I drove my Miata today, just driving home from work, was taking a datalog because I'm still messing with the tune, and it had these weirds dips in coolant temps. They happened at 410 and 495 seconds. The one at 410 seconds had the coolant drop from 183 down to 172 and then back up to 180 in less than 2 seconds. The other one at 495 had it drop from 179 down to 173 then up to 180, also in less than 2 seconds. I've attached the log and tune.

These dips do not seem normal, I don't notice anything wrong with the car, and nothing else in the logs points to anything specific causing these dips. I've checked previous logs and dint see anything resembling these dips. Any Idea what caused this, should I be concerned, or is this just something kind of weird?

 

Looks like electrical noise to me. If you want to mask it you can probably filter it out using the lag setting. Full disclosure I have no first hand experience here. I had to increase filtering on my Speeduino in the past to mask out some weird spikes on my coolant temp sensor. If it's not causing drivability issues it probably doesn't matter too much, but depending on how bad the dips get they could trigger some fueling corrections. If nothing else it might be worth checking/cleaning the connections on the sensor.