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i updated buy track car build thread with the installation of the S2 radiator. my first track event is in two weeks, so i'll have some data, although ambient temp will be 60-70, so wont be anything valuable.
first picture is Teamsrx8 work and second is mine.
it’s correct?
kind regards.
Was just looking at this for someone else and realized that I messed up a bit here; the wiring diagram above is for the S1 RX8 and this thread was for the S2. I had forgotten that the S2 has a revised fan strategy with four relays that provides an additional speed. The main thing to note for an S2 installation is to wire in the new fans with the wiring aligned to the OE fans as indicated above and confirm that they both rotate in the proper direction when running.
had a really hot race this weekend. ambient temp was around mid 90s. coolant temp was mostly hovering around 205 with a few peak of 210. I checked vids from my previous years with similar ambient temp and coolant was around 215 with peaks around 220, for the koyo S1 radiator.
I went to Suzuka a 10 days ago, ambient temps were 26c and track temp 51c. I saw a maximum of 105c on the water temp and 110c on the oil temp. Turbo car running about 0.8bar. Non vented hood and oem oil coolers, no mods to the fender guards for the oil cooler either. I'm also running VR-1 20w50. A bit on the high side so I will vent the hood and mod the fender guards for more airflow.
well we might disagree on some things, but not on motor oil
but I’m getting at some other points on the oil side that have been discussed in the past and people ignored that just like the fan shroud setup, blocking off the radiator, and so on …
there’s not really any point talking to the wall again on it, other than to say the two are more closely related than most people seem to accept
I do find most of your technical posts interestings and do agree with quite a few of your points, I just don’t get into the other stuff or name calling, just makes it harder to browse or find the actual interesting information.
Regarding the oil, I used to run 10w40 idemitsu but quickly changed it to 20w50 after looking at the oil temps at the track, the oil in rotaries does a lot of cooling work specially on the rotors. Never had a problem since but it’s getting to the limit with the turbo setup, i’m cool with it running at 110c, a bit at the hot side, i’d like it to be closer to 100c in this “hot” weather hence the planned fender liner mods.
About the radiator, it’s clear that proper sealing and venting is crucial to it’s efficiency. Fan shrouds are a good idea in stationary motors or cars/trucks that do a lot of idling or their use is at low speeds. The OEM design is good.
In my case, I noticed that the floor temp (right next to where the turbo is, turbo has a blanket and there is heat shielding to the floor) gets noticeable less hot at the track than stationary. Probably the air into the engine bay going out under the car in part where the turbo is.
Those are some enviable temps. I ran my S2 at THill West (2 mile) for the first time (completely stock setup) and it ran extremely hot.
Ambient: 95 F
Peak Coolant Temps: >230 F
Pretty much every session, I would end up hitting my coolant temp alarm set at 230 and have to back off. And here I thought I'd left at least some of my overheating woes behind tracking the 8 instead of the FD
Has anything heard of test results using the PWR radiators? Not sure if more-expensive means more-better but given how high the temps were, I think I need to majorly consider doing some cooling modifications.
Those are some enviable temps. I ran my S2 at THill West (2 mile) for the first time (completely stock setup) and it ran extremely hot.
Ambient: 95 F
Peak Coolant Temps: >230 F
Pretty much every session, I would end up hitting my coolant temp alarm set at 230 and have to back off. And here I thought I'd left at least some of my overheating woes behind tracking the 8 instead of the FD
Has anything heard of test results using the PWR radiators? Not sure if more-expensive means more-better but given how high the temps were, I think I need to majorly consider doing some cooling modifications.
wow that's some hot temp. mine never reached that high even with koyo S1 rad. maybe because im running e85.
i used mobil 15w50 synthetic the first season. when i drop the oil pan, there was a lot of sediment at the bottom. so i switched to Redline Race 20w50 and been on that for the last 3 years. i probably wouldn't use 20/50 if the car is street driven in winter colder climate.
Those are some enviable temps. I ran my S2 at THill West (2 mile) for the first time (completely stock setup) and it ran extremely hot.
Ambient: 95 F
Peak Coolant Temps: >230 F
Pretty much every session, I would end up hitting my coolant temp alarm set at 230 and have to back off. And here I thought I'd left at least some of my overheating woes behind tracking the 8 instead of the FD
Has anything heard of test results using the PWR radiators? Not sure if more-expensive means more-better but given how high the temps were, I think I need to majorly consider doing some cooling modifications.
The temps in my post above were recorded at thunderhill west, but in much cooler (feb) conditions.
Those temps seem a little high, but not that different to what I've seen in the past on the east side with a stock s2 radiator.
What laptimes were you running?
Sealing and baffling will probably help. I don't have any data on the PWR radiators, but should get some data on my current setup in comparable conditions this weekend. I'll actually be happy if it keeps to around 220F or so.
What baffling is done to help the stock radiator performance?
I've seen the AC foam being used to seal the perimeter of radiator, which I think I'll try before jumping on an aluminum rad. Not sure how much a difference it'll make given the temps I saw.
I was running a 1:37-1:38 and as is "racer" tradition my excuses are:
-all seasons
-about 45 degrees of positive camber in the front (need an alignment real bad)
-I think my front pads are going out or the RX8 has some gnarly rear brake bias, under hard braking it felt like I was pulling a hydro...
i used mobil 15w50 synthetic the first season. when i drop the oil pan, there was a lot of sediment at the bottom. so i switched to Redline Race 20w50 and been on that for the last 3 years. i probably wouldn't use 20/50 if the car is street driven in winter colder climate.
Well I doubt anyone will be overheating their engine then and need to take heed to the context of the discussion, but then that's usually how these threads go.
What baffling is done to help the stock radiator performance?
I've seen the AC foam being used to seal the perimeter of radiator, which I think I'll try before jumping on an aluminum rad. Not sure how much a difference it'll make given the temps I saw.
I was running a 1:37-1:38 and as is "racer" tradition my excuses are:
-all seasons
-about 45 degrees of positive camber in the front (need an alignment real bad)
-I think my front pads are going out or the RX8 has some gnarly rear brake bias, under hard braking it felt like I was pulling a hydro...
Foam of some kind around the sides of the radiator to seal it. Or at least mostly seal it. I meant to say ducting rather than baffling... basically making a straight channel from the front bumper to the rad. I've seen it done to good effect, but have not been that creative with mine. Keeping these cars cool in 100F weather is a challenge for sure, and a radiator upgrade alone has not been a magic bullet for me.
Tires are worth a lot of time. I don't even know what a representative lap on all seasons would be, but 1:37 doesn't sound bad. My reason for asking was to get an idea of how much throttle you are using.
All seasons are great for learning and practice, so don't feel you need to change them straight off.
Brakes, not sure. Might need a good flush and fresh fluid as well as pads. If the tires and alignment are bad, that might affect things as well. It should stop in a straight line and the abs take care of the brake bias for you. If the abs goes out, it will put all the braking to the front wheels (fronts will lock while the rears do almost nothing).
I guess in the end, it's all the same bars of aluminum, I don't think a $700 radiator from Australia is going to be much different from the Koyo tbh.
I'll have to explore under the front bumper on the 8 for some improved ducting as you mentioned.
Something I did notice on the S2s is the front grill is perforated in a pattern rather than completely being open. Maybe opening those up would get some more airflow? See below:
As for track performance, I want to give it another shot with a proper alignment before I start messing with the car. I am also very spoiled since before I tracked the FD for the first time, I already had 200 TW tires, poly bushings and ohlins on that car.
had a really hot race this weekend. ambient temp was around mid 90s. coolant temp was mostly hovering around 205 with a few peak of 210. I checked vids from my previous years with similar ambient temp and coolant was around 215 with peaks around 220, for the koyo S1 radiator.
I'm still trying to figure out how to reduce temps...
At thunderhill (5 mile) 91F last weekend coolant reached 216F shifting at 8500rpm.
In the afternoon air temps reached 100F. Coolant peaked at 220F ECT but I was already lifting at that point. With more lift & coast plus some short shifts I got it back down to 212F for the rest of the afternoon.
I see hood vents in your pic. Did you have those with the s1 rad as well?
Here in Arizona, the only way I was able to reduce temps was to plumb in a second radiator. Not, racing, either, just driving on the street. With the OBD2 showing 212, my other gauge was getting almost 260 using the racing beat fitting coming off the back coolant return line. I think that is darn hot for this engine. That was with a Koyo radiator already in place, stock fans running at high speed all the time, foam in place, etc. That was why I went with 2 radiators.
Last edited by kevink0000; Sep 18, 2021 at 12:09 PM.
I was at that time, I changed to FAL 480, after the second radiator addition. and noticed little difference, other than more noise and vibration. My approach to the problem will change on my other RX8.
I chased a similar problem here in AZ with AC in a 1988 BMW 535i that was my daily driver at the time. I tried moving more air through the condenser to eliminate the heat soak I was getting, but it made little difference. The AC was marginal at all times over 100 degrees ambient. The biggest change happened when I went to a more modern parallel flow condenser from the original tube and fin type. But the AC was still weaker than I liked until I added a second PF condenser in series. Then, airflow rate through the condensers became much less important. I was able to run the condenser fan on low at all times and get ice cold AC even when idling for long periods. That became a "robust" system at that point in my opinion. Now, AC has issues that are dissimilar to the cooling system on a car, but there are similarities as well. I am looking to do the same with my second RX8's cooling system. I want it to handle the heat here without issue. Most of my other vehicles have no trouble with the stock systems in place, they are built with some margin. Mazda saw fit to give this car a very small radiator and threw in airflow issues to boot, a problem they avoid very well with their piston engine cars. (I have had experience with 2 generations of Mazda 3, and both had great cooling systems). Probably a longer answer than you wanted, but I see lots of people on here having cooling issues when temps get near the magical 100 degree mark, where the inherent lack of cooling capacity really begins to manifest. Just wanted to give my 2 cents, again.
I guess what I am trying to say also is, venting, better radiators, bigger, better fans, are incremental improvements. If you are having cooling issues under power, the answer is More Radiator Needed. The oil coolers can keep oil temps in check if the cooling system is not losing ground constantly. If your cooling system is able to keep 185 while under power, oil temps should be fine, is what I have found.
Not sure what Mazda was thinking when they gave the FD a civic-sized radiator (300 sq in, yowza)....... I like my box of Wheaties in the morning, but not for my twin turbo rotary radiator core size
Weight reduction is an admirable pursuit, but sometimes you need to give pause to 'less is more' when it comes to oil and water heat exchangers.
This may not be the ideal place to ask this and of course I can go search, but how many 8 guys are running Evans NPG+ in their steeds?
I’ve run it for many years, but imo it’s more a boilover vs not scenario than temp reduction
though NPG+ no longer exists, being replaced by the “High Performance” version. I also don’t necessarily agree with the prior comments, but rather choose not to argue against or otherwise challenge them. There are other experiences on here that suggest otherwise, but not to say they’re not valid, but that other not well understood or known factors might be involved. Also the area is not necessarily a true measure of a radiator or overall assessment of a cooling system. Or that those piston engines had dual oil coolers or equivalent capacity thereof.
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My point is that many racers here seem to have problems with temps getting out of control on hot tracks, with long intervals under full power. ("it got to xxx degrees and I shut it down". ) Everyone tries this, that, or the other, with meager results in my opinion. Maybe try something different and plumb in a good size second radiator, ( not some dinky oil cooler sized thing, I mean something with at least 1.25 inch inlet/outlet adding 75% or more surface area) even if the venting is sub-optimal, (factory battery and airbox in place, or part of the front "stack", blocking the main radiator. Yes, you read correctly. There is enough air there if you take advantage of it, contrary to years of RX8 lore.) you will notice a bigger favorable difference in cooling than what you been able to achieve with your other mods. It will be worth your time. People can disagree if they want, based on this principle or that, but if they actually try it, even with cheap components, they will disagree no longer, and a $500-800 single radiator will not seem like a good use of available funds.
Last edited by kevink0000; Sep 20, 2021 at 07:57 AM.
My point is that many racers here seem to have problems with temps getting out of control on hot tracks, with long intervals under full power. ("it got to xxx degrees and I shut it down". ) Everyone tries this, that, or the other, with meager results in my opinion. Maybe try something different and plumb in a good size second radiator, ( not some dinky oil cooler sized thing, I mean something with at least 1.25 inch inlet/outlet adding 75% or more surface area) even if the venting is sub-optimal, (factory battery and airbox in place, or part of the front "stack", blocking the main radiator. Yes, you read correctly. There is enough air there if you take advantage of it, contrary to years of RX8 lore.) you will notice a bigger favorable difference in cooling than what you been able to achieve with your other mods. It will be worth your time. People can disagree if they want, based on this principle or that, but if they actually try it, even with cheap components, they will disagree no longer, and a $500-800 single radiator will not seem like a good use of available funds.
Where are you fitting the 2nd radiator? I guess I'm lazy, but I'm not sure where I'd even start with that in a way to get good airflow through it.
The Koyo s2 radiator is ~$300-350. As a drop in option with minimal modification I don't think it's a bad deal.
A lower price option for s1 owners would be to get an oem s2 radiator (or of course the s1 koyo which is a direct fit).
I still have the oem fans. Removing those would remove some restriction to help on track. I think my next step is going to be hood louvers though. I should probably relocate the battery to the trunk at the same time. If that doesn't solve it, then I'll look into cutting the fan shroud or replacing the oe fans with some less restrictive aftermarket ones. I need to keep a decent fan setup as I still drive to/from the track and sometimes that can be in traffic at 100F.
