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 internally wastegated 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.
Today we will focus on the design around the glorious CST5, specifically the theory and design around the wheel selection for the CST5 and why it works.
CST5 Wheel Design
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. 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.
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.
Inducer & Exducer
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.
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 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
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 truly be.
The original “CS Turbo” is now the CST4 to follow the turbo line-up that is soon to launch. The CST4 took a fresh approach to “big turbo” with all the included hardware, gaskets, and of course direct drop-in fitment. It removed the guess work 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.
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 also. You will now have a 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.
The CST5 bridges the gap between drop-in performance and 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 4in anti-surge compressor inlet which will require an up-sized intake system.
Unlike the CST6, the CST5 will be offered in both internally waste-gated and externally waste-gated setups. This provides you with the flexibility to setup 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.
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 out powers the CST4 & CST5, but that’s point remember?
The CST6 is a legit big turbo, spool will be later, but still sub 3900rpm for full boost, however a turbo setup like the CST6 is not intended for low-end response. If top-end power is your goal, the CST6 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.
In the coming months, we will be sharing more information about the CorkSport Turbo Line-Up; the design, the testing, and validation of each. For more information about the CST5 & CST6 along with the new EWG turbine housing option, check out these sneak peek pages.
Thanks for tuning in with CorkSport Mazda Performance.
-Barett @ CS
It doesn’t take long for those building power to use up the stock K04. They are prone to fail, especially when you start shoving that extra air through it. A common question is, “My Mazdaspeed is smoking, is my turbo bad?”
First things first. There is a BIG difference between replacing a bad turbo and upgrading to a more efficient one for more power. If you want to replace it, go with OEM and just plug and play, you’re good to go, wash your hands and get on with your life. This will have your car up and running pretty quickly. However, your maximum power output will be limited and you will eventually have the same problem – the KO4 will fail.
If you are saying to yourself, “It’s time to upgrade…I NEED more power in my life!” Then this blog is for you. Below, we lay out the basics needed to successfully install a CorkSport Mazdaspeed Turbo, highlighting the required supporting modifications to keep your Mazdaspeed safe. And as an added bonus, we keep our installation instructions on each of our product pages, so you can preview how easy the install will be for your experience level.
Here it is, the list is comprised of the BARE essentials to run the 18G CorkSport turbo.
Giving you 50% more efficiency with your fueling system, as well as, a strong base to build power for your Mazdaspeed. The CorkSport Max Flow Fuel Pump Internals are built to directly replace your stock fuel pump internals and perform with immediate improvements.
ACCESSPORT (or VERSATUNE if you have a CX-7)
The Cobb Accessport will give you the basis for tuning, and since this is required with the CorkSport turbo – you’ll want to make sure you have this in hand and ready for when you install your turbo.
These are the basic foundation to our Mazdaspeeds, without these two items you cannot operate your Mazda after installing an upgraded turbo. You will need your Mazdaspeed tuned, and your tuner is going to say the same thing.
That’s it, that’s all you need to run the CorkSport Mazdaspeed turbo safely. With this proper foundation, you can put yourself in a position for efficiency, or more power.
Now the question is do you want to make it go fast and harness the power that this turbo is built for? Keep reading and we’ll provide some other awesome upgrades that are the next step once you have your turbo installed and running. Oh, and if you are looking for a proven path to make 400WHP, check out our Chasing 400 WHP Blog here!
The CorkSport turbo is rated for up to 450WHP with the right set up. Unless you are going for the MOON and shooting for over 700WHP a 3.5” intake will be more than sufficient for this turbo. Giving you some extra airflow to increase your power range, and harness what your Mazdaspeed3 is capable of. Note: Will require additional tuning!
Doesn’t matter if you go with a high flow catalyst or opt-in for one without, the choice is yours. However, if you want to utilize its flow you are going to have to upgrade to a bigger diameter. Our 80mm one does really well, plus it sounds GREAT. Note: Will require additional tuning!
It’s no secret that car engines are just big air pumps, the faster you can shove air into the engine and how fast you can expel it efficiently is what it takes to make more power. No need to run the stock 63.5mm exhaust when you can run our 80mm (like to wake up the neighbors every morning, go with our non-resonated, you can’t beat the cold start)
If your power goal is 450whp or less you can get away with just upgrading your TMIC and be on your way and they look great in your engine bay. Note: Will require additional tuning!
If you have the 2nd gen you can really utilize that hood scoop from the factory. Not only that but you can even see a noticeable performance gain with our larger hood scoop and a TMIC set up.
When it comes to your Mazdaspeed we know you want to create safe power and harness the true potential of your ride. Be sure to build upon the proper foundation and head in the right direction for your build. Our techs are available for any questions you have and are ready to assist with planning your Mazdaspeed build path! Any questions – give us a call directly – (360)260-2675, email to email@example.com or leave a comment and we’ll get back to you!
If you haven’t heard already, the CorkSport Dyno Day and Summer Event was a blast with food, friends, raffles, a Show-N-Shine, and the continuous string of dyno runs. The highlight of the dyno runs came when one of the CorkSport Engineers, Barett, put his car on the rollers. With a few minutes of warm up and anticipation building, it was finally time to see what the “CorkSport Speed” could do.
Getting past the ecstatic crowd to see the dyno screen showed an impressive 620whp/530wtq. Now, whether you were at the show or not, you may be wondering what Barett’s setup is to support these numbers. It’s not a short list but is simpler than you would expect.
In this blog, we are going to layout the WHOLE build to show you how your Mazdaspeed can make 600+whp.
The engine was built by CorkSport in preparation for setting up the Dankai Engine Program. It features Manley Connecting Rods and Platinum Pistons, head work very similar to the Dankai 2 Built Longblock, along with the CS BSD (balance shaft delete) and CorkSport Camshafts. Holding the block together are L19 head studs and ARP 2000 main studs.
To get the air in and out of the engine efficiently we have an assortment of bolt-on parts and some prototype parts because what kind of CorkSport R&D car wouldn’t have some prototype performance parts on it? To break this down in the simplest way possible we have laid out a full build list:
600hp Mazdaspeed Build List:
- CorkSport Built Engine:
- CS HPFP Internals
- Cobb Accessport
- CS Intake Manifold (Coming Soon!)
- CS 72mm Throttle Body
- CS 3.5” Intake
- CS FMIC w/Big Core
- CS GEN1 Crashbar
- CS Dual VTA BPV
- CS CBE Exhaust
- CS Prototype “Bigger” Big Turbo (Check out pics below!)
- XS Power Exhaust Manifold (Soon to be replaced with a CS Prototype Exhaust Manifold)
- Depo Racing Catless Downpipe
- Other Essentials:
Now, this isn’t the complete list, but it does lay out most of the essential parts to get your Mazdaspeed over 600whp. You might have picked out a couple “prototype” mentions in that list above…well we can share a bit on the new CorkSport Turbo. You’ve seen the power it can make…and it still has some more left in it up top, now check it out some sexy billet and massive turbine.
Lastly, none of this power would be possible without the fuel to support. As you may know already, the OE direct injection fuel system taps out around 380whp on an efficient build so how do we make another 240whp? Auxiliary fueling is the key my friends, and we recently posted a blog to help you explore Methanol Auxiliary Fueling that I invite you to read. To stay focused on Barett’s 600+whp build we have made an auxiliary fueling build list below:
Methanol Auxiliary Fueling 600hp Mazdaspeed Build List:
- AEM Boost Based Pump Controller
- Snow Performance 5 Gallon Cell Trunk Mounted w/CS Prototype Mounting Bracket
- AEM 80 micron in-line filter pre-pump
- ProMeth 220psi Pump (Essential for flowing this volume of methanol)
- Snow Performance Solenoid
- Devil’s Own 1in/4out distribution block
- 4x Devil’s Own 90degree nozzle holders
- 4x ProMeth Compact Check Valves (Essential for proper AFR control between shifts)
- 4x Devil’s Own D07 Nozzles (One per intake manifold runner; each flowing ~10gph)
Despite that this auxiliary fuel setup is providing the fuel required to support just over 600whp; it is at the ragged edge of what can be supported. Looking at the dyno graph further up you can see torque decline after 6000rpm and horsepower go flat. This is due to the auxiliary fuel system reaching its maximum fueling capacity and thus forcing us to reduce boost pressure as engine RPM goes past 6000rpm.
At this power level, true port injection auxiliary fueling is the correct step to take. Lucky for you guys and gals, we are currently exploring this path with our product R&D. We plan to give you guys and gals a full breakdown of our experience and how we built a full port injection auxiliary fuel system that can support over 600whp.
AND…I forgot to mention one very critical aspect of this entire build. Professional Tuning! This specific build was E-Tuned on the CorkSport in-house dyno by Dale Owen of Gem Tuning. E-Tuning is a great way to set up your car with the tuner that is the best suited for your platform and vehicle build because it doesn’t require the tuner and the vehicle to be in the same place at the same time.
Hang tight for more on the PI Auxiliary Fueling and thanks for tuning in with CorkSport Performance.
-Barett @ CS