2018+ Mazda6 Performance Exhaust for the 2018-up 2.5T

Mazda did a great job bringing a turbocharged engine back to the Mazda 6 (Mazda 3 next please?), but may have done too good of a job of keeping it quiet. Say hello to the CorkSport 80mm Cat Back Exhaust and Axle Back Exhaust for 2018+ Mazda6 equipped with the turbocharged 2.5L engine. If you’re interested in waking up your SkyActiv-T in both excitement and power, read on as we breakdown the newest CS exhaust.

As with all CorkSport exhausts, the goal of the MZ6 2.5T exhaust is to improve power and sound by improving the flow of the OEM exhaust. We started by increasing the size of the piping from 60mm to 80mm. That is an increase of over three-quarters of an inch to really help your turbocharger breathe better. In addition, the CS exhaust system eliminates the crushed areas present in the OEM exhaust and replaces the restrictive muffler sections with pass-through resonators. These resonators control volume and drone without affecting power output.

All that extra flow does mean a power increase. In our in-house dyno testing, we saw an increase in 5-6WHP just by bolting on the CorkSport  Cat Back Exhaust. Check out the dyno sheet down below to see. This increase came with no tuning changes, no check engine lights, and the only other mod being the CorkSport Short Ram Intake, which was installed for both tests. With the 80mm piping size, this exhaust is ready to support future modifications and would likely show more power gains with proper tuning.

The CorkSport MZ6T exhaust is more than just function. We went through multiple iterations and designs to ensure the best sounding exhaust for your 6. The finished product ups the volume without being annoying to daily drive yet still sounds great when in hard acceleration. We strongly recommend you watch the video below to hear what to expect from this exhaust.

If you feel the video below gives you too much volume for the daily, then check out the Axle Back Only Exhaust.  Recently added to the CorkSport line-up, the Axle Back alone adds a mellower, but still noticeable tone to the exhaust.  This is a great middle ground between the CorkSport Cat Back and the stock exhaust.

To give a great looking, long-lasting finish to each exhaust, they are manufactured from fully polished 304 stainless steel. To ensure a high quality fitment, all components are precision TIG welded together on jigs made from OEM exhaust components. Lastly as a finishing touch, we use 100mm dual wall exhaust tips. They fill out the bumper cutouts and are extended slightly to give a classy look and enhance the new Mazda 6’s styling.

The CS Mazda 6 Turbo Exhaust comes with all the hardware and gaskets you need for installation, high quality instructions, and CorkSport support for any questions you may have. Pick up a CorkSport MZ6 2.5T Exhaust today and liven up that daily commute.

The Design – 2.5L SkyActiv-G Exhaust Header

CorkSport 2.5L SkyActiv Header

A few months ago we broke down the complicated design of the exhaust manifold found on the 2014-2018 Mazda 3 & 6 2.5L SkyActiv.  Mazda put extensive R&D into the design and packaging of the OEM header to optimize the exhaust gas pulses and overlap.  

In this blog we are going to explain some of the design features in the CorkSport 4-2-1 header and why those features are important.  

Below is a diagram showing the primary, secondary and collector routing of the OE header.  

Mazda 2.5L SkyActive Header
The OEM header for the 2.5L SkyActiv engine has a 4-2-1 design.

When designing a performance header we have to ask ourselves, “what is the goal with this performance part?” and then fulfill that goal.  With the performance header for the 2.5L SkyActiv our goal was to increase mid-range torque, retain good fitment and user installation, and improve the sound output of the exhaust system.  

CorkSport Aftermarket Exhaust Header
CorkSport 2.5L SkyActiv header design.

Immediately you’ll notice a significant difference in the design of the OEM header and the CorkSport Header.  There are three major differences:

  1. Primary, secondary, and collector diameters have been increased to promote better exhaust gas flow.
  2. Primary and secondary runner lengths have been increased to optimize power/torque lower in the RPM range.
  3. The design is two-piece to drastically improve the installation process.  

The primary runners (these are the runners that mate directly to the engine) have been increased in diameter from 1.55” to 1.75” and the secondary runners (these are the runners that combine only two cylinders before the collector) have been increased in diameter from 1.87” to 2.00”.  Both of these changes improve peak flow per cylinder throughout the RPM range. Lastly, the collector has been increased from 2.00” to 3.00” to be paired with the CorkSport 60.5mm or 80mm Cat-Back Exhaust Systems.

CorkSport Exhaust Header Installed
CorkSport Header Installed.

Here’s where things got a bit tricky.  Increasing the length of the primary and secondary runners forced us to be a bit creative in routing all the piping.  In order to achieve the primary runner length we wanted, we had to route the piping upward first (as you can see below) then back down between the engine and firewall.  The results were better than we expected with a “Medusa” style header peeking out of the engine bay and the lengths we wanted.

It makes us grin every time we pop the hood open, we hope you love it as much as we do.  

CorkSport 2.5L Exhaust Header broken down for install.
The final design of the CorkSport 2.5L header is installed in two pieces.

However, the complicated CorkSport design did create a new problem.  Installation! We always try to create a performance part that can be installed by the average enthusiast in their garage and this was no exception.  In a one-piece design, the header was nearly impossible to install. We went to the drawing board and realized that separating the upper and lower halves of the header was the best option.

We considered a conventional flange, gasket and hardware setup, but realized it to was far too complex in the close quarters behind the engine.  We then moved to a v-band connection that proved to be the best setup for installation, weight, and sealing ability.

That wraps up the design, next we’ll breakdown the testing and results! Let us know if you have any questions or thoughts down below.

-Barett @ CorkSport

2018+ Mazda 6 Turbo Lowering Springs

2018 Mazda 6 on CorkSport Lowering Springs

We at CorkSport are happy to introduce the Sport Lowering Springs for 2018+ Mazda 6 equipped with the 2.5L turbocharged engine. We took a fresh approach to spring design to offer you the best combination of style, ride quality, and handling in a package that fits just like OEM. The new Mazda 6 looks great, but a functional drop gives it just what it needs to look even better. Combine this with the new handling characteristics and your MZ6 2.5T transforms from a fun grocery getter to something you can actually enjoy on backroads.

Mazda 6 2.5T CorkSport Lowering Springs
2018+ Mazda 6 2.5T CorkSport Lowering Springs

Ride Height

Let’s start off with the big one: ride height changes. These springs offer a conservative drop from the stock springs with about 1 inch lower in the front and about 0.75 inches lower in the rear. We chose this height as it offers a great new look without sacrificing any of the daily drivability of the Mazda6. This height clears the typical driveway with no issues, and retains plenty of suspension travel, even when fully loaded with 5 adults and weight in the trunk. Check out the image below for a direct comparison to a fully stock MZ6.

Lowered 2018 Mazda 6 vs. Stock Mazda 6
Black: Stock Springs Red: CorkSport Lowering Springs

Handling

The height drop will be noticed when you’re outside the car, but the handling improvements will be apparent when driving. By lowering the center of gravity and stiffening the springs, body roll is reduced in corners, giving you extra confidence when attacking that backroad. In addition, we stiffened the rear springs more than the fronts, reducing understeer. By number, this meant 3.8K front springs (25% stiffer than OEM) and 7.3K rear springs (45% stiffer than OEM). Derrick, our resident racecar driver and MZ6T owner, loves the new setup.

2018 Mazda 6 on CorkSport Springs

While this may sound like a big jump, they ride similarly to the OEM springs. We used a natural frequency analysis to ensure we achieved comfortable characteristics over bumps. Read the last half of this blog for more info on what that means (it’s complicated but awesome). Part of the great ride is the OEM dampers (shocks and struts). The spring rates we chose fit well with the stock shocks and struts to prevent any bounciness, plus, the conservative drop ensures you are in the normal operating range of the dampers. This means no prematurely worn shocks/struts due to springs that are too low.

Lowered MZ6T

Material Quality

Last but not least, the CS Sport Lowering Springs are made from high tensile strength spring steel and come powder coated in an OEM style black for long-lasting quality and corrosion resistance. They install just like stock, reusing all your OEM components. The only permanent modification is trimming the bump stops to match OEM suspension travel.

Be sure to check out the product listing for more images, a product video with more comparisons to OEM, and pricing. Make your new Mazda 6 yours with just the right styling and handling boost from CorkSport.


That about does it for the Mazda 6 2.5T Sport Lowering Springs. Be sure to let us know if you have any questions-suspension is hard, even for us! Lastly, be sure to share your MZ6T with us by using #CorkSport.

-Daniel @ CorkSport

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Let’s Get Chilly: CorkSport Intercooler for SkyActiv 2.5T

It’s time to break down our design for the CorkSport Performance Intercooler Upgrade for the Mazda 6 2.5T. We have covered both the OEM intercooler and piping, and our design plan for the upcoming Sky-T intercooler piping upgrade in previous blogs, but today’s focus is the intercooler itself. Intercoolers are a delicate balancing act between size, cooling efficiency, and pressure drop so naturally things can get a little complicated. Buckle up and stay with us, and be sure to drop any questions you may have down below.

Taking a look at the stock intercooler mounted on the Mazda 6 (shown above) shows us quickly where our size constraints lie. With the large crash bar, we cannot go too much larger in height without trimming the crash bar, bumper, or both. However, there is a ton of room for added thickness and better end-tank design that can really help increase the width of the intercooler. The stock intercooler core is 24.5” wide, 5.5” tall, and 2.625” thick. Our plan is to fit a 27” wide, 6” tall, and 3.5” core without any trimming. This sizing combined with a low-pressure drop will be good for 400WHP with no issues! Because the Mazda 6 comes with just around 200WHP from the factory, this sized core provides plenty of room for upgrading down the road without causing excessive boost lag that can occur if an intercooler is simply too big. Check out a prototype CorkSport intercooler mounted on the car below.

Now that size is taken care of, let’s move on to cooling efficiency and pressure drop of the CorkSport intercooler for the SkyActiv 2.5T. These are tied closely together as getting extremely high cooling efficiency usually means high pressure drop and vice versa. Just so we’re on the same page, cooling efficiency is how well the intercooler cools off the pressurized air that passes through it. So a highly efficient intercooler will be able to bring the boost temperatures down similar to the ambient air temperature. Pressure drop is exactly what it sounds like, a loss in pressure from the inlet to the outlet of the intercooler which can be caused by a number of things: poor end-tank design, too many intercooler fins, or simply poor flow distribution in the intercooler. Too large of a pressure drop means lower boost pressures reaching your engine and/or your turbocharger working harder to achieve the same boost levels.

Pressure drop and cooling efficiency are influenced primarily by two things: fin density and end-tank design. Fin density is basically how many fins the boosted air must pass over when traversing the intercooler. More fins = better cooling efficiency, but also more pressure drop. To choose the best core for the SkyActiv 2.5T we plan to use multiple different fin densities and test each for power, cooling efficiency, and pressure drop. While we can get pretty close based on our work from the CS Mazdaspeed Intercoolers, it’s always best to test and identify the best one for each platform. With this extensive testing, we can reach our goal of improved cooling efficiency, lower pressure drop, more power, and no CELs.

End-tank design is critical as it determines how the air reaches the core of the intercooler. Sharp bends, poor air distribution, and small inlet/outlet size all adversely affect the performance of the intercooler. To fit the core size we want, we had to do away with the plastic inlet and outlet pipes of the stock intercooler. This was advantageous as it gave us more room to have a smooth flowing end-tank that distributes air well to all the runners and does away with the sharp corners present in the OEM end-tanks. In addition, we were able to increase the inlet and outlet size of the intercooler to 2.5”. This is a fairly standard size that has shown to work well for the Mazdaspeeds with stock power and without choking flow way up to Barett’s 600+ WHP.

Those of you with a keen eye have realized that the connection between the CorkSport front mount intercooler (FMIC) and the OEM Intercooler is not the same. As shown in the CAD rendering above, each intercooler kit will come with the silicone and custom adapters that are needed to work with the OEM piping. If you decide to upgrade to the CS intercooler piping kit, later on, the CorkSport Intercooler for SkyActiv 2.5T will not need to be removed, and you will only need to change some silicone parts.

We will have more info on this kit coming soon, with the next blog covering our testing of the different core designs using a few new toys from AEM Electronics. Be sure to check out the product listing for more info, and to be notified when the intercooler is available. Last but not least, CX-9 Turbo and CX-5 Turbo owners, we are 99% sure this kit will also work on your rides but we plan on validating fitment before release!

-Daniel @ CorkSport

Mazda 6 2.5T Stock Spring Evaluation

Today we’re taking another dive into OEM Mazda parts to better understand how they function. Specifically, OEM suspension springs, since there are CorkSport Lowering Springs coming soon for the 2018+ Mazda 6 2.5T. While a simple concept, springs are very important to the handling, appearance, and comfort of your vehicle.

The new Mazda6 Turbo uses a lot of the same components as the GEN3 Mazda3 and Mazda6, however the suspension has been optimized for the new “premium” feel and to deal with the extra weight that comes when adding a turbo. The SkyActiv chassis has largely remained the same though, with the same MacPherson strut front suspension and multi-link rear suspension shown below.

Now, onto the springs themselves; both the front and rear suspension of the Mazda 6 use standard compression springs. The springs job is to support the weight of the vehicle when at rest and adsorb impacts when hitting bumps or going quickly around a corner. That’s it. Seems simple enough right? Since the springs are the parts of the suspension that “suspends” the vehicle though, their characteristics and how they interact with the rest of the suspension system are critical.

There are two main characteristics that define a spring: rate and free length. Both are pretty easy to understand. Free length is simply the length of the spring with no weight or force acting on it. So set a spring by itself on a table, measure how tall it is, there’s your free length.

Spring rate is a little more complex, as it is the measure of how much weight it takes to compress a spring a given distance. So, if you have the same weight and put it on two different springs the one with the higher rate will compress less. The rate is usually measured in kg/mm (often shortened to K) or lbs/in.

For example, if you had a 2K spring and a 4K spring and applied 100kg to each, the 2K would compress 50mm and the 4K would only compress 25mm.

What do these measures mean for your car though? If we keep the rate the same but only change free length, the shorter the spring, the lower the car. For a given car, a spring can be too short, causing poor ride (sitting on the bump stops all the time), or the risk of a spring coming out of place, causing noises or at worst, the spring falling out of the vehicle.

If we change the spring rate and leave the free length the same, things are a little more complicated. The higher the rate, the stiffer the ride is, plus your ride height will increase. Since the weight of the car is not changing, the higher rate spring will now compress less when the car sits on it, meaning your car sits higher at rest. Too large of a rate and your OEM shocks cannot keep up causing a bouncy ride, and vice-versa if too soft you are hitting bump stops over the smallest bump. Obviously there is a balancing act to get the spring rate and free length correct for the application for the best in appearance, handling, and comfort.

Now that the basics are covered, let’s look specifically at the Mazda 6 2.5T. The OEM springs give a good ride as to be expected (likely very soft spring rates) as this can be a huge issue for potential customers if the car ride quality is harsh. Handling is decent overall but has a few quirks. When going around a corner quickly, the car rolls over onto the rear springs excessively before settling, and getting through the corner. When at the limit of traction, the car understeers severely, like most cars sold today.

Finally the ride height is pretty high, likely to prevent any issue with driveways saying hello to the new front fascia. Interestingly, the MZ6T sits a little higher in the rear; we think to ensure enough suspension travel in case there’s a full load of passengers and a full trunk.

For further analysis we also had the OEM springs tested for rate and ended up with the following: 3.05K front, 5.05K rear. While these numbers are fairly arbitrary right now, they are a necessary data point to have when designing lowering springs. These rates also contradict a very common misconception. Many people think that because there is less weight in the rear of a front wheel drive car, the spring rates must be softer in the rear for a good ride & handling. This is simply not true in most cases, after all why would Mazda do the opposite? Due to the design of the rear suspension, the spring is basically being pushed on by a lever. This means the spring needs to be stiffer in order to support the same amount of weight as if the lever wasn’t there.

So overall, the OEM springs are good, but have plenty of room for improvement. I just touched the surface of suspension design and as we go through more of this project we’ll get into dampers, natural frequency, and much more. Stay tuned for more info and if you have any questions, don’t be afraid to ask!

-Daniel @ CorkSport