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High EGT Alarm--Need Rotax Guru input

yankee-flyer

Well Known Member
912 ULS Rotax installed in an RV-12. 22 months/127 hours on the engine. Everything OK at 100-hour inspection.

This morning on taxi out the left EGT readout spiked up to 2000+ degrees in just a couple of seconds. I shut everything down waited a minute and re-started-- everything normal. Flew 1.2 hours to a family reunion with no problems and the airplane sat fro almost 4 hours.
About 15 minutes after takeoff the left EGT reading spiked; I reduced power from 5200 to about 4200 and the temp started to drop slowly and then instantaneously dropped to normal, Back to cruise power/altitude (Density altitude 7700 and yes, the fuel flow was reading 5.9 again) and about 15 minutes later the same thing happened, including instantaneous return to normal ( the display actually blinked as it changed) I noted the conditions as follows:
EGT L 1265 then up to 2079
EGT R 1240 (Normally seem to read 25-50 deg cooler than left side)
RPM 5200
MP 22.7/8 (reading fluctuates rapidly in the decimal digit)
Oil Pressure 68
Oil Temp 214
CHT L 187
CHT R 186
OAT about 55 F

There was NO CHANGE in engine sound, power output, manifold pressure, RPM, or anything else I could see while the EGT was climbing (less than 10 seconds from baseline to 2079), 3-4 seconds to instantaneous drop).

Same thing happened a third time with me keeping a close eye on alternate airports along route.

Then during descent from cruise altitude to home base at about 4500 RPM it spiked again. Pulling power all the way back had no affect, Going to FULL power brought an instantaneous return to normal.

I can't think of any mechanical problem that would cause this other than something hanging up a carb float (lean mixture) but it happens most often after 10-15 minutes at constant power setting>Need input on what to look at. Loose EGT probe? Loose connection back at the firewall? Or ????

On the positive side, at about 1025 Lbs gross weight, take off from a not particularly manicured grass strip at 2500 density altitude was not more than 1000 feet ground roll-- what a change from my AA-1!!!l

Thanks guys-- need to fix this before flying Young Eagles Saturday.

Wayne 120241/143WM
 
Wayne, I had the exact same problem at 100 hours. I replaced the egt probe and life is good again. It is a Dynon part and I think it is either 30 or 60 dollars.
 
High impedance connection?

Wayne,

Your thoughts about a loose connection are sound reasoning. I would be suspicious of a poorly crimped spade connector first. The Dynon is very susceptible to high impedance connections. I doubt if there is any way the readings could spike like you describe because of an actual engine problem. You should be able to make a visual check of the crimps on the connections as a first step.

Tony
 
Wayne,
I had a similar problem and found that the left and right EGT wires were crossed in the connector to the D180. After I found out I was chasing the wrong side, I corrected the wiring and recrimped the spade terminals and have not had a problem since.

Hal
 
I agree with those who suspect a bad connection at the spade connectors forward of the firewall. Page 45-05 deals with their installation. I suggest replacing the spade connectors.
Joe Gores
 
temps

I agree with those who suspect a bad connection at the spade connectors forward of the firewall. Page 45-05 deals with their installation. I suggest replacing the spade connectors.
Joe Gores

Hi if it spikes it is a thermocouple or cable fault check all the connections it wont be a real temp problem
 
Spike on #2 EGT

I have a Dynon D-120, and after about 58 hours on my -6A I suddenly saw the #2 EGT spiking to a high (maximum?) temperature last evening. As soon as I noticed it, the reading went back to normal, but repeated this process several times before I got back to the airport and shut down. The CHTs were all good, and after shutdown the EGTs were all pretty much in the same ballpark.

I never really suspected anything other than a probe or wiring issue, but it's very comforting to know others have experienced the same problem.

Jim Bower
St. Louis
RV-6A N143DJ (flying since 9/2011)
 
Occam's Razor

Wayne, Been through this... Find the EGT connectors on top of the engine. Pull 'em apart. Check for corrosion. Put some dielectric grease or vaseline on them. Now get two pairs of needlenose pliers and firmly push those connectors together. If this doesn't work you may have to replace the spades.

Jim
flyin' 140 hours
SB complied with
 
New Probe

Checked, crimped, and even replaced one terminal without success. Called Dynon and ordered a new probe. Installed that and everything's been fine for 15+ hours. Apparently those probes aren't real durable.

Wayne 120241/143WM
 
I have a GRT instead of the Dynon, but also had to replace one after a short period of time. I agree they are sensitive and can be damaged easy. Don?t know how much the Dynon's were, but the GRT were not too expensive, just the hassle factor
 
Can someone elighten me as to why you have EGT on a Rotax in the first place?
 
E-LSA

Because Van's put them on the prototype and we have to build the airplane exactly like that. Not a darn thing we can do about the EGT except jump out of the seat when the overtemp alarm goes off.

Wayne 120241
 
You can throttle back. You can also worry about maybe that the premium car gas you bought wasn't really premium, that might be a symptom of a lower octane.
 
Jump out of your seat

Especially on a "touch and go" during rotation. That actually happened to me. :eek:
 
Throttling back

seems to be the universal first response-- see my post at the start of this thread. After the temp suddenly returns to normal the cycle will repeat every 10-15 minutes. It does sharpen your "look for emergency fields" skills.

Wayne
 
This may be a case of too much info is dangerous, or "what you don't know may never hurt you." Small airplanes have flown around for decades without all these extra indicators, and the ignorance was indeed blissful.

At first blush, it would seem to me that the CHT and EGT are not only not needed, but - having installed them, are cross-checking and confirmational. In other words, I don't see how you can get one parameter to go abnormal without the other param confirming to some degree. Furthermore, any spiking as you describe - especially spiking and unspiking instantaneously and repeatedly - cries out for an electrical intermittency of some sort. Strongly enough for me, to not start looking for emergency landing spots. Or wondering about the gas. You don't jack up the temp 1000 degrees in a second.

The spade connectors are problematic, and I believe some folks have replaced them, where able, with ring terminals. A while back, Tony T was describing an intermittent problem he was experiencing. I recommended he look into DeOxit by Caig

http://store.caig.com/s.nl/sc.2/category.188/.f

I have used it on my ham gear for years - coax connectors - it especially shines on mutli-pin connectors like D-subs. It does what they claim - improves conductivity, reduces oxidation (like on spades), and preserves the electrical integrity of the connection over time. As stated - it "reduces intermittent connections."

I call it a ham's best friend and my "magic elixir." I use it extensively. Tony tried it and I believe says his intermittent problem (fuel pressure?), has been eliminated. There are assorted versions - some good for temps up to 500 degrees C.

As a war story, this past Monday, I powered up my airplane for the first time. The Skyview could "see" the EMS and Transponder, but could not "see" the ADAHRS - hence no PFD. Before powering up, I had done a continuity check on the 8 wires running from the ADAHRS to the Vans 50000 Control Box D-sub. All OK. I troubleshot extensively, and removed, checked, and carefully reinstalled all the D-subs. No Joy.

So I called Dynon. After listening to my "no-handshake, no connection" hard-luck story, they said I should remove the ADAHRS and either hook it directly to the SV or send it in to them. Grrrrrr - remove it? Send it in? After all my hardwork? Bobby was not a Happy Camper. But Bobby remembered The Magic Elixir".

I pulled the D-sub 9 connector off the ADAHRS, and sprayed the pins with my Deoxit. Then I powered up again. Voila! - Skyview sees the ADAHRS, the PFD is operational in all respects, and has run all week with numerous re-starts and shutdowns etc. I advised Dynon who found my tale of interest. It's important to remember some of these pins and wires are not transmitting power or binary (on/off) information, but are transmitting data streams which are even more susceptible to faulty connections.

De-Oxit - like they say - "Don't leave home without it." I wonder if I can drink that stuff???

Bob Bogash
N737G
 
"Magic Elixer"

OK, I'll be Bogey's wingman here. Since he recommended the elixer I have used it on all of my slide together connections everytime I take the cowls off and have had no spiked readings since. Good stuff...I think. Can't hurt anything.

Tony
 
Pondering life mysteries!

I wonder how this magic elixir would work on the D-180s where we lose our Nav data stream from the 496 to D-180 to the AP74 autopilot Nav function':confused:.
 
I think I have a similar problem. All my probes are reading really high temperature. For instance, on idle, they read 1600F. At 50% power, they read over 2000F. The funny thing is that they all read about the same and it looks like a permanent issue. I observed that if I power up the EMS with the engine turned off, it reads 360F. I was expecting to read the current ambient temperature (around 60F in my hangar). The funny thing is that if I disconnect the probe (there is a spade connector in the middle of the wire), it reads 61F.

I can't believe that 6 probes died at the same. Any idea?
 
I think I have a similar problem. All my probes are reading really high temperature. For instance, on idle, they read 1600F. At 50% power, they read over 2000F. The funny thing is that they all read about the same and it looks like a permanent issue. I observed that if I power up the EMS with the engine turned off, it reads 360F. I was expecting to read the current ambient temperature (around 60F in my hangar). The funny thing is that if I disconnect the probe (there is a spade connector in the middle of the wire), it reads 61F.

I can't believe that 6 probes died at the same. Any idea?

How many hours have you been flying? More info on your plane would be helpful.

There must be a setting that is off somewhere. Contact Dynon.
 
How many hours have you been flying? More info on your plane would be helpful.

The engine has 250 hours. It is a Chevy Vortec v6 4.3l. The sensors look just fine. I'm reading the EMS manual. My bottom temperature scale is set to 200F. I'll try to set it to 0F and see if I can get the ambient temperature with the engine turned off.
 
The engine has 250 hours. It is a Chevy Vortec v6 4.3l. The sensors look just fine. I'm reading the EMS manual. My bottom temperature scale is set to 200F. I'll try to set it to 0F and see if I can get the ambient temperature with the engine turned off.

You have a Bowtie V-6 in your RV-12? Or were you experiencing similar issues in another model?
 
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