Based on our excellent crossflow radiator, this twin-pass setup was designed specifically to mate with the LSx V8 engines. The inlet and outlet are on the same side of the radiator and are the appropriate sizes for the big V8s. There's also a fitting for the steam vent. The twin-pass design makes it very efficient as well. Available for all 1990-2015 Miatas.
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. This is the result.
The final design is a dual pass 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 and back again. 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 V8-specific airflow kit and you'll maximize the ability of your radiator to shed heat.
Includes radiator and cap only. The NA/NB version can accept either stock NA fans or the FM Airflow kit. If you want to fit stock NB fans, you'll need the NB bracket kit.