EGT False Indication

[ncq6c1eq4u]

Rotax 912 ULS in Vans RV-12, Dynon 180 Left side EGT (only two on this installation) perodically ran into redline for 10-30 seconds at a time. Power reduction did not seem to change the very high reading. Would suddenly revert to normal indication, in line with other EGT.

Download showed *no such variation* at all. What's going on here?

Not related: RPM's sometimes jump around at run-up level (4000) from 3850-4100, making mag check difficult. Other times RPMs rock steady when throttle locked at 4000.

Would appreciate some guidance here. Thanks, Jim

 

[dynonsupport]

Was the datalog capturing data often enough that it would definitely show the excursion?

Generically, I'd suspect a bad probe or loose connection to it. The datalog thing is strange.

Not quite sure what to make of the tach issue. Are you using the standard 5th trigger coil pickup method? Do you have any resistors inline on the RPM pickup?

 

[ncq6c1eq4u]

These indications are intermittant. F'rinstance, on 1/2 hour flight yesterday EGTS were steady and normal. RPM at run-up was steady. Can humidity or ambient temperature be a factor? Jim

 

[jakej]

Not quite sure what to make of the tach issue. Are you using the standard 5th trigger coil pickup method? Do you have any resistors inline on the RPM pickup?

Jim

We need you to answer the question from DS, please    

As for EGT - did you use a double jaw crimper (crimps terminal in 2 places at the same time) when you crimped on the male terminals ?

Another check is the female connectors on the probe wire - the crimping (from their supplier) can be sporadically poor ie it's a very small diameter solid core wire straight into the terminal (really needs to be bent around double) which can be loose or have some of the fiberglass sheath within the terminal also resulting in a poor connection.

Try pushing/pulling on the female terminal to determine if it's poorly crimped.

HTH

Jake J

 

[ncq6c1eq4u]

Jake, don't know about a fifth trigger coil or resistors; installed per Van's instructions and everything was fine for 20 hours or so. Crimps are solid. No problems in flight today. My Dynon problems all seem to be intermittant... Jim

 

[ncq6c1eq4u]

EGTs were solid for 1/2 hour of flight.  Got intermittant alerts of overtemp on left EGT.  After landing, still indicating redline but dropped to nomal before I could pull cowl and check for loose wires.

Download showed minus-2000 some odd for the time periods when the alert sounded.  Why am I getting redline and alerts on panel when download shows a negative reading?

Jim  RV-12  Rotax 912ULS Dynon 180 no autopilot

 

[jakej]

Jim

I've seen that too & found the cause, no way are you going to get an actual reading of 2000  ;D

Read my post above re crimping - fault will usually be on the probe side of system.

What I'd suggest is cut off booth female terminals and recrimp new ones on, be careful not to include any of the fiberglass insulation into the terminal, scrape off coating on solid core wire & bend it back so in effect you have 2 pieces of wire in the terminal.  This will give a much better result.

Let us know how it goes  

Jake J

 

[ncq6c1eq4u]

Jake, Thanks for the suggestion. Will try this and will post results.

 

[ncq6c1eq4u]

Jake, the wires did not lend themselves to easy replacement of the terminals so I decided to re-set them one more time.  This time I used two needle-nose pliers to really jam them together, as they are a tight fit.  So far, so good.  EGT's back to normal.   Thanks much for your help.