CorkSport is happy to announce touring car availability for those people/teams who want a fun-to-drive and great-looking race/track-focused Mazda 3! The goal of the build was to make a competitive and reliable TC race car and get Mazda back into multi-make competition, which goes back to the Speed Vision and World Challenge days of the early 2000s.
For the 2024 season CorkSport has been validating the design work and lessons learned racing the CorkSport Mazda 3 TC in the SRO TC America TC class. We had multiple podium finishes and ran at the front proving the competitiveness of the Mazda platform against the Hyundai, Honda, and Mini TC class cars.
The base of the build is the Mazda 2.5 Skyactiv engine with a CorkSport bespoke turbo kit developing well over 300 wheel hp in TC trim. The TC car engine management is handled by a Motec M1 ECU, in conjunction with a Bosch Motorsports LC2 wideband controller, and a Motec C125 dash/logger.
The 6 speed Mazda gearbox is equipped with a clutch type LSD and upgraded 3-4 gears with a transmission cooler, while the clutch is an off the shelf X-Clutch single disc clutch/flywheel combo.
Penske shocks/Swift springs, CorkSport upper mounts, and upgraded suspension pick-up points handle road racing while allowing for accurate suspension settings.
Braking is handled by a 364x32mm 6 piston CorkSport race brake kit which uses floating front rotors paired with upgraded rear pads and brakelines on OEM calipers. The brakes are covered with 18×10 Enkei lightweight RPF1 wheels.
To top off the build is the widebody kit which includes, front bumper, splitter, front and rear fenders, side skirts, rear bumper and TCr spec rear wing.
SRO Circuit of the Americas 2024
There is limited availability for the start of the 2025 race season. Currently 2 cars are left for delivery early 2025 for the 2025 TC America race season.
A few years back, I had grand plans of going Spec Miata (SM) racing with a good friend in southern California during the winter months, intent on improving my on-track driving and racecraft overall. After the 1st event, things changed as my friend passed away.
My SM was only raced a few times during 2022 season, but after that, it was parked along with its fellow spec Miatas.
I brought the car back home in December 2023 along with an additional spec Miata on the trailer – with the intention of racing this year. I finally got the car out of the trailer to start cleaning it up and making sure it was solid to race.
Besides cleaning the car inside and out, and ensuring all its safety parts were still good, the car was pretty much ready to go. The biggest challenge was cleaning up from the cheese bois, which made the trunk a party house for a while.
I had several sets of Toyo RR tires that had been purchased back with the grand plans that were made in 2021. They had been sitting in a trailer since then and baking in the California sun. I chose a few that looked like they may still be soft and signed up for the race weekend.
The Friday test day, gave me a few chances to remember how to drive this car fast, as it had been more than five years since I raced an SM at Portland Intl Raceway. I double-checked the alignment settings and headed off to my weekend racing adventure.
Test lap times were pretty slow compared to what I needed for the PNW Spec Miata Tour. I was turning 1:35 lap times, and if you want to be in the top ten, low 1:32s or better were going to be needed to get there. I focused on cleaning up the exits to turn 7 and 12, which lead onto the straights, as these were the sections of the track I was losing time according to my lap timer.
After consulting a few friends about the tire pressure settings and how to close up the gap, I headed out Saturday morning in qualifying to see what I could do. After dealing with a bit of traffic, I got some breaks from people who let me through, and I hit a 1:32.595, which I felt was about as good as I was going to get, so I called it quits for the sessions.
After a quick driver’s meeting and 30 minutes doing a nut and bolt check, I was ready for the afternoon race, which is a 25-minute affair. I have been racing for ~13 years now, and it is fun how you still get the butterflies heading around the last corner in double formation for the start heading for the green flag.
The starts at PIR, as always, are pretty wild mid-pack, and everyone is trying to get an edge on everyone else around you. I made it through the first corner without hitting or getting hit and proceeded close up on the car in front of me as much as possible.
During the race, I noticed that the car felt a little numb on feedback, and I found myself waiting for my Miata to respond to inputs. Waiting is relative, as I am talking about milliseconds, which seems like forever when racing cars. There were plenty of spots swapped, people spinning off the track, and great race action!
I started in 13th, and by keeping it clean and on track, I made it up to 11th place when the check flew. My goal was to be in the top 10, so I was pretty happy that I ended up 11 out of the 32 cars that had signed up for the weekend.
I also improved my fastest race lap, which means I would start higher up the field. I wasn’t the only one who was faster, so starting on Sunday for race #2, I was in 18th, and it was all downhill from there…
Race 2 TL;DR
I spun a few times and lost one spot overall during the race. Long version, the “wait” for the front end to turn was getting worse as the race progressed. There wasn’t a lot I could do with that so it was a race full of trying to drive around my problem by braking in different areas and turning in early to try to hit the apex and marks to make the corners.
Race 3
I got to start in 18th place again, as no one made up any more time/places in order to change the starting position in the middle of the field. The start went okay, and I didn’t make up or lose any spots as the field sorted itself out.
Lap 4 I went up the inside of another driver into turn 4 and lifted as I felt the car start to slide out. This was the wrong thing to do as it upset the chassis as I was ½ on a curb and ½ on the track, so around I went off into the grass. I felt a little boop from the other driver I was passing as he bailed out. I got stopped before the tire wall and headed back on the track now in 24th position. I was able to get a pass on another car and get back to the 23rd position, but I was really struggling to get the car to bite on the front-end grip.
Lap 13, heading into turn 1, aka the chicane, the car pitched more into the corner than I expected, and I looped it. I got going again and in turn 4 the car cut out briefly which means I was running out of gas. I limped it back into the paddock and called it a day.
I made sure to go talk to the other driver, which I failed to execute the pass on, and apologized for dragging us both off into the grass. He was pretty cool about it, but his wife gave me the stank eye the whole time. There is not much you can do but go say sorry, and he was happy with that. I would be if I were in the same position.
The fuel calculation miss was all on me. You usually run a specific amount of fuel per lap and toss in some extra for wiggle room. I did not put any wiggle room in the SM, so I ran out.
The front-end grip problem was due to the tires. When you usually get off track, you can feel the heat from the wheels and tires. After many sessions, you can barely touch the wheel because the heat is being transferred from the brakes to the wheels and the tires. The tires are normally very warm/hot to the touch after coming off the track. The Toyos were barely warm, which means they were not hitting the operating temperature, which is needed to generate maximum grip and allow me to do what I wanted to with the car.
The picture above of the left front tire from the car after 3 test sessions, a qualifier, and 3 races looks like it has been out for a warm-up only. The left front tire takes all the abuse at Portland, so it should show signs of heavy wear. The racing season is over for the Northwest, so I will be sure to get some newer tires on the car next season.
Want to race Spec Miata with the rest of the NW people? The PNW Spec Miata tour page is NWmiata.com. Shout out to A-Aron for hanging out and watching me spin off the track and having a good time doing race car stuff.
Welcome to part 5 of the Mazdaspeed3 AWD Swap (sorry for the delay; things got really busy for a bit)! This blog covers the rear-end drivetrain and the huge modification that makes it all work.
There are a lot of images and explanations of those images so you can see and understand the differences between the Mazdaspeed 6 and CX7 rear drivetrain.
What is the Rear Differential
Jumping right into it, let’s identify what the rear differential is. The rear differential transfers power from the transfer case via a PTO/driveshaft, through the ring and pinion, out to the axles, and then to the wheels and tires.
CX-7 vs Mazdaspeed Differential Comparison
However, as with many modern AWD systems in compact cars, there is a clutch mechanism between the PTO/driveshaft and the differential. This clutch mechanism controls the percentage of engine torque transferred to the rear tires.
In the diagram below, we’ve identified the two major sections of the differential assembly. The line demonstrates the connection point between the two sections. The rear section is the gear housing, and the front is the clutch housing.
Now that you understand the differential assembly. Let’s identify the difference between Mazdaspeed 6 and CX7. There are two major differences.
Differences In Differential
The first difference is the clutch housing mounting points for the front subframe mounting brackets. In the image below, you will see two mounting points with threaded holes on the right side of the differential, while the other differential does not have those mounting points.
The CX7 differential is on the left, and the Speed 6 is on the right. The CX7 on the left)has TWO front mounting points whereas, the Speed 6 only has a ONE mount. While this may not be a big deal for a daily driver with modest power levels, it’s a huge advantage for a racecar with nearly 900whp.
Left to Right: CX-7 and Mazdaspeed Differential
Moving to the inside of the gear housings, the CX7 uses an open differential setup, vs the Mazdaspeed 6, uses a Mazda proprietary LSD (limited slip differential). The LSD is more desirable because it will provide better power distribution to both rear tires vs the open differential.
Fun Fact: the Mazda-developed LSD uses “friction cone washers” sandwiched between the spider gears and differential carrier housing to create the limited slip effect. As load is applied through the spider gears, the increased load presses the spider gears against the friction washer, which makes this a very street-friendly and progressive type of LSD. Check it out below.
Mazdaspeed limited slip differential
So here we are at a point where we need to use the CX7 differential because it has the ideal two-mounting front section, and we have a CX7 subframe, so…duh, but we want the rear LSD for better power distribution.
Time to split these differentials in half and see if we can swap things around.
Rear Differential Separated
Splitting them in half to separate the clutch housing and gear housing, we can see a splined connection that interlocks the two halves.
Mazdaspeed 6 Rear Differential Gear Housing
On the gear housing side, the pinion gears are retained by an internal nut, which is good because splitting the assemblies did not affect the pre-load on the bearings.
Mazdaspeed 6 Rear Differential Clutch Housing
Let’s look at the clutch housing side. The clutch pack is retained by the external nut on the driveshaft flange; again, splitting the assemblies did not affect any bearing pre-load.
Things are looking great! And with that, we assembled the CX7 clutch housings with the Speed6 gear housings without issues!
Now to review: if you are doing this swap, you will NEED a CX7 rear differential assembly, but you DO NOT NEED a speed6 rear differential assembly. We only did that to learn and to get the LSD. You can use the CX7 as is because the gear ratio is the same, and the LSD is not required.
Next up are the suspension trailing arms; when using the OEM Speed3 suspension, the trailing arms need to be modified to use the OEM CX7 wheel bearings.
Modifying the Trail Arms of the Mazdaspeed
Mazdaspeed 3 Trailing Arm Plate
The OEM trailing arm has a beefy steel plate welded to the stamped steel structure. While the bolt and center holes look correct, they are slightly different in bore and location.
Mazdaspeed Trailing Arm
To make the Mazdaspeed 3 trailing arm work, modification was needed via welding the original bolt holes shut and then redrilling the holes in the correct bolt pattern for the CX7 wheel bearing. Along with that, the center bore diameter had to be increased slightly as well.
New Welded Holes for the MazdaspeedFitment of the Rear Trailing Arms & CX7 Wheel Bearing
Modifying the rear trailing arms is only 1 of 3 major fabrication projects needed for the AWD swap. The others are building a Rear Motor Mount (which I designed a badass billet one for) and the center driveshaft mounting plate which I also designed.
Now, with the trailing arms and wheel bearings in place, we can finally figure out the rear axle lengths. Checking both the Speed 6 and CX7 rear OEM axles, I found they use the same wheel bearing and differential inputs, which is great. However, The lengths are not the same.
Unfortunately, in test fitting the Speed 6 and CX7, we found that both needed to be shorter for the Speed 3 application. With that fact, the cost is a lot more expensive for anyone swapping because of the needed custom rear axles.
I was personally going to get custom rear axles either way due to the power levels and use of the Halfmilespeed3, but it’s not a requirement.
700WHP Rated Custom Rear Axles
Fast forward many weeks, and we have a set of custom-length 700WHP-rated rear axles to compliment the front DSS 5.9 axles.
All bolted in and looking great! While doing this I learned a few things and realized that one of my assumptions was wrong.
The front axles work and don’t work from the MS3. The driver front MS3 axles will interface perfectly with the Mazdaspeed6 transmission. However, the inboard CV housing/spline section for the passenger side front will need to be replaced/modified to work with the speed6 intermediate shaft.
The rear ABS sensor for the Mazdaspeed3 will not work with a Speed6-style ABS trigger wheel. They use a much different and more modern magnetic trigger wheel incorporated in the rear ABS sensor for the Mazdaspeed3 will not work with a Speed6-style ABS trigger wheel. They use a much different and more modern magnetic trigger wheel incorporated inside the wheel bearings…which we don’t have when using the CX7 wheel bearings. This has led me to develop custom ABS trigger wheels to work with the OEM Mazdaspeed 3 sensor. More on that later.
Alright, that wraps up the rear drivetrain setup. There are plenty more huge milestones to overcome, which are coming up in this multi-part blog series!
I hope you are enjoying this series about the Mazdaspeed 3 AWD Swap. Stay tuned for more blogs to come!
We (CorkSport) showed off our work-in-progress TC America TC Class Mazda 3 race car at the CorkSport Mazda Showdown event on August 5th. If you are asking yourself why this is a big deal and why I am reading a blog post about it, here’s the explanation.
On October 1st, 2019, Mazda announced they would join the TCR ranks with the car attending the 2020 season opener at Daytona with IMSA. The bodywork was excellent; it captured the body lines and presented an absolute WOW factor!
Unfortunately, the car was a no-show at the first round or any round scheduled in 2020. On August 15th, Emily Taylor from Mazda announced they had canceled the TCR program, citing the coronavirus as the explanation.
What About The Body Kit?
So what happened to everything from Mazda’s race program, and why is the bodywork a big deal? There were two sets of original molds made for the bodywork. The 1st set of molds went to the constructor Long Road Racing, and the second set sat at Mazda’s design center in Irvine, California.
The molds in Irvine were the first set made off of TCR “Show Car” bodywork and were not production-ready. The “Show Car” Mazda used for their 2019 announcement and future marketing campaigns wasn’t an actual race car. It was a production car with the bodywork on it, but the engine & drivetrain was stock.
CorkSport has been racing a 3rd generation Mazda 3 in the TC class for several years as the development tool for the Skyactiv Turbo kit we offer.
When running in a professional series, the series works with manufacturers and wants the newest models competing on the track to keep the series fresh and relevant for marketing for both the auto manufacturer and the race series. The last 3rd Gen Mazda rolled off the production line in early 2018, making our race car over a year old when the TCR program was announced and over two years old when the program was canceled.
We needed to race the 4th Gen Mazda 3s to keep competing in TC America,
The Journey For the Mazda 3 TCR Kit
This may seem like an exaggeration, but I spent over 200 hours on the phone, in meetings, writing emails, and talking with employees, ex-employees, and contractors that Mazda used to chase down where the bodywork went, who was ultimately in charge of it, and to see if we could get our hands on it.
Once I knew the molds still existed, additional meetings, phone calls, and emails were required before signing an, “OK, we will consider it. Your plan and history jive with a company (CorkSport) that can use the parts and provides a benefit to Mazda.” type of agreement. During this time, I learned the first set of molds had been destroyed, making the motorsports molds the only set left.
In October 2022, snagging the TCR bodywork molds became a strong possibility. I was headed to Texas to drop off some racing equipment to a friend. I decided to leave my truck and trailer in Texas since the bodywork molds were now located on the East Coast. If Mazda agreed we could pick up the molds in the next few months, the truck and trailer would already be halfway there.
December 12th, 2022, Mazda gave me the green light to gain access to the molds after several more phone calls, ZOOM meetings, and agreements were made. I flew back to Texas and headed to Multimatic in Mooresville, NC, to complete this epic quest. After one very long drive, including a massive ice storm, and making it home on Christmas Eve, Mazda’s TCR molds were at CorkSport.
Since then we have been planning and slowly building the new TC Car – We cannot thank Mazda Motorsports enough for choosing to partner with us as we continue to shape our racing program!
The body kit is thick and the ride height was not adjusted prior to the reveal .Rear wing is not to racing spec and was added temporarily to represent what it might look like in the future – rear window will eventually be plexiglass.
Are These The Real Thing?
A common question that will get asked is, “I have seen the Mazda 3 TCR kit overseas, how is what you have the real thing?” Well, my friends, Technology and replication are a wonderful thing.
I asked the same question about the hill climb machine that TCP put together for Mike. If you compare the kits, you can see there are some differences in the kits with the aero, brake cooling, grill area, and more.
It was unofficially stated there were body scans done of the show car with Mazda Japan and those are the results. I cannot speak about the Thailand car but a handheld scanner and some import auto salon are my best guess.
Look forward to more updates on our build over the next several months, This is going to be fun!
Welcome to part 4 of the Mazdaspeed3 AWD Swap! If you missed the previous posts, you can catch the Intro, (Part 2), and Part 3. This blog will cover the rear suspension design, specifically the rocker arms, and how we came to the size, shape, and overall design. This will get technical with numbers, angles, and CAD models.
Before we get into the technical jargon, let’s cover the “what” with rocker arm suspension.
Mazdaspeed 3 AWD Swap Rocker Arm Suspension
Let’s break down this diagram as it is 100% not OEM for the Mazdaspeed 3:
Rocker Arm: This is the keystone of the suspension design and does all the work. The rocker arm connects the push rod and the damper to transfer suspension force at a different angle. The rocker arms can also go by a few names: rocker arm, bell crank, cantilever, and pivot arm, to name a few.
Push Rod: This is a simple rod with spherical rod ends on each end. This connects the OEM suspension to the rocker arm. The push rod is in a similar location as the OEM suspension.
Suspension Mounting Bracket: This is the mounting point for the push rod to the OEM suspension trailing arm. This must be added because the OEM damper mount is below the now-new axle shaft.
Coilover/Damper: This is an off-the-shelf damper that can have a coil spring installed on it. It features independent rebound and compression damping adjustability.
Cross Member: This is the cross member that is welded between the chassis shock towers in the car to support the new rocker arm suspension.
Here you can see the design tack welded in the car. This should help you understand how the design fits and is used in the car itself.
Mazdaspeed AWD Suspension Corss Member TackedMazdaspeed AWD Suspension Push Rod Mount
Now that we have a basic understanding of this rocker arm-style suspension let’s get into some more details!
First, let’s talk about suspension and the forces they deal with. Gravity pushes you and your car down to the ground, and road imperfections (bumps, potholes, unlevel surfaces) try to push you and your car up/down/all around while driving. If vehicles did not have suspension and instead the wheels were rigidly attached to the vehicle chassis, we would have all sorts of issues. Comfort, control, and tractions are the big concerns, amongst many others.
The suspension’s job is to soak up and move with many road imperfections like bumps, potholes, and unlevel surfaces. Every time your tire goes over a bump or pothole, it moves up or down, resulting in a force transferred into the suspension.
Check out this quick illustration to see the rocker arm suspension in motion:
As the tire moves up/down, you can see that the rocker arm pivots and transfers that motion into the coilover/damper.
Now let’s break down those forces a bit more. The rocker arm allows us to change the angle of the forces transferred to a new angle that is easier for us to deal with. Instead of being required to have a coilover/damper in a vertical suspension down around the tire (like OEM), I can now change the angle so I can put the coilover/damper in a position that is much easier to deal with.
Rocker Arm Suspension Mazdaspeed Swap Forces
The rocker arm has two major features about it.
The angle change of transferred forces, as we just discussed. This is mainly to help with “positioning” the suspension components.
The rocker arm lengths allow us to define the “motion ratio” of the suspension. Looking at the diagram, you can see a blue line and a green line. These effective rocker arm lengths affect the suspension and result in a motion ratio.
The resulting ratio is 1:0.7 meaning the damper compresses 70% of the amount that the wheel moves up/down.
The wheel/tire has a maximum range of 5.55 inches of travel, while the damper has a maximum travel of 3.875 inches.
Designing the rocker arm with this 1:0.7 motion ratio allowed me to use a smaller, lighter damper design with limited travel and still get the desired wheel suspension travel I needed. We use a stiffer spring to compensate for the extra leverage of the motion ratio.
Motion ratios in suspension are common. For example, the Mazdaspeed 3 suspension has a unique motion ratio in the front (1:0.98) and rear (1:0.71) from our calculations. These numbers are typical of the style of suspension found in many commuter cars these days.
Now that we understand the forces and the intent with the rocker am…we have to design its shape and size to do the job. Angles are the tricky parts of the rocker arm design. Defining the angles (and thus shape) comes down to understanding the push rod input angles and the desired damper output angles while in motion.
Rocker Arm Suspension Mazdaspeed AWD Swap Angles
When we say “angles,” we are talking about the red arrows in the above diagram. These red arrows are the angles between the rocker arm and the push rod, as well as the rocker arm and the damper. Ideally, these angles are always 90 degrees through the entire motion you see in the GIF, but that is not physically possible, so we had to find the correct balance of angles while in motion.
A whole lot of math encompasses this, but the upcoming diagrams will help break it down to a very understandable level for everyone! We are breaking it down to the three major suspension travel points: droop, bump and ride height.
First, we are going to look at the angles for the push rod in Bump, Ride Height, and Droop.
Bump is when the suspension is fully compressed.
Ride Height is when the car is sitting stationary (static).
Droop is when the suspension is fully decompressed. Image your car sitting on jack stands with the tires hanging in the air.
Mazdaspeed 3 AWD Rocker Arm Angle Bump Pushrod
In full bump, the push rod angle to the rocker arm decreases to 67 degrees which is 23 degrees off the “ideal” 90.
Mazdaspeed 3 AWD Rocker Arm Angle Ride Height Pushrod
Then looking at ride height as the suspension moves downward from full bump. The damper-to-rocker arm angle decreases to 82 degrees which is 8 degrees off the “ideal” 90.
Mazdaspeed 3 AWD Rocker Arm Angle Droop Push Rod
Lastly, with the suspension traveling to full droop. The push rod to rocker arm angle increases to 117.5 degrees which is 27.5 degrees off the “ideal” 90.
What does this mean? This is great, actually! Ride height is where the suspension will function most of the time, and that is only 5 degrees off the ideal 90-degree angle. When the car is launched in a drag race, the suspension is going to compress, and that angle will decrease, passing through the ideal 90-degree angle and further. This is precisely the balance we are looking for with the rocker arm design. To keep it functioning most of the time as close to 90 degrees as possible.
Ok, let’s look at the angles from the damper side of the rocker arm.
Mazdaspeed 3 AWD Rocker Arm Angle Bump Damper
In full bump, the damper angle to the rocker arm increases to 111.5 degrees which is 21.5 degrees off the “ideal” 90.
Mazdaspeed 3 AWD Rocker Arm Angle Ride Height Damper
Then looking at ride height as the suspension moves downward from the full bump. The damper-to-rocker arm angle decreases to 82 degrees which is 8 degrees off the “ideal” 90.
Mazdaspeed 3 AWD Rocker Angle Droop Damper
With the suspension traveling to full droop, the damper-to-rocker arm angle decreases to 62 degrees which is 28 degrees off the “ideal” 90.
Again we have the damper near the “ideal” 90-degree angle at ride height and then pass through the 90-degree angle zone when the suspension compresses at launch. Again, the balanced angles we are trying to design for so the suspension function in the “ideal” angle range most of the time.
Why are the angles so important? The further you get from the “ideal” 90-degree angle, the more non-linear the suspension acts. When the suspension acts in a linear function, it is tunable and predictable to drive. If it is non-linear, then it makes tuning and use much more difficult…this results in inconsistent launching and driving, which is not good in a racing environment.
Mazdaspeed AWD Swap Racecar Suspension
This seems like a lot of work…why do it?
A few reasons, really:
Moving to the rocker arm design gave me a lot of control over how I set up my Mazdaspeed for racing.
It also gave me the ability to use readily available off-the-shelf dampers. This allowed me to get double adjustable dampers (rebound and compressor) for a very cost-effective price.
The CX7 AWD swap rear axle shafts did not allow me to use the OEM dampers anyways.
This design moves more of the suspension component’s weight to “sprung mass” which is better.
I love the challenge of designing a suspension system like this, and this was a great opportunity!
Before we wrap things up, note the rocker arms are 6061-T6 billet and are massive! We knew they were big, but it didn’t really sink in until we saw them firsthand.
Rocker Arm Size ComparisonRocker Arm Size Comparison 2
Alright, that wraps up the rocker arm suspension design, a huge novelty for the build. There are plenty more huge milestones to overcome, and those are coming up in this multi-part blog series!
I hope you are enjoying this series about the AWD Swap Mazdaspeed3, stay tuned for more blogs to come!
