| Of all the R31s that were ever produced, the most sought after model is the special batch that was released in 1987. Homologated, there were only 800 of these GTS-Rs ever produced, aimed for the Group A class racing. The twincam 24 valve RB20DET engine was used as a base with added goodies such as an stainless steel equal length exhaust manifold, Garret T04E turbine, and a front mounted intercooler. The maximum horsepower output for this RB20DET-R reached 210 horses, 20 more over the stock RB20DET. It's a known fact that more than 300 horsepower can be achieved with a simple boost increase. By swapping in strengthened pistons and connecting rods along with proper fuel management and flow modifications to the turbine, this machine can be classified as a 400hp Group A machine. This is what the GTS-R is known for, its immense potential.
When it comes to modifying the R31 in Japan, everyone knows that the shop R31 HOUSE holds the crown. Shop manager Mr. Shibata claims “In order for our customers to enjoy the true performance of the R31, I urge them to try the vehicle with 30% more power! If the catalog claims a 210 horsepower engine, the vehicle will realistically be around 250~260 hp.”
Their shop demo car that they have brought out today basically has Tomei camshafts (in/ex 256deg. 8.5mm lift), and a strengthened turbo actuator for increased boost. 260 horses were achieved after 0.9 bar of boost.
| Just making gobs of power in the RB20DET-R is not the only fun factor for this motor. “If you want power, all it takes is to swap in the RB25 or 26. To truly enjoy the RB20DET-R's performance, a mild tune that really brings out the harmonic sound produced from the equal length manifold will just melt your ears!” states Mr. Shibata. From hearing those words from Mr. Shibata, many R31 fanatics come seeking to the shop to experience that thrill.
At the time of this interview, the R31 had their shop original front pipe and muffler installed. The amazing sound this machine generates at the top end can partly be blamed at the aftermarket camshafts. The owner of this vehicle stated that the reason why he chose to modify and keep this R31 was simply because of the “sound” that this machine spits out.
If speed is the objective, there are other countless setups available, even with the R31 chassis. The main tuning theory for the GTS-R seems to be “the sound” the vehicle is able to produce.
It's no surprise that this is one of the most sought after models ever produced. With only 800 of these machines floating around, everyone seeks to experience that ecstasy the exhaust note produces.