Nissan 240SX Performance Modification/Engine Swaps/RB25DET

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Specs and Versions[edit]


Displacement: 2498cc
BoreXStroke: 86mm X 71.7mm
250PS or 246.58HP @ 5600rpm
216.90 ft/lbs @ 4800rpm
Compression Ratio: 9.0:1

Required Items[edit]

  • Engine R33(S1 or S2)
  • Transmission
    • Use of the RB25DET transmission is highly suggested since it is much stronger and specific to this exact engine. RB26 owners commonly use this transmission since it bolts directly up, and can handle high torque loads. This is very similar to the Z32 N/A internally which helps when sourcing parts.
  • Engine's accompanying ECU
    • Make sure you receive the proper ECU to match your engine (S1 & S2 - they _ARE_ different)
    • A'Pexi Power FC stand-alone can also be used.
  • Engine's harness
  • Your chassis' harness
  • Custom wiring is required. You can either splice the KA harness with the RB (which can get hectic at times) or purchase a pre-made harness from a provider or specialist such as Wiring Specialties or run a standalone such as a Painless harness.
  • Clutch - Z32 N/A
  • Flywheel - RB 25 flywheels are specific and are not interchangeable with any other engines. Also do not be fooled by thinking you can use a flywheel from the 25DET Auto. This will _not_ work.
  • Modified 5-speed driveshaft, or aftermarket
    • McKinney Motorsports, Top Hat Performance, Shaftmasters
  • R33 cross-member or aftermarket motor mounts
    • McKinney Motorsports, Top Hat Performance, Syko Performance
  • 6-cylinder calibrated tach
    • LSauto
    • Tach recalibration using the stock DOHC (S13-DE or S14; NOT SOHC 89-90 "Pignose")
  • Modified Downpipe
    • Depends on whether or not you use the R33 x-memeber and which chassis. For the S14, a custom one may be needed, but results vary depending on the mounts you've gone with. SR20 downpipes are commonly used with the stock turbo since they both share a 2.75" flange. In my instance (S13-DE with R33 cross-member) I had to lengthen the 'down' area of the SR20 downpipe approximately 2", but it cleared the steering shaft by about 1/4".

Step by Step[edit]