It’s no secret that rotary engines make more heat than a pizza oven, and the Renesis in our RX-8 is certainly no exception, even in naturally aspirated form. Now that we’ve decided to add some compressed air to the equation, we knew it was time to get serious about heat control. So in preparation for a supercharger, we’ve begun the heat management process with a couple of key upgrades, starting with a Mazdaspeed radiator.
This motorsports-grade all-aluminum radiator, built by Ron Davis Racing for Mazdaspeed, is designed to be a direct drop-in installation and has proven itself as a highly effective cooling upgrade in some of the most demanding environments, including Grand Am and World Challenge road racing. Its performance gain is primarily the result of its highly efficient dual pass cores and the use of an aggressive fin count for maximum cooling.
Aggressive fin counts are more expensive, so they’re not widely used in the industry, but the combined experience of Mazdaspeed and Ron Davis Racing determined that it maximizes cooling capacity for hard to cool applications like rotary engines. The fins on this motorsports radiator are also multi-louvered for enhanced air turbulence to maximize heat rejection. And as you can see, the build quality is truly top-notch thanks to CAD design, CNC-cut sheetmetal, and perfect welds with consistent bead width, spacing, and penetration.
It should be noted that we bought this radiator through Mazda’s motorsports program as a registered racer at mazdamotorsports.com, something anyone who races a Mazda in autocross, time attack, or road racing can do at no cost. All you have to do is participate in at least two events a year and you qualify for the deep parts discounts available to all registered racers. There’s also a lot of highly useful technical information available via the program, both online or if you call the 1-800 number.
One of the other big challenges with rotary engines is underhood temperature control. Ask any turbo FD or RX-8 owner about how everything in the engine bay gets cooked from the radiant heat, and our next upgrade will make perfect sense—especially when you consider that a lot of the underhood radiant heat comes from the exhaust manifold or header.
TurboSource—a widely respected name in turbocharged performance that’s headed by Nick Worley and rotary fanatic Elliot White from Turblown Engineering—now makes a wide variety of Inconel heatshields. Inconel, an aerospace alloy, is ideal for heat management as it produces an oxide barrier protecting against temperatures up to 3,000 degrees F. Silica fiber is enclosed within two layers of Inconel to further protect against radiant heat.
The Turbo-Source shields’ design also provides a critical air gap that reduces convective heat transfer and allows for the expansion of the shielded components (in our case, a Racing Beat tubular header).
TurboSource’s Inconel header heatshield will usher all the exhaust heat out the tailpipe instead of letting it radiate into the engine bay. This should be a huge help in controlling underhood temps.
Part of the beauty of TurboSource’s Inconel heatshields is that they’ll never break down or burn up like wraps, blankets, or shields made of lesser alloys. So although these shields do come at a premium price, they also deliver premium performance and durability. By reducing underhood temps dramatically, they also lengthen the service life of hoses and electrical wiring, both of which tend to suffer badly in the extra-crispy environment of a rotary engine bay. A cooler engine bay also means your engine will benefit from lower intake air temperatures, which not only means more power but increased reliability.
TurboSource offers a growing number of prefabricated Inconel heatshields that are molded to the shape of popular components, including turbocharger turbines, turbo manifolds, downpipes, and wastegate dump tubes. The company also offers a custom heatshielding service for any component you ship it. So in our case, we shipped them our Racing Beat header, and a few weeks later we got it back in the custom Inconel shield you see here.
Since we’ve started to bolt up the supercharger, we also decided to fill our Renesis with Royal Purple motor oil, since it’s a proven product in these engines.
We spoke to Jim Mederer at Racing Beat about oil options for rotaries and he had this to say: “Over the years, I have seen some small power increases from changing to Royal Purple from the mineral oils we use for break-in. These increases are not consistent in all cases, so we avoid making claims in our advertisements. However, we have seen drops in oil temperatures—particularly in the trans and diff—of about 10 degrees F. Even more important, we have seen reduced wear, particularly in high output turbo engines. Since no two engines have the same service life, it is not possible for us to quantify the wear reduction, but it is enough to be easily visible on inspection.”
Jim’s endorsement is enough for us, since few rotary specialists have more experience going fast than he does. But if you still think conventional (non-synthetic) motor oil is best for rotaries, keep in mind that Mazda won the 24 Hours of Le Mans with its 4-rotor 787B race car with synthetic oil, and Mazdaspeed also recommends synthetic oil for racing purposes.
Royal Purple’s XPR racing oil is a full synthetic formula that’s durable enough to provide maximum protection, even with the high oil temperatures our Renesis produces.
Royal Purple makes a wide range of lubricants for all kinds of engines, as well as race-specific motor oils like the Extreme Performance Racing (XPR) formulation we’ve opted for. XPR has been put to the test in all sorts of professional racing, from NASCAR to NHRA, and is based on a high-quality synthetic base oil that Royal Purple has added its proprietary Synerlec additive package to. This additive package is designed to maximize horsepower and torque while providing the highest level of protection against heat and wear.
We also opted for a Royal Purple oil filter, which uses a 100 percent synthetic micro-glass filtration media that filters out particles as small as 25 microns, more than 10 times smaller than a conventional cellulose fiber filter catches. It also has a silicone anti-drain back valve to prevent dry starts.
We do have more heat control upgrades coming from DEI, but in the meantime, we’re forging ahead with the supercharger install with the help of our local rotary guru Joe Ferguson and his right-hand man, Dave Sibbitt. By the time you read this, we should be up and running on Adaptronic’s new plug-and-play RX-8 standalone ECU, too, so stay tuned for lots more Renesis tuning in the next few issues.