Description:
APS has designed and produced what is arguably the ultimate in bullet proof extreme flow Twin Scroll turbochargers for the Subaru Impreza enthusiast.
Unencumbered by the limitations of current off the shelf WRX turbochargers, APS has totally engineered a "no-compromise" turbocharger from the ground up to match the exact requirements of extreme performance Subaru Impreza engines.
APS has utilized extreme flow Ball Bearing Turbochargers, rotated to avoid the restrictive standard intake duct, in its race cars for many years.
The twin scroll design of the APS TSR turbocharger permits separate exhaust gas pulses from each cylinder bank to effectively drive the turbocharger's turbine with the maximum exhaust gas energy possible. This results in quicker turbocharger response and higher horsepower than an equivalent non-twin scroll design.
The APS TSR turbocharger incorporates innovative anti surge ports that effectively broaden the turbocharger compressor's operating range particularly near the surge line of the compressor map. At the surge point, compressed air is permitted to pass through the compressor wheel and into the anti-surge slot and ports, thus drastically reducing compressor surge.
Unlike turbochargers designed to suit the stock position and orientation, APS TSR Series turbochargers are supplied as a comprehensive and complete bolt-on system.
To coincide with the release of the APS TSR70 turbocharger system, APS has designed the ultimate Twin Scroll up-pipe that delivers a double blast of separate exhaust gas pulses to the turbocharger. The true twin scroll design completely eliminates the mixing of exhaust gasses from left and right cylinder banks. This delivers a huge amount of energy (hence horsepower). In addition, the APS up-pipe included with the APS TSR 70 turbocharger system incorporates a remote wastegate connection.
Though it does not end there!
A completely new APS High Flow Cold Air Intake system delivers a huge straight-shot of chilled fresh air directly into the wide compressor mouth of the APS TSR turbocharger.
The APS cold air intake system accommodates stock style MAF metering through the MAF venturi supplied with the APS system. Best of all, for those Subaru horsepower enthusiasts who overwhelm the stock MAF meter at extreme horsepower levels, the MAF venturi is removable and markedly increases the cross sectional area at the MAF metering point. This now gives huge headroom for even greater air flow, larger fuel injectors, more effective air flow metering at high horsepower levels - and of course far greater tunability from the MAF meter.
Ultimately, a complete extreme horsepower turbocharger solution that leaves nothing to chance. Highly engineered and manufactured with great precision, this range of components from APS represents many years of research and development and is arguably the ultimate in high horsepower turbocharging for the Subaru WRX/STI.
The TSR70 Turbocharger System is a perfect partner for the APS Twin Scroll Header and precisely matches any of the APS High Output exhaust systems.
The TSR 70 Turbocharger system connects directly to either the APS DR 725 or DR 525 front mount intercooler systems for complete ease of installation and maximum efficiency.
NOTE: An external wastegate is not included with the APS TSR 70 Turbocharger system.
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.
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.
Liquid 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 liquid 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 liquid 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 liquid 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.
Features
- 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 tur
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 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.
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