The turbocharger was specifically developed for the GT-R application by IHI.

The turbocharger was specifically developed for the GT-R application by IHI. The RHF6CB turbocharger has a 62.0-mm diameter turbine and a large 65.0-mm compressor. By comparison the turbo for the type BPD 1.8 liter engine that powers the GTX has a 52.5-mm diameter turbine and a 52.5-mm compressor. It is commonly believed that a big turbo is employed for high rpm power. The Mazda and IHI teams have proven with the GT-R turbo installation that this is not necessarily so. They have sought and achieved an optimum balance between high power and quick mid-to-high rpm response. A relatively small "A/R" ration, a value of 16 to the GTX's 15, was one of the means they adopted to assure these desirable characteristics. "A" is the smallest scroll area and "R" the distance between the turbine-shaft center and the center of area "A", the two factors used in calculating turbocharger's performance characteristics. The turbocharger employ's a steel turbine wheel for its proven reliability under the rigors of competition. In Mazda's testing it suffered little in responsiveness when compared with a unit fitted with an experimental ceramic turbine; the latter may be decelerating too quickly for any appreciable difference in pickup that follows. The turbocharger shaft is supported by ball bearing, which improves turbo response by as much as 7% by Mazda's testing.


The turbocharger is watercooled. Boost is controlled by a dedicated computer map, and its maximum pressure is 450 mm of mercury (Hg). The standard air-to-air intercooler is about twice the size of the unit fitted in the GTX (235-mm wide, 225-mm high and 65-mm deep), and has a heat dissipating capacity of 6,150 Kcal/hour which is 36% more than the GTX's. It features efficient "zig-zag" fins which increase cooling surface area. The intercooler is located in the nose of the car, immediately ahead the coolant radiator. the path the boosted air takes to the engine's intake system is as direct and short as possible, so that pressure loss is minimized.

Manifold System:
With the "Big Turbo", it has become critical that boosted air is distributed to the individual cylinders in equal volume and pressure. Likewise, the energy of exhaust gas must be fully exploited to quickly "spin-up" the big turbine in order to obtain high power and minimum turbo lag.
The Mazda engine design team has perfected a unique manifold system, combining the air volume and pressure equalizing intake and exhaust extractor manifolds.
It was Mazda's finding that with more a more commonly used equal-length intake manifold, the tract nearest to the air entry received the least volume/pressure, and the farthest tract the most. By trial, measurement and testing, the engine team perfected a cast aluminum manifold that has intricately curved and sized "walls" between the individual tracts leading to the intake ports to equalize air volume and pressure. A bonus is that the manifold's swirl generating effect contribute to efficient combustion. The equalizer intake manifolds have shown its effectiveness in improving torque from idling to the Group-A 300-bhp-plus output level and all the way up to maximum revs.
The exhaust manifold has individual tracts collecting at the turbocharger entry. These tracts are in two groups; the tracts from cylinders 1 and 4 are routed to the center, and those from cylinders 2 and 3 to the outside. This routing allows nearly equal tract length. The complex manifold is made of cast ferrite steel, for which the lost-form casting method is employed. Not only is this about 20 percent lighter, much stronger and its passages much smoother than a conventional cast iron one, but also its surface finish is much smoother.
The exhaust manifold's extracting ability precludes an unwanted rise in exhaust back-pressure, which would cause the dilution of the combustion chambers with exhaust gas. This would, in turn, raise cylinder temperatures. Enriching the fuel/air mixture to lower combustion temperatures would obviously deteriorate fuel economy.
The GT-R exhaust system adopts a 3-way catalytic converter with larger capacity but a reduced number of cells, and a new main silencer that assures reduced resistance to gas flow.