CHT sensor anomaly

The external thermometer confirms that the High Temp is real.

Does your cooling system include a Thermostat?

It is possible that the Closed Thermostat has a preference to restricting the flow more on one side and once it actually opens fully, the flow becomes equalized.

Yes, we measured with external source, maximum difference was 10 degrees of Celsius between the heads, but the cowling were down for the test and it is possible that this caused the difference as the head2 is in front head3 is on the back. Anyway we did not managed to measure such a high difference what was Dynon showing, please check the first post graph for reference.

Yes, we have a termostat right front of the cooler but it is mounted on the common hose for all the heads so if there is some problem it will appear on all the heads simuntaneusly.

So there is a difference between Dynon and External source/measurement?  Yes, I did see the graph very interesting problem.

We were not able to measure the same but we measured small difference. Not even close to that we had on the onboard system. The confusing part is that after you rise the RPM the problem disappears and it it is ok for the rest of the test/flight even flights.