We've taken advantage of volume purchasing to drop the cost of this radiator even further! The current version keeps the 3/8 NPT sensor bung, bleed vents at the top of each tank, twin drain plugs and high-flow filler as well as our high density, high efficiency core and adds nothing but savings.
In order to test the Miata's cooling system, we built a special rig for our dyno. We used it to run a Miata engine at a set load for hours at a time. We tested stock radiators. We tested custom-built crossflow radiators. We tested dual pass radiators. We tried fin densities from 10 to 24 fins per inch, core thicknesses ranging from 16 to 56 mm and fin widths from 6 to 10 mm. Read more about it.
This is the result.
The final design is a cross flow. This means that instead of having the coolant run from a tank at the top of the radiator to the bottom, it moves from one side to the other. The longer tubes mean the coolant is able to transfer more heat to the ambient air.
But there's more going on here than just turning the core sideways. The core also has a fairly high fin density, giving a greater surface area for the heat transfer. Most importantly, our fin width is fairly narrow which means more tubes per inch. Due to this efficient core, we were able to use a thinner design. The end result is improved cooling under all circumstances. Mate it with our airflow kit and you'll maximize the ability of your radiator to shed heat.
We also designed the radiator to fit all 1990-05 Miatas, with the only difference being some bolt-on fan brackets. There is no modification required to install the radiator in the car - the factory mounts are used. The drain plug is in the left side tank, integrated into one of the mounting bosses so you can use the factory access flap and drain the radiator without pulling the engine undertray. A new high pressure radiator cap is included, and you can use any cap designed for a Miata.
The cross flow design moves the upper radiator hose over slightly, so you will probably have to replace your upper radiator hose. We have a special one just for the crossflow rads. You'll also need to make modifications to your factory fan shrouding, although we highly recommend using our Airflow Kits for full effect. May not fit with all intake systems - please call us to confirm. Does NOT fit with a TDR intercooler on a supercharger. 1999-05 models may have to reshape the hood prop slightly.