MazdaSpeed 6 | CorkSport Mazda Performance Blog

September 26, 2019October 31, 2022

Mazdaspeed EWGs Made Easy!

We’ve talked a lot about external wastegates with our recent CST6 development but today we are happy to announce the standalone CorkSport External Wastegate Housings for the CST4 and CST5. Available right now as an update for your existing IWG CST4 or CST5, the CS EWG housings make it easy to get the best in boost control for your Mazdaspeed 3, Mazdaspeed 6, or Mazda CX-7 Turbo.

Bolton upgrade to go external wastegate with your Mazdaspeed

While the CST6 will only come with an EWG housing, the external wastegate (EWG for short) is a new concept for the CST4 and CST5. Both of these turbos originally hit the market with an internal wastegate (IWG) only option that has a small flapper valve on the inside of the turbine housing to let off excess exhaust gases. Instead, the CorkSport EWG housings use an offshoot from the turbine scroll that has a v-band flange on the end. This flange allows for the fitment of an external wastegate for improved boost control. To run an EWG on an original CST4 or CST5 previously, you needed an EWG capable exhaust manifold and some sort of block off for the IWG port.

Mazdaspeed 3 turbo internal and external wastegate housings

The new CS EWG housings make running an EWG on your Mazdaspeed3 easier than ever. Each housing comes with the elbow and clamp needed for great fitment. We even offer a dump tube/screamer pipe that works for both MS3 and MS6 as an add-on option. If you pick up the screamer pipe to go with your housing, all you need to supply is the EWG itself.

Mazdaspeed external wastegate installation kit includes everything but the Tial wastegate

We strongly recommend a Tial MV-R 44mm wastegate as all design work and testing used this specific wastegate. Other wastegates may require modification for use. The 44mm size is a great fit for the Mazdaspeed engines, whether you are running an upgraded turbo on the stock block or fully built one that you intend to push to the limits.

Tial wastegates are a proven turbo commodity for the Mazdaspeed 3

So why would you want an EWG? For starters, EWGs truly offer the best boost control setup for any turbocharged car. Because the wastegate is separate from the turbocharger itself, it is easier to place for optimum boost control, plus, the design of the actuator itself can be optimized. As a result you get a wastegate that hits boost targets more accurately and responds quicker to changes in boost. This means no more boost spikes right when the boost hits (a common problem with poor quality IWG setups), and a near-flat boost curve. The isolated actuator also makes for faster and easier spring changes should you need to service or change your wastegate preload. For more info on the design behind the CS EWG housing, check out the full blog HERE.

A direct flow path for the exhaust gas on the Mazdaspeed 3

One of the best parts of EWG over IWG is the sounds that come with a screamer pipe! While only intended for off-road use, a screamer pipe dumps the exhaust from the EWG directly to the air. This allows for a fantastic noise during a WOT pull, that sounds truly unique. It’s not all just noise though, by venting the EWG to the atmosphere instead of venting the IWG in your downpipe, you are decreasing exhaust turbulence right after the turbine wheel, reducing backpressure. On very high horsepower setups, this often generates some extra power as the turbine housing can be used more efficiently. Check out the product video below for some great EWG sounds from Barett’s MS3.

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There’s one final benefit of the CS EWG housings: housing design itself. Without having the IWG in the way to worry about, we were able to do some optimizing on the scroll and A/R. For CST4 owners, this means an increase in A/R from 0.66 to 0.82. Typically an A/R change like this will cause a slight decrease in spool time but an increase in max power potential. CST5 owners have this 0.82 A/R even with the IWG setup but there’s another benefit: greater swallowing capacity. This refers to the amount of volume in the turbine scroll. By increasing the swallowing capacity the turbine can ingest air more efficiently at the peak, which is especially important if you have an upgraded exhaust manifold or high flowing head. After all, an engine is an air pump – what good is shoving more air in if you can’t get it out?

Easy bolt up external wastegate upgrade for your Mazdaspeed 3

If you’re in the market for a change on your Mazdaspeed, check out the CorkSport EWG housings for the CST4 and CST5 turbochargers. Better boost control, a more efficient housing, and best of all, a great new sound. Be sure to check out the listing for even more images and don’t be shy to ask questions we’ll be happy to help!

February 28, 2019August 17, 2023

CST5 Mazdaspeed Turbo Spools!! Testing and Validation

We’re back on the new CorkSport turbocharger lineup again with today’s blog, this time focusing on the testing & validation of the “medium big” turbo, the CST5. Just in case you missed it, the CST4 (formerly known as the CorkSport 18G) is getting some company to go along with its new swanky name. Check out the full lineup here and the design behind the CST5 here. Now that you’ve read all that, let’s get into what you’re really here for, testing & dyno numbers.

Mazdaspeed turbo CST5 Replacement for K04 Turbo

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We started with the internal wastegate option, to validate the CST5 for drop-in fitment. Since we’ve had a great experience with the drop-in CST4, we knew how to design a turbo around the tight confines of the Mazdaspeed engine bay. The CST5 Mazdaspeed Turbo fits great in the OEM location with just a few minor revisions for proper fitment. It looks pretty good in there too if we do say so ourselves!

Mazdaspeed turbo installed with the CST5

Next the car got put on the dyno for tuning and to push the new CST5 to its limits. With a little help from our friend Will at PD Tuning, the CST5 was soon putting down some impressive numbers. We started off with a “calm” boost level of ~25psi. This netted us 450WHP and spool time which surprised us, achieving 20psi by 3500-3600RPM. Turning up the boost and pushing the turbo to its limits, we achieved 519WHP at ~30-31psi on Barett’s built GEN1 MS3. Check out the dyno graph below.

Taking the car out on the street surprised us further at just how early the car was building boost for this size of turbo. Road logs showed that we were making 20psi slightly sooner than on the dyno (3400-3500RPM) but even more surprisingly the CST5 was making 30psi by 3700-3800RPM! Obviously, this is an aggressive tune that would most likely kill a stock block, but, the CST5 Turbo can be tuned to be stock block friendly and still make good power.

Best Mazdaspeed turbo for K04 Replacement

Then came the testing on the EWG variant of the CST5. We had developed a fitment for the CST6 which meant the CST5 had no issues upon install on both Mazdaspeed 3 and Mazdaspeed 6. Next was a quick retune and some power runs. The larger swallowing capacity of the EWG housing meant some extra power at peak, yet spool was nearly unchanged. We made 525WHP at the same ~30-31psi.

Comparing the IWG and EWG turbine housings you can see a small variation in the graphs. This variation is mainly due to the change from internally waste-gated and externally waste-gated. The EWG setup provides more precise boost control through the RPM range. The EWG setup allows us to better tune the “torque spike” around 4200rpm vs the IWG setup. For peak power the IWG and EWG housings are within the margin of error which makes since because they are both 0.82 A/R housings.

Further supporting the IWG and EWG setups, both options allow you to tune the spring pressure so you can better setup your CST5 Turbo and Speed for the fuel and boost levels you want and of course the most noticeable difference is what you hear. What’s an EWG without a screamer pipe!

Wrapping up testing showed exactly what we were hoping for with the CST5: a great middle ground between the existing CST4 Turbo and the upcoming CST6 Turbo that can be used on both high-powered stock block and fully built cars. Our testing continues as this blog is written as the CST5 is being beta tested by a close friend of CS with a freshly built Dankai 2.

There’s more to come from the new CorkSport turbo lineup so stay tuned for more info on the CST5, CST6, and EWG housings.

-Daniel @ CorkSport

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February 19, 2019August 17, 2023

CST6 | Behind The CorkSport Turbo Design

A few weeks ago we discussed some of the design intent behind the CST5 turbocharger for the Mazdaspeed platform. Today, we want to follow up with the CST6. The CST5 and the CST6 both were a result of CorkSport’s desire to develop a new stock flange turbocharger that goes beyond the power limits of our FANTASTIC CST4 Turbo.

During the development of a higher power stock flange performance turbo, we found that we were asking too much of the CST4 Design. The result of our efforts is the CST5 Turbo which you can see here and the CST6 Turbo which we are about to dig into.

In this blog, we’ll dig into the wheel sizing, the CHRA, and some of the challenges we faced in the development and testing stages for the CST6.

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Compressor Wheel

The compressor wheel utilized on the CST6 is well-known and trusted, GEN1 GTX76. The GTX76 compressor is rated for 64 lb/min and is capable of boost pressures that will require a 4 bar MAP sensor upgrade. Like the CST5, the compressor housing is a 4-inch inlet with anti-surge porting.

Ball Bearing Design for the Mazdaspeed Turbo

Unlike the CST4 and CST5, the CST6 Mazdaspeed Turbo uses a completely different CHRA and bearing system, and for good reason. As the turbocharger wheel sizes increase so do the weight and potential boost pressure. This results in higher loads on the wheels, turbine shaft, and bearing system. To increase the durability and performance of the CST6, we opted to move from a conventional journal-bearing design to a more modern and robust ball-bearing design.

The ball bearing system improves durability and stability for high horsepower/high boost operation along with improved spool and transient response. Changing the CHRA did pose some new challenges, however. Ease of installation has always been a key feature with CorkSport products and that’s not lost with the CST6. The CHRA has been modified to support the use of the OE oil drain line and all necessary oil feed components and coolant components are included for seamless installation.

Turbo Compressor Wheel

Like the CST5 Turbo, we’ve put a focus on the wheel size ratio and have validated its performance. The CST6 Performance Turbo uses the Gen1 GTX76 compressor wheel paired with the Garrett GT35 turbine wheel…aka GTX3576r. This wheel combination provides us with a ratio of 1.12 which falls well within the rule of thumb discussed the in the past CST5 blog.

In testing, we found that increasing the size of the turbine wheel from a GT30 to a GT35 with the same GTX76 compressor wheel resulted in more top-end power and no penalty in spool time. This combo also provided a good power delta from the CST5 to better provide an optimal power option for the community. Since then the CST6 has proven power at 600+whp at ~34-35psi and testing will continue past 40psi.

External Wastegate

The initial testing of the CST6 Mazdaspeed turbo started with an internally wastegated turbine housing as that was the original goal with the CST5 and CST6. However, it quickly became obvious that a turbocharger of this size and power potential could not be safely controlled with an internal wastegate. The amount the wastegate port and “exhaust” or flow was not nearly adequate for proper boost control.

The boost would creep to nearly 26psi with no signs of tapering off. Nevertheless, we continue testing knowing that auxiliary fueling was necessary. Once the CST6 power and durability were validated we moved to design a turbine housing that could provide the necessary boost control and power potential.

Above is the removed CST6 internally waste-gated housing. In our testing, we pushed the turbo to nearly 600whp with 40gph of methanol auxiliary fueling. This amount of heat combined with a turbine housing that was literally being pushed to its limits resulted in a great learning experience. As you can see, the turbine housing was cracking! The GT35 turbine wheel and power was just too much.

From this discovery and analysis, we developed the EWG turbine housing with the CST6 in mind. The scroll size was increased, wall thickness increased in critical areas and the 44mm EWG port added.

With the use of the EWG turbine housing, boost control is now spot on and can easily control from spring pressure to an excess of 35+psi. Stick around as we continue to push the limits of the CST6 Mazdaspeed Turbo as we continue testing and validation of the CorkSport V2 Intake Manifold w/Port Injection.

Thanks for tuning in with CorkSport Mazda Performance.

-Barett @ CS

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February 5, 2019September 11, 2023

Inside look: CorkSport Mazdaspeed Turbo Design

The development and evolution of the CorkSport Performance CST5 and CST6 turbochargers are uniquely intertwined. We’ll be honest, we started with the goal of a single larger turbo than the CST4 in mind, but as development progressed we were not getting the exact results we wanted. We wanted fast spool & transient response, huge power, and to retain the internal wastegate system. Something had to give…we realized that we were asking too much from a single turbocharger, thus we redefined what we wanted and realized that two separate and focused turbochargers for the Mazdaspeed platform were the ideal choice.

CST5 Mazdaspeed Turbo Billet Compressor — CST5 Billet Compressor

Today we will focus on the design around the glorious CST5 Mazdaspeed Turbo, specifically the theory and design around the wheel selection for the CST5 and why it works.

CST5 Wheel Design

CST5 Turbine for the Mazdaspeed turbo — *CST5 Turbine*

The compressor wheel utilized on the CST5 is the well-known and trusted GEN1 GTX71. Compact and efficient, this compressor is rated for 56 lbs/min flow rate with a relatively high-pressure ratio threshold. Paired with a 4-inch anti-surge compressor housing and we have a very versatile and responsive compressor setup.

Now here is where the design begins to deviate from the standard path. The turbine wheel is an MHI TF06 design that is designed for high-performance applications. The TF06 turbine wheel is the key to the performance of the CST5 Mazdaspeed Turbo. Let’s see how and why below.

If you are unsure of the turbine wheel size don’t worry, that will get covered shortly. For comparison, the MHI TF06 is very similar in size to the well-known GT30, but there are a few very specific differences that affect performance.

Turbine Blades

The first and most obvious difference is the number of turbine blades; this difference has a couple of benefits. First, less weight; even a small difference in weight can make a significant difference in the spool and transient response characteristics of the turbocharger. Second, reduce flow restriction; with one less blade, the “open” area through the turbine wheel exducer is increased which increases the peak flow potential for top-end power.

Mazdaspeed Turbo Inducer & Exducer

Inducer & Exducer Comparison for the Mazdaspeed turbo and K04 — Inducer & Exducer Comparison

Next, are the less obvious differences. The GT30 has a 60mm inducer and 55mm exducer which equates to an 84trim turbine wheel vs the TF06 with a 61.5mm inducer and 54mm exducer which equates to a 77trim turbine wheel.

There are two key values to pull from this: First, the turbine wheel inducer directly relates to the peak flow of the wheel and the overall wheel size balance which we will cover next. Second, the turbine wheel trim affects the spool and response characteristics of the turbocharger. The smaller the wheels trim the faster the spool and response.

Size Matters in the Mazdaspeed Turbo

Mazdaspeed CST5 turbo Sizing — CST5 Sizing

Alright here is the most important and commonly overlooked aspect of a turbocharger. There is a rule of thumb when sizing the compressor and turbine wheels for a turbocharger.

If the turbine is too large then the turbocharger will be very “lazy” and have trouble building boost.

If the turbine is too small then the compressor may be overpowering the turbine wheel causing excessive exhaust gas buildup that can rob power even though you may be running a very high boost pressure.

So what is the right balance? From our experience in turbocharger design, development and validation along with industry professionals we have consulted there is a rule of thumb we have found when sizing the compressor and turbine wheels. The exducer of the compressor wheel should be 10-15% larger than the inducer of the turbine wheel as shown in the image above.

So why does this work? Well, let’s look back a bit first. Many think you can just install a larger and/or higher flowing compressor wheel onto the turbocharger to make more power. Now that is true to a point, but quickly the approach becomes very inefficient for the engine. Forcing more air into the engine without improving the flow out of the engine can only go so far.

Everything that goes into the engine must come out, right? Increased A/R sizing and turbine wheel sizing is the key to exhausting all the gases from the engine efficiently, and efficiency is key to making power.

With both the CST5 and CST6 Turbo development we focused on the overall performance of the engine, not just the development of a high-performance turbocharger.

Thanks for tuning in with CorkSport Mazda Performance, more to come…

-Barett @ CS

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January 24, 2019May 28, 2024

Best Mazdaspeed Turbo Upgrades – Choose Your Boost

May of 2015, CorkSport launched its first high-performance drop-in turbocharger for the Mazdaspeed platform. Fast-forward almost 4 years and CorkSport again is about to redefine what a stock flange turbocharger for the Mazdaspeed platform can indeed be.

The Best 400 WHP for the Mazdaspeed

The original “CS Turbo” is now the CST4 Mazdaspeed Turbo to follow the turbo line-up. It is the best turbo used to upgrade the OEM K04 Mazdaspeed Turbo. The CST4 took a fresh approach to “big turbo” with all the included hardware, gaskets, and, direct drop-in fitment. It removed the guesswork for a quick and easy installation, but the benefits didn’t stop there. This “little big turbo” packs a punch for its compact TD05H-18G wheels. We think it’s best for Mazdaspeed turbo to get started.

Best Mazdaspeed 3 Turbo K04 Upgrade for 400 WHP

With the CST5 and CST6 just around the horizon, it would be easy to forget about the tried and true CST4, but don’t worry this Mazdaspeed Drop-In Turbo got some new love making it one of the best turbos on the market. You will now have an EWG housing option for the CST4. You can pick it up in EWG setup from the start or if you already have a CST4 that you love, you can get the EWG housing kit to do the upgrade yourself.

Moving onto the CST5 & CST6 the possibilities for the MZR DISI have moved up significantly. What started as a single “bigger big turbo” has morphed into two “bigger big turbos” that, we feel, better provide for the various power goals of the community.

Best 500+ WHP Mazdaspeed Turbo

We present to you the CST5

CST5 is the Best 500+ WHP Mazdaspeed 3 Turbo

The CST5 Turbo bridges the gap between drop-in performance and Mazdaspeed’s big turbo power. The journal-bearing CHRA uses a hybrid TF06-GTX71 wheel setup that provides more top-end than the CST4 with minimal spool and response penalty. Upping the big turbo feel is a 4-inch anti-surge compressor inlet which will require an up-sized intake system.

Unlike the CST6, the CST5 turbo will be offered in internally waste-gated and externally waste-gated setups. This provides you with the flexibility to set up your Mazdaspeed just how you see fit and both have been proven 520+ whp on our in-house dyno and tuning courtesy of Will Dawson @ Purple Drank Tuning. This has been the best turbo to achieve 500 WHP.

The Best 600+ WHP Mazdaspeed Turbo

Now… We present to you the Stock Flange Record holder…the CST6

The CST6 redefines what the community thought was possible from the stock turbine housing flange, but first some details. The ceramic ball bearing CHRA uses a GTX3576r wheel setup that clearly outpowers the CST4 & CST5, but that’s the point remember?

The Mazdaspeed CST6 Turbo is a legit big turbo. The spool will be later, but still below 3900rpm for the full boost! However, a turbo setup is not intended for low-end response. If top-end power is your goal, the CST6 is the best turbo for your Mazaspeed and will deliver. In-house testing has pushed the CST6 to 633whp at a fuel limited ~33psi and 7900rpm redline.

Unlike the CST4 & CST5, the CST6 will only be offered in EWG setup.

Best Mazdaspeed 3 EWG For Turbos CST4, CST5, and CST6

In the coming months, we will share more information about the CorkSport Turbo Line-Up; the design, the testing, and validation of each. Check out these pages for more information about the Mazdaspeed CST5 Turbo & CST6 Turbo along with the new EWG turbine housing option. Get and boost on!

Thanks for tuning in with CorkSport Mazda Performance.

-Barett @ CS

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-Daniel @ CorkSport

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Stay up-to-date on the latest news and product updates from CorkSport.

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Compressor Wheel

Ball Bearing Design for the Mazdaspeed Turbo

Turbo Compressor Wheel

External Wastegate

Stay up-to-date on the latest news and product updates from CorkSport.

CST5 Wheel Design

Turbine Blades

Mazdaspeed Turbo Inducer & Exducer

Size Matters in the Mazdaspeed Turbo

Stay up-to-date on the latest news and product updates from CorkSport.

The Best 400 WHP for the Mazdaspeed

Best 500+ WHP Mazdaspeed Turbo

The Best 600+ WHP Mazdaspeed Turbo

Thanks for tuning in with CorkSport Mazda Performance.

Stay up-to-date on the latest news and product updates from CorkSport.