Coolant Temps Higher Than I'd Like
 

Hiya all, I've been reading tons of threads on coolant temps & how to keep a boosted street car cool, but I figured I'd make post #83 on this exact topic.

I've got a '97 Miata running a FM turbo kit. On wastegate pressure now, but slowly but surely (due to some pesky leaky heater hoses) working my way up past that with the help of Shane from AIMTuning (awesome folks btw)

As for cooling, here's what I've got done:
SuperMiata Crossflow radiator
Flyin' Miata Coolant Reroute (with turbo connection kit, so the reroute feeds my turbo)
180 degree stat
Stock fans and fan shroud, stock wiring
Stock undertray with cutouts for radiator hoses, no other ducting to close holes on the side (thinking this is my issue based on research)
Roughly 60%water/40%coolant (hooray for Wisconsin)
20psi CSF cap
Stock AC condenser & FM intercooler.
MS3Pro is set to turn fans on at 204f, and off at 193f. I have verified the fan is turning on, AC fan works as well when toggled.

Yesterday it was 85 degrees or so, and on highway going 75mph the car was sitting around 212f. When getting off the highway, it goes down to around 205f. This is with AC off, heat on (because I was getting nervous) On a cooler day (mid 60f) I was cruising on a county highway going between 45-60mph, and the temps were bouncing between 200-205f.

I know this is in no way overheating yet, but I'd really like to see the highway temps lowered. Maybe I need to burp the car again? I had the nose in the air for a good 3 fan cycles before sealing everything up.. but from what I've been reading, this sounds like a ducting issue, especially with the car getting so warm at highway speeds. I'm taking my car to the Tail later next month, and am nervous about it overheating during long sessions of spirited driving, seeing as it gets pretty warm just cruising, despite the good amount of cooling system upgrades.

Let me know what you guys think. I'm going to grab some scrap cardboard from work today and see if I can draft up some makeshift ducting templates.

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you need to state your ambient temp.

I did. It was about 85 degrees fahrenheit outside when I was driving yesterday.

my fans are set to come on at 197, and off at 193.

also, are the fans on like all the time?
whats your histerisis setting set at?
are you sure your T-Stat is opening at 180?
i had. at-stat become stuck and blow my head...
i fucking hate t-stats so i run a restrictor plate instead, takes longer for wam up, but the bitch won't blow up.

Maybe I'll have the fans come on earlier. But yeah, I've got the TPS shutoff set to 80. So if I'm low throttle and the temp is above 204, the fans are running.

As for whether or not the t-stat is opening, I would think so - it's a brand new unit that came with my FM reroute. I didn't test it before I put it in though.

Attachment 227069

i would test it....chances are its faulty.

is the radiator brand new?

Yes it is. Rad and reroute are both new.

where is the temp sensor located? i assume bakc of the cylinder head by the reroute.

Yes it is. The 2 extra fittings feed the turbo directly with coolant btw.

Attachment 227068

something seems to be slowing down the flow of water, many people run that FMIC wihtout issue, but the water may be staying in the block longer than normal.

remove the t-stat completely and replace with one thats gutted, meaning no piston. see if it does the same thing.

It is hard to make a turbo work with AC. I have mine working ok, but still can't track it in ambient temps above 90F. I had to seal everything around the rad, plus add, hood louvers, oil cooler, large single Spal fan with PWM controller and a mostly water coolant mix.

This was with AC off. Heat was on.

I'm going to burp the car again, and see if anything comes out. Will also be making proper ducting this weekend.

It's not about the A/C being on or off, it's about having three heat exchangers in a row instead of two.

I don't know if having the fans on at speed is going to hurt, but it's probably not going to help.

Have you read https://supermiata.com/na-nb-cooling...rformance.aspx ?

Oop, yup, I totally misread their reply. Yeah, I gotcha.

I have read that document, yes. I am running 60%water/40%coolant now, but I think this weekend I'll move to a stronger dilution with more water. I have about a half bottle of water wetter left as well that I can throw in, then will give the car a very good burping. I also intend on getting better ducting in there, as although the OE undertray is in tact, there's still some huge holes to the left and right. Not sure I want to cut up my stock hood for hood vents quite yet though.

It will indeed run hotter with the AC on, but I was referencing what it took to get a handle on the coolant temps with the AC off. I started out with a splash of the green stuff and 1 bottle of water wetter. Maybe a 90% to 10% water mix and had some orange rust color starting to develop. I'm now running 20% green stuff and a bottle of the WW. Its almost impossible for me to run the AC unless I'm going 30mph+. My next cooling mods are a different return pipe from the re-route, possibly a secondary mini rad and shut off valve to the heater core.

i'm going to be in this same situation soon, thanks for sharing!

IMO, you're cooling mods exceed your cooling needs (street car, big rad, reroute, low boost, wisconsin...), I think your issue may be with flow rather than capacity.

At the back of the head, it looks like you've got a big port supplying your heatercore, which returns directly to the low pressure side of your water pump. I suspect that path of flow is less restrictive than the path through your thermostat, through your radiator, and back to the low pressure side of your water pump. If you can downsize that heatercore supply, or add a restriction in that coolant line, it will force more flow through the radiator allowing the car to cool properly. The best radiator/coolant/ducting/etc is completely useless if the water can just run through a loop that entirely bypasses any opportunity to cool down.

I believe the heater core is fed by a smaller restrictive port.. The heater core and lines are more restrictive than the radiator return line. Definitely an airflow issue. For me the biggest improvement was a larger fan and second was the hood vents. The larger fan required a PWM controller.

If you are using an intercooler don't block up the bumper mouth. Air to radiator is the priority, not the intercooler.

The slender port on the side is what feeds the heater core. It is made to be restrictive to prevent excessive flow through the heater circuit which bypasses the radiator. There is a FM vid that explains the development of their reroute.
https://cimg1.ibsrv.net/gimg/www.mia...052a11df9.jpeg