Need Help With Cooling System
 

Hey, i have a turbo 1.6 with FMIC. Car never runs cooler then 95 celsius coolant temp when moving, and when i stop and idle it goes up to 102 celsius and possibly more since that is as high the ms gauge will read. My temp gauge for car is always at 1230-1 o clock. If its 25 celsius and up ambient temp and i idle long enough car will get close to over heating.

My cooling system right now has:
-Mishimoto aluminum rad with only 1 stock rad fan
-Rad cooling panel
-50/50 water coolant mix
-Stock 195 thermostat
-All bumper shrouding is in place and engine under tray
- My intercooler does not cover whole bumper mouth, one of those buck tooth looking ones so decent enough airflow at sides to rad and through it.
-Still have heater and lines, have used this to help get rid of some heat and it helped.
-No re route but am looking into setting it up.

So what can i do to help bring temps down a bit, will a 180 thermostat make any difference?

Thanks in advance!

Simple answer is get another fan.

70/30 mix, roughly 2 cups of coolant and rest distilled water.
2 11/12" spal, or 1 larger one.
1 water wetter if you want

Do not use Redline Water Wetter with coolant. See here:

https://www.google.com/search?q=water+wetter+brown&ie=utf-8&oe=utf-8

Have you seen this thread?

https://www.miataturbo.net/race-prep...-thread-79930/

Just came in here to point out that this is normal for a Canada car.

A 195 degrees F thermostat is about 91 degrees C. It may only be fully open at 95 degrees Celsius because of variations in thermostats. I would personally run 180-degree thermostat.

If you are going to run that radiator then you're going to need both fans, probably.

Hmmm... Let's discuss the thermostat idea...

The thermostat sets the floor temp or minimum operating temp. It has very little effect on peak temp, unless it is defective or on the high side of its manufacturing tolerance. Managing peak temp is up to the heat exchanger. Swapping a 195 for a 180 should result in the car taking longer to reach peak temp, but it should still get to the same place a few minutes later than it normally would. Running a lower temp thermostat can have consequences, however. The design center for materials expansion in a modern engine is normally 200F +/- 5*. Running much below that for extended periods of time can cause premature engine wear.

Personally, I think the OP should focus on the radiator and fans. That Mishimoto unit is barely better than stock, in terms of cooling performance. I think I saw somewhere that the stock MSM unit actually outperforms it. If it were me, I would do the re-route with a new OE thermostat and add back the 2nd fan and see what effect that has. If the water temp doesn't come down enough, I would upgrade to the 949 Crossflow radiator. If that doesn't cut it, bigger SPAL fans and/or hood vents.

The OP should also think about adding an oil cooler, if he doesn't have one.

Yeah, but I think his floor is too high. 195 is for emissions compliance, not performance or long engine life. Besides that, 2nd fan is a good start.

The 20+ year old motors on our stock fans get weak with age. I swapped the motor out on my cooling fan (RockAuto was having a clearance, it was CHEAP!). Night and day, especially in that stationary idle situation.

It's common for a trailer-towing package (even back in pre-emission days) to include a warmer thermostat. The reason for this is to raise the temperature of the coolant in the radiator. This allows more heat transfer from the radiator (since heat transfer for conduction and forced convection depends upon delta-T). It may seem counter-intuitive, but if you're having overheating issues a warmer thermostat is better. OTOH, if you have excess cooling available, a cooler thermostat can increase output and resist detonation.

The Mishimoto radiator isn't particularly good. If 949 is out of stock on their crossflow, the Koyo Hyper V-Core is another quality bolt-in solution.

Also, as someone else mentioned, water cools a lot better than antifreeze. I understand that you're in Canada, but in the Summer you can safely reduce the amount of antifreeze.

Does not compute.......a 185 and 200 degree thermostat are both wide open at 230 degrees, explain to me how one helps over another with overheating? The only purpose of a thermostat is to keep the coolant from being too low, simple as that.

Hey, thanks for all your comments. Lots of great info!

I did not know the mishimoto was so bad, its gotta be double the capacity of a stock rad so i cant see it being as bad. I am looking into adding a second fan but cant run a stock fan because of my over the rad ic piping and with where i put bov i have little room. Just need to run a smaller then stock fan. I had an oil cooler installed before, did not notice a big difference temp wise if any at all. Also it made my oil pressure too low i found, would only get 45-50 psi when i got on it once everything was warm. I think it just opened the system too much and oil pump could not flow enough.

I cant decide on the thermostat. What is considered a warmed up engine temp, my WUE ends at 165 so not sure why it would take longer to warm up with a 180. The thermostat would start to open at 180, i still think it would eventually run as hot just take a bit longer to get there. Then i guess there would be less time for coolant in the rad. That is where i am lost and cant decide.

Am i okay to tie a second rad fan into the first one, so they kick on together. Or is that too much for that circuit?

How about you post a pic of your setup, you never mention the over the top intercooler piping. There's a lot of ways you can screw up the ducting with that setup.

You have more efficient heat transfer but only until the thermostat closes again? I don't see how more Q for potentially shorter time (I'm making lots of assumptions here) would help you run cooler if you're limited by the thermostat temperature. With a colder thermostat you'd still get to a higher delta T if you're having cooling issues at low delta T.
Legitimately interested, I may be completely wrong.
IMO if you have all the airflow you can get and everything is in working order, and you're still overheating, you need a larger radiator.
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Guys, trailer tow packages of old generally included big radiators, tranny coolers and hotter thermostats (195 back when most cars left the factory with 180). The operating theory of a properly designed cooling system is that you have enough radiator and cooling air that the thermostat can cycle to maintain an engine coolant outlet temperature. In this circumstance, a hotter thermostat produces hotter coolant entering the radiator which allows the same size radiator and airflow to transfer more heat to the air because there is more delta-T. That's it. It's not mysterious.

If you have an overheating turbo Miata with an inefficient radiator and chocked-off airflow and your thermostat (whether 160, 180, 195 or whatever) is wide-open anyway -- then the thermostat obviously doesn't matter. You've got to fix the radiator and/or airflow.

OP, if it is an issue mostly when idling at rest but otherwise OK, then you've got an airflow problem. The OEM fan is really good PROVIDED the motor is up to snuff. The motors get weak with age and yours is probably several decades old by now. I recently replaced my motor with a new one because I was having your issue. It was cheap and easy to do. It made a HUGE difference. Basically, problem solved.

So what does this have to do with the price of tea in China? It's not relevent to the conversation, or cooling a car in general. If you're riding the thermostat then the cooling system is going to transfer any heat made by the motor no matter what the set point of the thermostat is. A 200 degree thermostat isn't going to move any more heat because the thermostat will just choke the water flow back. Pick your temperature floor by your thermostat rating, that's it's sole purpose.

The topic at hand is discussing heat transfer with the thermostat open.

The topic at hand is discussing OPs issue with temperature rise while stopped at idle. You can see in both of my posts that I urge him to look at airflow and, in particular, consider whether his OEM fan motor might be weak.

The discussion on why people select certain thermostat temperatures was a fun side topic that I elected to participate in -- although I did not originate the discussion. It's tangentially related because OP asked whether a lower-temp thermostat might help his problem. Everyone here understands that it will not.

Are you the MT discussion topic police? You really seem perturbed about this. :magna:

I was just thinking that the thermostat might be bad and might not be opening fully and needed replacing. The car should not run that hot at highway cruise with the under tray and bumper mouth plastic intact at 70*F ambient even if it had no fan.

Ooops. I missed that he was complaining about cruise temps too. Celsius confuses me.

Look into putting a slim spal fan. Your stock fan alone and the mishimoto are not enough. I know it because I drove around with a broken fan and a mishi for a few weeks until I got a new one.

The performance of a particular radiator has at least as much to do with the design as with the size. I don't have direct experience with the Miata version of the Mishimoto, but I have helped friends with installations of Mishis in other cars, and besides not fitting 50% of the time, those friends saw little to no improvement in peak temp over whatever stock radiator they replaced. Sometimes, saturation times were longer, and recovery times were shorter, but peak temps were within 2 to 3 degrees F. All you get with the Mishi, besides all-aluminum construction, is increased capacity in an old technology core. That increased capacity alone is probably enough for N/A, but not for F/I.

From Brian Goodwin:

AFAIK, those in the know on this site recommend the Koyo, CSF, 949, and Trackspeed, depending on application.

What oil cooler setup did you have? Were you running at least -10AN lines? Mocal sandwich plate plus -10AN lines plus quality cooler equals success.

As I suggested above, change your thermostat, when you do the re-route. Yours may be at end of life and not opening completely. A 180 thermostat may hold off the peak temp and delay saturation, but only for a matter of minutes. Peak temp is still dependent upon the cooling system's ability to exchange heat, and that delta T is determined by the efficiency of the radiator and the pressure differential surrounding it. You may see lower cruising temps with a 180 thermostat, but only if your other thermal efficiency problems are solved.

There is a prescription for most Miatas detailed in the thread I linked above. The cooling performance you seek is as simple as following it. Lots of experience and wisdom in that thread.

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Got some pics to see the set up.

I did use a mocal sandwich plate with thermostat for oil cooler. But i had 3/8 lines going to a 8'' x 8'' cooler. I think it was more to do with the stock oil pump not being able to flow enough for such a bigger area to keep pressure up. I found that when i added the turbo oil pressure went down around 5 psi at every point. Coolant temps were same with oil cooler anyways.

Looking at the pics; engine under tray is all there un modified, everything in bumper is there but i did cut a rectangular hole in that shroud on bottom for IC to sit in its exact size for IC to drop in. There is room below BOV for a 10-11'' diameter fan just oem fan cant fit there, so looking for a fan.

As i drive coolant temp seems to stay at 95 celsius so around 200-205 F, this normal for a turbo car i think oem is 92 celsius but maybe im wrong. At idle is just where it gets hot, the hotter ambient temp the faster it goes from 95 to 102 and above. There was one day where ambient was 30 celsius and i got stuck in some stop and go traffic for 20 mins, car came like 80% to overheating according to dash gauge. Im thinking with second fan it will still get hot just take a bit longer.

So looking to add fan, undecided about thermostat, looking into reroute, im stuck with the mishimoto for now since i got it all modified to work with my IC piping. https://cimg0.ibsrv.net/gimg/www.mia...af662abb4e.jpg
https://cimg2.ibsrv.net/gimg/www.mia...0a26a86408.jpg
https://cimg3.ibsrv.net/gimg/www.mia...ad0a518f58.jpg
https://cimg4.ibsrv.net/gimg/www.mia...91114b0910.jpg
https://cimg5.ibsrv.net/gimg/www.mia...c1b173ef55.jpg

Yup 3/8" lines and possibly the type of cooler is the reason for your oil pressure loss. You need 5/8" (-10) lines and a stacked plate type cooler.

If your overheating is only when stopped and fine when moving then it's a fan problem, plain and simple. Your ducting around the intercooler piping looks good so that's not the issue.

And that grill isn't helping your airflow either. It's not the cause of your overheating, but every little thing helps.

My car came with that grill. Ditch it because it hurts air flow more than you know.

I went from the stock radiator to the thicker mishimoto and it did make a significant difference on cooling especially doing track days here in Florida. I was using two stock fans. Once I added boost a better radiator and oil cooler were needed for the track, but probably wouldn't be necessary for the street. It shouldn't be so tough to get it cool in Canada.

If you decide to go the way of a reroute, we've got you covered. :bigtu:

Very clean build.

If it were my car, I would ditch the grill, add a fan, do the re-route, and add a proper oil cooler setup. A 180F thermostat won't hurt anything, so you can do it while you are in there, if it makes you feel better. I believe the Stant Superstat is the favored one.

On the oil cooler topic, when you are pushing the limits of cooling, you need to cool everything you can cool. Bear the heat load everywhere you can. Oil is typically 20 to 50F hotter than coolant, so yours is pretty hot. Here is the Oil Cooler Bible:

https://www.miataturbo.net/race-prep...er-tech-80234/

Agreed that you need at least 5/8 or 10AN lines to maintain oil pressure. Known good oil coolers are Long (TrueCool), Koyo, Mocal, and Setrab. Make sure whatever oil cooler you choose accepts the appropriate size hose without the use of adapters.

Ok will look into all of that.Thanks for all the comments!

Couple more questions;

Am i ok to tap a second fan into the first one so they kick on together, at what point will it put too much load on that circuit?

Will lowering my fan on temp help? Currently set to 215 so 102 celsius, maybe setting to 212 or 100 celsius could help delay the heating a bit.

Definitely lower your fan-on temp. It is not a coincidence that your fan-on temp matches where your water temp seems to settle while stopped.

This makes a huge difference on our old cars (based upon direct, personal experience) . . .

More Information for FOUR SEASONS 35240

I think I would start at 205F / 96C for my fan turn-on temp; that is the factory temp.

Use the original wiring for your 2nd fan, and set the ECU to turn it on with the 1st fan. Barring that, jump the relay inputs on the 2 fan relays, so the 2nd fan turns on any time the 1st is triggered. Two fans on 1 circuit will be too much current draw for that circuit. Each fan needs its own relay.

For < $30, the fan motor hornetball is recommending is a definite no-brainer.

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Woah! 102c is your fan-on temp? Now I see why you overheat. Stock ecu turns the fan on at 96c (Or 205f).
For turbo cars usually sooner is recommended. You can set it at 94-95c.
The point of overheating is 98c. Very difficult for the cooling system to cool down from there.

If the bov was located differently you could use a stock fan.

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Ok thanks for the feedback.

Hornetball, i am looking into what you suggested just forget to mention it.
Yeah BOV can be relocated just need modify the pipe. I can fit a slim 10-11" fan under so ill do that instead of trying to get another stock fan on.

Fan is not used while moving, so thats why i gotta play with the fan on temp a bit. Dont want fan to turn on while moving. Since i cant get it to be cooler than 95 celsius while moving i will set fan on to 97ish for some head room. Not ideal but will help. Basemap had the temp set to 215 F.

This car never had a second fan, did not come with AC. Can you spoon feed a bit more, where are the relays and hows it get wired.

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And definitely remove that grill. You are recirculating the air under the hood through the radiator and getting very little flow from the outside when standing still..

Can anyone recommend which spal fan is best? Need to be slim as I plan on using a koyo 37mm Radiator and I don't think stock fans will fit with my Intercooler piping.

You are over-thinking the fan turn-on temp. The running fan does not become an obstruction until somewhere around 60mph. It is much better to have it on than not, when moving at speeds below that. Set it back to 96C.

[ReallyBasicRelayPrimer] A relay is a remote switch, that allows you to control a high current circuit, with an isolated low current circuit. The switching side of the relay is activated by a constant 12VDC signal and a switched ground signal. In the case of the fan circuit, the "ground" signal is sent by the ECU, when it determines the fan should be on. These 2 signals "flip the switch" to activate the high current circuit, which powers the fan. Obviously, you do not want high current coursing through your ECU, so a relay is used to isolate the ECU from the 20 to 60 Amps required to run the fan. [/ReallyBasicRelayPrimer]

If the NA relays are in the same location as the NB relays, they are near the cowl on the passenger's side. There are 2 of them in cars that ship with A/C. One is obviously already in use for the 1st fan. Hopefully, the 2nd one is there, and you can just use it for the 2nd fan. If not, the signal wires may be in the bundle, and you may still be able to use them to easily wire in a new high current relay. (Find the wiring diagram for your car to determine wire colors and verify with a multimeter.) If you need a new relay setup, SPAL makes a wiring kit that greatly simplifies things. With that kit, you would need to tap the signal wires for the 2nd fan, which allows you to control the fans independently with the ECU. Or, tap into the ones for the 1st fan, which will turn the 2 fans on in parallel. Another option is Spal's thermostatic wiring kit, which will turn the 2nd fan on, at a fixed coolant temp, using its included sensor.

There is no "best" fan. There is the one that is appropriate for your application. Go to Spal's web site, click into the area for the fan diameter you need, and click on the specs link for each fan you think might be suitable. Find one with the dimensions that will fit, with a current draw that is appropriate for your circuit, and that pulls enough CFM for your application.

I don't see an issue with the fan running while the car is moving. I'm pretty sure FM or someone had data showing a fan can help even at relatively high speeds.

I'll see if I can find it again, but I authored a thread on the Rx8Club forum about this, wherein I tested the effectiveness of the so-called "Fans on Low" mod for those cars in 95F ambient temps. That mod turns both fans on low speed, using a remote switch. The results proved having the fans on low aided in cooling at least up to 50mph. There was no penalty up to at least 60mph. Above that, things were murky, but having the fans on did not seem to be a problem at normal driving speeds.

I know there isn't a "best" fan, I'm just looking for a recommendation for a 12" spal fan, stock wiring with ac..

The two spal fans that come with the FM stage 2 airflow kit are pretty baller. This is the smaller of the two :3010.1522 It still kicks much ass. The larger one is the 30102029. I would recommend either of them to you. They are not inexpensive because they are real fans. One of them set to turn on at 95c or even a bit lower will be very effective.

Cognitive dissonance.

This is still the correct answer. You need to measure how much clearance you have and pick the highest flowing fan that will fit in the space provided, based upon the published specs. I don't know the maximum current draw of the fan circuit off the top of my head, but I think I remember the fuse or relay being 25A. Find out the current capacity of that circuit and choose a fan that draws a lower amount of current, preferably with maybe 5A of headroom.

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Thanks, didn't mean to be so vague in my first post,:doh: I don't think I'll be running a shroud as it seems not usually neccesary. Ill look into the two fans that Mobius reccomended, and see what would fit my car better.

Messed around with this a bit today. Set fan turn on temp to 205F or 96C, helped a bit took a bit longer for coolant to get to 102C. Still working on 2nd fan, reroute etc.

One thing i noticed though is that my coolant stays at 97-99C all the time while moving. It just cant come back to 95C, which is what i saw it at before. I don't know if its because ambient was 25-30C or what. Random question, would advanced ignition timing make the engine run hotter?

Retarded makes coolant hotter.

Did you remove the stupid grill?

^ This

The grill is probably blocking 50% or more of your airflow.

Can confirm retarded timing can make a car run hot. Had a friend finish his motor rebuild in his Amx, how many of you even know what that is, and we accidently set timing too far retarded, aside from the car running like crap, it overheated despite a 3 core Radiator and 2 spal fans.

Ok i advanced my timing map from basemap values a bit since last year. That is why i asked.

I did not have the grill off, will take it off for driving this week and see the difference. I know before this grill went on i had one that was a bit less restrictive but coolant temps were not any different. Also drove with out a grill for a bit before this one was installed and temps from what i saw were not any different. Maybe im overthinking it a bit here but with the grill that stops bugs and rocks from flying in and clogging up and damaging my IC and rad fins, not good for flow and cooling, with the grill just give it a quick clean weekly. Pros and cons i guess. Still fully agree with you guys that it is a flow restriction.

Im not sure how much the airflow while driving would have been an issue yesterday probably half the problem, or if it was just the hot ambient temp making it harder to cool things down was around 25-30C. Obviously my heat exchangers are not effective.

I did find out from previous owner of car that this rad fan is not too old, was installed in 2012 with a new stock rad. This was when car was stock. The fan looked newer to me based off its physical condition, and it pulls hard i can feel the hot air under the car if im in drivers seat and put hand under car. So i think this one is ok, just looking to add the second one.

How much of a difference in temp did you guys see before and after reroute install?

Re-routes don't actually help overall cooling, they just make the head temperature more even to prevent cyl 4 from melting before the rest.

Even an open mesh is still 50% blocked...... You wouldn't tape up half the nose opening and expect the car to still cool sufficiently would you?

If you want to do a quick check to see if airflow helps the car stay cooler when moving just pull the hood off and go for a drive. Takes 2 min with a buddy.

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Car ran fine stock. Only came with one fan, since no AC. I have retained this fan and it is set up on the new rad. Ppl have suggested adding a second fan for more flow at idle, and changing the motor on my current fan in case its old and tired. So all good there, im looking in to this.

Will run without the grill and watch my coolant temp, to see if there is any difference.

Once i added the turbo is when things started getting hot. Just the turbo itself makes things hotter, IC in front of rad restricts flow etc. I just need to make things more efficient to compensate for this.

My tune is ok and conservative id say, only advanced timing a bit through out the map. I wanted to ask in case adding timing could make it run hotter. Just getting ideas for what to do and doing one thing at a time to see if there are any gains.

Thanks for all the interest and feedback in this thread, lots of help and great info!

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When you take the grille off, put it in the passenger seat and go out on the highway with the top down. At about 60mph hold it up in the airflow above the windshield and see if it blocks any airflow. I bet you won't even be able to hold onto it because it catches so much air. Just food for thought.

No doubt grill restricts airflow. Drove with out it today, being completely honest it made no difference in temps from what i saw before. Had laptop hooked up during morning commute and afternoon, was around a 8-10C difference in ambient temp between morning and afternoon. Coolant was 93-95 during cruising in morning and 95-97 in afternoon. Was maybe a 1 minute difference between morn/aft for how long it took to reach 102C coolant temp at idle. Had fan kick on at 96C. Within 3 minutes of stopping coolant reaches 102C, probably keeps going tuner studio gauge reads 102C max.

From what i know the 195 thermostat starts to open at 195 and is fully open by 212? Shouldn't my engine coolant temp go down a bit once its flowing through, would rad coolant not be a bit cooler? This is where i keep thinking a 180 might help, so coolant does not stay so long in engine.

Second rad fan is needed asap, right now only half the rad is getting cooled. No way just the one fan can keep up with keeping the whole rad cool.

System designed like yours with only one fan can actually have the spent hot air coming out of the fan pulled backwards through the other half of the radiator and back through the fan again when sitting still. I would either want two fans or a larger single fan and proper shrouding across the entire back of the radiator.

Again, I don't know that your thermostat is opening completely at the prescribed temperature. They are not foolproof devices and they do fail. They fail open, they fail closed, they fail to open at the proper temperature, or they fail to open completely. I have seen every one of these failure modes and have seen some of them several times, having spent years working in an auto parts store and turning wrenches in auto repair shops.

I would definitely move to 180 for the additional room between operating temperature and overheating temperature and would heed Joe Perez's warning from 10 years ago to avoid the Stant super stat. I would also make sure that it had a tickle valve or a small hole drilled at the 12 o'clock position to allow air to escape to prevent hot spots and help burping, but that's just years of experience and reading talking. Replacement thermostat and a gasket used to be under $12 and if you don't have a reroute you can put one in in about 15 minutes.

Everything sixshooter said, plus...

That grill is blocking airflow at speed, but not at idle. The grill has a maximum flow rate, and your single fan is not enough to exceed that rate, when sitting still. As already mentioned, your cooling problems at idle are caused by not enough fan / shroud.

Side note: Did not know there are problems with Stant Superstats. Will research. I have used them for years without no problems, and IIRC, emilio includes them with his re-route kit.

I was just thinking the same thing as I was reading this thread.

I feel it's worth mentioning that Mishimoto's "warranty" for their radiators is sending you a bottle of stop leak. I wish I were kidding.

Wait is that true? That is honestly a really crappy policy. I guess this is why I only buy the cheapest aluminum radiator on eBay or a TSE one. If the $100 goes bad, I don't feel bad at replacing it. If the TSE one has issues up front I know Savington will stand behind it.