EMS - EGT Difference

JohnAJohnson

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I'm currently installing and configuring an HDX with EMS system and can't find anything that'll alarm when the EGT temperatures differ. My last plane had a JPI and I set the "diff" to alarm with 200 degrees difference between any two EGTs. I found this very useful in detecting FF, spark plug, or other problems. Is there anything like this available with the EMS?
 

DBRV10

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The DIFF function really has no useful purpose, because your typical plug failure is yielding only a 75dF rise. So it would only work if there was say 130dF difference to start with.

What the diff function was useful for was using it on a carby engine, and using carb heat to bring the EGT difference down as much as possible, this enables better F/A ratios and smoother LOP ops with a carby engine.
 

JohnAJohnson

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The DIFF function really has no useful purpose, because your typical plug failure is yielding only a 75dF rise. So it would only work if there was say 130dF difference to start with.

What the diff function was useful for was using it on a carby engine, and using carb heat to bring the EGT difference down as much as possible, this enables better F/A ratios and smoother LOP ops with a carby engine.

We'll have to disagree on usefulness. I found it very useful on my previous O-360-A1F6D when it would alert me that something was wrong when there were no other symptoms. On Lycoming engines with a D prefix, which use either the Bendix D-2000 and D-3000 magneto, 240 degree differences were not uncommon when you foul a plug or if you develop and intake leak, etc. You could add "injector problem" to the above list for my current engine, a Lycoming IO-360-A1B6D.
 

kellym

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We'll have to disagree on usefulness. I found it very useful on my previous O-360-A1F6D when it would alert me that something was wrong when there were no other symptoms. On Lycoming engines with a D prefix, which use either the Bendix D-2000 and D-3000 magneto, 240 degree differences were not uncommon when you foul a plug or if you develop and intake leak, etc. You could add "injector problem" to the above list for my current engine, a Lycoming IO-360-A1B6D.
If you program you temperature limits appropriately, the change in color will get your eye quickly. Given that your normally aspirated engine should be in the 1300-1500 degree range when leaned appropriately, if you set a caution range from 1500-1550, and alarm at 1550, you will see a yellow or red indication instead of white. One fouled plug will only give a 75-100 degree temp rise, normally, and you WILL feel the roughness. One failed mag will make all the temps rise a similar amount and likely go above 1500.
 

DBRV10

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We'll have to disagree on usefulness. I found it very useful on my previous O-360-A1F6D when it would alert me that something was wrong when there were no other symptoms. On Lycoming engines with a D prefix, which use either the Bendix D-2000 and D-3000 magneto, 240 degree differences were not uncommon when you foul a plug or if you develop and intake leak, etc. You could add "injector problem" to the above list for my current engine, a Lycoming IO-360-A1B6D.


John......You can disagree all you like, but the JPI function that you should be using for that is actually NOMALISE mode, not the DIFF function. ;-)

One day we will get that in a SV release......Its only been 10 years of asking :cool:
 

JohnAJohnson

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David,
Normalise would be fine too but again, useless, unless you can see where one EGT has moved away from the rest of the pack without having to visually scan for it (DIFF). I'd rather hire a piece of code to do that for me. I like looking out the window and getting audio annunciations.

... the JPI function that you should be using for that is actually NOMALISE mode, not the DIFF function. ;-)

One day we will get that in a SV release......Its only been 10 years of asking :cool:

Kelly,
Problem with programming bands for EGT temperature ranges is that there are so many, with none really being normal. EGT changes with mixture of course, but also with outside air temp, humidity, altitude, manifold pressure and rpm, horsepower output, and probably a few other things I can't think of. I have found peak at 65% power, for example, at 1500 degrees, and on a different day, over 1600 degrees. I have seen full rich takeoff EGTs of 1200 degrees at one airport, and 1350 at another airport (different day, altitude, temperature, etc.) . Then, you get into a pattern of ignoring your range marks, negating their usefulness. Absolute EGT numbers mean nothing. A single, rogue EGT has a story to tell.

If you program you temperature limits appropriately, the change in color will get your eye quickly. Given that your normally aspirated engine should be in the 1300-1500 degree range when leaned appropriately, if you set a caution range from 1500-1550, and alarm at 1550, you will see a yellow or red indication instead of white. One fouled plug will only give a 75-100 degree temp rise, normally, and you WILL feel the roughness. One failed mag will make all the temps rise a similar amount and likely go above 1500.
 

kellym

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David,
Normalise would be fine too but again, useless, unless you can see where one EGT has moved away from the rest of the pack without having to visually scan for it (DIFF). I'd rather hire a piece of code to do that for me. I like looking out the window and getting audio annunciations.



Kelly,
Problem with programming bands for EGT temperature ranges is that there are so many, with none really being normal. EGT changes with mixture of course, but also with outside air temp, humidity, altitude, manifold pressure and rpm, horsepower output, and probably a few other things I can't think of. I have found peak at 65% power, for example, at 1500 degrees, and on a different day, over 1600 degrees. I have seen full rich takeoff EGTs of 1200 degrees at one airport, and 1350 at another airport (different day, altitude, temperature, etc.) . Then, you get into a pattern of ignoring your range marks, negating their usefulness. Absolute EGT numbers mean nothing. A single, rogue EGT has a story to tell.
With a normally aspirated engine, you should never see above 1550 unless you have an ignition problem. Likewise, if your power enrichment circuit and main jet are correct you should not see above the low 1300s for takeoff at sea level at standard temp and pressure. Higher altitude will mean lower temps. If the density altitude is below sea level, you could see higher temps.
If your normal cruise mixture isn't in the 1300-1500 range, there is something wrong. For example, a failed mag will likely put you above 1500 while the engine runs smoothly. If temp is below 1300 you haven't leaned into a cruise mixture. For my fuel injected engine, it is rare the peak will be below the low 1400s regardless of power or OAT. Occasionally peak will be a little above 1500 for a few cylinders. Normal will be plus or minus 75 degrees for most power, altitudes and OAT. Yes, carbureted engines will have a wider spread, but you have a fairly narrow burn temp for optimal mixture and a fixed distance to your probes, so temperature relationships don't change that much. There really are only two conditions that you want your EGT to alert you. First is ignition problem...on a four or six cylinder you will feel a fouled or non-firing plug. You have to be alert to catch a failed mag, as the other mag will keep things smooth.
The other condition is an induction leak. Again, very likely to be rough as some portion of the power range. Since I believe you have a carbureted engine, you don't have to worry about a problem injector.Just my experience flying over 30 years with EGT with both carbureted and injected engines. So an alarm is really only going to alert you to a mag problem. The other two situations you will feel, and you will have to examine actual numbers to figure out which plug is not firing.
 

DBRV10

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David,
Normalise would be fine too but again, useless, unless you can see where one EGT has moved away from the rest of the pack without having to visually scan for it


John..........as per your comment above, you may not have actually understood what the normalise function does. Trust me please, along with my colleagues John Deakin, George Braly, Walter Atkinson and Andrew Denyer in Advanced Pilot Seminars engine management training classes, we have learned a thing or two about engine monitors in the last 20+ years.

I hate to appear to disagree with you publically, but perhaps we should have a face time discussion. Normalise mode is not at all useless as you describe, rather that is exactly why it was created.

I am happy to help you here, but you must be willing.

All the best

David Brown
davidbrown'at'advancedpilot.com
 

JohnAJohnson

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John..........as per your comment above, you may not have actually understood what the normalise function does. Trust me please, along with my colleagues John Deakin, George Braly, Walter Atkinson and Andrew Denyer in Advanced Pilot Seminars engine management training classes, we have learned a thing or two about engine monitors in the last 20+ years.

I hate to appear to disagree with you publically, but perhaps we should have a face time discussion. Normalise mode is not at all useless as you describe, rather that is exactly why it was created.

I am happy to help you here, but you must be willing.

All the best

David Brown
davidbrown'at'advancedpilot.com

David, normalize simply places all EGT bars at the same level, to make it easy to discern an outlier.

Actual:
edm2.jpg


Normalized:
edm1.jpg


Normalize (and range marks) present a visual means of detecting when an EGT goes rogue.

My comments stand. I am looking for an audio annunciation to tell me when a normalized display is no longer straight across. A DIFF. I now understand that such a function does not exist on the Dynon EMS, and I accept that.

We are not disagreeing, and in fact, are talking about the exact same thing. Difference is that I want the engine monitor to tell me when any EGT moves away from the "normalize" straight line, and it appears you feel I should be content to simply look at the EGTs and detect it with my eyes.

And even if we were disagreeing publicly, there is nothing wrong with that, if kept civil. Your last post, with name drops and years of experience, and a "I am happy to help you here, but you must be willing" could come across as condescending/elitist, so as I did in my third post, I'll again thank you - My original question has been answered.
 

DBRV10

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David, normalize simply places all EGT bars at the same level, to make it easy to discern an outlier.

That is exactly what you want is it not, to make it easy to discern an outlier? Either a faulty plug, lead or some ignition related defect, as well as a partially blocked fuel injector?

The DIFF function will not alert you if your error does not exceed a limit, and that limit is variable based on what ever the other values are (and can also change. Thus this is nowhere near as good as a diagnostic tool.

As for an alert to the EGT bars, if Dynon ever get a normalise mode, it would be really nice for your purposes to have an alert band of say 30dF and an audio alert. Is that what you really want? Then hit them up for it. Because I have been for a very long time. The more folk that ask the sooner it will get looked into. Sadly not enough people seem to value these things over other frivolous things.

All the best,
 
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