Hi, I wonder what is the nominal water temp I can push my car to a track day without causing any damage.

Any track day drivers?

 

I, unfortunately, have a fair amount of experience with this, so I will give you my opinion - which will probably be roundly challenged by every Tom, Dick and Harry on this site.
There are 4 temperatures worth noting for the Renesis

Optimum power: About 185°F
Optimum efficiency : About 205°F
Maximum "safe": About 240°F
"Oh ****": 260°F

I know first hand about all of those ranges. The "oh ****" range is almost immediately followed by the coolant (and sometimes oil) leaving the motor in copious quantities through newly formed passageways between the housings and the irons.
Generally, if you are pushing the car and it starts advancing past the 230°F point, you should consider an immediate cool-down lap, though you won't destroy the motor at that temp.

 

What MM said. Plus this:

https://www.rx8club.com/showthread.p...=cooling+quest

 

Fantastic post !! Thanks MazdaManiac.

Recently several RX-8 performed a track day having ambient temps at 80.6 F and we noticed a max limit of 221 F water temp. (about 6-7 laps track)

 

good writeup....MM