TurboSource Variable A/R EFR Turbine Housing

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We are currently machining our latest gen samples, and updating the actuator assembly. All test vehicles have been lined up for current samples.

The TurboSource Variable A/R Turbine Housing is designed to increase the responsiveness of the EFR turbocharger lineup even further. This external waste-gate configuration housing is designed to lower the boost threshold by 600-800rpms. Most enthusiasts are torn between the ultra responsiveness of the 7670 turbocharger, and the higher peak RWHP numbers of the larger b2 frame turbochargers( 8374 through 9274). The goal here is to combine the best of the both worlds through increasing shaft speeds in the lower RPM regions( below 4K rpms for most smaller displacement engines), while being able to deliver the high RPM power of the 62-68mm B2 frame EFRS( 8374, 8474, 9174, and 9274). 

The beauty of the EFR turbochargers is already dramatically increasing how wide the powerband is by the use of the Gamma-TI turbine wheel, which is half the weight of the Inconel found is most traditional turbine wheels. Less mass, means shafts speeds increase even easier, and your power band starts faster. With the valve in the open position, all of the exhaust energy is forced through half of the turbine volute, increasing exhaust velocity dramatically. This is similar to a very small turbine A/R. As RPM and boost pressures increase one will outflow the smaller turbine a/r, or in this case one side of the turbine volute and dramatically increase pre turbine back pressure. Too much pre turbine back pressure will effectively choke the engine, and the torque curve will nose over. This is where one is able to close the valve, doubling the turbine A/R, and allowing the engine to flow properly, reducing pre turbine back pressure.


This turbine housing is cast with twin 1/8 NPT ports, one per volute, to measure pre turbine back pressure. This with the use of the EFR shaft speed sensor allows the user to dial in the optimum valve close timing( both volutes open). This will be achived via a boost control solenoid with the mechanical actuator option, or directly with the electronic actuator option( not available yet). A standalone ecu is ideal to control the variable housing( plot emap vs valve opening). Those without can just change spring pressures inside the mechanical actuator option to achieve desired close timing vs IMAP(intake manifold pressure) only.

This turbine housing features a stepped turbine discharge, to allow an interlocking downpipe flange to be used for even better sealing than the OE BW discharge. One does not need to change their current down pipe flange or turbo manifold to use this housing. The physical mounting dimensions are identical to the BW T4 1.05 70/74/80mm b2 housing in terms of downpipe, T4, and CHRA dimensions.  One will have to take into consideration the physical clearance needed for the valve actuator. We will have dimensions drawings available, and shops will be able to borrow 3D printed models for Jig updates/testing etc. 

The ideal use of this housing is for fully divided twin-scroll EWG turbo manifolds. With the valve in the open position( only one side of the volute open) the exhaust energy collects right behind the T4 flange, when the valve closes the entire system returns to a fully divided twinscroll system. A properly designed twin-scroll system will make more power as cylinders experiencing high pressure pulses are not allowed to force exhaust into cylinders experiencing low pressure pulses. This lowers engine VE, as more unburnt gases remain in the cylinder after the exhaust stroke. 

This turbine housing is made from investment cast 347SS. The valve is cast inconel to ensure long term durability. In the closed position the valve is not taking a direct hit of exhaust gas, like other products. This allows the valve to be less susceptible to failure, and allows maximum high RPM/Boost power levels. This unit is designed to be fully serviceable, one can replace all moving parts.


80MM  EFR housings are currently under construction.