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Mazdaspeed 3/6 CST4 Turbocharger

Old price: $1,199.99  
Price: $1,099.99
You save: $100.00 (8.33%)
Price in points:  What are Points? 1100 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. 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

The Corksport turbo is a great replacement choice for your k04 if you have suffered from a smoky or blown turbo, or just want more reliable power. My turbos blades had been damaged and were making a screaming noise so I needed to replace that.

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!
Hi. I have a 09 mazda 6 mps completely bone stock. Im very interested in purchasing this turbo for my car. My q is, do i have to change internal components (pistons, conrods) to run this turbo effectively? Will this turbo kill the lifespan of my engine internals? Thanks
just installed the corksport turbo,3"intake,and corksport boost controller and just came back from tpg tuning in pa all i can say is wow!! I made 329whp and 352 torque on 20psi. (dont have the 3 bar maf sensor yet would of gone more) this turbo is so much smother than the junk k04 i am extremely happy with my purchase and would recommend this turbo to anyone
perfect alternative to the stock paper weight . dont let the size of this turbo fool you it builds to about 15 pounds really smooth then gets violent to 27 pounds fitment was perfect
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.

Write a review

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