Mazdaspeed 3/6 CST4 Turbo Upgrade

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.

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.

CorkSport definitely did their homework with this one. Swapped the K04 for this with a built bottom end. This unit is more than enough to max the stock fuel system with internal. I ran 24lbs on E30 mix all day long. Logged 390 grams / second on the big end. Has excellent spool and flows until you want to shift. Very very smooth unit with highly responsive wastegate. Would recommend the other supporting mods to get max potential. The venerable TD05H CHRA paired with the 18g billet wheel and 9cm^2 hotside is a wonderful combo on the MZR. Very very happy with my decision.

Replaced my K04 with thisturbo and so far so good im on my second revision of my custom tune and its already way faster than my maxed out k04 tune. Pulls till redline, sound really nice and is a direct replacement.





P.S. add 2 more hours to install time for MS6 owners because that car is just a cramped inconvenient nightmare to work on.

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