Testing & Validation: CorkSport 2.5L SkyActiv Race Header

mazda 6 exhaust header

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.

mazda 3 skyactiv 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
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 Mazda 2.5l SkyActiv Engine
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.

Mazda 6 Race Header Dynograph
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.

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!

SkyActiv-G 2.5T Intercooler & Piping Testing

The CorkSport Intercooler and Piping upgrade kits for the Mazda SkyActiv-G 2.5T are inching closer to release and it’s time to share more of the R&D that goes into making these kits perform the best. We went through extensive testing to determine which intercooler was the best fit and to validate that our changes were worthwhile. If you missed any of the previous blogs on these kits be sure to check them out: OEM IC & Piping Breakdown, CS Piping Upgrade Design, and CS Intercooler Design.

AEM CD-5 Digital Dash on Mazda 6

AEM CD-5 Digital Dash

Testing Preparation

To start, we got some new toys from AEM Electronics. The main brain of the entire testing operation for the intercooler is an AEM CD-5L digital dash with logging. This dash allows us to tap into the vehicle’s ECU to see the same information that the OEM sensors are reading. To go along with the CD-5L, we got new AEM sensors that can be positioned to get the data that we need to see how our intercoolers perform.

We used the CD-5 to datalog our dyno runs so we can see what the car is doing while simultaneously seeing power levels from the dyno. To get the data we need, we tapped into the OEM intercooler and 3 intercooler core designs that we created to get pressure and temperature data before and after the intercooler core. In case you were wondering, drilling into a brand new intercooler is stressful!

Mazda 6 on Dyno
SkyActiv-G 2.5T Intercooler Testing

Once we got everything wired up and the AEM properly set up, we were ready for testing to begin. There were multiple rounds of testing, each consisting of a string of dyno pulls back-to-back to test heat soak. We also performed standalone power runs with the intercooler setups. During testing, we used the full OEM intercooler and piping kit, and each of the CorkSport Intercoolers with the CorkSport piping. Of the three CorkSport intercoolers, we took the best setup and tested it with and without our piping kit.

Conditions were near identical for all tests, with the CS intercooler tests being ~10°F. warmer than the OEM tests (65° vs 55°).

Testing Intercooler Pressure Drop

OEM Intercooler pressure testing graph
Pressure testing the OEM intercooler.

Starting with pressure drop, the OEM intercooler performed better than we initially expected. The graph above shows the pressure drop across the core through a dyno run. In this case, the smaller the number the better. Starting at around 0.5psi at low RPM and peaking at around 2.4psi at higher RPM is pretty good for a core with fins that are fairly dense.

CorkSport Intercoolers pressure testing graph

Pressure testing the CorkSport intercooler cores.

Shown in the graph above are the CorkSport intercooler pressure drop results. Core A has the densest fins, while Core C has the least dense fins. Looking at the graph above, you can see that Core A and B had a larger drop in pressure than OEM. Meanwhile, Core C had a smaller pressure drop than the OEM core. Having a smaller pressure drop than OEM means that your turbocharger can make less boost at the turbo yet still hit the boost target in the intake manifold. In other words, your turbo is working less to make the same power levels! Based on our results, option C appears to be the best option due to the low drop in pressure, but first, we will test temperature drop to be certain.

Testing Intercooler Temperature Drop

OEM Intercooler Change in Temperature Graph
OEM Intercooler Change in Temperature from Inlet to Outlet.

The graph above shows the change in temperature from the inlet to the outlet of the OEM intercooler during a dyno run. As you can see, there is a temperature delta (the amount of heat being removed from the boost air) of approximately 100-110°F through the majority of the dyno run. Not bad for the OEM intercooler as larger the better here, but we can do better.

CorkSport Intercoolers Change in Temperature Graph

CorkSport Intercoolers Change in Temperature from Inlet to Outlet.

The graph above shows the same temperature drop data for each of the three prototype cores. Please note, the difference at the beginning of the runs is a result of using the run with the best temperature change for each core. With this comparison, larger numbers mean that the intercooler is cooling the boosted air efficiently. As you can see, the very dense cores (A and B) with a high-pressure drop, cool better. However, there are diminishing returns that come when you make a core denser. Through the meat of the dyno run, Core C has approximately 140-150°F of temperature drop, Core A has 150-180°F of temperature drop, and Core B has 140-170°F of temperature drop. This data shows that Core C cools almost as well as A and B despite having a drastically lower pressure drop. Core C is definitely our winner, but we have one last thing to test: heat soak.

Testing Intercooler Heat Soak

OEM Intercooler Heat Soak Graph
OEM Intercooler Heat Soak

The graph above shows the OEM intercooler tested for heat soak by being run on a dyno in back to back runs. The graph is showing the intercooler inlet and outlet temperatures, so the boost temperature before the intercooler and the boost temperature after the intercooler that your engine sees. Over the runs, the inlet temp increases as the engine and turbo get hot. The OEM core does a pretty good job at preventing the outlet from increasing over the pulls (heat soak), but the CorkSport core can do better.

CorkSport Intercooler Heat Soak Graph
CorkSport Intercooler Core C Heat Soak

The graph above shows the results of the same test that was performed with the CorkSport prototype Core C. The inlet temp follows a similar path of heating up drastically as the run’s progress, but the improved cooling efficiency is highlighted when you look at the outlet temps. The CorkSport intercooler core cools better and also shows less heat soak, leaving you with 20+ degree cooler temps after the same tests. During testing of the CorkSport core, ambient temps were slightly higher than the OEM test, having been done on a relatively cool day in the mid to upper 50s. If the tests had been performed at 100% identical ambient temps or overall higher ambient temps, the results would be further skewed in the CorkSport kit’s favor!

Testing Intercooler Power

Last, but certainly not least, is power. We tested back to back with the OEM setup, CS FMIC only, and then the CS FMIC with the full piping kit. With the CorkSport FMIC alone, we picked up 3WHP at peak but more importantly, 3-9WHP and 3-12WTQ from 2250-4250RPM. Seen in the graph below.

Dyograph comparison between CorkSport and Mazda Intercooler Cores
Dyno Testing OEM Intercooler and CorkSport Intercooler

With the CS intercooler and piping Kit, we picked up around 6WHP at peak compared to full OEM but even more WHP and WTQ through the midrange. For clarity, the graph below is the full CS setup vs. full OEM setup; without tuning!

Dyograph comparison between CorkSport and Mazda Intercooler setups

Dyno Testing OEM Intercooler and CorkSport Intercooler with Upgraded Piping

While these gains are decent, the intercooler and piping kit will truly shine once we are able to tune the car for different boost and load targets. In addition, we checked for changes to spool time and throttle response with the piping kit but only noticed marginal gains as we are limited by the current tune on the car. Based on our testing though, it is clear that we are increasing the efficiency of the turbocharging and the intercooling system, which future proofs your ride for further mods and tuning down the road.

Let us know if you have any questions regarding our testing, we can’t wait for you all to get these parts. Look for the CorkSport Intercooler Upgrade and CS Piping Kit coming soon, along with more fun parts for the 2.5T!

-Daniel

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Pssst. You can’t buy it yet…. Soon.

Mazda 6 Turbo Lowering Springs Release!

2018+ Mazda 6 Lowering Springs

We at CorkSport are happy to introduce the Sport Lowering Springs for 2018+ Mazda 6 equipped with the 2.5L turbocharged engine. In our last post, we talked about the height, handling, and quality of our new springs. If you haven’t seen it, check it out HERE. Today we’ll cover how we tested the ride quality and go a step further to talk about damping and natural frequency. I’m going to warn you now; this gets a little bit complicated, but we’re happy to answer any questions you may have.

Spring Damping

Let’s start with a basic example–your car hits a bump which compresses the spring. It “springs” back to its normal length. In a perfect world with no friction or damping, the springs in your suspension would keep bouncing up and down forever, this is called oscillation. Add back in dampening and friction, and the spring will settle out to its normal length pretty quickly. How different strengths of damping affect the “oscillation” can be seen in the graph below.

Spring damping graph
Spring damping example.

The car has hit the bump at the bottom left of the graph. As time goes by, you can see the spring expand and compress and so on. The Greek letter is not important but what is important is the numbers. When it is 0 (black line) the spring compresses and expands over and over to the same height. As the number increases, you can see that the spring returns to its normal length faster until it gets too large and overpowers the spring (dark blue line). For a car, the 0.4 to 1 range is ideal as there is minimal “bouncing” without having too high of damping.

What does all this mean though? Let’s say from the factory the car is in the 0.7 range (orange line). If we went to a drastically stiffer spring, but kept the OEM dampers, we may end up in the 0.2 range (light blue line), which would be uncomfortable due to all the bouncing every time you hit a bump. The CorkSport front and rear spring rates chosen are small enough of a change to fit well with the OEM damping, ensuring no bouncing.

Stock 2018 Mazda 6 and CorkSport Modified Mazda 6
Stock height vs. CorkSport Springs

Natural Frequency Analysis

To go along with this, we did some natural frequency analysis. Natural frequency simplified is how quickly the suspension responds to a bump. Higher the natural frequency, the harsher the ride in a car is. Most “regular” production cars sit in a 1.0-1.6 Hertz (Hz) range for a comfortable ride. Sports cars are usually in the 1.6-2.3Hz range. Full race cars are usually 2.3-3.0 or even higher. An average person will start thinking a ride is stiff/harsh at around 2.0-2.2Hz. Using a special app that ties into the accelerometers of a cell phone we can approximately measure the frequency of a specific suspension setup. With stock suspension on the Mazda 6 2.5T, this yielded ~1.4Hz front and ~1.7Hz rear.

With a stiffer spring, these frequencies will increase, but we wanted to be sure to only increase them slightly, to not severely affect comfort. We went through a few different combinations to get our ideal result. Our final setup ended up at ~1.5Hz front and ~1.85Hz rear. This is enough to notice the suspension feels “sportier” without riding harsh.

2018+ Mazda 6 Roller Shot

There is one other big thing to highlight with frequency. Notice that both the OEM and CorkSport springs have a higher rear natural frequency than front. If your natural frequency front to back is close to equal, the car has a tendency to “pitch” front to back over bumps. Since your rear tires hit the bump slightly later than the fronts, to have a comfortable ride the rear suspension has to “catch up” to the fronts to prevent this pitching back and forth. If a frequency is too much higher in the rear, it can be too fast for the fronts and cause the same pitching issue.

Natural frequency was always on our minds when designing the CS springs and we tested a bunch of different combinations to determine the optimum balance of ride and handling.


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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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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