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
- Comment
- Comment
Corksports turbo feels very much like the k04 but with more kick in the upper middle RPMs. On my fully bolted 2007 Speed3 I am pushing 23psi making 330whp and 350wtq on 94 pump gas. The turbo definitely has more to give and I can easily see it running more boost reliably.
The instructions provided by CS are very detailed with great pictures, and are my go to source for anytime I need to take something apart on my car. I attempted the install myself but had to take the car to my mechanic as the downpipe I have (cpe) had gotten the best of me. This turbo was actually his second CS turbo install that week!
So far I have put 2500km on the turbo and have had no issues. Of course that is not a long time for something to be on a car but it has definitely been an abusive 2500km. Thank you Corksport for the wonderful product and your great customer service!
- Comment
P.S. add 2 more hours to install time for MS6 owners because that car is just a cramped inconvenient nightmare to work on.
- Comment
- Comment
- Comment
- Comment
This is by far the best drop-in replacement turbo available for the MS3/6. And it IS drop-in. No modifications necessary.
But the 4 hour install estimate is off by about 1000 percent, especially for a MS6 which has the transfer case in the way and has had 10 years to weld all the various fasteners in place by natural processes. ;-) And no, my car has never seen salt, it's just old. About 50% of the work is done completely blind and by feel. If you don't have a history of wrenching on things for years and don't have a great set of tools, beware. There is a lot of potential here for mushrooming and breaking nuts/bolts/studs and essentially totaling your car because the cost will be so high to enlist a mechanic or machine shop to fix your eff-up. I don't think I would have attempted this if I didn't have a friendly mechanic with a flatbed right down the street.
None of this is CorkSport's fault and they provide excellent instructions and help over the phone if you need it.
It took me and a buddy about 36 hours over three weekends to complete the removal and install. Patience, persistence, teamwork and a sense of humor are key. We didn't break anything and the process wasn't horrible, but there were are lot of "are you kidding me?" moments when we realized we had to work blind.
Some specific tips from our experience:
1) One of the bottom oil return flange bolts, although clearly visible, is next to impossible to remove. There is zero clearance. Try using a zero offset box end wrench.
2) If you can't remove the bolt securing the turbo to the turbo bracket, try removing the turbo with the bracket attached. It can be done and it's not that bad. It took me standing on a 3 foot breaker bar to remove it once it was out of the car.
3) Stubby combination wrenches and wobble extensions are your friends.
OK, but what about the turbo after it's installed, you ask?
It's great, no buts.
For one thing, my exhaust no longer looks and smells like a BBQ run amok. My K04 was pouring a steady stream of oil into the hot side and the bearings had what seemed like 1/8" of lateral play. To be fair, this is partly a symptom of poor crankcase ventilation and oil control on the DISI motor, but less awful turbo bearings definitely help.
I'm still in the middle of an e-tune, and will provide an update when it's done. But the CS turbo provides 20+lbs of boost quickly and without much effort. Even with a sissy tune, the car is really strong from 3000-6000rpm. It sounds great, too.
Finally, as with all CorkSport products, this thing is so well made it makes me smile. One look at the stamped metal can that is the OEM wastegate actuator compared to CorkSport's machined aluminum one is pretty much representative of CS's philosophy.
To summarize, I believe this is the best drop-in turbo replacement for the MS3/6 platform that isn't just a rebuilt K04. This is basically a "big or semi-big turbo" that bolts right up without modifications. Just be sure you understand what you're getting into before you start tearing things apart. Now that I've done it once, I could probably do it with a helper on a younger MS3 in under 8 hours.
If you own an MS6, purchase a CS turbo and need help with the install, ask CS to ask me if it's OK to send you my email address. I'd be more than happy to assist via phone or email. There are a ton of resources out there for the MS3, not so much for the MS6.
- Comment
I love this freaking turbo so much. It spools so good and man that whistle puts a smile on my face every time. I was finally able to break my 400hp (hit 420) benchmark goal on 100% meth at 24 psi with the help of Will Dawson at Purple Drank. That's nuts to me. But this turbo, you won't be disappointed.
- Comment
At first I was skeptical due to the long process of tuning it has taken due to it being race season. I was coming from an E33 tune on the K04. But now on my second revision on a E25 mix, I am loving the way it pulls. It will still roast the tires if you want it to, but it is a lot easier to manage when you don’t. This is comparing it to the monster torque early rpm K04.
Yes it spools slightly later then the stocker, but it pulls up until redline. Unlike that massive, uncontrollable surge you used to get. You may have hit 320-330 hp and whatever torque, but was it useful that low in the rpm range? No. No it wasn’t, was it?
Bottom line is; if you’re on the stock block this is the turbo for you. If you decide to go built in the future, then you can have fun with this now, and get CTS5-6 when you are.
- Comment
