MGL Avionics User Forum

I have an Explorer lite with an RDAC XG running four Swift EGT probes on a Jabiru 2200.

All four probes display between 400-520 degree C during a normal flight. This seems exceptionally cold! The engine runs beautifully, plugs are a lovely tan colour etc so I believe the problem is not the engine.

I also notice that the EGT display seems to lag heavily or be in-sensitive. Videos I have seen of other MGL setups show the EGT's changing every second (by about 5-10 degrees) and show instant response to throttle changes. My EGTs do not wander at all, even with change of power it takes 20-30 secs to display an appreciable difference.

EGTs are setup on TC 5-8 (1-4 are CHT) and I don't see any other options to try in the Efis menu.

Is there anything I can do?

Rainier has the correct info on EGT probes and possible problems when connected to your RADAC.

Cecil.

Our systems always use K-Type EGT probes - you cannot choose. You can only choose the type of CHT probe from either J or K types.

There are some other but quite rare EGT probes around with very different characteristics. I know the EMS that was made for Rotax used unusual probes - Type E.

Other than that the only real problem we are aware of is if your EGT probe cables have been extended incorrectly you can introduce issues. For example if you use ordinary copper cable you will introduce an error that is equivalent to the temperature difference between each end of the copper cable. If one end is close to the engine (hot) and the other inside your cockpit (cold) you could get very significant differences.

Lastly - the location where your probes have been inserted into your headers plays a major role. For 4 stroke engines we use a distance of about 7-8 cm measured from the cylinder head flange. As you move further the gas temperature cools rapidly. On older engines you can see this very nicely by looking at the discoloration of the header - this follows the temperature profile of the gas very nicely.

Hi Rainer,

Thanks for the reply.

The Swift EGT probes are K-type and there are no extensions fitted. I started off with the probes at Jabirus recommended 120mm from exhaust outlet and then after seeing the low temps, filled the holes and moved the probes to 70mm (recommended by Jabiru engineer) but there was absolutely no difference to the displayed temperatures.

The RDAC also used to be mounted engine side of the firewall but I had issues with it giving false CHT readings when the engine compartment got warm (circa 35 - 40 degrees C) so the RDAC was moved to the cockpit side of the firewall. That stopped the erronious CHT readings but the EGT's still appear to read low.

Maybe my engine is running very rich...but the plugs always check out at a nice tan colour, no smoke and easy starting/smooth running so I am not convinced there is anything wrong there.

Steve_r wrote: ↑Sun Jan 17, 2021 11:32 am... the EGT display seems to lag heavily or be in-sensitive. Videos I have seen of other MGL setups show the EGT's changing every second (by about 5-10 degrees) and show instant response to throttle changes. My EGTs do not wander at all, even with change of power it takes 20-30 secs to display an appreciable difference....

Steve,
Did you ever figure out what was causing your EGT response to be slow?
My MX1 is having the same issue and it makes tuning the engine a challenge. Temps look good but it appears that things are being averaged or something.
-brs