Understanding the RB20DET Engine

The RB20DET is a 2.0-liter inline-six turbocharged engine that first appeared in the late 1980s and early 1990s Nissan Skyline (R32, R31 GTS, R32 GTS-t) and other models like the Laurel and Cefiro. Its iron block, aluminum cylinder head, and relatively strong bottom end make it a favorite for budget-minded builders who want serious power. The stock engine is rated at 210–215 horsepower from the factory, but with proper modifications, 350+ horsepower is not only achievable but sustainable for street and track use.

What makes the RB20DET particularly attractive is its compact displacement and high-revving nature. The bore and stroke are 78 mm × 86 mm, giving it a square-ish character that responds well to forced induction. However, reaching the 350 hp mark requires addressing two critical weak points: the cylinder head's airflow limitations and the cast pistons' inability to withstand elevated cylinder pressures and heat. This article covers head porting and piston upgrades as the foundation for a safe and reliable 350+ hp build.

The Case for 350+ Horsepower

While the RB20DET can make more power with a larger turbo and aggressive tuning, 350 wheel horsepower (approximately 400 crank horsepower) is a sweet spot where the stock block and crankshaft remain reliable without sleeving or billet upgrades. At this level, the engine will support a responsive street turbo, such as a Garrett GT3071R or BorgWarner S200, while maintaining good drivability. Staying below 400 wheel horsepower also keeps heat loads manageable and reduces the risk of head gasket failures or rod bending—common issues when pushing beyond 400–450 whp on a stock RB20 bottom end.

To safely hit 350 hp, the two highest-impact modifications are head porting to increase volumetric efficiency and forged pistons to handle the increased thermal and mechanical stresses. Without these, the stock head will choke flow at higher boost levels, and the cast pistons will likely fail under sustained high-power operation.

Head Porting for the RB20DET

Head porting modifies the intake and exhaust ports to improve airflow into and out of the combustion chamber. The RB20DET cylinder head flows reasonably well for a 1980s design, but the intake ports have sharp turns and casting marks that create turbulence. Porting smooths these areas, reshapes the port volume, and matches the port to the intake manifold gasket profile. The goal is to increase flow without losing velocity—especially important on a 2.0-liter engine that relies on port velocity for good throttle response and low-end torque.

Porting Methods: Hand vs. CNC

Hand porting by an experienced cylinder head specialist can yield excellent results, especially when tailored to a specific camshaft and turbo combination. CNC ported heads offer repeatability and precision, but the RB20DET aftermarket does not have as many off-the-shelf CNC programs as the SR20DET or RB26DETT. Many tuners recommend a mild hand port with a three-angle valve job and a bowl clean-up for 350 hp targets.

Valve Job and Spring Upgrades

While the head is off, upgrade the valve springs to higher rate springs compatible with the stock or upgraded camshafts. The RB20DET stock valve float occurs around 6,500–7,000 rpm, depending on cam profile. A freshened head with new valve guides, a multi-angle valve job, and heavy-duty springs will let the engine safely rev to 7,500 rpm, which is beneficial for keeping the turbo in its sweet spot.

Do not skip the valve job: a proper three-angle (or five-angle) cut on the seats significantly improves low-lift flow and scavenging. This is especially important for turbocharged engines that need efficient exhaust gas evacuation to spool the turbine quickly.

Piston Upgrades: Forged for Strength

The factory RB20DET pistons are hypereutectic cast aluminum. While adequate for the stock 7.5:1 compression ratio and up to around 280 hp, they quickly become the weak link once boost exceeds 15–18 psi or when nitrous is used. Cast pistons tend to crack the ring lands or experience disintegration under detonation. For a 350+ hp build, forged pistons are mandatory.

Compression Ratio Choices

Most RB20DET builds targeting 350 whp use a compression ratio between 8.5:1 and 9.0:1. The stock ratio is 7.5:1, which is low even for a turbo engine. Raising compression improves off-boost response and thermal efficiency, but too high can cause detonation with aggressive boost. For a street car running 91–93 octane, 8.5:1 is a safe starting point. If you plan to run E85 or race fuel, 9.0:1 is feasible and will deliver a snappier throttle.

Selecting Forged Pistons

CP-Carrillo, Wiseco, JE Pistons, and Ross Racing Pistons all offer RB20DET forged pistons in various oversizes and compression ratios. Look for a design with a moly coating on the skirt to reduce friction and an anodized crown to resist heat. Choose pistons with a thick ring pack and a large pin boss to handle the increased combustion pressure. The weight of the piston matters: lighter forgings reduce reciprocating mass, allowing the engine to rev faster and reducing stress on the rods and bearings. Expect to pay $600–$900 for a set of quality forged pistons.

Rod and Pin Considerations

The OEM RB20DET connecting rods are forged but relatively thin; they are adequate for 350–400 whp if the engine is tuned well and not subjected to constant rev limiter bouncing. Many builders opt to replace them with Eagle H-beam rods or Manley I-beam rods for added safety margin. Pair the pistons with wrist pins sized to the chosen rods; most aftermarket rods come with a compatible 21 mm or 22 mm pin diameter.

Supporting Modifications for 350+ HP

Heads and pistons alone won't get you to 350 hp. You must upgrade several supporting systems to deliver the fuel and air needed and to keep temperatures under control.

Fuel System

  • Fuel Injectors: Stock injectors are 270–380 cc/min (depending on model). For 350 whp, use 550–750 cc/min injectors with high impedance. Brands like Bosch EV14, Injector Dynamics, and DeatschWerks are popular.
  • Fuel Pump: A Walbro 255 lph in-tank pump is the minimum for 350 hp; for higher flow, a Walbro 450 lph or AEM 340 lph is recommended.
  • Fuel Pressure Regulator: A rising-rate (1:1) regulator helps maintain consistent pressure when boost varies.

Turbo Upgrade

The stock RB20DET turbo (a small T25 or T28 hybrid) will run out of breath before 300 hp. For a linear 350 hp, a Garrett GT3071R or BorgWarner S256 with a 0.63 A/R turbine housing spools quickly and delivers strong midrange. A twin-scroll manifold and turbo can help spool even further.

Intercooler

An air-to-air intercooler with a core at least 600×300×76 mm is essential. The stock side-mount is too restrictive for sustained boost. Larger front-mount intercoolers drop intake temps and allow denser air into the engine.

Exhaust System

A full 3-inch turbo-back exhaust with a high-flow catalytic converter (if legal) or a test pipe eliminates restriction. The downpipe should be at least 2.5 to 3 inches to reduce back pressure.

Oil System Upgrades

High horsepower increases oil temperature and load on the bearings. Install an oil cooler with a sandwich plate adapter (Setrab or Mocal) and consider a baffled oil pan or an Accusump to prevent oil starvation under high-G cornering. The RB20DET is prone to oil starvation in hard right-hand corners, so a larger oil pan with windage tray is a good investment.

Tuning and Engine Management

All the hardware in the world is useless without proper tuning. The stock Nissan ECU is not programmable and will not handle larger injectors, boost control, or altered timing curves. You need a standalone engine management system such as a Haltech Elite 750, Link G4+, AEM Infinity, or a plug-in ECU like the Nistune board if you want to reflash the stock ECU (limited but possible).

Dyno tuning is mandatory for safety. A competent tuner will adjust the fuel and ignition maps for the new hardware, set boost levels, and verify that air-fuel ratios stay in the 11.5:1–12.0:1 range at full throttle (for pump gas). They will also set a conservative ignition timing curve to avoid detonation while the engine breaks in. Expect to pay $500–$1,000 for a proper dyno tune.

Monitor critical parameters: oil pressure, exhaust gas temperature, and cylinder head temperature. Wideband oxygen sensors and a boost gauge are not optional; they are essential for ensuring the engine lives a long life.

Putting It All Together: A 350 HP Build Roadmap

  1. Remove the engine and disassemble completely.
  2. Machine the block and hone to the correct bore size for the new pistons. Check main bearing clearances.
  3. Send the cylinder head to a specialist for porting, valve job, and new valve springs. Rebuild the head with OEM or better seals.
  4. Assemble the short block with forged pistons and optional rods, using ARP head studs and a metal head gasket (Cosworth or Tomei).
  5. Install the upgraded turbo, intercooler, and fuel system.
  6. Plumb the oil cooler and any additional monitoring sensors.
  7. Install the standalone ECU and wire in a wideband O2 sensor.
  8. Break in the engine on a dyno using conventional oil and proper procedure (vary rpm, no full load for first 500 miles).
  9. Tune for 350 hp at a safe boost level (e.g., 18–20 psi on pump gas).
  10. Enjoy a responsive, reliable RB20DET that can handle daily driving and occasional track days.

Conclusion

Reaching 350+ horsepower with an RB20DET is a well-established recipe. The two most important modifications are a properly ported cylinder head and a set of forged pistons to handle the extra heat and pressure. With the supporting upgrades outlined here—fuel system, turbo, intercooler, oil system, and standalone tuning—you can build an engine that is both powerful and durable. Avoid the temptation to cut corners: cheap pistons or a rushed valve job will lead to failure. Invest in quality parts and a professional tune, and your RB20DET will reward you with years of satisfying performance.

For further reading and parts sourcing, consider these resources: