So after searching and reading the previous threads about radiators, im am none the wiser in what to choose. I have heard that radiators are one of the reliability mods i just have to get done to this car.

My current options after some reaserch are:
- Koyo N-Flo (HH(48mm) or R(55mm))
- Koyo Regular (HH(48mm) or R(55mm))
- Mishimoto

Reasoning: They are all in the $300 range. Get good reviews.

My car:
- 100% currently stock engine wise
- Will go BNR twins, Autoex Intake and larger SMIC in the future
- 400RWHP as a max future goal (twins wont get me higher i guess)

Driving:
- Mostly daily driving and cruising
- Track and AutoX once or twice a year
- Rarely over 25C/77F outside temps (in the shadow) in Norway

I am at the moment tilting towards a regular radiator, since i will do little or no track/autoX, and mostly cruising or regular driving. Both Mishimoto and Koyo are equal there i guess? Also, it wont put that much strain on the engine, hoses and water pump due to better flow than the N-flo.

Do you know if the regular Koyo got the bleed valve on top like the N-Flow have?

 

I would probably go with the regular Koyo. You can go too big on a radiator - if the car never warms up, it uses more gas and it's still trying to richen the mixture to compensate for the engine being cold, which means you are way down on power.

I have a regular Koyo and mine doesn't have a bleed at the top. But, with it mounted in the stock position in the car, that would be really hard to get to. Also, using the Lisle funnel, I've NEVER had problems getting air out of the system.

Dale

 

I have never tried bleeding mine, so i cant say anything on how hard it is except what i have read. And i dont have Lisle tools/Equipment easily available, so i am not sure exactly how it works, and if it is possible for me to make a tool that does the same, using a hose or something?

 

I've had several leaks from mishimoto on multiple radiators from them. They are cheap and they have a lifetime warranty because of the poor quality.

 

If you track your car, you may want to look into a V-mount set up. They are expensive, but are best at keeping both coolant and IAT temps down (especially if you are looking at upgrading both radiator and IC). Since I already had a med SMIC, I went the stock route with a Ron Davis rad, but have not yet installed it to report any findings.

You should also focus on cooling your oil as well. Dual oil coolers are a must

 

I want to keep it as stock looking as possible because of traffic laws here. Tuning is in fac illegal, and all must be done as anonymous as possible. And from what i have seen, thats hard with V-mount.

Since i got a eurospec, i got twin oil coolers already.

Are Koyo better quality than Mishimoto? They are the same price:P
I like to purchase from places like ebay cus of cheaper shipping, last time i checked a Ron Davies they wanted $500 to ship here, ebay only $60.

 

The consensus seems to be Koyo and Fluidyne are good stock replacements and that there are some reported quality control issues with Mishimoto, but I have no experience with any of them. Suggest you search the forum for previous posts.

I believe Ron Davis was/is the manufacturer of Mazdaspeed radiators. While it may be cost prohibitive to source a RD radiator, you may be able to get your hands on the Mazdaspeed one. Koyo is probably the best bang for the buck though

 

I guess you have to flip the stock radiator mounting pieces when installing the thicker Koyo N flow to fit the stock fans, airbox, IC duct back in.

Bodyshop did not know this and told me the stock fans, airbox, IC duct did not fit with the Koyo N flow installed and put the stock radiator back in.

Banzai Racing really prefers the Koyos over Fluidyne from their experiences.

https://www.rx7club.com/3rd-generati...estion-894363/

Mishimoto is real ebay crap. Just google "Mishimoto quality" and the horror stories pop out.

 

I do not ever flip the mounting brackets, I mount them exactly the same as the OE radiator. Flipping the mounting brackets actually raises the radiator. The trick is the remove the upper passenger side A/C condenser bracket and straighten out the tabs on the lower radiator support/ sway bar mounts.

Just finished a Koyo install the other day with factory everything but AST, perfect fitment.

Notice the mounting brackets are flush with the fan side of the radiator, if they are flipped over they raise the radiator about an inch.

 

Cool, i read the thread linked over here, and from that deducted that for my use (99% daily driving, cruising and having fun on the street) the regular Koyo would be better. Is that a safe assumption to make?

Should i then get the R(55mm) or HH (48mm high fin density) version?

@Banzai: Thanks for the pictures! Since you got experience with the Koyo, how would you rate the Koyo vs stock in terms of performance (temperature and system pressure)? And does it fit with stock AST?

 

I do not ever flip the mounting brackets, I mount them exactly the same as the OE radiator. Flipping the mounting brackets actually raises the radiator. The trick is the remove the upper passenger side A/C condenser bracket and straighten out the tabs on the lower radiator support/ sway bar mounts.

Thanks for clarifying that!

I got the wrong idea from Post # 16 (below) in that thread I linked.

Captain_Panic

I bought the koyo Nflow as well, and the only fitment issue is just one of flipping the clips so it sits as low as the stock rad. You may have to eye ball it or measure to get it to fit as low as possible, but flipping the stock clips allows it to fit right in.

I also noticed on my standard single oil cooler car, the lines were slightly in the way making it a tougher fit. I have upgraded to dual oil coolers and it wasnt a problem.

 

Yes, of course it works with the stock AST, but that should be upgraded immediately. The old cores do not exist any longer, they were 52 not 55mm, the only Koyo currently available are the 48mm. Anything is better than stock

Blue - I see incorrectly installed parts every week, it is unbelievable how much rework I have to do

 

Remove the upper passenger side A/C condenser bracket as in remove completely and don't use again or as in remove while installing the radiator and then reinstall? You posted a link to a UK RX-7 forum with a reasonably thorough Koyo radiator install. If I remember correctly, that guy had to not only bend the sway bar mounts, but trim the bumper and bumper support as well.


I had a Fluidyne circa 2002 that looked great and worked very well; beautifully constructed piece. Went with it over the Mazdaspeed/Ron Davis/AWR unit because it was thicker, and over the Koyo because it fit without modification (other people reported issues but the Fluidyne fit perfect for me). Tried to order another Fluidyne a year or so back from two shops who carried their products and they recommended against the "new" brand. Apparently company ownership and/or manufacturing has changed hands and locations several times since that original radiator purchase and quality is inconsistent on the new stuff.

 

I posted a link to a how-to in a different thread so that I would not have to create one. I have never trimmed anything on any stock location installation, otherwise I would have mentioned it above.

EDIT: Just found the link to the AUS how-to, on the 99 front bumper support they are notching it and having to trim another piece of plastic. http://www.fdrx7.com/forum/showthrea...nzai%2A&page=2

 

In my opinion, I do not believe you can overdo the radiator on rotary. The thermostat will maintain the temperature of the car unless you live on the south pole.

I've used the stock radiator, the regular koyo, and the n-flo.

The n-flo is extremely impressive. The air bleed screw works wonders. The triple pass design seriously helps more than you may expect.

Temperatures on the 20b stay around 190-200 in 85F temps in heavy traffic. Temps on my 13b dropped around 15F averaged from switching koyo regular to koyo n-flo.

In my opinion, skip everything else, koyo n-flo or custom larger intercooler

 

^I agree with Monster. A bigger rad will have the ability to disperse more heat from your coolant based on the larger size, material its made from, and flow. The engines operating temp is controlled by your thermostat.

 

I have heard mishimoto has stepped up their game recently quite a bit when it comes to radiators..

was hoping to hear that echoed here.....maybe I will just go koyo!

 

This thread was really helpful. I think installing my radiator (which I haven't started but was clueless on how to do) is a less daunting task now. I do think I'll need to order some replacement brackets because I think I'm lacking the stock ones.

https://www.rx7club.com/build-thread...s-tlc-1083431/

 

My car dropped coolant temps by 4c at idle switching from Fluidyne to N-Flo. I was impressed.

 

A Fluidyne was my first 'mod'. Still no complaints but djseven's post in interesting.

Zepticon...with those current and future mods and looking for reliability, I also recommend you consider a simple (boost activated) water injection system. They reduce load on the cooling system... alot. They're also inexpensive, reliable and you get knock and carbon control with it. ---> Auxiliary Injection - RX7Club.com

 

That is on my list of things i need ;D
And since its a euro, i got that nice window washer fluid tank in the trunk to store the methanol

 

Koyo or Fluidyne all the way. I've seen the Mishimoto in person and I have a bunch of friends running them and the other cheap chinese knockoffs from ebay. They don't ever seem to last very long until a pin hole leak forces you to get a new one. Hopefully the leak is noticed before you cook the engine....

 

Same here... they're used often in the miata community and we've had so many fail. The Koyos rarely seem to have issues. We sell both, but I only recommend one

 

Thanks for all the input! Think Koyo will be my choise then.


Did you test the N-FLO vs normal on the electric waterpump kit you sell at Sakebomb?

 

We haven't, but the N-FLO radiators are quite good, and usually what I end up recommending to customers. While the standard one will work just fine, the multi-pass radiators do perform better with the same airflow. Any radiator works with our EWP kit but obviously the better the efficiency, the more heat it can extract from the coolant regardless of which pump you're running.