As we’ve discussed before, rotary engines make a lot of heat, and the RX-8’s Renesis 13B is no exception. As Jim Mederer from Racing Beat explained to us, one of the reasons the Renesis runs hot is poor airflow through the radiator because of how jam-packed the engine bay is. More specifically, the huge OEM battery and battery box that’s mounted tightly behind the radiator on the passenger side is a major airflow impediment. To give you an idea how poor the airflow is here, the RX-8 has an air duct to the bottom of the battery box to help keep the battery cool.
Although kits exist to relocate the battery within the engine bay (mounting it against the firewall where the windshield washer reservoir normally lives), we prefer the trunk-mounting approach using a dry cell (sealed) battery. We like the idea of moving a bit of weight to the rear of the car over the drive wheels, and we also like the fact that the Odyssey PC680 battery we installed is a whoppin’ 26 lbs lighter than the OE battery.
As you can see, the installation is relatively straightforward, and for you DIY types who don’t have a welder, you should still be able to use the West Coast Batteries hold-down box we used (which is specifically designed for the Odyssey PC680 battery) by bolting it to the sheetmetal bracing behind the rear seats.