Shadowrx

It has been warming up outside recently and I have noticed that my coolant temps seemed higher than they have been. So I researched and installed the "fan relay switch" in the diy forum except I simply just grounded the wire. This seems to help unless I turn my A/C on or I'm idling for a while. I wanted to know if I could put a switch on the other relay to turn the higher speed on for better cooling. Is this possible? Or is it a good solution? What are my options? My temps get into the 200s often with the A/C on. Is this even a big thing to worry about? I know in the new and potential owners thread says that 220 is bad for the coolant seals and 240 is extremely bad. But I'm sure to never let my temps get that high, I either turn my A/C off or get up to speed and coast to cool it down. I have never pushed it to see if my temps will get that high or not. But seeing people say they hardly ever see temps in the 200s made me nervous to try test it.

poacherinthezoo

I see temps in the 200's pretty regularly on my unmodified fan set up. As long as they stay below 215 F I'm ok with it, and have my alarms set for 212 F. The coolant seals ability/affinity to the give up the ghost at 220 F isn't comforting (I know that for sure), but from my experience 205 F is relatively normal for stop-and-go type traffic in hot (70-100 F) weather.

I've noticed that once my oil temperature goes beyond 230 F, and I'm not moving enough air through the oil coolers and radiator - the coolant has a hard time staying below 205 F. This has prompted me to do a cool-down lap (coasting down to the end of the paddocks and back) after autocross runs to get the coolant below 200 F.

kevinande

How are you monitoring the coolant temps? I believe both fans run at their highest settings when the A/C is switched on. If it's hot out, it is best not to idle the car for extended periods with the A/C running, and if you do, I would shut it off if you reach around 220 no more than 225. 240 is not bad, it's terminal. Unless you are thrashing the car pretty hard in hot weather, the cooling system should be able to handle normal everyday driving.

Shadowrx

I monitor my temps with a blue tooth OBDII adapter and the torque for android app.

RIWWP

iTrader: (2)

The factory fans don't turn on with the stock tune until 207F. 200-215 is fine, as long as they stay there. You have almost no headroom though, if something were to go wrong. I prefer keeping them down in the 175-185 range, for significantly more headroom. With a factory 185F thermostat, your temps will tend to bounce between 185 and ~210ish when not moving.

Thumbs up on monitoring your actual temps. It's the first step in preventing any future problems.

Shadowrx

What are some ways to keep the temps down that low? Not wanting to spend a ton if there's nothing wrong, I just prefer the extra headroom to react of something does go wrong.

RIWWP

iTrader: (2)

For the 8 on the street, my preference for steps would be:
- Mazmart 172F thermostat
- Replace the radiator with a new OEM one if the current is > ~70,000-90,000 miles old
- AccessPORT or MazdaEdit to change the fan trigger temp down to ~180.
- Ensure that the radiator has proper shrouding

With that, my 8 sat at ~175F on the highway, and parked I'd hover around 180F.


For some comparison of the degree you can go to if you want to ensure solid cooling...

On my MSM (with an aftermarket ECU), I have more complicated logic set up to turn on one fan if I'm >176F and <20mph, or >190F at any speed, and the other fan at 195F, with a 180F thermostat. This is coupled with the highest efficiency and 2nd highest capacity radiator available for the Miata, SPAL fans that flow 4730 m3/h, proper hood venting, and radiator shrouding. Even on track for 20 minutes (with turbocharged heat), my temps stay under 195F. When sitting still, one fan cycles on and off every ~10 seconds, and my temps stay between 174F and 182F. I also have a reduced rev limiter down to 4,000rpm if my temps are under 170F for the same reason the RX-8 has a lower redline when cold, a warning light at 210F, and a 4,000rpm rev limit at 215F. Those temps aren't dangerous for the Miata, however if my temps hit that, something in my system is broken, and they probably aren't going to stop there. And 4,000rpm is enough for me to drive the car around, and maintain safe speeds on the highway, but I am over 4,000rpm so often, especially on the track, that it will be really obvious, and an effective way to prevent me from adding even more heat into the system.

kevinande

Unles you have a problem, the car should maintain the temperatures RIWWP mentioned on its own. I am pretty sure the fans are triggered by turning the A/C on though. Depending on the outside air temp, maintaining that in hot weather can be a challenge. I have seen temps as high as 224 in traffic (which is my max) and I shut the air down and turn on the heater. Yes its very uncomfortable, but it beats buying an engine. I live in Texas and I speak from quite a bit of experience. The A/C works reasonably well when the car is moving, but not us much when standing still which is an indicator of how effective or ineffective the fans on this car are. If there were an aftermarket solution that was actually capable of moving more air acrosss the radiator and condenser, I would be interested myself.

Edited to add: I am referring to 100+ degrees F temps, not 80's and 90's.

niteshade247

The fact your temps are going up sitting still with the AC on is troubling. I recently was stuck sitting still for 30 minuets in 90 degree heat I started seeing temps creeping to 210 and switched the AC on to kick the second fan in and in 60 seconds I saw temps drop till it hit 180 and stayed there.

RIWWP

iTrader: (2)

It's not entirely unplausible. I generally don't recommend turning on the AC when hot. I understand the goal of getting it to kick on the AC fan for more airflow, but especially in high ambient temperatures the AC condenser is the one getting all the cold air, and the radiator can be getting even hotter air, to the point that there isn't enough of a temperature differential to shed the heat in the radiator.

Turning on the heat is generally more preferred in my opinion, as it turns the heater core into a secondary radiator, nothing is working against the goal.

niteshade247

I agree and I had thought of that the added heat from the condenser would only compound the rad temps but on this day it proved bouth us wrong. I do agree 100% on turning the heat on I've saved a piston engine or two with doing this.

logalinipoo

This is going to vary a lot with the charge pressures of your A/C system. If they are in the upper range, thae condensor is going to run much hotter and preheat the radiator air.

RIWWP

iTrader: (2)

Yes, I agree it can work, but I see it as towing around a trailer with a gas tank on it to improve fuel rank. You are increasing airflow at the same time as reducing radiator effectiveness. You have to hope that the increased airflow will net more cooling than the reduced radiator effectiveness will hurt it. Plenty of circumstance exist in which it would work, and plenty of circumstances exist in which it wouldn't work, and these will change from car to car, season to season, mechanical condition to mechanical condition. So I don't provide a blanket recommendation to do it. Someone who isn't thinking things through and isn't watching temps closely could lose an engine by following it blindly.

Using the heat instead will never harm the engine. It may never help, but it definitely won't cause harm.

Shadowrx

Thank you both for all the information. I did quite a bit of research and kept reading different things. I will more than likely start down that list or save up for an AP. either way, thanks guys

logalinipoo

Well the shrouding is cheap and it is very effective. a swimming pool noodle or some pipe insulation will fill in the gaps and make a big differance if it's worn out or missing. I'd do that as your first step.