Shipping Estimator Shipping Estimator

Mazdaspeed 3/6 CST4 Turbocharger

Old price: $1,199.99  
Price: $977.69
You save: $222.30 (18.53%)
Price in points:  What are Points? 978 points

Products in package


Since 2015, the Mazdaspeed 3 Drop-In Turbo has been one of the best performance upgrades for the platform.

Proven by thousands of community members, the CST4 is a perfect fit for the mildly modified Speed 3 and Speed 6 using stock fueling up to budget built engines with FBO and auxiliary fueling. Replace your KO4 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.

Mazdaspeed Mistu 18G turbocharger upgrade

Drop In Performance:

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

a better Mazdaspeed 3 turbo than the BNR S3 turbocharger

Stock Flange Fitment:

The CorkSport CST4 was designed with simplicity and bang for the buck power in mind. Maintaining the OEM compressor inlet size means you can use any intake on the market designed for the stock K04. The same goes for the turbine side with OEM flanges for compatibility with your OE fit downpipe and exhaust manifold.

MPS3 Turbo Upgrade

Billet Compressor:

Utilizing a custom MHI 18G billet compressor wheel, the CST4 can efficiently support 50 lbs/min flowrate 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 form a small package.

how to get a 400hp Mazdaspeed 6

High Flow Turbine:

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.

Better performance Mazdaspeed 3 turbo over the BNR S3

High Performance CHRA:

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.

CNC Billet Speed3 Wastegate Actuator

Billet Wastegate Actuator:

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

Mazdaspeed 3 turbo installation hardware

All Hardware Included:

The CST4 comes will all the necessary hardware for installation saves you time and money on gaskets, studs, and the specialty parts.

MPS3 turbocharger upgrade

Choose your Boost Control:

Do you want an easy to use Internal Wastegate setup or an External Wastegate setup and screamer pipe? You decide with the CST4!
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.

Check Out the External Wastegate Development Blogs Below

Does your Mazdaspeed need an EWG:

Click To View

External Wastegate Testing:

Click To View

Additional Features
  • Vehicle Fitment: 2006-2013 DISI MZR found in the Mazdaspeed 3/6 & CX-7.
  • Designed in America: in Vancouver, Washington, in the Pacific Northwest.
  • CorkSport Service & Support: 1 year limited warranty, full color installation instructions, all necessary components, and knowledgeable telephone support at (360) 260-2675.

  • Upgraded HPFP Internals and COBB AP/Tune is required with this product.
  • Auxiliary fueling required for peak power operation of this turbocharger.
  • Some aftermarket and all OEM downpipes will NOT clear the EWG elbow that is included with the CorkSport EWG Turbine Housing. Check the "Fitment Notes" tab for details.
  • EWG variant designed for Tial 44mm or equivalent external wastegates (not included but available).
  • External wastegate is NOT included with turbo. Did we mention it is not included, because it is not.
  • EWG dumptube/screamer pipe is NOT included with turbo but can be added as an option.

How To Install Your Mazdaspeed 3 and Mazdaspeed 6 Upgraded Turbocharger

It will take you 5 hours to install the CorkSport Mazdaspeed CST4 with our easy-to-use instructions.

5 Hour Install Time

5 Hour Install Time

Difficulty: 4/5

4/5 Difficulty

1-Year Warranty

1-Year Warranty



View Instructions

Very happy with this turbo! Has been in my Gen2 Speed3 for about 1.5 years. My setup FBO on 93oct tuned by PD @ 20psi, factory internals. Turbo pulls hard all the way through redline with plenty left for more. My Speed is the perfect sleeper now. Catches many people by surprise. I have a great set of tires and still spin the wheels at full throttle. Under 60 degrees I have to ease into it or wheel spin all day. With this turbo the car is an absolute weapon. No regrets with this turbo. In the future I plan on building the motor and turning up the boost with more aggressive timing. This turbo is more than capable for a mild/wild street setup.
Awesome turbo a must to upgrade to. The power this turbo makes is night and day difference from the K04. The K04 runs out of breath in the higher rpms were the CST4 keep on going though the whole power band. On pump gas here crappy 91 octane. My car made 336 hp and 366 torque @ 25 psi on a mustang dyno.
Great turbo, installed on car for 4 months without a tune. Still ran amazing. With corksport cat less down pipe. Spools up to 23psi with a box tune at 3200 rpm. Would recommend to any other speed that wants to go big turbo.
Very impressed with turbo it made 430whp/424tq on e30 @24psi stock block.
Phenomenal turbo. Boost holds all the way to redline, spools quick, and sounds amazing. Just looking at it compared to the k04 you can tell it's much better quality and slightly bigger. Don't even need to know all the numbers to notice that. All around am very happy with it. Can't wait to see what it can do on e85.
I just bought this a few days ago. I was not expecting what this is. I have seen many speeds get 400whp safely and reliably without any meth, ethanol or port injection so I bought this one over the other options. But oh boy I just got done installing this. I made a slow pull of only 11psi and this thing sounds amazing. Ive never heard a turbo make such a noise. With the reliability, power and awesome sounds it makes it gets 5 stars. plus discount and free map sensor. Why would I not give it 5 stars?
Amazing medium turbo for the stock block.

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.

I've had this turbo for close to a year (or whenever they introduced the version one's) and decided to come back and write a review.

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.
First, although I'm giving five stars because the product is superb, I considered giving four due to the difficulty of the install, but decided it really wasn't fair to CorkSport.

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.
This turbo has transformed my car with the inclusion of the Corksport 3 inch intake. Went from 275 whp on the stock K04 to 350 whp and 350 torque at 22psi so my target of 24psi should be fun, this is on 99ron pump fuel with an e-tune from the master Justin (j-tune).
Write a review

Hi, could you confirm this turbo with IWG is compatible with a cpe downpipe? Thanks.

Asked by bill | 10/02/2022, 07:04 AM | 1 answer(s)

Do you think its possible at all to fix a Turbocharger in an Mazda 2 2011 Petrol

Asked by John  | 09/28/2022, 02:04 AM | 1 answer(s)

What intake would be best for this turbo? I’m currently running the Cobb sf intake and inlet pipe.

Asked by Zak | 04/26/2022, 11:58 PM | 1 answer(s)

Can this turbo be clocked to work with underside intercooler piping?

Asked by bill | 04/02/2022, 06:43 PM | 1 answer(s)

I'm planning on using underside tubing for my fmic. Can the CST4 turbo be clocked so I can run the piping from the bottom? Thanks in advance.

Asked by bill | 04/01/2022, 07:31 PM | 1 answer(s)

Hello. I somehow misplaced a few of the turbine studs that came with this kit and need to find replacements. I did not see the size and thread pitch of these studs listed in the installation instructions - instructions list them as "Nine (9) Turbine Studs." What size, length & thread pitch stud would I need to purchase to replace these? Thank you for your help!

Asked by Michael | 03/17/2022, 06:27 PM | 1 answer(s)

Does this turbo come with everything needed to run EWG or does it just come with the dump tube?

Asked by Nick Kucera | 01/26/2022, 11:04 PM | 1 answer(s)

Is this compatible with 2018 mazda Cx5 AWD?

Asked by Gautham | 01/03/2022, 11:29 AM | 1 answer(s)

My K04 went out, Im having this installed because its $600 cheaper then a stock k04 from mazda. Here is my mods list: CS stage 2 intake with turbo inlet Autotech hpfp internals 3 port boost controller catless test pipe resonator delete Cobb AP Will this be ok? Im not looking for a crazy tune just a moderate tune, that will be reliable. Im wondering if I need to get a 3 or 3.5 inch intake?

Asked by Dee Code | 11/27/2021, 12:11 AM | 1 answer(s)

does the CST4 Turbo IWG comes with a 3.5 map sensor ?

Asked by Robert  | 10/05/2021, 07:03 PM | 1 answer(s)

I'm from Guatemala, the 1 year warranty applies if I'm using the turbo outside US ?

Asked by Angello Galindo | 08/24/2021, 07:19 AM | 1 answer(s)

Can this be used as a replacement for a stock k04 turbo with bad seals? Car has fmic catless 3" downpipe injen intake (plan on swapping to 3" soon) and hpfp internals

Asked by Kohl gossler | 04/14/2021, 06:40 PM | 1 answer(s)

How well do these turbos handle off-throttle compressor surge?

Asked by jack | 11/14/2020, 11:00 AM | 1 answer(s)

will this turbo work well with a catless downpipe and turboback exhaust? Also how are the seals on these turbos in comparison to the ko4? Currently I am burning oil and see lots of oil in my hot ic piping.

Asked by andrew  | 06/24/2020, 07:02 PM | 1 answer(s)

Is the cst4 turbo legal in California?

Asked by Alex  | 05/13/2020, 06:30 PM | 1 answer(s)

Is there any mods outside of hpfp that are needed to run this turbo reliably?

Asked by Jared Turney  | 04/15/2020, 05:27 AM | 1 answer(s)

This is a question from Japan. I'm sorry if the text is wrong because I'm translating. Does this product come with a Mazdaspeed 3.5 Bar MAP Sensor? Is there a manual for resetting COBB AccessPort V3?

Asked by KEIJI SHIRAKATA | 03/19/2020, 09:05 PM | 3 answer(s)
Mazda performance parts financing is available with CorkSport

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.

2007-2013 Mazdaspeed 3
2006-2007 Mazdaspeed 6
2007-2013 Mazda MPS 3
2005-2007 Mazda MPS 6
2007-2012 Mazda Cx-7 Turbo

NO Stock Downpipes will fit the EWG version of the turbo for any model of Mazdaspeed or the Cx7 turbo. It does not work.
Some aftermarket downpipes will NOT clear the EWG elbow that is included with the CorkSport EWG Turbocharger.
If the downpipe is not listed here then it has not been test fitted with a CorkSport EWG Turbocharger.

Mazdaspeed 6 Fitment:
CorkSport Catted Downpipe - Confirmed
CorkSport Non-Catted Downpipe - Confirmed

Mazdaspeed 3 Fitment:
CorkSport Catted Downpipe - Confirmed
CorkSport Non-Catted Downpipe - Confirmed
Cobb Catted Downpipe - Confirmed
Depo Racing Non-Catted Downpipe - Confirmed
XS Power Non-Catted Downpipe - Confirmed
Manzo/Ebay Non-Catted Downpipe - Does NOT fit. Will require custom EWG elbow and dumptube
CPe Non-Catted Downpipe - Does NOT fit. Will require custom EWG elbow and dumptube
CPe Catted Downpipe - Does NOT fit. Will require custom EWG elbow and dumptube