it should also be noted here for anyone who may come across this later that the FAL 490 is rated for 3000 cfm vs 2400 cfm for the FAL 420 and also supposedly fits despite being thicker. The 420 should be fine for most people, but for those who want more flow and don’t mind paying extra it will also install the same.

Note that the 440 is listed initially in this link, but the 490 is the correct 3000 cfm model:

https://www.rx8club.com/assaultech-1...8/#post4485426

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Important!

kind regards.

 

I m buying one of these for my swap

 

adding to the database here

so recently Koyo introduced a “Type F” radiator in Japan and has been hyping it up some; they love and eat up hype in Japan.

I sent Koyo a note asking about it and this was conversation


So this will answer some questions about the various radiator types that have been discussed previously

S2 48mm core = Type F

Race 53mm core = Type Z (discontinued, now Type F is used)

S1 36mm core = Type M

It appears that the S2 48mm core will offer the most heat transfer capability, but there are potentially some fitment issues on the S1; likely the more factory stock it is as far as the battery, intake box, etc. the more likely there might be interference with the thicker Koyo radiator (S1 thickness is only 27mm, so the S2 Koyo is almost twice as thick)




In the graph above, the water flow rate on the horizontal axis can be seen as an increase in engine speed, and the vertical axis can be seen as the cooling performance at that time. As far as you can see in this graph, the heat dissipation effect is higher in the order of TYPE-S, M, R & RII, F = Z. The more power you power up, the higher the heat dissipation effect required by the engine, and the same is true for vehicles that ride in situations where the WOT time is long. .

TYPE-F, the flagship model of KOYORAD Racing. The difference in heat dissipation effect from other models is as shown in the graph above, but this is a graph comparing the air side pressure loss with TYPE-Z (discontinued product) that exhibits the same amount of heat dissipation. As you can see, the pressure loss on the air side of TYPE-F is improved by about 35% compared to TYPE-Z, and the running wind efficiently passes through the core, so you can expect more heat dissipation than TYPE-Z. .

Compared to TYPE-Z, the dry weight is about 1kg (*), and the weight including cooling water is about 1.5 to 2kg (*). (* There are differences depending on the model) The heavier the car and the farther the heavy object is from the center of gravity, the greater the moment of inertia during cornering and the lower the handling performance. By reducing the weight of the radiator, it leads to the weight reduction of the vehicle body overhang (the part of the total length of the car that protrude .

 

I've been using the Type F for 3 years here in Japan, excellent radiator. I'm running about 280whp with a turbo setup and ran at Suzuka for 9 laps straight and water never went more than 93 to 95c according to the obd2 logs and temperature gauge. It's completely sealed, no fitment issues. Highly recommend it.

 

Thanks for the confirmation. Did you import one or do you have an inside connection?

Because it was only just recently released for sale in Japan as stated above and also tagged as “NEW” on the Koyo Racing Japan webpage. I had previously posted info from them stating the performance was similar before this most recent exchange and information.

We also discussed in this thread wondering why they didn’t just have one radiator for both S1 and S2. Koyo themselves had experienced an interference with the 48mm core on some S1s as per my posted reply from them above.
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I've got the S2 rad in my car. Temps seem "fine" but I did a track day before realizing the installer (previous owner) didn't properly seal around the radiator... 217F in short blips, but I had the defrost on to keep the windshield from fogging up in the rain so the A/C was dumping heat into the radiator. Around town and autocross it never gets very hot. Bumps up to ~200F and immediately drops to 180F stable when I start driving.

I'll need to log some more data on track without the A/C on, haha

 

Team, sorry I took some time to reply, had to figure out where I bought it. Finally found it. Bought it off Yahoo auction here in Japan on June 2nd 2018, paid 51,960 yen, about 500 usd. When I was looking for radiators I found it on the Koyo radiator page in Japan, they had it listed on the model compatibility. So it's been available for at least 2 and a half years here. Sounds like Koyo US doesn't talk too much with Koyo Japan, which doesn't surprise me lol. Anyways, it works great, highly recommend it, no fitment issues, it was installed by a Mazda dealer here.

Cheers

 

I recently installed the Koyo 53mm N core, which I sourced from the UK via ebay. No fitment issues, but it might need some adjustment in a stock engine bay. I had already hacked up my engine bay to fit an rx8performance radiator, which this one is replacing...
I had to piece together a new coolant pipe to reach the lower connection on the radiator as it is shifted over to the drivers side from the original position. I did this by cutting a straight aluminum pipe to length and then cutting some old coolant hoses to fit to each end of that.
Also trimmed the upper radiator hose slightly to avoid kinking due to the extra depth of the radiator.

Still need to track test. First impressions on the street are good, but the weather is cool here right now so that is very subjective.

This UK store offers a custom hose kit, so there is an off the shelf solution to that if you want it:
Koyo Racing Radiator 53mm Core for Manual RX-8 ? Essex Rotary Store
Essex Rotary Exclusive RX8 Radiator Hose Set for Koyo 53mm Radiator ? Essex Rotary Store

 

it’s a shame you went through all that unnecessarily

 

Hmm. Somehow the images you posted with the info on Z vs F didn't show up for me earlier so it took a moment to understand your point.

So I guess type Z is 53mm N flo, and koyo are actually saying the 48mm (s2 racing rad) performs better. That is unexpected for me :-/

I'll try and report back how this one does when I get it on track...
Consider my pain an experiment for the community 😅 I've been through s2 oem->s2 koyo (this thread) -> s1 oem (temporary replacement) -> rx8performance and now 53mm n flo. I guess we'll see how this one does and how long it lasts me. I killed every other one on track aside from the s1 oem which was really just a temporary emergency fix!

So far the different radiators don't make a massive difference, but I need every degree I can get. I don't exactly have apples to apples data since engine power and conditions have varied, but I can say that a healthy engine with the s2 koyo from this thread, in an s2 chassis (so also had the slightly improved oil coolers) was overwhelmed by a healthy engine in 100F ambient temps on track.

Going from s1 oem to rx8performance gained at least 10F. For the back to back data I have it then comes close to thermostat opening temps, so the true gain might be more at higher temps, but that radiator developed a leak so I'm now back with koyo. If this one can cool at least as well as the rx8perf and be reliable I'll be happy.

 

At the moment with the 36mm and FAL420 all cools properly in my driving conditions.

kind regards!

 

yeah, he’s racing at the track in hot, humid summer conditions

glad to hear your street situation is resolved

there seems to be a lot of conflicting information from Koyo, but in theory they did say the S2/Type F was same heat capacity as the 53mm race radiator despite being thinner, but also lighter having less coolant volume due to it being less restrictive and allowing more to flow through it.
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With the Mazdaspeed front bumper, cruise on highway at 139km/h almost flat with 20°outside and without foam all over the radiator jet: dashboard says 84-87° and 90° for the oil.

different story will be on summer but with my manual fan controllers, I’m relax. :-)

kind regards Mark!

 

I do think that you need to seal the radiator completely for it to be as good as it can be. If you still have some heat issues you can try a vented hood, with vents where the battery and air filter are so that you have the pressure differential working for you. Anyways, I tested this radiator with 30+ degrees C ambient and it works great.

 

Thanks,

yes! I know that’s important just like Mazda designed. Only I’m going to let free pass through the manifold exhaust for fresh air because it’s reported overheating in all the engine bay, specially thermostat housing, manifold exhaust and coolant hoses.

kind regards.

 

would the type US type "HH" be equivalent to JDM Type "F"?

Koyo Radiators (04+ RX-8)

 

yes (according to Koyo USA Racing) again:

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What I don't understand is the second graph. It compares type Z and type F and shows the difference in "the pressure loss on the air side of TYPE-F is improved by about 35% compared to TYPE-Z" so is there a change in design to achieve this difference? So type F does not equal type Z? By equal do you mean this is it a nomenclature change as well as design change? Or just a nomenclature change? Confused.
I run the CSF 55mm core by the way, the single pass with B tube and that thing fits in the stock location and cools very well. Of course not as good as dual pass.

 

No, that’s why it’s equal in cooling performance despite being less thick/having less coolant capacity/less weight. The core re-design is such that more air can flow through it, yet still have enough surface area to provide the increase that makes it have equivalent cooling capacity.

It’s that combination that makes it do as it does ...
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The s2 48mm rad arrived. What's the deal with cuts on the side support? Looks like they were cut after the rad was assembled. Are they for heat expansion? I just never notice them before on other aluminum radiators.

 

expansion/heat growth I suppose to keep it from tearing itself up from heat cycling

seem to recall the OE radiator is the same more or less in that regard

 

@trackjunkie

How well did your fan shroud fit the Koyo radiator? Mine had about 1/4in gap on either side from the radiator standoffs being so tall, so I'm thinking I will need to install a gasket to help direct air.

 

i have not installed mine yet. i was considering going with a single FAL fan to reduce some front weight. just need the fan on while sitting in grid.

maybe you can trim down the mounting post. but a rubber or foam gasket would probably be better.

 

First proper test with the 53mm N-flo I ordered from the UK.
Top two sessions are with the koyo. Bottom two are with the rx8performance radiator ~2 years ago.
Motor has been rebuilt since I last ran at this track with the rx8performance radiator so it's not exactly apples to apples. I think I'm making a touch more power, but had a little less grip this time out. The driver was also a little rusty :-)
I might have done a slightly better job with the foam this time as well.

OK, enough disclaimers... Overall the laptimes and delta to intake temps are very similar, slightly favoring the koyo which had coolent temps at ~200F in a 72F session vs 200F on a 68F session with the RX-8 perf radiator.
This is at a pretty tight and slow track, one short straight with a max speed ~96 mph.