Introduction

Originally released in 1985 in the Nissan R31 Skyline and the 200zr, the Red Top RB20DET was the first RB engine to enter production. These engines get their signature name from the burgundy red finned rocker covers. They may also be referred to as a "NICS" due to the "Nissan Induction Control System" fitted to the engine, a fancy name Nissan calls the intake system. The NICS intake system on these engines is what makes them unique. The NICS system has 12 intake runners, 6 long runners which air flows through at low rpm, and 6 short runners that see air flow via vacuum controlled butterfly valves a higher rpm. This system was designed to give the engine more torque in the low rev range while providing more peak power at higher rpm. The NICS intake design was replaced by the "ECCS" (Nissans Electronic Concentrated Control System) intake manifold design in 1988. These engines are also fitted with the first ever production ceramic turbo charger. This turbocharger features a T25 flange and is smaller than the later T3 flanged Silver Top turbo. The Red Top engines also come factory with "Square" type plugs on some sensors. Later RB20DETs come with a "Oval" type plug on sensors. To my knowledge the sensors and electronics function the same on all RB20DETs, but the connectors are different. Red Top engines featured 248/240 intake/exhaust cams with 7.8/7.8mm lift.

The acceptations to these these rules is the RB20DET-R fitted to the R31 GTS-R and the R31 GTS Autech. The RB20DET-R came with the signature finned valve covers (they are a dull greenish color on the Autech), but comes equipped with an ECCS intake manifold. Each dawning a unique badge, "RB20DET-R" or "Tuned by Autech" respectively. These engines also came standard with a Garrett TO4E turbo chargers and high flowing exhaust manifolds unique to the RB20DET-R. The GTS-R comes equipped with a long runner low mount tubular exhaust manifold to provide maximum power while the Autech comes with a short runner low mount tubular manifold to provide maximum response. 

The Red Top engines are the black sheep of the RB20 family and are criticized for there lack luster performance when compared to the Silver Top engines. Information is limited for these engines, parts can be hard to find and modern aftermarket companies have just ignored their existence. Having personally owned both a Red Top and Silver Top engines in stock form, they are extremely similar in daily driver applications. Pushing the engines a little harder you can definitely feel the slightly more torque down low with the Red Top, but the Silver Top feels like it has significantly more peak power. I am just now getting into modifying my Red Top, but so far it is an identical process to the Silver Top. For mild builds either engine is perfectly fine. The biggest difference is the lack of parts availability for the Red Top.

The release of the C33 Laurel, A31 Cefiro and R32 Skyline in 1989 marked the start of the Silver Top RB20DET engines. The Silver Top engines maintained the bottom end frame work and design as the Red Top engines, but featured a new intake manifold design, some new electronics and increased performance. The new "ECCS" (Nissans Electronic Concentrated Control System) intake manifold ditched the 12 smaller runners controlled by butterfly valves for 6 larger runners. Along with the new intake, the Silver Top engines got new electronics with "Oval" shaped plugs, a new T3 flanged turbocharger and 240/240 intake/exhaust cams with 7.8/7.8mm lift. I want to note a few differences in the R32 RB20DET and the C33/A31 RB20DET: the early C33/A31 engines maintained the older "Square" style electronic plug and all of the C33/A31 engines came without blow off valves, beyond that they are identical. The R32 and A31 were also available in an awd version and this had changes to the oil pan and suspension of the cars. The majority of accessories, electronics and maintenance items can used on either a Red Top or Silver Top engines; however the intake manifolds cannot be swapped without swapping the entire cylinder heads.

The simultaneous release of the RB26DETT in 1989 meant the RB20DET was not longer Nissans top performance RB engine. The RB20DET was eclipsed by the massive technological advancements and high tunability of the R32 GTR. It was pushed even further down the RB line up with the release of the RB25DET a few years later. That being said, the RB20DET remains a cheaper staple with tons of aftermarket support and tuning potential. With basic bolt on modifications factory sealed RB20DETs are easily capable of a reliable 300~350 whp with fully built engines capable of reaching 450~500 whp. 

I have personally logged 10s of thousands of kms in RB20DET powered cars with a variety of modifications from a stock Red Top to a fully forged Silver Top and I absolutely love them all. The short stroke makes the engine extremely responsive especially when paired with a lightweight flywheel. The true thing that sets these apart from other RBs, is the sound. Revs are an RB20DETs best friend and they absolutely love them. Screaming at easily 7,500+ rpm, they make a sound like not other engine. RB20DETs probably wont win you any serious races, but in my opinion they are the perfect street car engine with enough power and all the right noises.