Rotax EGT

[BirdDog]

Hello all, 

 

my Rotax 912 ULS likes to sit with its EGTs up around 850 on the cruise. 
 

Where does yours sit?

[Garfly]

I don't have an EGT indicator, though I'd certainly like to.  I remember watching this seminar video on the topic, a while back - the take away message seems to be that comparing absolute EGT values is not really a valid exercise. 

But whether that message applies to your question and your engine, i'm not sure.

 

Anyway, although the seminar's a long slog, it might be of interest to some.

 

 

 

 

 

Edited August 22, 2021 by Garfly

[IBob]

Crikey, that is a long one, in this age of ever shrinking attention spans!

But I am interested, so mental note for rainy day......

[Thruster88]

54 minutes ago, IBob said:

Crikey, that is a long one, in this age of ever shrinking attention spans!

But I am interested, so mental note for rainy day......

This is a more enjoyable and shorter vid about mixture control and egt, cht. He flies a Bonanza but all aircraft work the same way.

 

[skippydiesel]

As unmodified Rotax 91 series engines do not have mixture control I suspect LOP to be of only academic interest in this conversation.

 

As Garfield said, comparing EGT between engines is not really a "valid exercise"  - I take from this, that what is of use is the EGT readings for your engine, during particular operational phases (eg climb, cruise) over time and between cylinders. keep a log and respond to significant changes.

[Yenn]

I didn't watch the video, my download speed is too slow.

EGT is a measure of the heat in the exhaust pipe at the location of the sensor. That dimension can vary from cylinder to cylinder in any engine and even more so between engines. What it tells you is what is happening in combustion. In an engine with a big diameter cylinder, the plugs are usually several inches apart and if one of them is not working it will make the combustion process slower, which results in hotter gases going out the exhaust valve, hence higher RGT. That information can tell which cylinder is misfiring in a normal aero engine. Maybe not in a small rotax cylinder.

If the mixture is too lean it burns slowly, again resulting in a higher EGT. If the mixture is too rich it will also result in a higher EGT, because combustion is still in process when the exhaust valve opens.

Have a look at what EGTs can tell you and you will see that in a Rotax with a Bing carby it is a nice extra, but nowhere near a necessary instrument and definitely not an instrument to compare engines.

[Garfly]

12 hours ago, skippydiesel said:

 

As Garfield said, comparing EGT between engines is not really a "valid exercise"  

Garfield!??  Such a know it all!      ;- ))