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

Let’s Get Chilly: CorkSport Intercooler for SkyActiv 2.5T

It’s time to break down our design for the CorkSport Performance Intercooler Upgrade for the Mazda 6 2.5T. We have covered both the OEM intercooler and piping, and our design plan for the upcoming Sky-T intercooler piping upgrade in previous blogs, but today’s focus is the intercooler itself. Intercoolers are a delicate balancing act between size, cooling efficiency, and pressure drop so naturally things can get a little complicated. Buckle up and stay with us, and be sure to drop any questions you may have down below.

Taking a look at the stock intercooler mounted on the Mazda 6 (shown above) shows us quickly where our size constraints lie. With the large crash bar, we cannot go too much larger in height without trimming the crash bar, bumper, or both. However, there is a ton of room for added thickness and better end-tank design that can really help increase the width of the intercooler. The stock intercooler core is 24.5” wide, 5.5” tall, and 2.625” thick. Our plan is to fit a 27” wide, 6” tall, and 3.5” core without any trimming. This sizing combined with a low-pressure drop will be good for 400WHP with no issues! Because the Mazda 6 comes with just around 200WHP from the factory, this sized core provides plenty of room for upgrading down the road without causing excessive boost lag that can occur if an intercooler is simply too big. Check out a prototype CorkSport intercooler mounted on the car below.

Now that size is taken care of, let’s move on to cooling efficiency and pressure drop of the CorkSport intercooler for the SkyActiv 2.5T. These are tied closely together as getting extremely high cooling efficiency usually means high pressure drop and vice versa. Just so we’re on the same page, cooling efficiency is how well the intercooler cools off the pressurized air that passes through it. So a highly efficient intercooler will be able to bring the boost temperatures down similar to the ambient air temperature. Pressure drop is exactly what it sounds like, a loss in pressure from the inlet to the outlet of the intercooler which can be caused by a number of things: poor end-tank design, too many intercooler fins, or simply poor flow distribution in the intercooler. Too large of a pressure drop means lower boost pressures reaching your engine and/or your turbocharger working harder to achieve the same boost levels.

Pressure drop and cooling efficiency are influenced primarily by two things: fin density and end-tank design. Fin density is basically how many fins the boosted air must pass over when traversing the intercooler. More fins = better cooling efficiency, but also more pressure drop. To choose the best core for the SkyActiv 2.5T we plan to use multiple different fin densities and test each for power, cooling efficiency, and pressure drop. While we can get pretty close based on our work from the CS Mazdaspeed Intercoolers, it’s always best to test and identify the best one for each platform. With this extensive testing, we can reach our goal of improved cooling efficiency, lower pressure drop, more power, and no CELs.

End-tank design is critical as it determines how the air reaches the core of the intercooler. Sharp bends, poor air distribution, and small inlet/outlet size all adversely affect the performance of the intercooler. To fit the core size we want, we had to do away with the plastic inlet and outlet pipes of the stock intercooler. This was advantageous as it gave us more room to have a smooth flowing end-tank that distributes air well to all the runners and does away with the sharp corners present in the OEM end-tanks. In addition, we were able to increase the inlet and outlet size of the intercooler to 2.5”. This is a fairly standard size that has shown to work well for the Mazdaspeeds with stock power and without choking flow way up to Barett’s 600+ WHP.

Those of you with a keen eye have realized that the connection between the CorkSport front mount intercooler (FMIC) and the OEM Intercooler is not the same. As shown in the CAD rendering above, each intercooler kit will come with the silicone and custom adapters that are needed to work with the OEM piping. If you decide to upgrade to the CS intercooler piping kit, later on, the CorkSport Intercooler for SkyActiv 2.5T will not need to be removed, and you will only need to change some silicone parts.

We will have more info on this kit coming soon, with the next blog covering our testing of the different core designs using a few new toys from AEM Electronics. Be sure to check out the product listing for more info, and to be notified when the intercooler is available. Last but not least, CX-9 Turbo and CX-5 Turbo owners, we are 99% sure this kit will also work on your rides but we plan on validating fitment before release!

-Daniel @ CorkSport

Mazda’s Dynamic Pressure Turbo – An Introduction

The SkyActiv 2.5T has been around for a few years in the CX-9 however, things started to get interesting when the engine was dropped in the Mazda 6 for 2018. While lacking a manual and not a true Mazdaspeed, it’s a step in the right direction for the enthusiast. With one of the new Mazda 6s in the CorkSport garage, we’ve been getting curious about where all of that 310lb-ft comes from. Well we decided to call up Mazda and purchase a turbo to see how it all works.

There’s a lot to take in on the turbocharger and there are quite a few things that have changed from the K04 that made its home in the Speeds.

For starters, this turbocharger is pretty big. The wheels themselves are not large, with the compressor wheel very close in size to the old K04 & the turbine wheel only slightly larger than the K04. However, with the dual inlet turbine housing, 90° compressor outlet, and lots of attached electronics, the whole package takes up a lot of room in your engine bay.

The turbine housing is not far from the old K04. A large five-bolt inlet flange has two rectangular inlets to work with the dynamic pressure system (more on that later) and even a port where the EGR system sources its exhaust gases. The outlet is much simpler, using a five-bolt flange to mount to the downpipe, yet does house a surprisingly large wastegate port.

From a performance standpoint, the large wastegate should help eliminate boost creep but the turbine housing will likely need a larger scroll to get some more serious power out of the engine.

The compressor side is packed full of features. As usual, the wastegate actuator bolts to the compressor housing, however, Mazda has switched to an electric actuator. Interestingly, the bypass valve is also electric and is even mounted to the face of the compressor housing.

Some fancy casting design leaves a pathway between the high and low-pressure sides of the compressor and lets the BPV decide when the passage is open or closed. These two electric actuators will mean easy and consistent boost control. The final plastic component on the housing we believe is a boost assisted vacuum source for the vehicle. Finally, the inlet is a typical clamp connection while the outlet uses a 90° turn and two-bolt flange for better accessibility around the wastegate actuator.

With the housings removed, the CHRA of the dynamic pressure turbo is very simple & standard. Oil feed in the top, two-bolt oil drain in the bottom, and standard crossflow engine coolant ports. The compressor wheel is a cast 6×6 unit and turbine wheel is a basic 11 blade unit.

We are looking forward to waking up the Sky-T in the coming months and making the 2018+ MZ6 into something a little closer to a Speed. Stayed tuned, there’s much more fun to be had from the 2.5T!

-Daniel

Mazda Hybrid?

Mazda 3 Hybrid??

I was looking at the Mazda Japan website the other day and noticed that there is now an option for a Mazda 3 gasoline hybrid listed.  Years ago Mazda announced that they were working with Toyota hybrid tech and this looks to be the result.

There isn’t a lot of detail listed with the description of the model so I decided to do a comparison of the Mazda 3 against the current model year of Prius as the 2 vehicles are most likely running the same hybrid drive setup.

Price:  With the current exchange rate the Mazda 3 hybrid is ~$23500 which is almost the same as the current Prius price shown of ~$23475.  You get more car with the Mazda 3 for the price and a car which handles like a car should. Win here for the Mazda.

Styling:  Right away I can tell you I prefer the styling of the Mazda 3 over the Batmobile inspired Prius which looks like someone used a late 50s Chevy and applied the styling.  

Fuel Economy: This one is the funniest thing and really shows where Mazda’s engine tech is beating all of the other manufacturers.  Toyota Prius 1.8 hybrid gets 56mpg in combined city/highway. Mazda 3 2.0 hybrid gets 63mpg. Caveat on this data, I took the economy listed on the Japanese page and converted it to MPG so they are not based on the same drive cycles.

If your Japanese skills are on point check out the landing page for the 2018 Mazda 3 Hybrid yourself here.  Just a note google translate won’t let you convert the page due to SSL from Mazda’s page.

So you are asking why do I care about a hybrid and in all honesty I probably won’t own one myself but if it does happen I prefer to at least own one that handles worth a crap and has decent driving dynamics.  I can’t say I have ever heard anyone raving about how good the chassis is in a Prius.

 

-Derrick

*Pricing reflects the current price at the time of writing

New “Mazdaspeed” Finally Coming Down the Pipeline

In case you haven’t heard, Mazda officially announced on November 15th that they are bringing the turbocharged 2.5L CX-9 engine to the Mazda 6.

Now, this announcement did not come with a huge amount of information, but it got everyone here at CorkSport all sorts of stirred up. This fantastic news comes coupled with a new facelift, better quality interior, and a few extra options. Check out the teaser shot down below, in my opinion the CX-5 grill looks great on the 6.

While we do not know if this new turbocharged Mazda 6 will carry the Mazdaspeed badge, we do know it will sure feel like a Mazdaspeed.

The SkyActiv-G 2.5T produces 250hp and 310lb-ft while on premium fuel. That power and torque are more than enough to move around the big CX-9 so it will definitely be interesting in the Mazda 6 that weighs almost 1000lbs less. Two more factors remain for the new 6 to truly be a Mazdaspeed6: manual transmission and AWD.

Since the CX-9 and Mazda6 are based on the same platform and have similar chassis, carrying over the AWD system with the engine is a distinct possibility. Plus, Mazda already offers the 6 in AWD in the European and Japanese Markets. The big question remaining then is the manual transmission. While the manual mode on the CX-9 automatic is nice, it is just not the same as a full-bore manual gearbox. It’s not looking too good as the CX-9 only comes in auto and the teaser images just show an automatic but hopefully Mazda can surprise us with a manual transmission.

Since this 2.5T has been in the CX-9 for a few years now we at CorkSport have had a few opportunities to check out the engine, see how it’s packaged, and look for potential performance gains.

What follows are simply observations that we have made, don’t get too excited (yet):

  • The turbo inlet pipe gets quite small on its route from the airbox to the turbo. Enlarging this would definitely help the turbo breathe better.
  • The exhaust is fairly restrictive at about 2 3/8”.
  • There is a good amount of space where the turbo lives for a high-flow downpipe and even turbo upgrades.

Additionally, this engine was designed to fit in the same compartment as the naturally aspirated 2.5L so we may even get some Mazda 3 love down the road if the SkyActiv-X doesn’t steal every engine bay.

This new Mazda 6 may be coming sooner than you expect.

All Mazda models have gotten a 2018 model year, except the Mazda 6 which is currently at 2017.5 and the Miata that’s stuck all the way back in 2017. Hopefully this means the 2018 model year Mazda 6 has the turbo option. Maybe Mazda is even planning a 2018 Miata update but only time will tell.

Look for more info on the new “Mazdaspeed” 6 during its full unveiling at the L.A. Auto Show on November 29th. We’re just as excited as all of you and to be honest, if a manual option gets announced, one will likely find its way into the garage. Stay tuned to the CorkSport Blog, Instagram, and Facebook to make sure you don’t miss anything!