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Updated on May 11, 2011

The HKS GT-SS Turbocharger

As I've written before, HKS is one of the most well respected aftermarket performance parts manufacturers in Japan.  The quality of their parts is always top of the line, with excellent fitment, build quality and longevity.  HKS has been working closely with Garrett turbo for years now, the two companies working on conjunction to advance turbocharger technology to the next level.  HKS uses Garrett turbochargers with custom specification turbine and compressor wheels, as well as unique high performance compressor and exhaust housings.  The end result is turbochargers with incredible response for their power levels.

Today, we are going to take a look at the smallest turbocharger currently offered by HKS, the GT-SS.  Officially, HKS rates the GT-SS turbo for 280ps, which is roughly 276hp.  It is worth noting that HKS power ratings are indicative of wheel horsepower, rather than flywheel horsepower.  In practice, the hks gt-ss has been shown to develop as much as 320ps, or around 315hp.  HKS currently offers the GT-SS in various engine specific packages to make installation and bolt on affair.  All GT-SS kits come with all required gaskets, bolts and fittings. 

The GT-SS does not have "HKS" stamped anywhere on either housings. No one is quite sure why HKS left their name off the turbo. Either way, the turbo is very similar, albeit slightly different from the comparatively sized Garrett gt2860 -9 turbocharger. The HKS GT-SS variant is said to have slightly better response compared to the -9 turbo. Whether the extra response is worth the extra investment is ultimately up to the consumer.

HKS GT-SS Specifcations (official)

  • Horsepower Rating: 280ps (276hp)

Compressor Wheel:

  • Trim: 60
  • Inducer (mm): 46.6mm
  • Major (mm): 60.1

Compressor Housing:

  • A/R: 0.60
  • Inlet: 60mm
  • Outlet: 50mm

Turbine Wheel:

  • Trim: 76
  • Major (mm): 53.8mm
  • Exducer (mm): 47mm

Turbine Housing:

  • A/R: 0.64
  • T25 inlet (T3 available for RB kits)
  • T25 Internal (T3 available for RB kits)

Unofficial Outputs

As mentioned above, the HKS GT-SS turbo is officially rated to around 280hp as measured at the wheels (all dynos will read differently, so take most official ratings with a grain of salt). Several users have discovered that the turbo continues to make more and more power as the boost is turned up. Many users report that the turbo is efficient at boost levels as high as 1.4 bar (20psi). Beyond those levels, power improvements dimished and intake air temperatures increased. It is also worth noting that the turbocharger's life may decrease, possibly significantly, at higher boost levels.

One example of the GT-SS exceeding official power ratings occurred in on an RB20DET engine, which was able to produce 320hp as measured to the wheels. This power output is what HKS rates their GT2530 turbocharger to. In another case, the GT2530 was able to produce more than 350hp as measured to the wheels. Could this be a case of HKS under-rating their turbochargers, or possibly just rating the highest power the turbocharger can maintain reliably for an extended period of time? It is a subject they will likely never comment on, but it provides an interesting topic of debate.

Bolt on GT-SS Kits

HKS offers the GT-SS in various bolt on kits designed for popular Japanese vehicles. Below is a list of applications that feature bolt on available kits.

180SX, S13, S14, S15 GT-SS Kit

  • Rated to 320hp (239kw). 
  • Dual ballbearing center cartridge
  • HKS strengthened actuator
  • T25 footprint (same as stock manifold)
  • Contains everything needed to bolt on

R32 GTR, R33 GTR, R34 GTR GT-SS Kit

  • Rated to 600ps (roughly 560hp)
  • Dual ballbearing center catridges
  • HKS adjustable wastegate actuators
  • T25 footprint (bolts directly to OEM exhaust manifolds)
  • Contains all gaskets, lines and bolts

HCR32, ECR33 GT-SS Kit

  • Rated to 320hp (239kw)
  • Dual ballbearing center cartridge
  • HKS Adjustable wastegate actuator
  • T3 footprint (bolts to OEM exhaust manifold)
  • Contains all gaskets, lines and bolts.

Final words

I am in no way affiliated with HKS, and have no financial or commercial interest in promoting them or their products.  I'm just a car guy who likes to write about car stuff that interest him.  Stay tuned for more detailed turbocharger specific articles in the future!


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