This is how the intake looked after fitting the Nissan Skyline GT-R HR33 FMIC -( Front Mount Inter-Cooler) to the front of the Skyline GTs-4. Obviously the air inlet tract is traversing the front of the engine over to the original position of the side mounted inter-cooler piping, then progressing along the original cast pipe with the BYPASS Valve (NOT BLOW OFF VALVE – ITS AN AUTO!!) to the original throttle body. The BYPASS Valve assy and tube was used to complete the factory look and function in final execution of the system.
This solution is not the optimum because of HEAT SOAK and the distance for the air to travel, creating lag.
The solution as it occurred to me was the manifold entry point and throttle body should be at the front of the manifold for efficient flow from the incoming inter-cooler piping. With the basic design in my head I worked out very roughly with foam and tube where the best location would be. There were many things to take into consideration in this complicated modification. Most of all efficient and safe operation with a factory look and feel determined the final outcome, including the crinkle black finish. This was done by the coating company that suggested it instead of polishing the aluminium.
Here you can see the original Intake Manifold has been cut in half to remove the original throttle body mounting and the Coolant Bleed Chamber. I mocked up the intended plenum and the front curved extension neck to mount the original throttle body back on to for ease of construction. I also wanted to reuse the original TB for continued integration into the standard Nissan ECU.
So considering that the best idea would be to shorten the inlet to the end of the front of the original manifold, I set about making a mock up of the shape I considered that would be the best in terms of flow and capacity for a decent reservoir of pressurised air ready to be used on the next intake cycle.
Considering that the Nissan RB20DET is not exactly a low RPM torque monster, I had dividers made up for each intake duct to lengthen the runners a few inches as the larger capacity plenum allowed.
Hopefully the dividers would create a bit more torque down under 3000RPM where the Nissan RB20DET 2.0ltr 6 Cylinder Engine is definitely lacking before getting into boost
Finished Job Xmas 2005 Notice Aluminium and Glass Bowl at rear of Manifold with pressure relief valve at top. This is the alternative engine coolant system that allows bleed off of any air in the coolant system that can reduce its effectiveness.