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 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
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…
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.
Designing For Efficiency
In this image, we want to direct your attention to a very unique and troubling design feature of the OEM exhaust manifold. There is a right way and 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!
Before we wrap here we do have one good thing to say about the EOM 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.
-Barett @ CS
Mazdaspeed 3 Exhaust Manifold Break Down July 9th, 2019CorkSport
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.
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!
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.
The SkyActiv-G Race Header Adds Power
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!
For the last four years, we’ve been asked countless times if the CST4 is a direct replacement for the OEM K04. With the number of cars experiencing their 2nd, 3rd or even 4th owner, this question is being asked more frequently. While CorkSport’s intent is to freely share information across the Mazda community, we cannot be everywhere all at once, and we will most likely miss the exact moment the debate explodes on your favorite Facebook page. For that reason…
Today, we’re setting the record straight: The CST4 is a drop-in UPGRADE from the ground up, and by no means is it an apples to apples comparison with the asthmatic K04.
How Does It Work?
Before we dive into the dirty details, you might be craving more details on how a turbo works? You are in luck! Check out our white paper on the CST4 and what makes up the anatomy of a turbocharger, bone up on the importance of a “bolt-on” vs a “drop-in” turbocharger, learn the difference between an internal vs external wastegate and finally why the turbine wheel design/materials make a difference. Now let’s get back to what this means for the CST4 and K04.
Is The CST4 Reliable?
The CST4 continues to prove itself as one of the best bolt-on options coupled with the needed reliability to withstand the additional demands of chasing 400 WHP – something the KO4 cannot accomplish. This is due to an upgraded center housing rotating assembly (CHRA) which has a larger center shaft and larger bearings than the OEM turbo. The CorkSport turbo also sports a performance journal bearing with a full 360° thrust collar, which is what allows the turbine shaft and compressor to spin freely. The OEM K04 turbo comes standard with a limited 270° thrust collar.
Does The CST4 Have Increased Airflow Over The K04?
Next comes wheels, which is where the CST4 really shines. Shown in the image above, we have the CST4 on the left and the OEM K04 on the right. The CST4 is 12% larger on the compressor inducer, and 21% larger on the exducer than the OEM K04. Combined with the use of a taller wheel (green line), every revolution of the CST4 not only brings in a greater quantity of air into the compressor, but has a higher airflow capacity, thus moving a greater volume of air. For those of you that need a few more key specific numbers; The OEM K04 uses a 45mm inducer; 56.25mm exducer cast compressor wheel, while the CST4 uses a 50.5mm inducer and 68.1mm exducer forged billet compressor wheel.
On the turbine side, the OEM K04 uses a 50.1mm inducer and a 44.5mm exducer 12-blade cast wheel. The CST4 uses a 56.2mm inducer and 49mm exducer high-flow 9-blade design. Again, the CST4 outshines the K04 with the turbine inducer being 12% larger and the exducer 10% larger. The 9-blade design has two key benefits: more peak exhaust flow as there is less material in the way of flow, and 21% lighter for a faster spool time.
The final component is the compressor and turbine housings. The K04 uses restrictive housings that cannot keep up at higher RPMs, and especially at higher boost levels. You can feel this as your stock turbo “runs out of steam” up above ~5200RPM. The CST4 housings may fit exactly in the OEM locations and use the OEM hook up points but that is where the similarities end.
Both the compressor and turbine housings were increased in size, increased in A/R, and optimized for the stock inlet and outlet sizes to provide better top end capabilities. The compressor ended up at a 0.53 A/R while the turbine ended up at a 0.66 A/R. This combo of housing and wheels keeps power all the way to redline, and in initial testing showed a 50WHP gain at the same boost pressure.
How Much Power Does The CST4 Make?
So what does all of this mean in terms of power? We’ve seen the OEM K04 pushed way out of its comfort zone and make in the 350-360WHP range with the right supporting mods. This is far out of the efficiency range of the little K04, and it’s a ticking time bomb when running at this power level. The CST4, on the other hand, is perfectly happy running in the 400WHP range all day, again, with the right supporting mods. We’ve even seen it pushed to its limit in the 450-460 range.
For those of you more interested in boost pressures, the K04 can hit a max of ~24-25psi in the midrange before it’s out of its efficiency range and starts producing just heat. At redline, the K04 is typically at a max of about 17-18psi. What you feel as your car seems to stop accelerating after ~5200RPM on the stock turbo. The CST4 does a lot better, hitting a max of ~29-30psi in the midrange but carries the high pressure into higher RPMs, with peak boost pressure at redline of ~26-27psi. This keeps you pushed into your seat with a smile on your face!
How Quickly Does The CST4 Spool?
We get a lot of questions on how fast this turbo spools, so let’s take a moment to discuss both. The OEM K04 spools very quickly since its housings and wheels are so small. If tuned incorrectly it can spool almost instantly and kill blocks with an extremely low-RPM torque spike. The CST4 also spools quick, making full boost by approximately 3300RPM on most cars. The big difference is that the CST4 carries power out to redline instead of falling off as the K04 does. To be clear, you still have to be careful with the CST4 as it too can kill a stock block with too aggressive of a tune.
Is The CST4 A Drop-In?
So bringing things full circle, the “drop-in” aspect of the CST4 means you can run it with almost no other supporting parts, only a HPFP upgrade, access port, and a tune are required. It also means that it hooks up directly to the OEM inlet and outlet flanges so that there is no excessive modification required to make the turbo fit. We even include new studs, lock nuts, gaskets, a custom upper coolant line, new coolant and oil crush washers, and the correct oil feed banjo bolt so there is no hassle of finding replacement hardware, gaskets, or lines to make your turbo function. We do strongly recommend picking up a CorkSport EBCS to best control boost on your CST4. We have also found that the stock intake size will be maxed out at around 18-19psi on the CST4. To get more power from there, a 3 inch or 3.5-inch intake will be needed.
By no means is the CST4 a K04 though as it’s larger and has much higher horsepower capabilities. For those of you more familiar with Garett turbos, the CST4 is just a smidge bigger than a GTX2867.
If you want even more info on what makes the CST4 tick be sure to check out the white paper on the subject HERE. As a final afterthought, remember that the CST4 is getting an EWG housing option in the coming months, for added features (and noise!) that just don’t come with the K04. Stay tuned for that, and be sure to ask any questions you may have.
CorkSport CST4 vs. OEM K04 July 10th, 2019CorkSport
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.
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!
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
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.
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
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.
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
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.
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.
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!
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!
SkyActiv-G 2.5T Intercooler & Piping Testing May 23rd, 2019CorkSport
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.
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.
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.
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.
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.
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 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.
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
Testing – CorkSport External Wastegate Housing for Mazdaspeed May 13th, 2019Kate Fischer
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