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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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Testing – CorkSport External Wastegate Housing for Mazdaspeed

Turbo EWG

Why EWG?  (it’s just about awesome turbo noises)

We hear this alot as the Mazdaspeed platform continues to grow and the 450-500whp build becomes the status quo. Following up the EWG Housing Design & Details Blog about the new CorkSport EWG Housing, we want to share some testing data and differences we saw between an IWG (internal wastegate) and EWG (external wastegate) setups.  

Details about design, flow, placement, data, and feedback from our CST4 EWG Beta Tester.  

IWG vs EWG comparison on the CST4
IWG vs. EWG on the CST4

Let’s jump right in!  First up is a spring pressure comparison between the IWG and EWG housing on a CST4 turbocharger.  Let’s first define what “spring” pressure is: this is the resulting boost pressure with 0 added wastegate duty cycle.  AKA we are not trying to add boost pressure.

Immediately you can see some very obvious differences.   The IWG setup has a taper up boost curve that could be considered boost creep.  Some boost creep is ok, but an excessive amount may reach the capacity of the fuel system or other systems in the vehicle.  In this setup that is not the case, but it does show that the IWG is at its limits for boost control.

With the EWG setup you see a much different curve.  The boost builds a few hundred RPM later (due to the larger 0.82 A/R) then climbs right to the spring pressure and then settles to a consistent plateau; very predictable and controllable.  

CAD EWG and IWG Designs
CorkSport EWG and IWG Designs

Now let’s look at the design to better understand why.  On the left is the EWG turbine housing with a 0.82 A/R and on the right is the IWG turbine housing also with a 0.82 A/R (we don’t want the A/R to be a factor in this review).   

The EWG housing has a very efficient flow path for the exhaust gas to reach the EWG control valve along with a much larger path to flow.  Both of these features provide excellent flow and thus control of boost pressure.

The IWG housing uses a side port in the turbine scroll to exhaust gas.  In this setup, the exhaust gas must make an abrupt turn and pass through a much smaller port.  Both of these issues reduce boost control.

EWG and IWG Explained

Here is a diagram showing placement of an EWG in the exhaust pre-turbine.  Granted we are comparing a EWG and IWG, but the concept of flow is the same.  

Exhaust gases will always take the path of least resistance and if the turbine wheel is the easier path than the wastegate then boost control will be more difficult.  

Internal and External Wastegate performance chart
(Left) Internal Wastegate Setup | Common Issues
(Right) External Wastegate Setup | Optimized Setup
Click to Expand

This graph was shown in the last blog, but we want to show it again so you can directly compare it to the data graph below.  

Below is the boost curves for the CST5 in both IWG and EWG setup.  Alone each graph actually looks really good, but when overlaid you can see some interesting differences.  

CST5 Dyno testing with IWG and EQG setup

IWG vs. EWG on the CST5

The purple IWG graph has a crisp spool and then flat-lines at approximately 30psi with a slight fall off at 6500rpm.  The CST5 IWG setup does control boost really well, but holding the turbo back at spool up and not over-boosting or spiking was a small challenge.  An abrupt boost curve like this can make the car somewhat difficult to drive because the torque “hits” very hard and you lose traction.

The EWG setup was a bit more controllable.  Not only did the CST5 Mazdaspeed turbo spool a bit sooner, but we were able to better control the spool up boost curve so we could create a torque curve that was more friendly to the FWD traction.  This makes the car more fun to drive. Looking at the higher RPM range we were also able to hold boost more consistently to 7500rpm.

CorkSport External Wastegate

We hope you guys and gals are as excited for the EWG options for the CST4, CST5 and CST6.  They really are an awesome setup for any driving style and power goal.  

Thanks for tuning in with CorkSport Performance.

-Barett @ CorkSport

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The CorkSport CST5 is HERE!

We are happy to release the new “medium big” brother to the tried and true CST4, the new CorkSport CST5 Turbocharger for the DISI MZR engine found in the Mazdaspeed 3, Mazdaspeed 6, and Mazda CX-7 Turbo. Finding a middle ground between response and top end power is always difficult when selecting a turbo, yet we believe we have nailed it with the CST5. You get the response of a smaller turbocharger yet retain high horsepower capabilities of a big turbo.

CorkSport CST5 Turbo Front
CST5 Mazdaspeed Turbo

Before we get into power, let’s first discuss what makes the CST5 tick. It’s all started with a proven MHI journal bearing center section. These offer great cooling capabilities and fantastic reliability, especially when combined with our high performance journal bearings and 360° high performance thrust bearing. The CST5 can seriously take a beating, and does it in a package that fits perfect in the OEM location.

Stay Up-to-date with CorkSport   

CST5 Billet Compressor
CST5 Billet Compressor

Attached to this center section is a compressor and turbine wheel combo that is a little unconventional. Creating boost is a tried and true GTX71 billet compressor wheel that is rated at 56lb/min. The turbine that drives the CST5 is where things get a little interesting. Instead of a standard GT30 10 blade wheel, we chose a MHI TF06 9 blade design. This offers a number of benefits that make the CST5 outshine a comparable 3071 setup. One less blade means lighter weight for faster spool times and higher maximum flow capacity. The TF06 design is also slightly larger than a GT30, yielding a better wheel size ratio for more efficient turbocharger and engine function. For full info on the wheels and what they mean for your Mazdaspeed, check out our design blog HERE.

CST5 Turbine
CST5 Mazdaspeed Turbine

The new wheels are wrapped in new housings. On the compressor side, there is a 4” inlet that includes anti-surge ports for optimum compressor operation and longevity. This large size also maximizes efficiency for 3.5” and 4” intakes. The turbine side is where there are the most differences from the CST4. The A/R has been increased from 0.66 to 0.82 which provides more top end power to match the rest of its big turbo characteristics.

CST5 Internal Wastgate
CST5 Internal Wastegate

Now, what does all of this tech mean for you and your car? If you have a stock block you can easily max out power (~400WHP) and stay safe on your rods. Due to the bigger size, the CST5 peak torque is slightly later than the CST4, keeping you safer even before tuning is considered. Having a built block is where things really get interesting. The CST5 will make~450WHP all day on a “calm” boost level of 25-26psi. If you really want to push it though, the CST5 has made ~520WHP on ~30-31psi. This versatility allows the turbo to grow with your build. So even if you are stock block now, the CST5 can carry you even after you build your block.

The wheel and housing options delivers great response as well as great power. When pushed to its limits on a built block, 20psi was hit at 3400-3500RPM with 30psi hitting by a surprising 3700-3800RPM. Obviously this isn’t stable for a stock block but is possible on fully built cars with full bolt-ons and a high flowing head.

CST5 Dynograph Comparison
CST5 Internal Wastegate vs. External Wastegate

The versatility continues as the CST5 is offered with internal wastegate or external wastegate turbine housing options. The internal wastegate setup is the best if you want an easy drop-in fitment with great boost control. The external wastegate setup if you’re willing to take a little bit more time for fitment and spend a little bit more money on the external wastegate itself for the best in boost control. The EWG setup offers some great new sounds from a screamer pipe as well. As for power, they are very comparable, as shown in the graph above. The EWG setup makes just a tiny bit more up at the peak, but that is likely due to small variances in tuning. While only the IWG setup is offered at the time of writing, the EWG is coming very soon! Lastly, if you must have a CST5 now, don’t worry, the EWG housing will be sold separately if you want to upgrade down the road.

Both the IWG and EWG options come with a full hardware kit that includes everything you need for install. This means all coolant/oil lines, new gaskets, new crush washers, and even new studs and crimp nuts for both the turbine and downpipe flanges. The EWG setup includes a custom designed elbow for great EWG actuator fitment on Mazdaspeed 3 and Mazdaspeed 6, and the correct clamp to attach it to the housing. More info to come later on an add-on screamer pipe option.

CST5 Included Hardware Kit

CST5 Turbo Hardware Kit – Included!

Each CST5 Mazdaspeed Turbo also comes with full CorkSport support, including full-color install instructions, a 1-year warranty, and assistance with any questions you may have. We are extremely excited for you all to get your hands on the CST5 and start making even more power so please check out the product listing for full details and to place to order.

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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 that 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. The 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 harshly.

2018+ Mazda 6 Roller Shot with lowering springs

There is one other big thing to highlight with frequency. Notice that both the OEM and CorkSport lowering 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