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Flyin' Miata crossflow radiator

Flyin' Miata crossflow radiator

Regular price $449.00 USD
Regular price Sale price $449.00 USD
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More expected on Aug 28, 2024.
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We've taken our crossflow radiator back into the shop to see if it could be even better than it already was. The filler cap is no longer on a neck, it's now right on top of the tank - which gives much faster filling than having it cantilevered out off the tank. It's a cleaner look and better fitment (especially on MSMs). It also has an honest drain, not a small drain squeezed into a compromised location. 

For manufacturing, we worked with Koyo, who brings well over half a century of experience to the table, to see what could be made better. Working with Koyo means that the latest version of our crossflow is manufactured by Koyo (not a third-party), has beautiful TIG welds, micro-welded O tubes (stronger and more reliable than B tubes), and NOCOLOK brazing for maximum durability and anticorrosion protection. We then use Koyo's Hypercore, which increases the effective surface area - i.e., the radiator's ability to shed heat. Finally, each radiator is individually leak tested three separate times to ensure no issues. To top it off, we back it up with an exceptional two-year warranty. 

But even though we're taking advantage of Koyo's manufacturing, it's nothing like the generic Koyo radiator you find elsewhere. The crossflow design, the drain, the core selection and the unique mounting setup in the car all set it apart.

Now that you know why the new crossflow is the best one over, why do you want a crossflow in the first place? In short, dramatically improved cooling. The coolant flows side-to-side instead of top-to-bottom, which means that it's in the radiator core (and shedding heat) for longer. Not only is the layout much better, the core itself is special - in our extensive testing (read more about it here), not only did we find that generic upright aluminum radiators weren't much better than stock, we also found that dense tube and fin counts, as well as narrow fin widths, cooled best. So that's what this radiator uses. We also found that while a thicker than stock radiator is better, there's absolutely such a thing as too thick - eventually, the thicker core just means more resistance to air flowing through the core, plus the air is so hot by the time it gets to the back of the core it's not doing any good anyway. A thicker radiator makes a better heatsink, but you're not looking for something to absorb the heat, you're looking for something to shed it. Ours hits the middle ground nicely at 36mm / 1.4" thick. You won't find a radiator that's better at shedding heat than this one. Mate it with our FM coolant reroute and our Stage 2 V2 brushless fan kit, and you'll have the ultimate cooling setup.

We also designed the radiator to fit all 1990-05 Miatas, with the only difference being some brackets. There is no modification required to install the radiator in the car - the factory mounts are re-used in NAs (no new NA mounts are included, you must reuse yours), new upper mounts (with stock lower mounts) are required on an NB. A new high pressure (16 psi) radiator cap is included, and you can use any cap designed for a Miata.

If you choose to retain the stock fans, you'll need to make modifications to their shrouding. We highly recommend using one of our Airflow Kits for multiple reasons. May not fit with all intake systems - please call us to confirm. Does NOT fit with a TDR intercooler on a supercharger. 

NB cars will need our upper bracket kit (not necessary for NAs). NB cars using stock fans will need our NB fan bracket kit as well. Add those parts to your cart above. If you're not using a reroute, you'll need a crossflow-specific upper radiator hose - this radiator fits really, really well with our reroute kit, though. 

Please note that this does not have a transmission cooler built in, so it won't work with an automatic transmission car unless you install a separate transmission cooler. 



Ships free in the US.

There are no shipping restrictions on this item.

What does it fit?


Emissions do not apply.


2 years


09-10000 1990-05

Customer Reviews

Based on 5 reviews

Great product. Does what it’s supposed to do and looks amazing in the engine bay!

Great radiator!

I installed this with the coolant reroute and the stage 1 fans three years ago right before driving from Seattle to Houston and back through Arizona in July, the system works and it works well. I've seen 105 degree temps in stop and go traffic and the gauge barely passed half. My only mild complaint is the drain plug; you have the remove the fans to drain it. It would be nice if it was on the bottom and you could drain it without removing the fans, but it's a mild inconvenience.

Blocking the drain plug was certainly an issue when we first moved to Koyo as the manufacturer of our Crossflow radiator, but we've since updated our shrouds. Current shrouds (in both stages) have good drain plug clearance.

Jack's 9.
Great product, excellent quality, and easy installation

The crossflow radiator was purchased to install in my 1996 turbo Miata. I live in Houston where summers are hot ad humid and quite taxing on any car radiator.

The radiator arrived in a very secure and protected package. The crossflow design and finish was impeccable and top notch (FM way). The installation was very straightforward like installing a factory unit. My only complication was turbo specific, where the a/c fan could not fully clear my intake tube. This was remedied with minor surgery to the fan housing and it fit like a glove.

After install, I let the car idle for over 35 minutes in the garage with the heater blasting; the temperature gauge never went passed the half way mark, actually it remained lower than the half way mark. I drove the car around and under boost to stress the cooling solution, but it performed valiantly as designed.

I recommend the FM crossflow radiator for any Miata from stock to heavily modified. Thank you FM for another well designed and executed product.

Great looking and performing radiator

I added this Koyorad radiator plus high airflow fans and the coolant reroute as part of my turbo build on my NB1 track toy. It's a beautiful piece of equipment and is functioning great during my ECU/turbo tuning stage before I can try it on a track. It fit well with minor mods to move power steering connections to give the lower radiator hose clearance for a good connection.

Also note the Koyorad paperwork said the warranty is voided if used without any coolant, which contradicts the FM instructions to allow the option of a distilled water and Water Wetter mix for max cooling.

Note from FM: We apologize for the mixed message on the coolant, but the warranty will still be honored (by FM) as long as you use distilled water (not tap) and check for electrolysis.

Nice radiator, but needs updated instructions

I'll start by saying this is a very nice radiator for my 1999 NB track toy. The welds are perfect and all of the bolts line up. All the rest of this is a little of me griping, a little hoping that they fix the documentation, and sharing my one lesson learned.

The instructions are a different story. Several places it talks about drain plugs in each tank. There is only 1 drain and it is on the passenger side. It talks about a 3/4" NPT threaded plug installed in the passenger side tank. It specifies that you need to tighten this NPT plug with thread sealer to finger tight plus 1.5 turns. This NPT bung and plug doesn't exist and is actually the drain plug. The drain bolt has a rubber gasket (no sealer needed) and finger tight plus 2/3 turns is all you are going to get. I'm assuming the docs were created from a prototype unit rather than the actual shipped unit.

I noticed that I had a leak after installing everything. It turns out that the NB radiator bracket prevents pushing the bottom hose all the way on. A simple fix is to cut the lip from the back side of that bracket. It would have been WAY simpler had I noticed that before putting coolant in the system.