D/R Series Turbocharger


"the fastest car ever recorded by our Correvit, pulled 1g in acceleration off the line, quicker than a $300K F355 Ferrari!"  

Motor Magazine  



APS D/R Series Rotated Mount Ball Bearing Turbochargers
APS has designed and produced what is arguably the ultimate in bullet proof extreme flow turbochargers for the Subaru Impreza enthusiast.

Unencumbered by the limitations of current off the shelf WRX turbochargers, APS has totally engineered a "no-compromise" series of turbochargers from the ground up to match the exact requirements of extreme performance Subaru Impreza engines.

APS has utilized extreme flow 650 horsepower Ball Bearing Turbochargers, rotated to avoid the restrictive standard intake duct in its race cars for many years.

Unlike turbochargers designed to suit the stock position and orientation, APS D/R Series turbochargers are supplied as a comprehensive and complete bolt-on system, which includes unique turbine inlet pipe and high flow turbine outlet assemblies, high flow air cleaner assembly and power steering lines. The turbine outlet is designed to bolt directly onto any of the APS exhaust systems and is an ideal partner to the mammoth 3.5 inch APS exhaust system.

Both turbochargers are available in either externally wastegated (upper right) or internal (lower right) variants, with a choice of three turbine housing A/R ratios (flow ratings).

Why Twin Ball Bearing?

Demands for improving acceleration response and for the reduction of so-called turbo lag are popular amongst performance enthusiasts who wish to take advantage of the enormous gains in power and torque delivered by turbochargers. In addition, bullet-proof reliability is required particularly at high turbocharger boost pressure levels as well as at extreme exhaust gas temperatures commonly found in high performance turbocharged engines.

In order to achieve crisp turbocharger response, a number of advances in turbocharger design have been utilized over the past decade. Primarily through the use of modern metals/ceramics in order to reduce the mass of the rotating assembly. However, significant gains have been made by reducing the friction of the rotating assembly - and this has meant a departure from traditional turbocharger designs.

Traditional turbocharger design employs a conventional plain bearing that runs on a film of oil. This is known as a floating metal bush.

The diagram above shows the turbocharger main shaft supported by floating metal bushes. Oil is fed through the bushes and forms a cushioning layer between the turbocharger shaft and the supporting bush. The shaft relies on a constant supply of fresh, clean oil over a very wide contact area in order to maintain sufficient clearance from the bush itself. A similar approach is used to support the turbocharger main shaft from thrust loads as well.

Whilst floating metal designs have served us well in the past, the frictional forces are relatively high. This results in sluggish turbocharger response and can be somewhat fragile in nature under extreme operating conditions.

Nissan attacked this very issue some 15 years ago on the GTR Skyline by developing a turbocharger bearing system that forms the basis of the true high performance modern turbocharger.

By utilizing robust ball bearings at either side of the turbocharger main shaft, this did away with the floating metal and thrust bushes.

APS turbocharger rotating group above is a true twin ball bearing unit that not only delivers huge power and torque, but is also extremely robust and incredibly compact in size.

As seen in the diagram above, the turbocharger shaft is supported by two ball bearing assemblies. These again are fed with engine oil, but no longer rely on a thin film of oil over a wide area to support the turbocharger shaft.

The result is an outstanding reduction of frictional torque on the rotating turbocharger assembly in contrast to the old fashioned floating metal bushes. The improvement in turbocharger response, particularly in the lower to mid turbocharger speed range is phenomenal.

The graph above shows frictional torque versus turbocharger speed of both old fashioned designs and modern ball bearing turbochargers. Clearly evident are the improvements with ball bearing turbochargers - especially at the low speed range of under 60,000 RPM where friction losses are reduced by 40% to 50%. This translates directly into a quantum leap in turbocharger response.

And best of all for those who wish to push the limits, ball bearing design turbochargers provide significantly higher robustness by better supporting the rotating turbocharger assembly, as well as better spreading thrust loads over old fashioned methods.

Water Cooling

Whilst turbochargers began to be applied to passenger cars in the late 1970's in response to the energy crisis, the first generation passenger car turbochargers were derived directly from commercial diesel engines. Engine oil was used to provide both lubrication and cooling and whilst this was an effective compromise between cost, durability and performance, in high engine performance applications durability suffered through fouling of the turbocharger bearings through high turbine and bearing temperatures.

By encasing the turbocharger bearings in intricate water passages, engine coolant is used to significantly reduce turbocharger bearing temperatures in order to eliminate the coking and lacquering issues that fouled old fashioned turbocharger bearings. Non water cooled turbochargers have no place in a high performance gasoline engine application and should be avoided at all costs.

The graph above shows the turbocharger bearing temperature leading up to engine shutdown and for 20 minutes following shutdown. The temperature is displayed relative to the coking threshold of high quality mineral based oil.

As is clearly evident, the old fashioned non water cooled turbocharger operates above the coking threshold when under high load and experiences a very high temperature increase through heat soak immediately after engine shutdown. The APS water cooled turbocharger on the other hand remains cooler than the coking threshold at all times and the bearing temperature increase through heat soak immediately after shutdown is reduced drastically.

By specifying the latest in turbocharger designs that incorporate both water cooling and true twin ball bearing designs, the APS turbochargers deliver bullet-proof reliability and durability along with exceptional power levels and unprecedented no-lag turbocharger response.

APS D/R Series Compressor Maps
APS D/R 65 - 65 lb/min max. flow

Click here for raw compressor map
The APS D/R 65 is the ultimate turbocharger for the ultimate WRX/STI. Intended primarily for the serious 2.5 litre engine, it will deliver 14.5 psi by 4,500 RPM in that application. However the APS D/R 65 can also be utilized on strip only 2.0 litre engines.

61.5 mm
68.0 mm
82.0 mm
62.5 mm

If you want ballistic power and outstanding turbocharger reliability then the APS D/R Series turbocharger is the perfect choice.

The APS D/R Series turbochargers should be used with upgraded internal engine components. Also an upgraded fuel supply system and engine management are required.

WRX and STI enthusiasts will be delighted to know that the APS Rotated Mount system has been designed as a do-it-yourself installation and we are sure you will find the experience personally rewarding.

Click on the diagram to the left for installation information.

With a basic tool kit and enthusiasm you will find the installation a breeze - 3 to 5 hours is all you will need.

P/N APSWRX-RMT/02 - D/R 65 Turbocharger, High Flow Air Intake, Up-Pipe, Turbine Outlet and power steering relocation lines.