over reading CHT

[masseyd]

I have just purchased a Jabiru J400 with a 3300 engine and a Dynon D180 installed - all seems to work ok except the CHT' appear to be reading about 40 degrees C high when compared to an external heat gun measurement - any ideas to help? thanks

 

[dynonsupport]

At what temperature is it reading 40 degrees high? That may help us narrow it down.

Does it read ambient temp when the engine is cool?

 

[masseyd]

when the engine is cold the readings look to be correct i.e. atmospheric - the egt and cht are about the same - the over reading appears to start circa 100 degrees C when compared to an external heat gun reading. At first we assumed it was a problem with the engine - but we have now rebuilt significant parts of the top end even though the engine is low time, to hopefully remove any known source of mechanical problem that could cause real overheating. Any ideas now would be apopreciated. The CHT sensprs are 12 mm rings under the spark plugs.

 

[dynonsupport]

Any way to verify what type those spark plug ring sensors are? They should be J types, and I wonder if they are actually K's.

The other thing is, what do you mean by "heat gun"? Do you mean a non-contact infared thermometer? If so, these can average over large areas, so there's a chance the heat at the spark plug is actually higher than the average of the larger area the thermometer is reading.

 

[masseyd]

thanks - that would certainly explain the readings if the sensors were K type - is it possible to recalibrate the Dynon for K ?

could you also confirm the correct sensor type for the EGT?

 

[dynonsupport]

CHT must be J. We don't support K for CHT.

EGT is the reverse- must be K.