Weird (?) coolant temp fluctuation
 

Data: 1.6 engine, td04 14psi, 42mm alu rad ducted, reroute, std Tstat. eMS2.

look how temp go up and back drop in a small time, is that normal?


https://www.miataturbo.net/attachmen...ine=1414415574

https://www.miataturbo.net/attachmen...ine=1414415574


i am looking to improve cooling as i use to track it, but i am having overheating in 2/3 fast lap, 110/120°C with 30°C outside temp, maybe obstructed coolant holes in the engine or poor water pump working?

This was talked about slightly in my build thread, but mine sure as hell didn't hit no 240F. I climbed maybe 15*.

Fix your AFRs.

AFR?

I'd look at your reroute, to me it looks like the thermostat takes way too long to open, has no problem shedding the heat. Is it a remote mounted thermostat setup?

Your AFR is all over the place, as well.

thermostat is in the spacer, and at 92/93°C "starting" temp should be already open, don't?

Not normal. Tracks RPM and MAP. That's a head gasket leaking cylinder pressure into a water passage. If you have a 1.6 with the OEM composite HG, it will not stand up to track use with a turbo. MLS gasket and ARP studs highly recommended.

Taking it back to basics, have you checked the coolant level? It would be all bad, but that could by why it's getting those funky readings. Just thinking out loud here.

level is ok


it overheated from the beginning when tracked it, and yes gasket is the oem...

Any other opinion?

coolant seems to be clean and there's a little smoke from exhaust but not on boost...

Giuseppe, I didn't give you an opinion. Your data is clear.

Had the same problem.

Replace your HG.

Rick is likely right, at least it looks that way

Well, swapped to cometic mls head gasket with new studs...

https://www.miataturbo.net/attachmen...ine=1415382445

Follows the duty cycle very well, electric gremlins in the injector harness? But I'm NB-focused, I have no idea where you have the temp sensor or where it's can get noise from.

Or there is a real problem from cylinder pressure, but why should then the temp drop so quickly?

ecu sensor is on reroute spacer, back side under coils, i also have a VDO sensor on inlet heater core hose and it read same fluctuations...

Does the VDO meter also drop that fast when you release the throttle (10(?) degrees C in one second)?

a little laggish but yes

other opinions?

You do have a thermostat yeah? what temp rating? Is it in backwards and do you have bleeding holes in it?

Well, I already screwed you once, so here goes . . .

Like Niklas said, it REALLY tracks the duty cycle trace (I wish your original graphs had shown duty cycle). I would be cleaning and refastening all engine grounds before doing anything else. I don't think what you're seeing here are real temperature fluctuations.

Sorry about the bad advice earlier. If it makes you feel any better, I'm pretty sure you would have eventually encountered head gasket issues with track driving. I sure did.

oem 1.6 thermostat (two valve 85/87°), no bleeding holes...

no problem, will try ground check...