The SkyActiv 2.5T has been around for a few years in the CX-9 however, things started to get interesting when the engine was dropped in the Mazda 6 for 2018+ models. While lacking a manual and not a true Mazdaspeed, it’s a step in the right direction for the enthusiast. With one of the new Mazda 6s in the CorkSport garage, we’ve been getting curious about where all of that 310lb-ft comes from. Well, we decided to call up Mazda and purchase a turbo to see how it all works.
There’s a lot to take in on the turbocharger and there are quite a few things that have changed from the K04 that made its home in the Speeds.
For starters, this turbocharger is pretty big. The wheels themselves are not large, with the compressor wheel very close in size to the old Mazdaspeed K04 & the turbine wheel only slightly larger than the K04 Turbo. However, with the dual inlet turbine housing, 90° compressor outlet, and lots of attached electronics, the whole package takes up a lot of room in your engine bay.
The turbine housing is not far from the old K04. A large five-bolt inlet flange has two rectangular inlets to work with the dynamic pressure system (more on that later) and even a port where the EGR system sources its exhaust gases. The outlet is much simpler, using a five-bolt flange to mount to the downpipe, yet does house a surprisingly large wastegate port.
From a performance standpoint, the large wastegate should help eliminate boost creep but the turbine housing will likely need a larger scroll to get some more serious power out of the engine.
The compressor side is packed full of features. As usual, the wastegate actuator bolts to the compressor housing, however, Mazda has switched to an electric actuator. Interestingly, the bypass valve is also electric and is even mounted to the face of the compressor housing.
Some fancy casting design leaves a pathway between the high and low-pressure sides of the compressor and let the BPV decide when the passage is open or closed. These two electric actuators will mean easy and consistent boost control. The final plastic component on the housing we believe is a boost-assisted vacuum source for the vehicle. Finally, the inlet is a typical clamp connection while the outlet uses a 90° turn and two-bolt flange for better accessibility around the wastegate actuator.
With the housings removed, the CHRA of the dynamic pressure turbo is very simple & standard. Oil feed in the top, two-bolt oil drain in the bottom, and standard crossflow engine coolant ports. The compressor wheel is a cast 6×6 unit and the turbine wheel is a basic 11-blade unit.
We are looking forward to waking up the Sky-T in the coming months and making the 2018+ MZ6 into something a little closer to a Speed. Stay tuned, there’s much more fun to be had from the 2.5T!
-Daniel
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