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
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
The CHRA has some differences so we made the new one to fit better. You might be able to use the OE part with some modifications.
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.
No, you will need a tune once it is installed.
Will this be better than the original turbo i have on my 2022 Mazda 3 2.5L Turbo sedan ?
This turbo is specific to the Mazdaspeed platform, and is not compatible with the 4th gens
What PSI or Bar is the internal wastegate spring pressure rating?
The factory preset is 14-16lbs
Hi, could you confirm this turbo with IWG is compatible with a cpe downpipe? Thanks.
Yes, the IWG CST4 should be compatible with that downpipe.
Do you think its possible at all to fix a Turbocharger in an Mazda 2 2011 Petrol
With enough time and money, anything is possible.
What intake would be best for this turbo? I’m currently running the Cobb sf intake and inlet pipe.
Any quality intake will pair well with the CST4, provided you get a custom tune to account for it.
Can this turbo be clocked to work with underside intercooler piping?
Our turbos can't be clocked.
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.
Our turbos can't be clocked.
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!
Please send this request to sales@corksport.com so we can help you out
Does this turbo come with everything needed to run EWG or does it just come with the dump tube?
It does come with the hotside, but not the dumptube.
Is this compatible with 2018 mazda Cx5 AWD?
No, the turbo is completely different.
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?
Your current intake will pair up with the CST4, the only change you will need to make is to get the car tuned for the new turbo.
does the CST4 Turbo IWG comes with a 3.5 map sensor ?
Yes it does.
I'm from Guatemala, the 1 year warranty applies if I'm using the turbo outside US ?
Yes, the warranty still applies.
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
Absolutely. The turbo itself is an upgrade, but works with all the components you list. Just make sure you line up a retune!
How well do these turbos handle off-throttle compressor surge?
They handle it fine as long as you have a proper functioning BOV
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.
The OEM k04 seals start to fail pretty quickly after you start pushing high levels of boost. This turbo is meant to handle quite a bit more a long time. Keep in mind that it varies depending on how hard you push the turbo etc.
Is the cst4 turbo legal in California?
Aftermarket Turbos are technically for offroad use only
Is there any mods outside of hpfp that are needed to run this turbo reliably?
You need a hpfp and the accessport to the tune car. Those are the two minimum requirements
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?
It does come with the free MAP sensor
This is a question from Japan. I'm sorry if the text is wrong because I'm translating. This product, Is there a manual for resetting COBB AccessPort V3?
To tune it? You will need to work with a protuner to do so. You may have better luck reaching out to Cobb directly if you are needing help with something else.
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
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