The data I posted earlier in the thread was with all 4 sides sealed. As you can see, removing the foam from the passenger side had little to no effect on coolant temps on the track. There may be some difference in ramp-up and recovery times, but it seems to be trivial--especially in recovery. There may also be some effect on lower speed driving. I have not logged any data in that regard, since my car spends most of its time at highway speeds and on the track.

I haven't read back over my previous posts, but I think I remember saying the improvement is slight, and I consider this radiator a reliability mod more than a performance mod. A couple of degrees here and there, slightly slower ramp-up time, and slightly faster recovery time is all I am willing to claim beyond that fact that there are no plastic bits to fail on this radiator. That result surprises me, considering this radiator is a good bit thicker, and about 0.7 gallon of coolant is added to the system (or distilled water in my case).

.

Alright, I've decided that I will be getting this thicker Koyo radiator, because my aging stock cooling system is not getting the job done in this 100+ F heat. On my way to work, I have to climb a mountain pass with a 2500 foot elevation change, 6% grade split into 2 parts, with a break in the middle. On the uphill parts I have to slow to 50 mph and turn off the AC to keep temperatures in check (less than 225F is my goal). Once over the top of the pass, recovery is pretty quick to 206 - 210 F range at proper highway speed.

Today there was a 45 minute traffic jam going up there. Once everything was heat soaked, it was game over for the cooling system. AC off, intake air temperature - 170F, ambient temp 104-109F. Had to turn crank the heat to keep the temperature down. :sweatdrop I know my fans aren't the problem, because they do a pretty good job of cooling when stopped, but there's a critical heat soak point, seems to be about 150 F IAT, beyond which they seem to loose ability to bring temperature down without help.

Maybe I can get some improvement by adding a bit of foam to the sides, maybe even a good flushing of the fins will help, but the fact remains that my stock radiator is 6+ years old, and has seen 123,000 miles and two Mazda re-man installations. Common wisdom around here states that excess sealant on Mazda re-mans clogs up radiators.

Eventually, once I get all her issues worked out, I want to take my car to HPDE/track days, so there's also that for a justification...

I think it is your fans. At 50mph you're not overheating, so it's not an airflow issue. This happened when you were stuck in traffic. That's when the fans come into play. Slow crawls. These fans slow down over time.

But that's the thing, normal traffic flow up the mountain is 65-70 mph. I can't do that for very long before ECT > 224F. I have to slow to 50 mph to reduce engine load & rpm, and allow the cooling system to keep up. The traffic jam was just an extreme case where everything was heat soaked, and it seemed the fans couldn't do much. I think radiator efficiency is my first problem. If I get to the point where I am fine at speed but only have problems in traffic, then I will tackle the fans next. With normal city driving, my coolant temperatures drop when I stop at a red light.

New radiator and silicone coolant lines are on order :) Which reminds me - I also need to procure some polyurethane foam, and a good adhesive to bond it to the radiator.

But I thought you said you already bought the Koyo radiator. That's why I suggested the fans. Yeah, if it's fine at high speed and only overheats at low speed, it's definitely the fans.

Doesn't it still have the factory foam? Fully sealing up the front will make a huge difference. I have a stock radiator with stock fans, prior to sealing my temps would go over 220F whenever it was over 90F outside. Now I can idle in 95F weather and keep the temps below 215F. It won't fix my problem. But it certainly helps. Mine is because the fans aren't spinning fast enough.

Just stuff em into the gaps around the radiator. That's what I did. It'll hold if it's tight enough... :yelrotflm

New radiator is going in my car today! I decided to basically replicate the OEM foam installation based on Steve's excellent pictures. I used 1" thick polyurethane (which was a PITA to cut because it is rather soft), and attached it with epoxy. I only added a few extra inches of length to the bottom foam, so hopefully I still get sufficient airflow to the engine bay.

https://cimg4.ibsrv.net/gimg/www.rx8...92adcb9080.jpg

https://cimg6.ibsrv.net/gimg/www.rx8...7af2e4e20c.jpg

Did the radiator cure your overheating issues?

It helped, but the cooling performance is still not where I want it to be. After the radiator was installed, ambient temperatures were still pretty hot for a few weeks. Climbing hills at over 100 F, I still had to back off the throttle and or turn/off the AC. Overall, I'd say the new radiator gave me a 15 degree ambient temperature operating range improvement. I.E. with new radiator it I would see the same max coolant temperature at 95 F ambient as I did at 80 F before. Also temperature ramp-up seems slower than before. Unfortunately I do not have detailed data logs to compare before and after.

My foam installation has resulted in more engine bay heat soak, unfortunately. My intake air temperature is now roughly 10 degrees > ambient during cruise, whereas before the difference was 4-5 degrees. Also it is quicker to heat soak when stuck in traffic or driving slowly. On a 100F day, after half an hour of essentially not moving, I was seeing intake air temp of 170 F.

To improve the situation I'm going to try some air flow tweaks. Next time I'm under the car, I plan on removing some of the foam from the passenger side to help with heat soak. For hill-climb performance, will try the zip-tying the undertray to the rad support as Steve has done. If still not performing as I like, I'm going to see what effect removing front license plate obstruction will have.

I think you need better fans. That should help.

LOL! Nisaja's answer is always the fans! [He could be right, though. Definitely worth checking.] The fans slow down over time. It is also possible a grommet from the airbox has fallen into one of the fans, stopped the blades, and burned out the motor.

Another possibility is that your thermostat is not opening completely.

I wish I could replicate the hill climbing you are doing to give you a baseline temp. What RPMs are you running uphill at 70mph?

Haha well if you're only overheating when moving slowly, and not when moving fast, it's definitely the fans. That's what happens in my car. And my fans are practically new! Last night I was sprinting in traffic. Getting up to around 80mph. Temps went up to 221F :( I had to back off. However, if I'm just flooring it on a straight road, it doesn't exceed 215F. So it's definitely an airflow issue. Even while moving fast, the fans still help. They turn on while moving if they're over the trigger temp.

I don't think a rubber grommet got stuck though. If one of the fans aren't spinning, you'd be overheating way sooner.

Question. I have read through this thread, but could not find if S2 Koyo 48mm could be retrofitted into S1...meaning if the holes and brackets all line up.

Any info would be helpful. Thank you.

I don't know about the Koyo S2 radiator but I recently installed the CSF 3164 and it's a perfect, direct drop-in fit.

http://csfrace.com/product/mazda-racing-radiators/

https://www.amazon.com/CSF-3164-High.../dp/B001FI1GXG

It's a 41mm core, all aluminum dual-row unit. It's probably about as thick as you can get without having to modifying the battery and airbox trays to fit the fan shroud.

I just purchased this koyorad, along with a mishimoto racing thermostat (169 vs stock 180 opening temp), autobauhn88 silicone hoses, Pettit Racing Aluminum Expansion Tank Spec. A Kit, and 3 gallons of mazda FL-22 premix. Besides from foaming at least the top and bottom of the new radiator, is there anything else I could get before installing?
Can I transfer foam from the stock radiator to new koyorad?
Would it be recommended to install a new water pump as well, stock replacements are cheap for the series II ($75)...?
Its a new Mazda-warranty replaced engine, with less than 10K on it...
Thanks

I couldn't get the S2 water pump that I order from MazdaSpeed Motorsports Development to seal properly, even after scraping off the old residue and trying a different S2 gasket. I ended up with the Mazmart RE-medy pump.

I also bought some 1" ID pipe insulating foam and used that to seal the bottom and driver side of the radiator. For the bottom, I cut it in half and used 3M Super90 to attach one half to the radiator. I let it cure for a few hours and then glued the second half to the first half. Then I zip-tied the belly pan to the lower radiator brackets so ensure a good seal. I did pretty much the same thing for the driver side.

This radiator and foam setup combined with a new OEM t-stat, OEM ECTS, and RE-medy water pump keeps me between 176˚F and 178˚F on the highway.

Thank you for the tips and products you use!
3M Super90 will have Adhesion Failure at 250F...
I would be interested in the Re-medy Hi-Flo Water Pump if it fits the series II engines...?
I also forgot to mention new "adjustable" hose clamps to replace all the OEM "fitted" hose clamps, as they were the source of a coolant leak.

You're going to be better off with an OEM pump in your S2. The OEM S1 and Mazmart pumps have one stud in a different location from the S2. It can be made to work but the Mazmart pump is only a huge upgrade from the S1 pump, not the S2.

Yah, the shear test failure at 250˚F concerned me a little bit. Ideally, we shouldn't reach that temp and if we do, we have bigger problems. Also, I used the undertray to help secure the foam to the bottom of the rad and the side of the rad has a lip that I nestled the foam down into. That said, "Rubber and Vinyl 80" will go up to 300˚F (I just couldn't find any locally so I went with Super90).

I get it that some people just like modding their car, but a lot of what you have listed doesn't do much that is useful. Using those parts certainly won't hurt anything, and there is nothing wrong with modding just because you like to, but...

A lower temp thermostat sets the operating floor of the car, which means the car will run cooler at cruising speeds, where heat is not a problem anyway. It won't do anything to help the car run cooler when stranded in traffic or at the track, where heat is an issue (it is all about the fans in traffic). Also, a low temp thermostat will cause it to take longer for the car to reach operating temperature, which is not a good thing. Engines are designed to operate at a particular temperature, and expansion of materials is calculated there during the engineering phase. Running it too cold can lead to premature engine wear due to slower expansion and/or lack of expansion. Finally, the thermostats Mazda uses are higher quality and better designed than most aftermarket units. Most of the Miata racers I know run OEM stats.

Silicone hoses offer no performance gains over molded rubber, and yours are not old enough to warrant replacement. Actually, some silicone hoses collapse under negative pressure, which makes them worse than molded rubber. I just changed all the hoses on my 2003 Miata and didn't need to. The OEM hoses were still fine. I used a combination of Gates and AC Delco hoses from Rock Auto and spent about $25 total.

Your OEM water pump should be good for at least 100K miles. You are only 10% of the way there, assuming you received a new one with your engine replacement. It is a good unit that does not need frequent replacement.

As for the insulation, I found that friction is enough to hold pipe insulation on three sides of the radiator without using any adhesive (assuming you wire tie the under tray to the lower radiator mounts). I glued mine in with high temp RTV, but later discovered I didn't need to. That adhesive did not hold on the bottom, and I lost that foam, which is why I went to wire ties on the lower mounts.

.

I installed this radiator yesterday in my s2. The condenser mounting bosses were off just enough on one side that one bolt would not fit. Since I was too lazy to pull the radiator/fan assembly back down to give me room to notch the condensor bracket, I opted for the weight reduction/3-bolt mod. Those installing this might want to compare the condenser mount locations with the stock unit to see if anything needs to be done before getting the radiator in.

After I poured my 25% coolant mix +water wetter in I noticed the paper that came with it says not to use any cooling additives. We'll see how it does, I don't recall ever seeing reports of water wetter causing corrosion so I'm not too worried.

Oh, and it turns out super glue will not hold AC unit foam to metal, but loctite extreme works well.

water wetter Seriously Why do you put that crap in your new radiator?

Just put in the correct coolant, I guess any mug can be sold BS (no offence), water wetter..

I suppose you put Nitrogen in your tyres also and oil additives in your engine.

One additive that can benefit any RE and that is pre-mix (lubrication) in fuel.

LESS IS BEST ;)

Flush your system to get rid of the Watter Wetter. It is an old formulation that is incompatible with many modern coolants. It polymerizes and creates a brown or black sludge in the system. Flush it out now or risk much more frustration in the future.

https://www.google.com/search?q=wate...utf-8&oe=utf-8

I've run it in basically every car I've had that's seen hard driving for the past 15 years or so. Hasn't caused any problems for me.

edit: After doing a little more research I've decided to pull that stuff out. Thanks!

Water Wetter is probably worth it if you're running straight distilled water (some race tracks or race organizations require glycol-free coolant).

But, yah, otherwise don't bother.

Well I started to go back in today for the flush and noticed a leak. From underneath it seems to be coming from the upper passenger side. All hose connections seem dry from what I can see and feel, though it is very difficult to check the lower reservoir and upper radiator connections while the car is running. Have a feeling the radiator is defective.

You can go to an auto parts store and rent a cooling system tester to help you find the leak.