Oil Catch Can Kit for 2016+ SkyActiv Turbo 2.5L

Skyactiv Turbo OCC Kit

When you think of a performance aftermarket component you typically think of a part that increases the vehicle’s power, but some performance parts don’t. Instead they have a more critical purpose, increasing the reliability of your performance engine and components.  The CorkSport Oil Catch Can Kit (OCC Kit) is just that type of component(s). 

CNC machined Mazda Oil Catch Can

Why is an Oil Catch Can Kit critical for your Mazda?  Despite the huge advancement Gasoline Direct Injection (GDI) technology there are still some downfalls.  Compared to the more conventional port injection fuel systems, GDI is much more prone to engine oil fuel dilution.  This is primarily due GDI injecting directly into the cylinder; in low speed operation and cold starts the fuel simply does not have enough time to fully atomize into a gas before ignition.  This results in some excess fuel seeping past the piston rings into the oil along with any combustion chamber blow by the pistons.  This is fuel dilution. 

OCC catch all the nasty build up from entering your Mazda Skyactiv engine

Here you can see the results of a CorkSport OCC installed for ~3000 miles on a 2018 Mazda 6 2.5T.  This engine only has 500 miles and has an average commute of 15 miles & 20 minutes of mixed traffic and speeds. 

Mazda’s OE design attempts to resolve some of this with a valve cover breather that vents directly into the turbocharger compressor inlet and a PCV (Positive Crankcase Ventilation) valve in the engine block that vents to the intake manifold. 

How the Mazda OCC works

Mazda’s setup depends on the fuel and water vapor inside the crankcase being drawn into the intake manifold and intake system to then be re-ingested by the engine.  This has two major flaws:

  1. The direct crankcase ventilation via the PCV valve only works while cruising (no boost).  Combustion gas blow by will occur most often while in boost under high throttle application when the PCV valve is closed.
  2. This forces the engine to re-ingest dirty air that carries contaminants in the form of fuel and water vapor along with carbon debris.  These containments then build up on the inside of the intake manifold, cylinder head runners, and the intake valves slowly degrading performance over time. 
Carbon build up on a Mazda engine without the catch can

The CorkSport OCC Kit provides you with two major features:

  1. Both the valve cover vent and the PCV valve are drawn from the turbo inlet directly ahead of the turbocharger compressor. Thus both the valve cover and PCV valve have constant vacuum in all driving conditions, both cruising and high throttle application.
  2. The oil catch can itself acts as a “filter” for the vapor and debris that would normally be directly ingested by the engine. The drawn crankcase vapor and debris is separates and collects in the catch can for easy removal during normal oil changes. 

As you saw above, there is a significant amount of vapor and fine debris that is being filtered out of the crankcase air that would have normally been ingested.  As you continue down the path of modifying and demanding more form your Mazda, the need for a OCC System only becomes more and more critical. 

Bolt on Mazda Cx5, Cx9, and Mazda 6 turbo

CorkSport Axle Back Exhaust for CX-9

Bolt on Cx9 turbo axleback Exhaust

With a shop full of enthusiastic car guys and gals we are in love with the look and sounds of the CorkSport Cat-Back on that larger than life CX-9. Customers love the sound, especially when completed with our Skyactiv Turbo Intake, but a few requested a little bit less racecar rumble.

Bolt on Cx9 turbo axleback Exhaust

We are here to give our Cx9 customer what they want which brings us to a new exhaust option for the Cx9 Turbo, an Axleback!

Better than 3 inch Cx9 Skyactiv Turbo exhaust

The Axleback exhaust setup is great because you are still getting the awesome 100mm double wall slant cut tips, the high flow 80mm stainless steel piping, and an exhaust note that will still capture your attention as well as the other Cx9 owners on the road.

Cx9 cat back exhaust system

The in-cab exhaust volume and tone are much more subtle than the catback exhaust setup.  This is your family friendly and wife approved exhaust for the Mazda CX-9. This is the “bluetooth office friendly meeting” exhaust system which is mellow at cruise but throaty when you get into the boost.

Performance Cx9 turbo exhaust system

You can have your cake and eat it too. Check out the product listing for full details.

Mazdaspeed EWGs Made Easy!

We’ve talked a lot about external wastegates with our recent CST6 development but today we are happy to announce the standalone CorkSport External Wastegate Housings for the CST4 and CST5. Available right now as an update for your existing IWG CST4 or CST5, the CS EWG housings make it easy to get the best in boost control for your Mazdaspeed 3, Mazdaspeed 6, or Mazda CX-7 Turbo.

Bolton upgrade to go external wastegate with your Mazdaspeed

While the CST6 will only come with an EWG housing, the external wastegate (EWG for short) is a new concept for the CST4 and CST5. Both of these turbos originally hit the market with an internal wastegate (IWG) only option that has a small flapper valve on the inside of the turbine housing to let off excess exhaust gases. Instead, the CorkSport EWG housings use an offshoot from the turbine scroll that has a v-band flange on the end. This flange allows for the fitment of an external wastegate for improved boost control. To run an EWG on an original CST4 or CST5 previously, you needed an EWG capable exhaust manifold and some sort of block off for the IWG port.


Mazdaspeed 3 turbo internal and external wastegate housings

The new CS EWG housings make running an EWG on your Mazdaspeed3 easier than ever. Each housing comes with the elbow and clamp needed for great fitment. We even offer a dump tube/screamer pipe that works for both MS3 and MS6 as an add-on option. If you pick up the screamer pipe to go with your housing, all you need to supply is the EWG itself. 

Mazdaspeed external wastegate installation kit includes everything but the Tial wastegate

We strongly recommend a Tial MV-R 44mm wastegate as all design work and testing used this specific wastegate. Other wastegates may require modification for use. The 44mm size is a great fit for the Mazdaspeed engines, whether you are running an upgraded turbo on the stock block or fully built one that you intend to push to the limits.


Tial wastegates are a proven turbo commodity for the Mazdaspeed 3

So why would you want an EWG? For starters, EWGs truly offer the best boost control setup for any turbocharged car. Because the wastegate is separate from the turbocharger itself, it is easier to place for optimum boost control, plus, the design of the actuator itself can be optimized. As a result you get a wastegate that hits boost targets more accurately and responds quicker to changes in boost. This means no more boost spikes right when the boost hits (a common problem with poor quality IWG setups), and a near-flat boost curve. The isolated actuator also makes for faster and easier spring changes should you need to service or change your wastegate preload. For more info on the design behind the CS EWG housing, check out the full blog HERE.

A direct flow path for the exhaust gas on the Mazdaspeed 3

One of the best parts of EWG over IWG is the sounds that come with a screamer pipe! While only intended for off-road use, a screamer pipe dumps the exhaust from the EWG directly to the air. This allows for a fantastic noise during a WOT pull, that sounds truly unique. It’s not all just noise though, by venting the EWG to the atmosphere instead of venting the IWG in your downpipe, you are decreasing exhaust turbulence right after the turbine wheel, reducing backpressure. On very high horsepower setups, this often generates some extra power as the turbine housing can be used more efficiently. Check out the product video below for some great EWG sounds from Barett’s MS3.

There’s one final benefit of the CS EWG housings: housing design itself. Without having the IWG in the way to worry about, we were able to do some optimizing on the scroll and A/R. For CST4 owners, this means an increase in A/R from 0.66 to 0.82. Typically an A/R change like this will cause a slight decrease in spool time but an increase in max power potential. CST5 owners have this 0.82 A/R even with the IWG setup but there’s another benefit: greater swallowing capacity. This refers to the amount of volume in the turbine scroll. By increasing the swallowing capacity the turbine can ingest air more efficiently at the peak, which is especially important if you have an upgraded exhaust manifold or high flowing head. After all, an engine is an air pump – what good is shoving more air in if you can’t get it out?

Easy bolt up external wastegate upgrade for your Mazdaspeed 3

If you’re in the market for a change on your Mazdaspeed, check out the CorkSport EWG housings for the CST4 and CST5 turbochargers. Better boost control, a more efficient housing, and best of all, a great new sound. Be sure to check out the listing for even more images and don’t be shy to ask questions we’ll be happy to help!

The CST6 has Arrived!


The long wait is finally over and you can now get your hands on the CorkSport CST6, which holds the record for the highest horsepower on the OEM turbine flange at 684WHP! In case this is the first time you’ve heard “CST6”, be sure to check out our blogs on the CS Turbo catalog, CST6 Design, and CST6 Testing. The CST6 is truly a big turbo, so if you’re ready for some serious power on your Mazdaspeed 3 or 6, read on!

CST6 with External Wastegate for Mazdaspeed

Let’s start by looking at the anatomy of the CST6. The backbone is a tried and true dual ceramic ball bearing Garrett CHRA. We opted for ball bearings to improve response and durability, especially when running at high boost levels the CST6 is capable of. As for wheels, the turbine is a 10blade GT35 while the compressor is an 11blade GTX76 that is rated for 64 lb/min. This combo provides fantastic spool characteristics for its large size, achieving 20psi by 3800-3900 with the appropriate supporting mods and headwork like on Barett’s GEN1.

Mazdaspeed Turbo

The quick spool is not due to the wheels and ball bearings alone though. A lot of research and development went into making the turbine and compressor housings the right fit for the CST6, and balance fast spool with top-end power. A 4” inlet with anti-surge ports provides plenty of air into that compressor wheel while a high swallowing capacity 0.82 A/R external wastegate turbine housing offers superior top-end power capabilities and optimum boost control. Even with all these changes, the CST6 fits in the OEM location; all you need is the external wastegate actuator and an intake that fits the 4” compressor cover.

CorkSport CST6

The CST6 is definitely not all bark and no bite though. We have thoroughly tested the CST6 up to its limits and beyond and have had nothing but success. Check out the graph below, that is the CorkSport CST6 in “calm” trim making mid-500s at 28psi. The difference in power on the graph was a back to back exhaust manifold change but more on that when we reveal more of the CorkSport Exhaust Manifold….

CST6 Dynograph

At the limit of the CST6 is a full bore 38psi, port-injected E85, and revving out to 8000RPM, resulting in 684.7WHP and 552WTQ. Check out the graph below. There may even be a little more to be had, with a larger 4” intake and 3.5” downpipe and exhaust.

CST6 Dynograph

Like every other CorkSport turbo, the CST6 comes with all new hardware, gaskets, and the needed oil and coolant lines to make your install as painless as possible. The CST6 is a little special though as it also comes with a v-band clamp and EWG elbow to help with the installation of your EWG actuator. While you will have to supply the EWG actuator itself, the elbow helps locate the Tial 44mm (or equivalent) wastegate in a usable location, whether you have an MS3 or MS6. In addition, we have a dump tube available for purchase to prevent any fabrication on your CST6 install.

So if you’re in the market for some serious horsepower on your speed, be sure to check out the CorkSport CST6. Let us know if you have any questions on the CST6, installation, or supporting mods, we’re happy to help!

P.S. If you buy a CST6 share your power graph with #CorkSport

CST5 Spools!! Testing and Validation

We’re back on the new CorkSport turbocharger lineup again with today’s blog, this time focusing on the testing & validation of the “medium big” turbo, the CST5. Just in case you missed it, the CST4 (formerly known as the CorkSport 18G) is getting some company to go along with its new swanky name. Check out the full lineup here and the design behind the CST5 here. Now that you’ve read all that, let’s get into what you’re really here for, testing & dyno numbers.

We started with the internal wastegate option, to validate the CST5 for drop-in fitment. Since we’ve had great experience with the drop-in CST4, we knew how to design a turbo around the tight confines of the Mazdaspeed engine bay. The CST5 fit great in the OEM location with just a few minor revisions for proper fitment. It looks pretty good in there too if we do say so ourselves!

Next the car got put on the dyno for tuning and to push the new CST5 to its limits. With a little help from our friend Will at PD Tuning, the CST5 was soon putting down some impressive numbers. We started off with a “calm” boost level of ~25psi. This netted us 450WHP and spool time that surprised us, achieving 20psi by 3500-3600RPM. Turning up the boost and pushing the turbo to its limits, we achieved 519WHP at ~30-31psi on Barett’s built GEN1 MS3. Check out the dyno graph below.

Taking the car out on the street surprised us further at just how early the car was building boost for this size of turbo. Road logs showed that we were making 20psi slightly sooner than on the dyno (3400-3500RPM) but even more surprisingly the CST5 was making 30psi by 3700-3800RPM! Obviously this is an aggressive tune that would most likely kill a stock block, but, the CST5 can be tuned to be stock block friendly and still make good power.

Then came the testing on the EWG variant of the CST5. We had developed fitment for the CST6 which meant the CST5 had no issues upon install on both MS3 and MS6. Next was a quick retune and some power runs. The larger swallowing capacity of the EWG housing meant some extra power at peak, yet spool was nearly unchanged. We made 525WHP at the same ~30-31psi.

Comparing the IWG and EWG turbine housings you can see a small variation in the graphs.  This variation is mainly due to the change from internally waste-gated and externally waste-gated.  The EWG setup provides more precise boost control through the RPM range. The EWG setup allows us to better tune the “torque spike” around 4200rpm vs the IWG setup.  For peak power the IWG and EWG housings are within the margin of error which makes since because they are both 0.82 A/R housings.

Further supporting the IWG and EWG setups, both options allow you to tune the spring pressure so you can better setup your CST5 and Speed for the fuel and boost levels you want and of course the most noticeable difference is what you hear. What’s an EWG without a screamer pipe!  

Wrapping up testing showed exactly what we were hoping for with the CST5: a great middle ground between the existing CST4 and the upcoming CST6 that can be used on both high powered stock block and fully built cars. Our testing continues as this blog is written as the CST5 is being beta tested by a close friend of CS with a freshly built Dankai 2.

There’s more to come from the new CorkSport turbo lineup so stay tuned for more info on the CST5, CST6, and EWG housings.

-Daniel @ CorkSport