Mazda Motorsports Keeps the MX-5 Cool with a New Differential Plate

September 1, 2024

Matt Wolfe

Mazda Motorsports, the company’s North American-based racing program, serves as a support network for thousands of professional and amateur racers at road courses around the United States. In addition to contingency programs, discounted OEM parts and a ladder system into the professional ranks, the program also maintains a catalog of competition parts designed specifically for the rigors of racing.

One of the recent additions to Mazda’s competition parts catalog is a differential cooling plate. The unit is intended for racers piloting the third generation MX-5 roadster (known by its model code, NC). The unit reportedly provides a significant upgrade in the cooling performance and improves longevity of the vehicle’s rear differential.

According to Mazda, the oil temperatures in a stock NC differential can become very hot during competition use. Mazda states that they have data showing operating temperatures of over 325 Fahrenheit (163 Celsius) on multiple occasions, which is too high for the fluid to work effectively.

To mitigate this issue, Mazda Motorsports has developed a plate that sits between the factory differential housing and cover.

It features strategically positioned ports for fluid circulation, including in/out oil lines and a dedicated temperature sensor port. The plate has fins on all sides serving as heat sinks. Dowel pins are included to ensure correct alignment during installation and a reusable steel/rubber-coated gasket simplifies rear cover plate removal for routine maintenance.

“The plate by itself is all most sprint racers are going to need,” said Josh Smith, business development manager, Mazda Motorsports, in an interview with SAE Media. “But if you’re running an NC in an endurance environment, it’s set up to attach additional coolers. We made sure (the plate) was spraying fluid on parts that need cooling by directing it where you want it to be on the gear stack.”

Smith explained the development process of the plate and how Mazda determined that this was a weak point for this chassis. “We had an Achilles heel in the NC differential from the OE standpoint and wanted to fix that,” he explained. “Our sprint racers did not want to justify the cost of an entire differential cooling system with fans and other components. So, we were trying to find an elegant solution that added minimal cost to the car, but reduced the operating temperature of the fluid and allowed an upgrade path for the future.”

Smith continued, “There’s no expensive fluid you can use to fix the issue because there’s no airflow and the exhaust is also located right next to the unit. So additional capacity and a heat sink was the logical solution.” Smith said that during testing of the unit, vehicles using just the just the plate saw max operating temperatures of 300 degrees versus the factory configuration.

“With just the plate, it took two hours of constant use to reach that temperature. That’s a 30–50-degree delta from the factory setup, which would reach those temperatures in just 20 minutes,” he said. “If you’re sprint racing for an hour or less, the spacer is all you need. If you’re running for over an hour, you’ll want the spacer with a pump and other components because it will eventually heat soak out.”

Smith estimates that there are between 25-30 examples of the plates currently in circulation. Mazda Motorsports is currently developing a comprehensive kit featuring a cooler, pump and filter. The system will be designed for ease of installation and maintenance and will mount on a removable plate in the trunk. In the meantime, if you’re a Mazda racer looking for a way to keep your rear differential cooler, look for part number 0000-02-5580 in Mazda’s catalog.

---