Nissan RB Engine - RB30DET

RB30DET

Nissan did not produce this engine. It refers to a turbocharged engine using an RB30E short block with the twin-cam head installed from another RB series engine. Common hybrid in Australia (referred to as the RB25/30 or RB26/30) using a RB30E bottom end mated to a RB25DE,RB25DET or RB26DETT cylinder head and turbo (RB20DE and DET heads are not used as the bores are different in size; RB30 86.0 mm RB20 78.0 mm but were originally modified and used on the Tommy Kaira RB30DE as the RB25 engine did not exist). The RB25DE cylinder head from the A31 Cefiro C33 Laurel or R32 skyline (aka: Non VCT) can be used, and fits perfectly on (although better valve springs are recommended, GT-R valve springs are a decent upgrade). The RB25DET (from the R33 Skyline or C34 Laurel or Stagea) head is also used, however an external oil feed must be fabricated for the variable cam timing (VCT) on the RB25DET, and the galleries at the front of the engine do not line up. The variable cam timing may be disconnected altogether. Also it is wise to reduce the size of the oil restrictors in the block and get a full face oil pump drive collar machined onto the crank which (solves it shattering at high RPM) with the use of a twin cam oil pump.

The fitment of a twin cam head from any of these engines onto a standard compression RB30E bottom end gives an ideal compression ratio for a mild to moderately modified street turbo engine around 8.2:1, (but always check your compression when building this engine as it may vary), making the conversion popular amongst those who would otherwise convert their RB30E to a high compression RB30ET using original ET bolt on externals.

Although it has a larger displacement than the RB26DETT, maximum possible horsepower is less, as the RB30 block lacks the RB26 block's internal cast-in bracing, and consequently cannot rev as high due to harmonic issues at ~7500 rpm. To compensate, the RB30DET produces more torque at lower revs due to its longer stroke. However they have been known to reach engine speeds up to 11,000 rpm with a lot of balancing and blueprinting. Power of the RB30DET in this form can far exceed that of an RB26DETT, RB30DET's are usually only found in RWD cars as it's a lot easier to install, with the 4wd setup in the GTR or GTS4 an adapter plate has to be made to fit the 4WD sump as its bolt pattern is different to the RB30, as there is a adapter plate between the sump it sits off on the gearbox bolt holes, they will have to be modified to fit.

There is also an 'RB30DETT' kit manufactured by OS Giken of Japan, which bolts an extension on top of the RB26 engine block, and fits liners, to give an 86 mm bore x 86 mm stroke. It is available as an assembled short block, containing billet chrome-molybdenum crank, billet chrome-molybdenum H-beam connecting rods, forged pistons, and costs ¥1,500,000.