RB20 Turbo Upgrades
The Torqueless Wonder
Nissan's legendary Skyline GTR captured the imagination of millions of fans, appearing in countless movies and video games. The GTS-T, GTS25-T, and even GTS-4 Skylines are more than capable performers on both the street and track.
This article focuses on the often-misunderstood, underestimated RB20DET, as found in various late-eighties/early-nineties Nissan's. Featuring an incredibly short stroke (under 70mm), the RB20 is an engine that was designed to rev. In fact, expecting any worthwhile acceleration below 4000RPM in the turbocharged RB20DET variant would leave one wondering where the power was.
Despite lacking displacement, checking in at a scant two liters, the RB20DET has developed quite a following, thanks to its robust build quality, rev-happy nature, and relative simplicity. The best part about the RB20DET engine is that if you push yours a little bit too hard, you may find yourself needing a new engine. No big deal really; replacements cost next to nothing on the used market. Expect to pay a small fortune should you buy new from Nissan, however).
Due to the RB20DET's small-bore, short-stroke design, the engine lacks sufficient torque below 4500 rpm. This "gutless" feeling can be fixed with some careful R&D around camshafts and turbocharger sizing. At the very least, a set of mild camshafts installed on a stock-turbo-equipped engine can really bring the engine to life with a proper ECU tune.
This article will focus only on turbocharger upgrades for the RB20DET engine. See my other article for information on RB20 camshaft upgrades.
There are many turbo upgrade routes one can take with an RB20DET engine. The easiest and cheapest is often upsizing to a larger OEM Nissan turbocharger. The RB25DET turbocharger is a quick and easy bolt-on upgrade to the RB20, is slightly larger, and can provide a bit more boost and power. Read on...
The stock RB20DET turbocharger is a tiny, T3 framed baby. Due to its ceramic turbine wheel and small size, the stock turbocharger begins producing useable boost very low in the RPM range on a stock RB20DET engine.
But because of its ceramic turbine wheel, the stock turbocharger is notorious for failing at higher boost levels. Most agree that 12 psi of boost is the maximum reliable output. In some motorsport cases, the stock turbo has been reliably stretched to 14.7 psi of boost, to produce a claimed 268hp on a stock-internal engine. The key to reliability at these higher boost levels was a rich ECU tune, which kept exhaust temperatures to a minimum. Heat breaks down the glue that holds the turbine to the shaft. Cooler temperatures mean more reliable operation.
RB25DET OEM Turbo
The stock turbocharger available on the newer RB25DET engine is larger than the stock RB20 turbocharger, and thus can provide more power in a very cheap upgrade. The downside to the RB25 turbocharger is that it too has a ceramic turbine wheel, which will fail if the exhaust temperature is too high. Maximum recommended boost is 14 psi with a safe tune. For the best results, transfer the wastegate actuator from your RB20 turbo onto your RB25 turbo, as it has a higher base-boost pressure than the RB25 actuator.
The video below demonstrates what an RB20 equipped with an RB25 turbocharger is capable of doing on a racetrack. The car has a very wide powerband, and seems to have a nice punch of torque in the midrange.
HKS Sport Turbo Upgrades
HKS has a line of "sport turbo" upgrades, which feature precisely sized turbochargers designed for that specific application. HKS offers a 2530kai turbocharger upgrade, which with the right supporting modifications, can produce as much as 350-360 horsepower. These results can be achieved with aftermarket camshafts and extensive ECU tuning. The 2530 is a smaller turbocharger which provides a healthy powerband, with excellent response on the RB20 engine.
HKS also offers various other turbocharger upgrades, such as the 2835 turbocharger, which can support up to 380 horsepower, making it slightly less responsive than the 2530 turbine. A newer GT-RS turbocharger upgrade is available, which is said to support up to 400hp in a very responsive design. Also offered is the much larger GT3037 and GT3037S turbochargers, which can support low to mid 400 horsepower outputs. As these turbos are much larger than stock, a significant decrease in response, and a much higher boost threshold should be expected.
Garrett produces a large variety of turbochargers for various general applications. As the turbochargers are not designed exclusively for one particular engine configuration, choosing the appropriate Garrett turbocharger is crucial to achieve the best possible performance. In addition to this, Garrett turbochargers do not come in complete "bolt on" kits, and thus require piecing together the various parts required to bolt a turbocharger up to your engine.
Many will argue that since Garrett produces HKS turbochargers, it is silly to pay the huge premiums for HKS turbochargers. But if you want a straight bolt-on upgrade, the HKS series turbochargers are the way to go, because they come with everything necessary to bolt the turbocharger onto your engine. Garrett turbochargers require shopping around for everything. If simplicity and perfect fit is what you desire, HKS is the way to go; if you like the idea of an adventure, save some initial cash and pick up a Garrett turbocharger.
"Trust" Turbo Kits
Trust (Greddy) produces various bolt on and full upgrade turbokits for the RB20DET series of engines. Various power outputs, from slightly more than stock, to a ton more than stock are available. The most widely reguarded Trust turbo kit available for the RB20DET engine is the TD06-20G full turbo upgrade. This kit includes a new manifold, wastegate, turbocharger, gaskets, lines and everything else needed for a complete bolt on upgrade.
The video below features a R32 Skyline GTS-T equipped with a Trust TD06 20G turbo kit, and demonstrates how responsive the turbocharger is, and how fast the car is with the kit equipped. Notice how fast the car transitions from negative to positive manifold pressure. Careful throttle control is needed to reduce wheel spin induced from the high power output.
In closing, the RB20DET engine, while lacking displacement and featuring a huge torque hole below 4000rpm, is a great bang-for-the-buck engine. Replacements are cheap, and due to their robust bottom-end construction, they love to be abused. While RB series engines aren't exactly known for having great oil systems, the RB20 is an engine that can spend all day bashing the rev limiter, only to come back tomorrow begging for more. Look after your RB20, and it will look after you.