912UL EGT`s Running HOT

[Morph]

800deg C normal, 850-900deg C Maximum

Trikenut

CHT - Cylinder Head Temperature
EGT - Exhaust Gas Temperature

Cylinder Head temps in the 912 and a 582 are controlled by the water cooling, and are typically in the 80 to 100deg C. This tells you how hot your engine is running.

Exhaust Gas temperatures measure how hot the gases are coming out of the motor, This is very very hot, usually in the 800 deg C mark. You do not want to touch an exhaust pipe. The EGT temps tell you how rich the mixture of fuel and air is. If there is a lot of fuel, the EGT's are lower, and if there is too little fuel the EGT's are higher. If they get too high the inside of the piston can melt, burning a hole through the piston and causing the engine to stop.

The standard 912 has only 2 CHT and 2 EGT, one on each side. The water used to cool the front left piston is the same as the back left piston so it is a waste to test both pistons, the temps will be the same. As far as the EGT is concerned, the 912 has one carburetor for the left and one for the right. EGT temps are controlled by the carbs so again, there is no requirement to measure both left pistons and both right. Some people do but that is their choice

A 503 normally has no CHT/EGT's you have to add them. Here the CHT's are connected to where the sparkplug is screwed into the head and the EGT on the exhaust.

a 582 has one Water temp guage, reading both pistons, so it does not need CHT's. It uses the same EGT probes as the 503.

[Trikenut]

Thanks Morph!

[Splinter]

Ok guys here is the update.....

I am happy to report that the EGT problem has been solved. After going through all the suggestions and finding nothing major I went for a flight above the airfield. Before taking of on the tar runway I did a mag check - all in order. Flying overhead the field the EGT`s were running as normal but then suddenly they started to climb again. After landing on the bumpy grass runway I did another Mag check in front of the hanger - One mag dead! The AP and I found that one wire earthing the mag at the inlet manufold was losing contact from time to time beacause of a bad connection due to years of vibration and age!

The AP rectified the problem and tested both mags again - This time no problems and hardly any rev loss while running on one mag! With the logbook completed and stamped I flew her again and was pleased to find that all was back in order.
These little wires are mostly hidden under a few other pipes and can easilly be missed during pre-flight! Please take a few minutes during your next pre-flight and have a decent look to see if everything is ok! To me the only explanation is that the loss of one mag had a small effect on the timing and caused the EGT`s to run hotter.

Thanks for all the suggestions that were made and please keep this problem in mind should you have any of the same symptoms!

Regards
RED