pressures. However in previous APS testing of older LS1 engines' oil pump systems, a reduction of up to 3 psi of effective oil pressure can be registered when the engine is at normal operating temperature. This experience is an engine wear related issue that is different to the change in the oil pressure reading after the installation of the twin turbo system described above.