With a shop full of enthusiastic car guys and gals we are in love with the look and sounds of the CorkSport Cat-Back Exhaust 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. As you’ve requested, here is the new CX-9 axle back 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!
The Mazda CX-9 Axle Back 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.
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.
You can have your cake and eat it too. Check out the product listing for full details.
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.
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.
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.
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.
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.
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.
Stay Up-to-date with CorkSport
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?
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!
Mazdaspeed EWGs Made Easy! October 31st, 2022Derrick Ambrose
The long wait is finally over and you can now get your hands on the CorkSport CST6 Mazdaspeed Turbo, 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!
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.
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 Turbo fits in the OEM location; all you need is the external wastegate actuator and an intake that fits the 4” compressor cover.
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….
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.
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
The CST6 has Arrived for the Mazdaspeed! January 8th, 2024CorkSport
Today we want to break down the OEM exhaust manifold for the Mazdaspeed platform so that you can better understand how and why the CorkSport Exhaust Manifold makespower.
If you haven’t heard, CorkSport has been developing a performance cast exhaust manifold for the Mazdaspeed platform. We’ve tested and validated samples on Mazdaspeeds ranging from 350whp to 684whp. We’ve done dyno testing on the OEM exhaust manifold vs the CS manifold, as well as on the XS Power V3 manifold vs the CS manifold with the man, Will Dawson of Purple Drank Tuning, setting the calibrations. Both tests showed good gains from just the CorkSport Exhaust Manifold alone. However, we can get into those details later.
Mazda Exhaust Manifold Design
OEM Exhaust Manifold Flange
This is the OEM (original equipment manufacturer) exhaust manifold found on the 2007-2013 Mazdaspeed 3 and 2006-2007 Mazdaspeed 6. Manufactured from cast iron and very compact in design, the OEM design leaves A LOT on the table in the performance department.
In the image, we’ve labeled each cylinder since that will be important for later discussion.
OEM Manifold Exhaust Flow
So now let’s talk flow. Fluids (or exhaust gases in this situation), will always take the path of least resistance. When the flow path is not clearly defined for the exhaust gas, such as a merge between different cylinders, turbulence is created which reduces the efficiency of the exhaust manifold.
A prime example of turbulence is shown in the image above with the orange arrows at the merge for cylinder 1 and cylinder 2. Cylinder 2 comes to a “T” and therefore could flow left or right. This creates turbulence which causes a loss in potential power.
Next is the yellow arrow. This is identifying the inner diameter of the runners in the OEM exhaust manifold. To our surprise, the inner diameter of the OEM exhaust manifold is actually pretty decent at ~1.48 inches. This diameter partially defines the power a manifold can support efficiently. Bigger is better in this situation, but small changes here will make big differences in the final performance.
Surprisingly, there are “performance” exhaust manifolds on the market for the Mazdaspeed platform that have smaller inner diameter runners…
OEM Exhaust Manifold Gasket
We also wanted to point out an unusual but important aspect of the Mazdaspeed exhaust manifold and gasket. Have you ever noticed the seemingly useless extend flange off of cylinder 4? This extended flange acts as part of the passage for the exhaust gas recirculation port.
You can more clearly see this port path in the gasket.
OEM Exhaust Manifold
Designing For Efficiency
In this image, we want to direct your attention to a unique and troubling design feature of the OEM exhaust manifold. There is a right way and a wrong way to pair cylinders on an exhaust manifold for a 4-cylinder engine, and this is the wrong way.
Referencing our cylinder callouts in the first image above; you can see that the OEM design pair cylinder 1 & 2 together and cylinder 3 & 4 together. This design physically works, but it is not ideal from a performance standpoint. In a divided manifold, you should pair cylinders 1 & 4 together and cylinders 2 & 3 together for optimal cylinder exhaust gas scavenging. To learn more about exhaust scavenging you can check out a blog on that here, or watch the video below!
Exhaust Gas Scavenging. See the difference between the CS and OEM Manifolds.
Before we wrap here we do have one good thing to say about the OEM exhaust manifold. It does sound really good and gives the Mazdaspeed platform a unique exhaust note, but don’t worry you don’t lose your unique rumble with the CorkSport design.
Thanks for checking in with CorkSport Mazda Performance. Stay tuned for more info about the CorkSport Performance Exhaust Manifold.
Over the past few months, we’ve been teasing you with tidbits of info on the CorkSport Race Header for the Mazda 3 2.5L SkyActiv-G in the GEN3’s. Today’s blog is a big one as we go through the testing we performed on the header and share some results, including power! Before we get too deep though, be sure to get up to speed with a breakdown of the OEM header and our design goals for the CS header.
2014+ Mazda 3 Header Installed
Addressing Underhood Heat
In our previous blog, some of you keen-eyed individuals were asking about underhood temperatures with the ram-horn style CorkSport header. Well, we went through testing to ensure everything will function as before when the new header is added. We’re happy to let you know that we saw very similar under the hood temperatures as the OEM header. As a double check, we applied some temperature sensitive stickers to some areas near to the CS header, as shown below. These stickers will fill in with color if a temperature listed is reached. While these ended up reaching higher temps than with the OEM header, no areas are at risk of damage or malfunction. Furthermore, both the CorkSport racecar and our beta tester have run the 2014+ Mazda 3 race header at the track with no issues with overheating, power losses, or engine bay damage!
2.5l SkyActive Race Header testing with temperature sensitive stickers
How Does The Header Sound?
Before we get into the really good stuff, let’s go through a side effect of freeing up the headers on any engine: volume. We tested the Mazda 3 SkyActiv race header with multiple different setups: OEM cat back, CS 60mm cat back, CS 80mm cat back, and straight pipe. The race header on an OEM cat back is something that will not likely be used often (who runs a racecar with a stock exhaust?) but offers some nice growl and extra volume over the OEM exhaust. Both the CS 60mm and 80mm exhausts sound fantastic, with the 80mm being louder and having higher power potential than the 60mm. Even so, the 80mm is not uncomfortably loud and could be daily driven if full catalytic converter deletes are street legal in your area. We cannot recommend the straight pipe though. It is extremely loud and very uncomfortable. If you want a tease of sound with the 80mm cat back, check out our feature on our beta tester’s car in the video below.
80mm Cat Back with the 2014+ Mazda 3 Header!
The SkyActiv-G Race Header Adds Power
Full Race Header for the 2.5l SkyActiv Engine
Alright, I’ve kept you waiting long enough, let’s talk power. The 4-2-1 design is very evident in our tests, as we did not see huge gains at peak WHP/WTQ. We did see very good gains throughout the midrange. From 2000RPM or lower all the way up to about 5300RPM we made 4-8WHP and 5-15WTQ. On our beta tester’s car with a good tune and supporting mods, this meant 194WHP and 226WTQ on 91 octane pump gas. The graph below shows a direct comparison of a 2016 Mazda 6 with a CS short ram intake, CS 60mm exhaust, and the same tune with and without the race header. Keep in mind, there is more optimization to be had with tuning with the header installed, and greater gains with an 80mm exhaust. The midrange gain may not seem like much but is extremely noticeable when driving the car.
That’s about it for our testing and validation blog. Next time you’ll hear about the CorkSport Race Header for the 2014+ Mazda 3, it will be released! Be sure to stay tuned to all the CS channels if you’re interested in being one of the first to pick one up.
-Barett @ CorkSport
P.S. We noticed a lot of you asking if this header will fit the auto transmission or 2.0L. The automatic transmission is 2-3” larger right where the lower section of the header sits, so for optimum pipe routing, we had to do away with automatic fitment. The 2.0L has a different bolt pattern and exhaust port spacing on the engine, so the 2.0L will not work with the CS race header either.
Please submit a product idea here if you would like to see automatic fitment, 2.0L fitment, or any other product for your car. The more submissions, the more likely we are to produce one so tell your car buddies!
