Proven by thousands of community members, the CST4 Mazdaspeed K04 Upgrade is a perfect fit for the mildly modified Mazdaspeed 3 and Speed 6 using stock fueling up to budget-built engines with FBO and auxiliary fueling. Replace your KO4 Turbo with the easiest and most complete performance turbo for the Mazdaspeed and have room to grow to 450whp capabilities with the CST4.
The CST4 features a MHI Journal Bearing CHRA, OEM Fit Compressor Cover, and choice between 0.66 A/R Internal Wastegate or 0.82 External Wastegate Turbine Housings.
The CST4 external wastegate turbine housing is designed for 44mm EWGs (Tial is a great option) w/included EWG elbow pipe & V-band clamp.
Includes a FREE CorkSport 3.5 bar MAP sensor for accurate boost pressure up to 37psi.
Read The BlogThe CorkSport CST4 – The Best Turbo for the Mazdaspeed
Don’t let the size fool you; the CST4 packs a punch for such a compact and OE fitment package. From full bolt-ons to fully built with auxiliary fueling, the CST4 will support power from 250-450whp while maintaining quick spool and great transient response between shifts. The CST4 replaces your Mazdaspeed 3 K04 Turbo and fits like OEM. Follow our step-by-step instructions to easily install the turbo.
The CorkSport CST4 is the best upgrade for your K04 Mazdaspeed Turbo. Designed with simplicity and bang-for-the-buck power in mind and maintaining the OEM compressor inlet size means you can use any intake on the market designed for the stock K04 turbo. The same goes for the turbine side with OEM flanges for compatibility with your OE fit downpipe and exhaust manifold.
Utilizing a custom MHI 18G billet compressor wheel, the CST4 can efficiently support 50 lbs/min flow rate and boost pressures to 30psi. Compared to cast counterparts, modern forge-milled wheels provide higher boost thresholds, improved response, and increased efficiency to get more power from a small package.
Paired with the compressor wheel is an MHI TD05H high-flow turbine wheel. This wheel uses a 9-blade design which reduces overall rotating mass and thus improves response and spool.
MHI Journal bearing CHRA housings are used for both the CST4 and CST5 turbochargers for their increased cooling capacity and proven reliability.
High-performance journal bearings and a 360-degree high-performance thrust bearing is used.
Comparing the compressor and turbine wheels, we have a wheel size ratio of 1:21.
One-off billet actuator is used for the CST4 so you can operate the turbocharger in bleed mode for the OE EBS or in interrupt mode with the CorkSport EBCS for increased boost control
The CST4 Turbo Upgrade comes with all the necessary hardware for installation and saves you time and money on gaskets, studs, and the specialty parts.
Do you want an easy-to-use Internal Wastegate setup or an External Wastegate setup and screamer pipe? You decide with the CST4 Mazdaspeed Turbo!
Internal Wastegate setup includes the 0.66 A/R IWG turbine housing and IWG Actuator.
External Wastegate setup includes the 0.82 A/R EWG turbine housing and V-Band Clamp & Elbow designed for 44mm EWGs. (EWG and Screamer Pipe Not Included).
Don’t worry, if you want to change your setup from IWG to EWG later you can.
It will take you 5 hours to install the CorkSport Mazdaspeed CST4 with our easy-to-use instructions.
5 Hour Install Time
4/5 Difficulty
1-Year Warranty
No CEL
Looking to finance your parts purchase and want to get 6 months NO interest on any purchase over $199? Click on the image above for more details.
Fits:
2007-2013 Mazdaspeed 3
2006-2007 Mazdaspeed 6
2007-2013 Mazda MPS 3
2005-2007 Mazda MPS 6
2007-2012 Mazda Cx-7 Turbo
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As others have stated, it spools for days and pulls like a pack of rabid dogs gunning for the finish line at the Iditarod.
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My turbo died. My engine died also a few months ago and I rebuilt it on fully forged internals but in rest my only mods are COBB SRI and Hypertech and BPV.
How will this work if I replace my busted turbo with this one? I need a direct replacement and didn't plan to buy the AP right now.
Thanks, Victor
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Installation is about as easy as it can get for a big turbo install, having an included coolant line, new studs and nuts for both the manifold and downpipe, quality gaskets for both sides and provisions for all heat shields but one, which is recreated to work with the new setup. It even retains the factory oil lines and ebcs mount.
But the real truth to its performance happens once it's bolted up and tuned. The only familiarity to any of my previous oil infested, self grenading k04s is that instant spool thanks to the high performance 9-blade turbine wheel. From that point forward it's everything you'd want it to be. The dyno graphs are about as perfect as you could ask for. Peak horsepower just before redline and a flat torque curve that brings a grin to your face driving the car at any throttle level. On just 92 octane I'm putting 350whp on my Genwon and the turbo isn't even breaking a sweat yet. I have far more room to grow with a built block and additional fueling if I ever go down that road. No more k04 flamethrower, no more power drop at 5500rpm. All smiles, all the time. This is the perfect turbo for this platform.
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