Save $10 On Orders Over $100. Use Code: CORKSPORT10
Vancouver, WA, USA 360-260-2675 M-TH 9A-5P | F 9A-12P PST

Shipping Estimator Shipping Estimator

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

I needed to change a smoking stock turbo and decided on this bad boy. I honestly chose it because it was a direct replacement and the price was perfect.

As others have stated, it spools for days and pulls like a pack of rabid dogs gunning for the finish line at the Iditarod.

Had this installed and dyno'd. Gotta say it is a top notch turbo and turned my car into a beast. It spools a bit later than the ko4 but the spool doesn't stop. Plus it whistles like a diesels turbo when spooling. Well worth the money especially since it really does drop right in with out issues. Time for a rear motor mount to get rid of the added torque steer.
Great turbo! The install was not difficult and I was not very mechanically inclined, I think changing breaks is more difficult. The turbo has a nice loud deep turbo noise and I cant get enough of it haha. It also makes the car move! I am currently running it at 21 psi and couldn't be happier the car is so quick I am very glad I went with corksport for the turbo. They are a great company and I had an issue with my points not going through but they fixed it right away. I would highly recommend this turbo to anyone looking to buy.
Hey Guys,

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
Looking at the spec list you can tell Corksport did their homework for building the most optimized turbo for this platform. Once you unbox the prize you can see first hand the level of quality in the castings not found in even the big name turbos. The forged billet compressor wheel is a work of art, as is the billet wastegate actuator housing. It's almost too much of a masterpiece to hide deep inside an engine bay.

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.

This things spools up quick! Running 17 psi going to about 20psi and it pulls strong. And it’s a lot smoother than the stock k04.
Overall I am very impressed with this turbo, not only does it look great but it performs amazingly! The install was very simple using the provided instructions from Corksport, after the install and the re-tune the performance of my car is night and day compared with the old Ko4. This turbo definitely out performs the BNR in many ways, first and foremost it flows more than the BNR, secondly the turbo comes with gaskets, studs, nuts, coolant line and a nice heat shield which the BNR does not come with for the same price. For me, choosing this turbo over the BNR was an easy choice and I am very pleased with it.
Write a review

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