What is considered normal hot track coolant temp?
 

For a mild turbo Miata and ambient temps of 90-95*F, what would be considered normal high coolant temp on the track? At what point should I consider backing off and letting it cool down?

I see 205-215 degrees on track in the Southern Cali summer (up to 100 degrees). I'm hotside supercharged with a Koyo 37mm radiator and 949 reroute.

Haven't had any issues yet. I would probably back off if I go to about 230 degrees.

Anything north of 225-230*F makes me nervous.

Depends on your radiator cap and oil temp differential.

I run ~250F water/270 oil on a hot day with a 21 PSIG cap. Not a lot of headroom there. I bail out @ 253.

I have my boost cutout set at 235F. It's what it was set at when I bought the car.

That's about what I was thinking.
Holy crap! I actually winced just reading that. On what oil?
That's a good idea.

I'll see what safety settings might be available in the various megasquirt menus that could keep me out of trouble.


Anyone else with experience?

Normal track temps?
 

I'm wondering if I should be concerned about track temps. In terms of basic setup and cooling, I have a 1.8L with Flyin' Miata turbo kit (and FM exhaust), Koyorad radiator, and the coolant reroute done with 185 degree thermostat. Last time I was on track in the summer, my water temp hit 258 degrees F, although that was before the reroute. That was pushing the car about 70-80% of what it could do. Additionally, I'm not sure where the water temp sensor is (for reference it's that Autometer digital one) but I can try to look for it if anyone knows where it should be. Previous owner said it's on the hottest part of the engine (whether that's the stock location or not, idk). What can I do to bring the temps down if this is too high? Thanks.

Improve Ducting. Undertray, and ducting in front and beside radiator.

Crossflow radiator from Supermiata or Trackspeed.

Oil Cooler with thermostat really helped us stabilize water temps

I would be concerned about that temp. I bail out around 235-240 F on the stock NB coolant sensor read through an ultragauge. I believe I've read that Miata make the best power around 200 F.

The first things to do is see where that sensor is in relation to the stock one and see what has already been done. Do you have a stock (plastic cap) radiator? Is there an existing coolant re-route? Is the plastic piece of ducting under the front of the engine in place?

Options for upgrade are:
- Better radiator (crossflow is usually best and lightest weight option. Alternatively, Megan Racing makes a super cheap traditional style radiator that is huge and worked well for me)
- Coolant re-route (I've read the supermiata/qmax one is absolutely worth the premium)
- Improve ducting (make sure the plastic shroud is there, add hood vents)
- Oil cooler (trackspeed makes a nice kit)

Our cars run <210 in the hottest weather during a race. In <85° weather, we usually see 192-200° coolant. BP's will survive about 250° with enough system pressure and a bit of water wetter. Much past that and you are losing a headgasket. Besides being risky, BP's make less power at those temps. One should try to get the car to run between 185-200°f if possible. We set our warning lights at 220°f. I would never intentionally run a BP in a track car above 220°f. That said, a bone stock but completely healthy NA or NB will usually see 230~240° on track in warm weather.

The other metric you should keep an eye on is coolant pressure. Depending on where you locate the sensor and cap rating, you'll need to fine tune low and high warnings. Low pressure on a hot car means you have a leak. That will trigger a warning 5-30s before the temps actually rise, giving you that much extra time to shut it down. High pressure warning light indicates a head gasket going. After a track session when you ease off on your cool down lap, system pressure will drop to near zero. That briefe low warning is a good indicator your caps high and low pressure seals are working. This is when the system draws coolant back in from the expansion tank.

I need to sticky this somewhere.

I second this.

I agree with the 230F/110C warning and 250F/120C shutdown. This is pretty standard across OEM's. We usually start dialing stuff back like A/C compressor cut and reducing alternator load between 110-115C and by 120C throwing in the towel and going back to the drawing boards (air and/or coolant flow rate increase). Most manufacturers actually shut the engine off around 130C/266F, which depending on cap pressure, is usually about the time you start doing damage. You will already be having localized boiling well before 130C due to the imperfect flow through the engine, and coolant flow will already be significantly reduced (without a proper coolant expansion tank setup) due to water pump cavitation at high engine speed.
***This is all assuming you have proper ignition/fuel control; i.e. you aren't knocking it to death because you're not retarding IG to compensate for high TW or melting shit because because you're retarding due to high TW and your exhaust temps are smoking. Obviously, if your calibration is lacking, it'll pop well before 130C.

@ ambient 10C <190F
@ ambient over 30C <215F
oil never over 240F.
stock 1.6, 2860RS @15Psi.. Shift light 6900 RPM, fuel cut @7100. Have done several 3hr W2W races.
Ducting. Ducting. Ducting.

Copy pasta into my important notes spreadsheet.

Below boiling :p

The good answer is already above

At at what pressure?
With what coolant type?

A modern OEM high performance car might see 250 degree coolant without issue. That of course, is well above h2o at sea level boiling point.

Yeah I did several cool down laps after that kinda temperature. I did the nice Supermiata coolant reroute kit which is high quality (and even traded the 195 thermostat that came with it for a 185 degree one). The reroute was done after that track day and I haven't been back on track since cause college. Planning on an oil cooler next oil change, just not sure where to place it. I'm willing to get a better radiator if absolutely necessary, but do you think the Koyorad is not enough? (I guess what I'm really asking is, does it really just replace the stock one rather than also upgrading it?) I saw a "heavy-duty" 3-row core from Mishimoto that looks pretty nice. Lastly, would hood louvers and better coolant itself help at all? I'm a pilot so I usually let air do all the cooling but I imagine a better liquid would be more efficient. Thanks again.

Check out the cooling system thread that is sticky in this section..