Mishimoto prototype 2 radiator (right) and stock radiator (left)

Mishimoto 2015 Subaru WRX Performance Aluminum Radiator, Part 4: Prototype Radiator Performance Testing and Project Completion

Now that we had a finalized prototype, it was time to test this component to ensure that our improvements over the stock unit resulted in real-world advantages for our customers. An aluminum radiator provides the instantaneous benefit of increased reliability over the stock plastic unit. Despite this, cooling performance is always our primary goal with a heat exchanger.

Prior to actual road testing, our engineering team put together a few charts illustrating the improvements over the stock radiator.

Comparison of coolant surface area in Mishimoto and stock radiators
Comparison of coolant surface area in Mishimoto and stock radiators

Coolant surface area refers to the space occupied by the tubes in the radiator. The amount of coolant surface area affects both fluid capacity and overall heat transfer contact points. A larger coolant surface area results in greater heat transfer and lower temperature. The Mishimoto prototype features a 42% increase in coolant surface area compared to the stock radiator.

Comparison of air surface area in Mishimoto and stock radiators
Comparison of air surface area in Mishimoto and stock radiators

The next improvement is seen in air surface area, represented by external fin surface area in the chart above. Airflow passes through the fins to transfer heat from the coolant tubes. Once again, a larger surface area will result in greater heat transfer. The Mishimoto prototype unit increases air surface area by 34% compared to the stock radiator.

With the additional thickness of the Mishimoto radiator and its dual-row core, the fluid capacity is increased significantly. The stock radiator’s fluid capacity is 0.39 gal, while the Mishimoto radiator’s fluid capacity is 0.84 gal. This amounts to a 117% increase in capacity of the Mishimoto radiator over stock.

Now to the road testing! First we installed our temperature sensors on the radiator hoses and prepared our data collection tools.

Mishimoto radiator with temperature sensors installed
Mishimoto radiator with temperature sensors installed

Our test vehicle would be the Mishimoto 2015 WRX CVT-equipped shop vehicle. All data points were collected on the highway and compiled on the same day. The vehicle was driven at 60 mph cruising speeds for 5 minutes, for each particular setup. Special attention was given to the traffic in front of the WRX to ensure that a fresh stream of airflow was supplied to the radiator. We used 100% distilled water in the cooling system. Check out the temperature results below!

Comparison of radiator outlet temperatures in Mishimoto and stock radiators
Comparison of radiator outlet temperatures in Mishimoto and stock radiators

During our controlled test, the Mishimoto radiator showed an average reduction in coolant temperatures of 15°F–20°F compared to the stock radiator. You will notice that the temperatures seem to fluctuate and spike at similar times on each plot. This occurs because uphill portions of the highway require greater engine loads and invariably produce hotter temperatures.

Radiator efficiency is based on the same data collected in the previous plot, but efficiency is based on a comparison of the radiator inlet and outlet temperature differences. The efficiency number tells us how effective the radiator is at transferring heat (lowering temperatures).

Comparison of radiator efficiency in Mishimoto and stock radiators
Comparison of radiator efficiency in Mishimoto and stock radiators

The Mishimoto radiator provides a 15% increase in radiator efficiency. This number is a performance value given to represent how well the radiator rejects heat. This efficiency improvement will provide a huge benefit under track and aggressive driving situations.

I would call this project a complete success! Let’s go through the benefits this radiator can provide to your 2015 WRX.

Aluminum Construction

As a standard, Mishimoto radiators are crafted from 100% aluminum. We braze the core to the end tanks so there are no effects from epoxy or glue. Each radiator is TIG-welded and leak tested to ensure a durable and reliable life of service. The use of aluminum provides increased durability compared to stock plastic end tanks. Stock tanks are normally crimped to the stock core and utilize a rubber gasket to seal. Common failures can stem from this seam failing between the core and tanks, or from a cracked end tank caused by repeated temperature variations that weaken the plastic. Additionally, the use of aluminum provides improved heat dissipation compared to the plastic units. This means quicker temperature recovery from high temperatures.

Greater Capacity

The Mishimoto radiator provides more than double the coolant capacity compared to the stock radiator. This increase in capacity has a direct impact on cooling performance, as we saw during our testing. Our engineers designed a specifically sized core to account for space around the turbocharger and the charge pipe for the intercooler.

Dense Core Composition

Following the lead of the stock radiator core design, our engineering team constructed an extremely dense core that features shorter fin height to allow for more coolant tubes. Our radiator features a dual-row design that provides great gains in coolant surface area.

Air Surface Area: 34% increase

Coolant Surface Area: 42% increase

These two increases in surface area result in improved heat transfer that translates into lower fluid temperatures.

Proven Temperature Reduction

Our road testing showed average temperature decreases of 15°F–20°F and radiator efficiency increases of 15%. These are huge gains from our radiator, and we anticipate even greater improvements during track and aggressive driving situations. These efficiency improvements are the primary benefits of upgrading your cooling system, especially if you intend to track your 2015 WRX.

With all of our testing complete, and a very solid product designed, we were ready to enter mass production and close the book on this particular project. We could now move on to additional 2015 WRX projects, including downpipe and cat-back exhaust development.

Swing by the blog for updates on our future projects. Thanks for reading!

Prototype brackets

Mishimoto 2015 Subaru WRX Direct-Fit Baffled Oil Catch Can System, Part 2: Product Prototyping

Time to start designing brackets! After a quick recap of the project goals, our creative engineering team began brainstorming. First, they selected a location for the catch can on the PCV valve side. It would need body mounting points for the can bracket, and preferably a short route for the hose so as not to complicate the engine bay. Our goal is a clean installation that appears stock-like, not a medusa of hoses routed about the engine bay.

The PCV valve on the 2015 WRX is located under the intercooler toward the rear of the engine block. You can see it in the image below, taken during a later stage of development of this kit.

2015 Subaru WRX PCV valve
2015 Subaru WRX PCV valve

We also needed to consider the differences between the RHD and LHD vehicles. In our US spec LHD model, both the brake booster and master cylinder are located on the left side of the engine bay. In the RHD model, they are located on the opposite side. To avoid developing a kit for each setup, we would attempt to keep this bracket toward the front of the engine bay.

Eventually we found an ideal location between the PCV valve and the intake, near the ABS block. Check out a few shots of our initial mock-up design.

Catch can bracket mock-up
Catch can bracket mock-up
Catch can bracket mock-up
Catch can bracket mock-up

Once the primary bracket was bolted into position, we attached the baffled catch-can bracket to this piece. These brackets were designed based on engine bay dimensions and fabricated from a sheet of steel. See the attached brackets below!

Catch can kit bracket mock-up
Catch can kit bracket mock-up

Then we attached the catch can to ensure proper clearance for servicing the can when fluid collects in it.

Catch can kit bracket mock-up
Catch can kit bracket mock-up

Once we were satisfied with the catch can on the PCV side, we moved to the other side of the system to address the CCV system. Previous-generation WRX models with the EJ engines utilized a port on each valve cover for the crankcase ventilation. That setup would have necessitated either a three-port catch can or dual two-port units. On the new FA20DIT, a single CCV port is used and can be found on the driver’s side cylinder head just behind the AC compressor. Check out the port in the image below!

CCV port location
CCV port location

This line then runs across the engine bay and down into the compressor inlet pipe, as you can see below.

Turbocharger compressor inlet hose
Turbocharger compressor inlet hose

Once we knew how the lines would be routed, we needed to select a bracket location and then mock-up a prototype. Again, we would be targeting the front area of the engine bay to reduce the chance of fitment concerns with RHD models. We found an optimal location right next to the battery. Check out the installed bracket and catch can with some prototype lines.

Driver’s side prototype bracket
Driver’s side prototype bracket

After our initial prototypes were fabricated, we put our 3D printer to work and began printing the brackets as well as a few of the catch can components.

3D printing of prototype brackets
3D printing of prototype brackets
3D-printed prototype brackets
3D-printed prototype brackets

Once completed, we test fit the modeled brackets on the vehicle to verify proper fitment. Take a look at the stages of bracket design in the following images!

Prototype brackets
Prototype brackets
Prototype brackets
Prototype brackets

Now that the brackets were completed, we needed to design our custom hoses for this kit and ensure that all components worked together correctly. Our team would be designing these hoses in silicone to provide improved durability and resistance to heat and the fuel/oil particles flowing through them. These particles accelerate wear on rubber components, and our silicone lines would be more resilient.

Check back next time for a look at our completed kit!

Mishimoto prototype 2 radiator (bottom) and stock radiator (top)

Mishimoto 2015 Subaru WRX Performance Aluminum Radiator, Part 3: Second Prototype Evaluation

No need for an introduction, let’s check out our second prototype!

Mishimoto prototype 2 radiator
Mishimoto prototype 2 radiator
Mishimoto prototype 2 radiator
Mishimoto prototype 2 radiator
Mishimoto prototype 2 radiator
Mishimoto prototype 2 radiator

So what can we tell from these images? The unit as a whole is very precise, and the TIG-welding is straight and accurate. All mounting points and adjustments to the previous version should make this a drop-in fit. One major difference you will notice from the GR radiator is the lack of an overflow port on the passenger top tank. On the previous generation, this line would run to the expansion tank located on the intake manifold. The FA20 does not utilize such a reservoir, so this port is removed.

Let’s take a closer look at the core of this prototype!

Mishimoto prototype 2 radiator core evaluation
Mishimoto prototype 2 radiator core evaluation
Mishimoto prototype 2 radiator core evaluation
Mishimoto prototype 2 radiator core evaluation

The fin height is a touch shorter than the stock core, allowing us to fit more tubes into the radiator itself.

A quick measurement of the prototype core thickness reveals the 35mm core we designed!

Mishimoto prototype 2 radiator core thickness
Mishimoto prototype 2 radiator core thickness

Here are a couple shots of this prototype next to the stock radiator.

Mishimoto prototype 2 radiator (right) and stock radiator (left)
Mishimoto prototype 2 radiator (right) and stock radiator (left)
Mishimoto prototype 2 radiator (bottom) and stock radiator (top)
Mishimoto prototype 2 radiator (bottom) and stock radiator (top)
Mishimoto prototype 2 radiator (bottom) and stock radiator (top)
Mishimoto prototype 2 radiator (bottom) and stock radiator (top)

The Mishimoto prototype unit dwarfs the factory radiator! This increase in size will have a substantial effect on cooling performance, something we plan to test very soon! After verifying that this unit fit perfectly in the vehicle, we set a plan to collect data  so we could compare the cooling efficiency with the stock radiator. Check back next time for a full rundown on the testing process and our results!

 

Untitled

Mishimoto 2015 Subaru WRX Direct-Fit Baffled Oil Catch Can System, Part 1: Product Introduction

If you follow our engineering blog or are involved with any of our social media outlets, you should be well aware of the new baffled oil catch can we recently released. This new product features a much smaller footprint compared to our existing catch can, allowing for fitment in tighter engine bays. In case you missed it, check out the full build at the link below.

http://engineering.mishimoto.com/?cat=124

While developing this catch can, we wondered about using it in direct-fit kits for popular vehicles. For most drivers, a catch can is a DIY project requiring only the routing of hoses and fabrication of brackets for mounting the can. Installing a DIY setup that appears like it was made for the vehicle can be quite a challenge. This is where we come in, to take the guesswork out of a catch can installation. We are planning to provide mounting brackets, hardware, silicone lines, and a detailed installation guide for these kits.

Our shop vehicle would be our first target for this new line of products. We have two 2015 Subaru WRXs that we have been using to develop a variety of cooling products, such as silicone hose kits, aluminum radiator, direct-fit oil cooler, CVT oil cooler, J-pipe, and cat-back exhaust. The WRX is the perfect vehicle for a catch can, thanks to its direct injection system that is known for producing carbon buildup on intake valves.

If you did not get a chance to see our catch can design, check out a few quick images of the final product below.

Mishimoto Compact Baffled Oil Catch Can
Mishimoto Compact Baffled Oil Catch Can
Mishimoto Compact Baffled Oil Catch Can
Mishimoto Compact Baffled Oil Catch Can
Mishimoto Compact Baffled Catch Can fully assembled
Mishimoto Compact Baffled Catch Can fully assembled
Mishimoto Compact Baffled Catch Can top
Mishimoto Compact Baffled Catch Can top
Mishimoto Compact Baffled Catch Can top disassembled
Mishimoto Compact Baffled Catch Can top disassembled

Since the primary component was already developed, this would be an easy project right? Not entirely. We would need to dig deeper into the CCV/PCV system of the FA20DIT and determine the locations for our lines. Additionally, we would need to find suitable underhood locations for the catch cans.

Before diving into the project, we set a few goals for our team of skilled engineers.

Project Goals

  1. Remove oil particles from PCV/CCV air before entry into the intake tract.
  2. Position catch cans with a strong bracketing system in ideal engine bay locations.
  3. Include direct-fit premade lines for easy installation.

Let’s break these goals down for a quick explanation of each.

Oil Separation

The primary goal for any catch can setup is to reduce the amount of oil particles entering into the intake tract. PCV and CCV systems work together to provide optimal crankcase pressures and to ventilate the air in a safe and environmentally friendly fashion. This air is then recirculated back to the intake to be burnt in the combustion process. Although this is a simple way to recycle these contaminants, the presence of oil in your intake system will result in carbon buildup on your valves and will lower the octane of your combustion mixture. This is not something you want in a performance vehicle. To reduce carbon buildup, a properly functioning catch can system will capture all oil and fuel particles and return clean air to the intake tract. Above all, oil separation will be our team’s primary focus.

Proper Placement

Although it may seem like a small detail, can placement will be key for this particular kit. We need to consider any other aftermarket components that could come into contact with our catch cans. We also need to locate ideal mounting positions and design our brackets to function with them. Finally, we must cater to both LHD and RHD vehicles, so as not to leave out our friends outside the US.

Ease of Installation

The entire premise of this project is to provide an easy-to-install kit that includes everything needed. We want to take any guesswork out of installing a catch can for your 2015 WRX. To be sure this kit is all inclusive, we will be including premade silicone lines that will route PCV and CCV air to the catch can and back to the intake. Our application-specific mounting brackets will include all necessary hardware to take this product out of the box and install it on the vehicle in very little time.

Now that we have the groundwork laid for this particular project, we could begin the design process for the catch can mounting brackets. We want a very clean bracket system that is subtle, yet engineered for a precise and strong securing point.

Check back with us next time to see the prototype and mock-up of our initial bracket design.

Thanks!

Mishimoto prototype 1 installed

Mishimoto 2015 Subaru WRX Performance Aluminum Radiator, Part 2: Evaluation of First Prototype Radiator

Now that we had our first prototype unit in, it was time to evaluate fitment and determine if any changes were necessary when compared to the stock unit. First, we swapped the shrouds to see if any fitment issues existed because of the added size of the Mishimoto unit.

Mishimoto prototype 1 (right) fan shroud fitment
Mishimoto prototype 1 (right) fan shroud fitment
Mishimoto prototype 1 (top) fan shroud fitment
Mishimoto prototype 1 (top) fan shroud fitment

Both the stock and Mishimoto plug-n-play aluminum fan shrouds fit perfectly with the mounting points on our prototype radiator. After verifying this fitment, we installed the prototype in the vehicle to ensure that all other fitment points were spec’d correctly.

Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed
Mishimoto prototype 1 installed

The prototype unit fit quite nicely! We had some minor adjustments to make with a few end-tank features, but for the most part, mounting points were spot on. The core we designed for this prototype is 42 mm thick, more than two times the thickness of the stock unit. Core fin density in this prototype was similar to the stock unit. After a discussion with our team we determined that the core on our first prototype would need a few modifications. First, we would reduce the thickness of the core. The FA20DIT front-mounted turbocharger setup would likely present some potential fitment concerns. We decided to allow for future turbocharger and charge pipe upgrades by providing some additional clearance for upgraded components in this area. By decreasing the core thickness to 35 mm, our radiator would still be double the thickness of the stock unit and would provide a nice increase in fluid capacity.

A second modification to our prototype core will be in the fin and tube composition. Instead of simply matching the density of the stock unit, we would be improving upon it. Our radiator will utilize shorter fins, which allow for more overall rows and a greater surface area. A greater fin surface area provides more heat-transfer contact points, which then result in lower fluid temperatures. This core would be a two-row design, providing greater fluid capacity.

Once we had a plan for our second prototype, we set to work putting together the models and drawings. Check back next time for the introduction and evaluation of our second prototype unit!

Thanks!

Prototype 3 cooler mounted

Mishimoto 2015 Subaru WRX CVT Transmission Fluid Cooler, Part 4: Prototype 3 Development and Final Results

For our third prototype unit for the CVT cooler, we decided to take a more traditional approach. We would place the cooler in a location that would guarantee airflow. The main concern was fitting our large 19-row cooler in a position that would not leave any space for other aftermarket components. First, we mocked-up the cooler and developed some basic brackets that would place the cooler in an angled position behind the upper grille area. Check out a few shots of the mounted cooler!

Prototype 3 cooler mounted
Prototype 3 cooler mounted
Prototype 3 cooler mounted
Prototype 3 cooler mounted
Prototype 3 cooler mounted
Prototype 3 cooler mounted

As you can see above,the cooler is mounted at a slight angle, with two brackets supporting the cooler from the upper mounting points. We added an additional bracket to one of the lower mounting points, which you will see in the renderings later in this blog.

During this product design process we installed our direct-fit oil cooler kit to ensure that the two components would fit together. You can see the oil cooler in the lower bumper portion with the “M” logo.

Once the fluid cooler was in position, we could run the lines from the cooler back to the liquid-to-liquid cooler. We used our -AN to push on fitting adapters shown below.

Mishimoto AN fitting adapter
Mishimoto AN fitting adapter

This adapter will allow us to convert to a rubber line for use with the cooler. A quality rubber line will provide the necessary pressure tolerance, as the CVT pressures never exceeded 50 psi during our testing conditions. Next, we routed the lines around the radiator support in a location away from any components that could rub or damage the line.

Prototype 3 cooler line routing
Prototype 3 cooler line routing
Prototype 3 cooler line routing
Prototype 3 cooler line routing

Once the lines were routed and installed, we buttoned everything up and set up our temperature sensors to prepare for road testing.

Temperature sensor preparation
Temperature sensor preparation
Temperature sensor preparation
Temperature sensor preparation

As you can see, we have a few other Mishimoto products installed on our CVT test vehicle, including our performance air intake, silicone radiator hose kit, and silicone ancillary hose kit. With everything ready to go, we hit the road to collect more data. This is the fun part!

Prototype 3 road testing
Prototype 3 road testing

Once complete we returned to the shop to crunch our data once again and see how the additional airflow affected our temperature numbers.

Prototype 3 data collection
Prototype 3 data collection

This was the data we wanted to see! As before, the stock plot begins at 201°F (94˚C) and peaks at around 213°F (106˚C) toward the end of the pull. In this run, the Mishimoto intake begins the pull at 193°F (34˚C) and peaks at 198°F (92˚C) after 20 seconds at full throttle. This is a 15-degree reduction in temperature! The added liquid-to-air heat exchanger is placed outside the engine bay. By doing so, heat-soak is reduced, which will affect temperatures during idle conditions. This situation is reflected in the plot above.

Along with temperature data, our engineers also monitored fluid pressures to ensure that the additional capacity and fluid routing would not negatively affect the overall system pressure. Extensive road testing proved that pressures were very similar to the stock system and well within a safe range during all forms of operation.

Check out our video from the testing process!

We were extremely pleased with the rigidity of the design, the location of the cooler, and primarily the results obtained from testing. All we had to do now was finalize our product drawings and begin mass production. Check out a rendering of the brackets (including the additional lower bracket) we designed to support the cooler.

Prototype 3 bracket rendering
Prototype 3 bracket rendering
Prototype 3 bracket rendering
Prototype 3 bracket rendering

Now that we had a final product, we could circle back to our goal list and ensure that our product was meeting all our original specifications.

Project Goals

  1. Kit must be easy to install and require no vehicle modification.

Although bumper removal is necessary, this kit is very easy to install with simple hand tools. The lines install similarly to the stock lines, and no irreversible vehicle modification is necessary. All components are engineered specifically for this vehicle. Installation will be demonstrated in a detailed video guide.

  1. Cooling performance gains must be proven through real-world testing.

Our road-testing results showed temperature decreases of 15°F compared to the stock setup. These data were compiled during a full-throttle launch control pull from idle through 4th gear in sport-sharp mode. Our engineers anticipate even greater gains during extended high-rpm driving such as during a road course or track event.

  1. Kit would supplement the stock liquid-to-liquid cooler.

The Mishimoto CVT cooler supplements the stock liquid-to-liquid cooler and functions perfectly. We achieved appropriate fluid warmup as well as large reductions in fluid temperature under load.

That puts another successful project in the books for the Mishimoto engineering team! These units are now in mass production so we can get them on shelves quickly! We know you guys are interested in tracking your CVT, and we want you to be able to do so without the fear of issues from high temperatures.

Thanks for following along with the development process. Feel free to follow up with any questions or comments. Keep your eye on the “Vendor Announcement” section of Nasioc for our CVT cooler pre-sale!

Thanks!

Stock 2015 WRX radiator core thickness

Mishimoto 2015 Subaru WRX Performance Aluminum Radiator, Part 1: Product Introduction and Stock Radiator Overview

The new 2015 WRX is a great toy for both daily use and as a weekend track warrior. The introduction of the FA20DIT into the WRX chassis has been well received, and from the reviews thus far, Subaru has done a great job with the new model. Although some might disagree with the styling, overall the car handles and performs very well. As for value, the 2015 model is a pretty decent bang for your buck. For those looking to track their brand new vehicle, a few bolt-on modifications will raise power levels significantly. A simple intake and tune will raise power to 275+ whp, which is a huge increase over the 210 whp we saw from a completely stock vehicle. Reaching 300 whp is potentially obtainable with a few additional exhaust modifications. We are currently in the process of testing our prototype J-pipe to confirm this!

With improved power comes the need to monitor and regulate fluid temperatures. Oil and coolant are the lifeline of your engine. Keeping these fluids properly regulated will extend the life of your FA and make your track days more enjoyable. Mishimoto already took care of oil issues with our direct-fit oil cooler kit for the 2015 WRX, which lowered temperatures by 25+°F. This is a huge drop in temperatures and will also make an impact on coolant temperatures for your Rex. For CVT users we developed a direct-fit CVT cooler that dropped temperatures by +15°F. The next component we want to bulletproof is the radiator; this is our most well-known product segment. Our GD and GR WRX/STi radiators are well received in the enthusiast world and are a fantastic replacement for the failure-prone stock unit.

Before diving into product design, we removed the stock unit to evaluate any changes made from the previous WRX generation. Take a look at the stock radiator after we removed it!

Stock 2015 WRX radiator removed
Stock 2015 WRX radiator removed

Once removed from the vehicle, we disconnected the hoses and the fans and inspected the radiator.

Stock 2015 WRX radiator removed
Stock 2015 WRX radiator removed
Stock 2015 WRX radiator removed
Stock 2015 WRX radiator removed

Although some features and dimensions differ, this radiator is similar to the previous generation. It features a fill neck and cap, fan shroud mounts, and similar inlet/outlet locations.

The key portion of this component that relates to performance is the core itself. Radiators on vehicles released in the past few years have been equipped with very thin yet extremely dense cores. This allows for greater fin surface area and a greater number of coolant tubes, which results in better heat transfer. Manufacturers can reduce the radiator size to create a more compact engine compartment. Every millimeter helps. Check out a few shots of the stock core!

Stock 2015 WRX radiator core
Stock 2015 WRX radiator core
Stock 2015 WRX radiator core
Stock 2015 WRX radiator core
Stock 2015 WRX radiator core
Stock 2015 WRX radiator core

As you can see, Subaru equipped this vehicle with an extremely dense core. It features a single-row core with straight external fins. Take a quick look at the thickness of the factory core.

Stock 2015 WRX radiator core thickness
Stock 2015 WRX radiator core thickness

The stock radiator is paper thin, measuring only 16 mm in thickness. This is an area where we can certainly improve.

Using the dimensions from the stock unit and our existing GR WRX radiator, we designed a prototype unit for the 2015 model. This first prototype would have a dual-row core with aluminum end tanks. We would be increasing the overall thickness of the radiator and evaluating the fitment once our prototype was complete. Check back next time for the fitting of our initial prototype.

Thanks for reading!

Prototype 2 air duct

Mishimoto 2015 Subaru WRX CVT Transmission Fluid Cooler, Part 3: Prototype 2 Development and Testing

After we witnessed reasonable performance gains with our first prototype, we decided to evaluate what we liked and didn’t like with the design.

Pros

  • Short line lengths
  • Efficient cooling
  • Compact design and packaging

Cons

  • Did not achieve the temperature decreases we wanted to see
  • Requires wiring of the electric fan
  • Airflow was not as sufficient as it could be

This first design was efficient but not ideal for what we wanted out of the project. To obtain the desired cooling benefits, the addition of an electric fan was necessary. However, the fan would add complexity and wiring to the product, which we would like to avoid. So we hit the drawing board to work on a second design. We would attempt to keep the cooler in the same location; however, we would work to improve airflow through the cooler. Dan set about to fabricate a new scoop that would pull air from a different location. Check it out!

Prototype 2 air duct
Prototype 2 air duct
Prototype 2 air duct
Prototype 2 air duct
Prototype 2 air duct
Prototype 2 air duct

Yes, we went a bit out of the box on this design prototype. The design placed a scoop that would gather more air due to its location. Unfortunately, this also placed it in a location that made it very susceptible to road damage. Although a reasonable idea for a specific race vehicle, this design was not going to be applicable for road-going vehicles. We decided to regroup for one more shot at the design.

Our primary issue up to this point was airflow. We wanted to keep the cooler away from the front of the vehicle for two reasons. First: line length. The added length of fluid lines would affect fluid pressure, and we were not sure how this would affect the transmission. Second: front bumper real-estate. We are aware that consumers would likely be installing front-mount intercoolers. Although this upgrade might not gain popularity until these vehicles are a few years old, we would still have to consider that possibility.

With these concerns in mind, we set out to design a third prototype in an attempt to gain greater airflow while allowing space for future vehicle modifications.

Check back next time where we fabricate and test our third prototype design!

Thanks for following along!

Road testing prototype with fan

Mishimoto 2015 Subaru WRX CVT Transmission Fluid Cooler, Part 2: Prototype 1 Development and Testing

Welcome back! The quest for low transmission fluid temperatures continues. Once we developed our goals and plan of action for this project, our engineering team went to work, grinding, welding, bending, and cutting. Our first prototype design was quite unique. We mounted one of our 19-row, stacked-plate fluid coolers next to the liquid-to-liquid transfer unit. This is the same location as the turbocharger on the previous generation of EJ engines. Check out the beginning of the mock-up below!

Prototype 1 mock-up
Prototype 1 mock-up

The primary concern with this location is airflow. This cooler utilizes external fins to promote the exchange of heat with the liquid running through the cooler. Without airflow, the effectiveness of this cooler is significantly diminished. The primary benefit of this location is packaging. Our lines will be short, which will alleviate any concerns about loss of fluid pressure. Also, it provides room in the front of the vehicle for a front-mount intercooler upgrade. To promote additional airflow, our team developed and fabricated a duct to pull air from underneath the vehicle into the cooler. Check out a few shots!

Prototype 1 duct fabrication
Prototype 1 duct fabrication
Prototype 1 duct fabrication
Prototype 1 duct fabrication

Another minor concern would be ground clearance. Enthusiasts use and/or modify their vehicles in various ways. Someone using a WRX for rally or rallycross events might be concerned with debris that could damage this cooler and scoop. Anyone who lowers a vehicle would need to consider the ground clearance of this component.

Now, once we had this prototype installed, we needed to test it adequately. To do so we would first require baseline data to compare with data for our kit. We stripped off our prototype and attached our temperature/pressure sensors.

Temperature/pressure sensors
Temperature/pressure sensors
Temperature/pressure sensors
Temperature/pressure sensors

Then we hit the road to capture some data!

Road testing prototype 1
Road testing prototype 1

We tested this kit in a controlled highway driving situation, and we also evaluated temperatures during launch control use and pulls to 60–80 mph. The chart below shows the temperature differences between the OEM cooler and the added Mishimoto unit from a launch.

Prototype 1 data
Prototype 1 data

As you can see, the stock cooler starts at around 201°F (94˚C) and then rises both steeply and quickly to around 213°F (101˚C) after 20 seconds at full throttle. The Mishimoto cooler starts at a similar temperature and rises to around 205°F (96˚C), which is not quite as high as the stock setup. The stock plot showed no signs of leveling off, while the Mishimoto setup began to taper down. This was only one pull; It would be interesting to see temperatures in a repeated environment such as a road course.

To take this design a bit further, we decided to strap an electric fan to the cooler to see the effect on temperature. A fan would provide protection against heat-soak during idle conditions when airflow would not be present. The final iteration would include an adjustable fan controller, which would allow the user to specify activation temperature. I’m getting a bit ahead of myself though!

Next, we needed to evaluate the performance benefits of adding a small fan, so we fitted our 8” fan to the cooler. Check out the setup below.

Prototype 1 with fan
Prototype 1 with fan
Prototype 1 with fan
Prototype 1 with fan
Prototype 1 with fan
Prototype 1 with fan

After we completed the temporary mock-up, we again hit the road to collect more data!

Road testing prototype with fan
Road testing prototype with fan

After the road test, we returned to our facility and dove into our data to compare the performance of this new setup with both the stock and the cooler alone.

Prototype 1 with fan data
Prototype 1 with fan data

The stock plot follows the same path as in the previous test. The Mishimoto plot with fan installed is quite interesting. As you can see, the temperature prior to the start of the run is much lower than both stock and the previous setup. At this time, the fan is in motion, which is why the temperatures start at around 176°F (80˚C). By the end of the pull, temperatures reach around 204°F (96˚C), which is not much improvement over the previous design. The major benefit, however, would be the reduction in heat-soak at idle, which certainly seems to help. Another interesting point is the plot line. The Mishimoto line is still on a steep slope upward, similar to the stock unit. It is likely being affected negatively by the airflow reduction from the mounted fan.

After observing this data, we realized we would need to improve airflow, so we decided to make a few additional prototypes. Check back next time for another round of product development!

Thanks!

Mishimoto CVT test vehicle

Mishimoto 2015 Subaru WRX CVT Transmission Fluid Cooler, Part 1: Project Introduction and Goals

Mishimoto CVT test vehicle

An automatic Subaru WRX … what has this world come to? We’ve read your comments on the forums and social media regarding our purchase of a CVT-equipped 2015 WRX for new product development. Why would anyone want this vehicle? Who would purchase it, and for what reason? Is this even an enthusiast’s vehicle anymore? All great questions. We’ve responded to these comments that we are developing products for both the 6-speed and CVT models. Our primary target/reasoning for the CVT purchase is to develop a transmission cooler, but the majority of our staff had a similar attitude as our followers: It just didn’t seem right. After spending some time with the vehicle and behind the wheel, however, most of our production team members are sold on the CVT. Of the ten vehicles I have owned, only one was an automatic, and it was sold for that specific reason. As I age gracefully, I have found an appreciation for automatics, especially for multiple drivers and multiple uses. Modern automatics are quite different compared to those from five or ten years ago. They are no longer considered as downgraded, less enjoyable vehicles, but more as an alternative. For those who are still skeptical, go to your local Subaru dealership and request a test drive; I bet you will be impressed.

I think these cars will become serious competitors in autocross in the coming years, especially since we recently uncovered the incredible power gains possible with a few minor bolt-on modifications. Anyway, let’s return to the project.

CVT transmissions do not utilize the internal components that previous standard autotragics used. Despite this, CVT transmissions still require fluid temperature regulation just like any other transmission. Fluid temperature is vital for component longevity and reliability.

We needed a way to regulate the temperature and assist the stock system. Subaru utilizes a liquid-to-liquid cooler for heat transfer. Engine coolant and transmission fluid flow through a cooler, working together to regulate fluids. These liquid-to-liquid coolers are generally quite efficient. This particular system has been designed for the stock 210 whp (or so) and does a decent job at keeping temperatures at bay under normal conditions. So what happens when you add around 100 whp? Engine and underhood temperatures are sure to rise in normal driving conditions as well as with track/aggressive driving. Reaching 300 whp is an exhaust, intake, and tune away, which are commonly the first modifications for the basic enthusiast. Check out this image of the stock cooler!

WRX stock liquid-to-liquid CVT cooler
WRX stock liquid-to-liquid CVT cooler

The lines are  rubber with a sheathing to protect them from any rubbing. This unit mounts to the side of the engine block on the passenger side. After evaluating the stock unit, our team decided to design a product to assist the stock unit. The stock setup also functions as a fluid warmer, which will help bring the fluid up to operating temperature, and then our supplemental cooler will help retain optimal temperatures. Check out our test vehicle below!

Mishimoto CVT test vehicle
Mishimoto CVT test vehicle

So we had everything we needed to start the project: a team of engineers, an office full of car enthusiasts, a 2015 WRX, testing equipment, and a shop full of fabrication equipment. First, we set a few simple goals to follow to obtain the results we wanted.

Project Goals

  1. Kit must be easy to install and require no vehicle modification.
  2. Cooling performance gains must be proven through real-world testing.
  3. Cooler must supplement the stock liquid-to-liquid cooler.

With these simple goals in mind, our engineering team began to envision and create the best-performing product possible A quick breakdown of these goals is detailed below.

Easy Install

We pride ourselves in developing products that are easy to install and bolt on to your stock vehicle. Our goal is to provide efficient, accurate instructions for our products, which can be installed with common hand tools. The WRX is a brand new vehicle. I am not sure that many folks would want to hack into their new vehicles. This kit will feature a completely reversible installation so if you choose to remove it, there will be no signs that it was installed. We too are consumers of the performance aftermarket world, and we can appreciate a product that installs perfectly and looks like stock equipment.

Cool It

The primary focus for this project is cooling performance. We want to reduce temperatures as efficiently as possible so you can drive your car in any way you choose, whether tackling those back roads you have been eying, or that weekend autocross. Our goal is to provide efficient cooling so you can truly enjoy your new WRX!

A Helping Hand

As mentioned before, our cooler would not replace the stock cooler; instead it would be supplementing the stock unit. This system is also rather efficient for engine oil cooling, as we found when testing our 2015 WRX oil cooler kit.

That’s all for our first installment of the build. Check back next time for the development of our first prototype design!

Thanks

An inside look at the engineering of Mishimoto products.

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