EGT/CHT combined widget

[swatson999]

(Stealing a photo from another thread just for illustrative purposes)...

For some reason, the layout of the combined EGT/CHT widget has always bugged me.  I continually want to associate the bar graph portion with the data on the LEFT of the widget, and the white marker with the data on the RIGHT.  My mind says that the bar graph, because it extends all the way to the left side, *must* represent the numbers on the left.

I know it's something that one can "get used to", but it just has always seemed backwards to me.  Anybody else?

Can I argue for Dynon to make an option to "swap" this setup? 

 

[RVDan]

Me too! The current layout is not intuitive and is more naturally read as you indicated.

 

[Eric_Greenwell]

My mind says that the bar graph, because it extends all the way to the left side, *must* represent the numbers on the left.

My mind said the same thing, even before I read your description. I've never used one, but was planning to add one soon.

 

[cmgolden]

Would I be crazy to suggest that the bar could be CHT and the line EGT?  After all, absolute temp for CHT is important, but not EGT (where relative temps are more important).  Is this just because JPI and others have always done it this way?

Any chance for this to be a user-selectable option?

 

[DBRV10]

JPI have always used the bar as EGT, and a missing segment for CHT.

I think there are far bigger improvements to spend R&D time on than this. Like a Normaise mode.

 

[mmarien]

I guess one of the solutions would be to show the CHT widget only. (duck)

EGT's can be used for engine analysis - GAMI spread, induction leaks, etc. Even if the widget is not present the data is output to the USER LOG file so it can be analyzed later.

While the EGT's can be used for engine analysis they are little use for leaning and the absolute temperature is useless information. SV does a good job of determining lean of peak and the the LOP INFO widget takes up little room.

A yellow or red temp to the left of the combined widget does grab my attention, but like those that posted here I do sometimes take a bit of time sorting it out on the gauge. With that in mind, I think I'll replace the combined widget with the CHT widget. I already made the entire upper range of the EGT green so there is little information for me other than wondering what the one low EGT indicates. Out of sight, out of mind.

 

[DBRV10]

I strongly diasgree,

A failing plug or a partial blockage of an injector show up by either fluctuating EGT values or one stepping out of the pack.

If Dynon were going to invest time doing anything on the EGT bars it would be to provide a normalise mode.

 

[mmarien]

I strongly diasgree

Hmmm. Good thing I ducked. I'm sure I recently read that a spiking CHT was an indication of the pre ignition caused by failed plug. Here is another flight similar to the article that resulted in a precautionary landing. Neither event shows up in the EGT readings.

The high CHT was controlled for a while by leaning the mixture (FF in the drop down). In the end it became a runaway event solved by a precautionary landing and all the fun of landing at the wrong airport when crossing the border. 

 

[DBRV10]

That recent story is Jonathan Fullers preignition event and yes it was caught well. You are correct that EGT does not spike with a preinition event, in fact it falls slightly. I have plenty of data files on them 

So just because preignition faults do not show much in egt changes you want to hide them and not worry about it? Sure thing. It's YOUR engine and your EMS. Fill ya boots!

As someone who teaches this stuff, and one of only a handful worldwide doing so, none of us would recommend the idea. Again I say keep the widget, but add normalise mode.

By the way, Jonathons preignition event story was not from a failed plug, it was magneto crossfire. The final diagnosis was with Jonathon and GAMI. Here is what he had to say.

The event Mike describes was on my engine on a flight over Labor Day weekend. I did a careful post event inspection of the affected cylinder including borescope and compression test, and discussed it with a number of experts including Mike and John Paul at GAMI. The anomaly that I ultimately identified was that the spark plug gaps were too large. Mixture sweeps done subsequently did not show that the #5 cylinder ran richer than the rest (which is what I had thought was the cause), and I think that supports George's opinion that this represented a preignition event rather than detonation. This problem never occurred at altitudes lower than 19,000, so I speculate that the combination of excessive spark plug gaps and high altitude led to crossfire. Since correcting the plug gaps, I have had no further events at any altitude.

And I asked John Herman from Tempest to make contact which he did immediately. All great service once again.

And last on that topic, Mike Busch did not write that story, his staff did and it has some serious errors in it. Mike did not get to proof read it either due to personal matters needing his attention elsewhere. So we don't want to hammer Mike too much.

 

[GlennB]

They can pry my multi-cylinder EGT display from my cold dead hands! 

While there are several ways to achieve a properly lean mixture (including AFR display or even a well-calibrated seat of the pants) there is only one way to show where the engine is on the HP / BSFC curve.  And there is only one display that will show when and why an individual cylinder goes rogue - OK, two, since the CHT needs to be part of the information.

That's a crucial benefit of EGT display: not just in adjusting the engine's settings in flight, but often as the first indication of a problem and assisting in its diagnosis.  A "normalise" function would heighten this awareness.

The Dynon ROP / PK / LOP indication is indeed useful, but it's still only a relative display.  And the "lean find" function, while a big help in initially setting cruise mixture, will also not flag a problem which develops in flight.

All the foregoing is why our Skyview setup has the CHTs and EGTs separately and prominently displayed.  The combination of the two tells a lot about what's going on in each cylinder, in both normal and abnormal operation.