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Vancouver, WA


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Mazdaspeed 3/6 CST4 Turbocharger

Price: $1,199.99
Price in points: What are Points?1200 points
Mazdaspeed Turbo with Stock flange fitment, boost by 3500rpm and power to 7000...the CST4 is the turbo replacement for the K04

Products in package

Stock flange fitment, boost by 3500rpm and power to 7000...the CST4 is the turbo for your Mazdaspeed

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 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

Mazdaspeed 3 turbocharger upgrade BNR k04 precision

Mazdaspeed Mistu 18G turbocharger upgrade BNR S3  k04 precision

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. The CST4 replaces your Mazdaspeed 3 K04 Turbo and fits like OEM. Follow our step-by-step instructions to easily install the turbo.

a better Mazdaspeed 3 turbo than the BNR S3 turbocharger k04 precision

Stock Flange Fitment:

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.

MPS3 Turbo Upgrade BNR k04 precision

Billet Compressor:

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.

how to get a 400hp Mazdaspeed 6 BNR precision k04 turbo

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 precision k04 upgrade

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 BNR k04 precision

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 BNR S3 k04 precision

All Hardware Included:

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.

MPS3 turbocharger upgrade BNR k04 turbo precision

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 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.

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, Mazdaspeed 6,& Mazda 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.

advisory notice
  • 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

Best mod for your stock block, stock fuel mazdaspeed! Wakes up your entire power band! And it comes with the option for EWG no other turbos in this class offers that! highly recommend!
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.
This turbo is awesome. installation is not for the faint hearted but with that being said, the rewards are ten fold. Boost can be felt from 3k up until nearly redline(6500-7k) one thing id like to add is going with a FMIC with this turbo(especially MS6 owners). the boost hits hard but with all that heat in the engine bay, a FMIC would be your best bet for cooler BATS. Corksport really knew what they were doing and looking for when R&D for this turbo was done. If at any time you doubt your K04, don't hesitate to upgrade to this turbo. it is LITERALLY A DROP IN TURBO and comes with the necessities( MAP sensor, hardware and COLOR instructions. Pair this with the EBCS and a good tuner, your GOLDEN.
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.
Write a review

Is this turbo compatible with my 2024 Mazda 3 carbon edition ?

Asked by Kid kid | 06/03/2024, 02:08 AM | 0 answer(s)

Will the factory heat shield work with the CTS4 Mazdaspeed 3 turbo? Or do I have to use the supplied heat shield? Thank you Ty

Asked by Tyler | 10/07/2023, 04:47 PM | 1 answer(s)

Could I run this on my untuned car for a while, while saving up for a tune? As long as I wasn't thrashing it, that is? My k04 is starting to puke, but it is also my daily. I have hpfp internals, 3" cold Air intake with CS big MAF, and C-pe top mount, with a recently relplaced timing chain and vvt sprocket.

Asked by Adam | 08/09/2023, 10:37 PM | 1 answer(s)

Will this be better than the original turbo i have on my 2022 Mazda 3 2.5L Turbo sedan ?

Asked by Zamora | 02/20/2023, 04:47 PM | 1 answer(s)

What PSI or Bar is the internal wastegate spring pressure rating?

Asked by Drew | 11/28/2022, 10:58 AM | 1 answer(s)

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