High EGT Alarm--Need Rotax Guru input

[yankee-flyer]

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

[Dave12]

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.

[Tony_T]

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

[Hal-san]

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

[Mich48041]

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

[crashley]

Originally Posted by Mich48041

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

[jimbower]

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)

[N223JH]

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

[yankee-flyer]

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

[Dvalcik]

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