RB25 Generic Information
RE25DE
The RB25 appeared in 1991 and replaced the RB20DE. The RB25DE uses a cylinder block similar to RB20, but with the cylinder diameter enlarged to 86 mm. It was also equipped with a crankshaft piston stroke of 71.7 mm, new connecting rods and pistons.
The cylinder head had two camshafts with 4 valves per cylinder. The early models (to 1993) were not equipped with variable valve timing system NVCS.
duration 240/232 deg,
lift 7.8/7.3 mm.
As such, the RB25DE S1 (Series 1) developed 180 HP at 6,000 RPM. These engines were installed on Nissan Skyline R32.
1993 seen the appearance of the R33 Skyline, and the NVCS system was used on the intake camshaft.
RB25DE camshafts:
duration 240/240 deg
lift 7.8/7.8 mm
Thanks to this, the power increased to 190 HP at 6,400 RPM. The engine was applied for Nissan Skyline R33.
1995 seen a different ignition system, Modified MAF, crankshaft position sensor and ECU.
In 1998, the new engine model RB25DE NEO was designed specially for the Nissan R34 Skyline. This engine is compliant with higher ecological standards at that time, and were equipped with a new intake manifold with thinner runners. The RB25DE NEO heads were fitted with modified compression chambers, new camshafts and improved exhaust manifold.
RB25DE NEO camshafts:
duration 236/232 deg
lift 8.4/6.9 mm
Also such engines do not have hydraulic lifters. RB25DE NEO power increased to 200 HP at 6,400, torque 231 NM at 4,800 RPM.
RB25DET
The first version (RB25DET S1) appeared in 1993 and was installed on Nissan Skyline R33. In contrast to the RB25DE, the RB25DET (S1) had reinforced connecting rods, new pistons (compression ratio is 8.5), 45V1 turbocharger. The turbocharger was larger than that of the 16V found on the RB20DET. Maximum boost pressure on RB25DET reached 7 psi (0.5 bar). Also equipped with variable valve timing system NVCS on the intake side, fuel injector 370 cc/min, and oil jets were installed in cylinder block. The engine’s power was 245-250 HP at 6,400 RPM, torque 272 m at 4,800 RPM.
By alongside the RB25DE, in 1995 the engine was restyled: ignition system, MAF, crankshaft position sensor and also ECU were changed. Besides, it was equipped with new 45V2 turbocharger with plastic impeller instead of the steel. Those were RB25DET S2 engines.
In 1998 the engine was modified and named RB25DET NEO.
These engines were in compliance with higher ecological standards set at the time. The NEO variant was fitted with a new crankshaft, RB26DETT rods, modified pistons, compression ratio increased to 9.0:1, oil jets, and an improved intake manifold. The intake ports and combustion chambers were also upgraded, and the head flow raised. This engine used solid lifters instead of the familiar hydraulic lifters.
duration 236/232 deg
lift 8.4/8.7 mm
Stock fuel injectors are 340 cc/min
RB25DET NEO engines used a 45V3 turbocharger with enlarged exhaust housing and plastic impeller, boost pressure is maxed around 10 psi (0.7 bar). All these performance mods increased the power to 280 HP at 6,400 RPM, and torque 334 NM at 3,200 RPM.
Since 2001 until the discontinuation of the RB25DET, a 45V4 turbocharger with steel impeller was installed.
There is no need to adjust the valves on RB25DE/DET engines, since they use hydraulic lifters, but if you have an RB25DE NEO or RB25DET NEO, then you should adjust valve clearance from time to time.
RB25 Complaints
Boosting your RB25DET
The stock turbocharger is limited to just 10-13 psi (0.7-0.9 bar) depending on the turbo originally installed. To comfortably hold 13 psi (0.9 bar), you need to run a 3 inch performance exhaust system, GTR front intercooler, Apexi power intake, Z32 MAF, boost controller, new spark plugs and new water pump. It's also recommended to purchase a GTR N1 oil pump, oil cooler, Walbro 255 LPH fuel pump, and an Apexi Power FC (or other compatible aftermarket ECU). With these performance parts you will get about 350 WHP and put down mid 13s in the 1/4 Mile time.
Wishing to gain over 350+ WHP? The stock turbo will be holding you back here, so therefore you'll need to swap out to a GT2835 T3 turbocharger. Many people have successfully swapped out to R35 fuel injectors @ 550 cc/min, NISMO fuel pressure regulator, NGK 48704 ignition coils, and 3 core Aluminum Radiator. With these upgrades, you should be able to set boost pressure to 15 psi (1 bar) to gain 350 WHP, and if the block is fitted with ARP head studs (ARP P/N 202-4301) and the boost increased to 22 psi (1.5 bar), you will get about 400 horsepower to the wheels.
Still not enough? In this case you need a GT3540 turbocharger, and also camshafts 256/256, valve springs, and fuel injectors 750 cc/min. With these mods you will obtain 400 WHP at 15 psi (1 bar) and bring your 1/4 mile time down to 11 seconds.
You can do all this using the stock pistons. Moreover, RB25DET stock internals will easily hold 500 horsepower, and if you use a water methanol injection kit, more than 500 HP. But to ensure the reliability of your engine it is worth buying GTR rods, forged pistons, MLS head gasket, ARP head studs and do some head porting. Upon this more than 500-600 horsepower will be available, however cracks may appear on the cylinder block if regularly abused.
More info can be found on: http://mywikimotors.com/rb25det/
(Images courtesy of Wikipedia)