Mishimoto oil cooler shroud/duct assembly installed

Mazda Miata (NB) Oil Cooler R&D, Part 2: Oil Cooler Shroud and Duct Development

Interested in picking up our NB Miata oil cooler kit? Check out our discounted pre-sale linked below.

Mishimoto 1999-2005 Mazda Miata Oil Cooler Kit Pre-Sale!

In our last segment, we outlined the goals of the project, and we started fabricating mounting brackets to position our heat exchanger under the front of the Miata NB (second generation). We also hinted at the use of shrouding to direct airflow properly through our cooler.

Optimal airflow through a heat exchanger is vital to the efficiency derived from an oil cooler system. In addition, we see value in retaining the stock engine undertray, which aids in the proper regulation of coolant temperatures. We will build our air duct into the undertray, with the goal of a stock-like appearance on the top of our list, right next to optimal airflow.

Air Duct Fabrication

First, we needed to create some space to fit our ducting. We ordered a stock undertray so we could make some cuts for our cooler.

Stock under tray ready for modification
Stock under tray ready for modification

A couple of cuts later, and our cooler was now visible with the tray installed.

Stock undertray cut for Mazda Miata oil cooler
Stock undertray cut for Mazda Miata oil cooler

Done! Plenty of space for fresh air to enter our cooler. What’s next? We need to tackle some ducting to guide airflow through the core and eliminate any gaps between the cooler and undertray.

Instead of starting with fabrication, we hit the computer and created a 3D model of the components that will attach to this duct. By designing the duct in 3D first, the fabrication process becomes quicker and more precise.

The templates shown below were printed out once we had a final design in Solidworks.

Mazda Miata oil cooler duct templates
Mazda Miata oil cooler duct templates

As you can see, the templates map out the cuts, holes, and bends necessary to create this piece. We glued these templates to our steel sheet and start the process of fabrication.

Mazda Miata oil cooler duct template fabrication
Mazda Miata oil cooler duct template fabrication

After some time in the shop, we had a completed prototype of the duct for the heat exchanger. Check it out!

Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype
Mishimoto Mazda Miata oil cooler duct prototype

Looking good so far! Next, we needed to work out a shroud that mounts to the undertray, which will enclose the duct and reduce the chances of improperly routed airflow.

We hit Solidworks once again and came up with a solution in 3D, which was printed out in template form.

Mishimoto Mazda Miata oil cooler shroud template
Mishimoto Mazda Miata oil cooler shroud template

Cuts and bends left us with the result seen below!

Mishimoto oil cooler shroud fabrication
Mishimoto oil cooler shroud fabrication

Due to the location of the bend shown in the image, we needed to cut out this portion of the shroud, bend the material, and then reweld the piece.

Welding the Mishimoto oil cooler shroud prototype
Welding the Mishimoto oil cooler shroud prototype

A few more adjustments were made to perfect fitment.

Mishimoto oil cooler shroud adjustment
Mishimoto oil cooler shroud adjustment

We then attached our shroud directly to the undertray, creating a nice fit between the duct and the shroud. This setup also allows for the undertray to be removed without affecting the heat exchanger.

Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed

Awesome! This setup looks great. The shroud and duct will both have a black powder-coat finish, which creates a subtle, stock-appearing setup. It will be interesting to see the temperature drops once testing is conducted.

For some extra protection against damage from road debris, we are planning to add some steel mesh into the design. Check out the mock-up with one of our potential material choices below.

Mishimoto oil cooler shroud/duct assembly installed
Mishimoto oil cooler shroud/duct assembly installed

We will also be adjusting the hardware used to attach the shroud to the undertray. More on that coming soon.

Coming Up!

We’ve reached the point where we can install our sandwich plate, oil lines, and testing sensors for data collection. Check back next time for our first round of product testing!

Thanks for reading!

-John

Interested in picking up our NB Miata oil cooler kit? Check out our discounted pre-sale linked below.

Mishimoto 1999-2005 Mazda Miata Oil Cooler Kit Pre-Sale!

2 thoughts on “Mazda Miata (NB) Oil Cooler R&D, Part 2: Oil Cooler Shroud and Duct Development”

    1. Yes, damage from road debris is certainly a higher probability with this particular mounting point, although it would still be possible if located in the front grille (take a look at damaged FMIC images). We will be using a steel mesh to prevent damage from normal sized debris. In addition, the lowest point of our heat exchanger does not sit below the undertray, so damage is relatively unlikely. Thanks for the input!

      -John

Leave a Reply

Your email address will not be published. Required fields are marked *