Background:
After testing the Shuenk IS48 turbo with a 5+5 splitter turbine wheel for boost onset, I set up to test the turbo under a full throttle pull. The goal of this testing was to see what, if any, changes could be detected in how the turbocharger and vehicle performed compared to the same setup using the IS38 turbine wheel, which the standard IS48 uses.
Test Processs:
The Mk7 GTI is operated in fourth gear, and the accelerator is depressed to full throttle when the engine speed is around 2,000 RPM. When the engine speed reaches around 6,500 RPM, the accelerator pedal is released. This data recorded during this range of engine speeds is compared with the standard version of the IS48 turbo, which uses an IS38 turbine wheel.
Test Results:
Boost pressure did not show any meaningful change.
The wastegate duty cycle (WGDC) with the splitter wheel is higher, as expected.
Most significantly, there’s no sign that the engine is producing more power with the splitter wheel. This is important because boost onset with the splitter wheel is slower, and the wastegate duty cycle is higher, so those are two factors that changed in an unfavorable direction.
Acceleration being unchanged meant there wasn’t any apparent benefit from using the 5+5 splitter wheel.
Later, I added 93 octane gasoline and operated the GTI with a lower boost tune, so that I could compare the WGDC at lower boost pressure. The difference is smaller, still showing the standard version IS38 turbine operating more efficiently, as expected given the blade surface area of the turbine wheels.
Conclusion:
The 5+5 splitter turbine wheel version of the Shuenk IS48 was operated on a Mk7 GTI at full throttle in fourth gear to compare turbocharger and vehicle data with an IS38 turbine wheel-equipped version of the same turbocharger, which is how the product is currently sold.
There was no sign of any benefit from the 5+5 splitter wheel at the operating pressures tested, given this vehicle’s configuration.