Hy there. Still have problems in EGT readings. It started 1 month ago, after 2 weeks no flying time. I´ve started the engine and the EGT readings went up to 593~603ºF and maintain. Yesterday I measured the resistance in EGT probes. The values looks like bigger than I´ve expected. Around 150 Ohms, in all of them. The CHT probes were 1,8~1,9 Ohms. The measurement point was on the engine side. I´ve been flying over the Brazil´s northeast beaches. O lot of marine salt environment. The other values looks like ok. The CHT and EGT readings are ok at ambient temperature. CHT increase to 340~360ºF after engine start, and reacts well during the leaning procedures. Any help will be so good. Yours thankfully, JC, RV-9A, PU-IJC, 143hs. Aracaju-Brasil.
EGT error
- Thread starter JCmmpt
- Start date
Hi Dynon,
While we are on EGT's, I have a small problem. Recently my EGT's on my Flight Design CT go up to about 1430, but then they start jumping around and go up to 1520 and back down. They are never consistent at any throttle setting. Sometimes they are together some times not. Sometimes they are down around the normal temp. (1430 area) and then they jump up to the 1520 mark, but then eventually come back down. They are constently moving up or down 60-90F.
They used to be steady as a rock.
Bad ground?
P.S.
My oil temp and pressure have started to jump around a little too, but only 3-6 gegrees or psi. Is this connecterd to the same problem. Bad ground?
While we are on EGT's, I have a small problem. Recently my EGT's on my Flight Design CT go up to about 1430, but then they start jumping around and go up to 1520 and back down. They are never consistent at any throttle setting. Sometimes they are together some times not. Sometimes they are down around the normal temp. (1430 area) and then they jump up to the 1520 mark, but then eventually come back down. They are constently moving up or down 60-90F.
They used to be steady as a rock.
Bad ground?
P.S.
My oil temp and pressure have started to jump around a little too, but only 3-6 gegrees or psi. Is this connecterd to the same problem. Bad ground?
Marc_J._Zeitlin
Active Member
See:
http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1201875572
Thanks Mark. Dynon support wrote there is no ground issues come in play on CHT and EGT. I understand there will be an increase in millivolts as the temp increase. If there is a bad connection there will be a millivolt decrease due to the resistivity. What I´d like to know is the Dynon EGT probe resistivity value. JC - Aracaju - Brasil
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EGTs are not resistive. Thermocouples generate voltage when there is heat put on one end.
The resistance of a thermocouple should basically be zero all the time. A few hundred ohms won't mess them up though, since there is basically no current draw, so no voltage drop with resistance.
Ground shouldn't affect EGT's unless it's really huge swings, and I imagine you'd have lots of problems with that much voltage change on your ground.
The resistance of a thermocouple should basically be zero all the time. A few hundred ohms won't mess them up though, since there is basically no current draw, so no voltage drop with resistance.
Ground shouldn't affect EGT's unless it's really huge swings, and I imagine you'd have lots of problems with that much voltage change on your ground.
Ok. I understood there is no problem with resistance. OK. I´ve cleaned all of contacts and measure again the resistivity. Now is 3-4 Ohms. It means no bad connection. Again the four EGT readings increase to 593-604ºF and stop at this level. What more items I have to check? Thanks in advance, JC - Aracaju - Brasil, RV-9A, PU-IJC 143hs.
Just to give more info about the equipment: EMS-120, version 4.0. The EMS D-120 showed the EGT readings problem even before the upgrade the problem. I can measure the EGT millivolts. What will be an expected value for ambient temperature? JC-Aracaju-Brasil
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Here is a pretty chart from the internet. It's valid for EGTs only (which are type K thermocouples)
Hi there! I´ve measured milivolts with a multimeter at 89ºF indicated in all CHT´s and EGT´s EMS D-120 display. The values are 0,02 mV. It is a 200mV bottom of scale multimeter. The milivolts values are the same for all EGT´s. The table DynonSupport sent to me tells 1,7mV. I don´t have another EGT to compare the values. Is that correct? What else I could do? Hope hearing from you soon, JC - Aracaju - Brasil. Pu-IJC - RV-9A - 147hs
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EGT's are difference devices. What matters is the difference between the hot end and the cold end. If it was 89 degrees out and both ends were at 89 degrees, you'd expect 0V, which is what you read. 1.7 mV is for 89 degrees DIFFERENCE, not 89 degrees ABSOLUTE.
Re: EGT's
I have exactly the same problem as Roger Lee at post #9 on one EGT reading, the reading is stable until about the 1430 to 1450 mark then it starts a rapid fluctuation of as much as 200 degrees. There appears to be some correlation with higher RPM, but only a vague correlation. All other EGT readings stable as a rock and all connections appear good.
I also have one CHT which will fluctuate about 6 degrees, rest of them stable, I have a feeling this one might be a bad connection at the thermocouple as they are not the most expensive CHT thermocouples installed.
Dynon any advice on the EGT?
Regards
Mick
I have exactly the same problem as Roger Lee at post #9 on one EGT reading, the reading is stable until about the 1430 to 1450 mark then it starts a rapid fluctuation of as much as 200 degrees. There appears to be some correlation with higher RPM, but only a vague correlation. All other EGT readings stable as a rock and all connections appear good.
I also have one CHT which will fluctuate about 6 degrees, rest of them stable, I have a feeling this one might be a bad connection at the thermocouple as they are not the most expensive CHT thermocouples installed.
Dynon any advice on the EGT?
Regards
Mick
Hi Mick,
I talked with Dynon and we went through everything going on on my D-100. They thought it might be the EGT probes were starting to go bad. I have 257 hrs. They said it could start being a problem at 200+ hrs. They could last much longer, but you never know. I just changed mine yesterday with new ones, but didn't get a chance to fly. Tomorrow I will try to fly and I'll let the forum know if it made anything better. If it doen't work then I'm going to reload my software.
I talked with Dynon and we went through everything going on on my D-100. They thought it might be the EGT probes were starting to go bad. I have 257 hrs. They said it could start being a problem at 200+ hrs. They could last much longer, but you never know. I just changed mine yesterday with new ones, but didn't get a chance to fly. Tomorrow I will try to fly and I'll let the forum know if it made anything better. If it doen't work then I'm going to reload my software.
Hi All,
I replaced the left EGT probe and did not touch the right on my Rotax 912uls. The left seemed to be up and down 100F from the right side and would go from the 1440F normal temp to 1520F high temp. The throttle did not seem to make a difference. Sometimes the EGT would go up with throttle changes and sometimes down, but it was usually on the high side. I pulled the probe and it physically looked good. I flew today and the EGT settled down on the left to just approximately 10F different from the right. It never went into the yellow and the temps never went over 1470F no matter what I did. Looks like the probe had degenerated internally.
I replaced the left EGT probe and did not touch the right on my Rotax 912uls. The left seemed to be up and down 100F from the right side and would go from the 1440F normal temp to 1520F high temp. The throttle did not seem to make a difference. Sometimes the EGT would go up with throttle changes and sometimes down, but it was usually on the high side. I pulled the probe and it physically looked good. I flew today and the EGT settled down on the left to just approximately 10F different from the right. It never went into the yellow and the temps never went over 1470F no matter what I did. Looks like the probe had degenerated internally.
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Just a note - EGTs are subject to some pretty high heat and stress. Because of this, they don't live forever. Also, they do tend to ablate away over time. Exactly how long they'll last is hard to say, but think of them like your car's clutch or tires - they're essentially items that wear.