EGT Sensor Reads Low

My EGT on my #4 Cyl is reading consistently 300-400 degrees F lower than all the rest of the cylinders on my O-320. It is the same dist from the exhaust as the other sensors. It reads the same as the others at room temp, but is colder than the others as soon as the engine is started.

Cyl head temps on #4 are in line with the others. I have been told that these sensors either work or don't - no middle ground. Could the splice from the sensor to the wiring harness be the culprit? The wire harness to the EMS is thermocouple wire.

Any thoughts appreciated.

Hi Pete. I had a sensor read about 200F low that was traced to a filament of shield penetrating the fiberglass insulation of one of the leads.

Simple fix and eveything worked fine.

If you truly have a 300-400F error, it sounds like a bad probe. Have you tried the boiling water calibration?

Vern

Hi Vern

I have 12 hours on her now! I'm going to look at the wires tomorrow after I fly. I'll check the shields for penetration and was planning to do calibration check, too. Did yours read the same as the others at room temp?

I'll send more pics when I get them from the guy in the photoship.

I've got over 100 hrs now and I'm currently doing some annual inspection work. I discovered that one aileron is 1/8" higher than the other, leading to a heavy left wing.

The EGTs all read similar values when cold. If they don't, check the wiring (proper polarity, both leads connected and for insulation shorts.) If you still can't find anything, swap a couple of probes at the engine monitor end and see if the problem follows.

You'll find it eventually.

Vern

swapped probes

Swapped the 2 and 4 probes today and the low temp followed the probe. Could not find any bad spots in the wiring, so it must be a bad probe. I sent a message to GRT.

Got 2.5 more in today. WX in Minne has been awesome. Will last one more day and then winter comes......

New probe fixed it

All the EGTs look good now.

LOW EGT - help requested

Yesterday was the second flight for 557BD, 9A, f/p cruise prop with an O-360 (low compression pistons). The only issue I'm having deals with EGT.

During my 90 min break in flight at 5000 ft, 52 degree temps, full throttle, full rich, the numbers were:

egt (1 thru 4) 1236 938 1325 1329
cht (1 thru 4) 347 385 385 408

The spread between the cht numbers narrowed as time passed. 4 came down, 1 remained the same. RPM varied from 2480 to 2510.

Prior to this test, I swapped spark plugs, probes and connections between cyl 2 and 4. The problem remains with cyl 2. The intake man tube is secure and in place. When cold, all cyl read equally.

What could be causing this? The engine ran great, no excess vibration. It lifted off in no time.

I've heard there is a GEM website with more info. I tried googling GEM to no avail. If anyone has that web addr pls send.

Aside from this issue, this old man was proud as a peacock in his new toy orbiting the field at 150 knots (no wheel pants). When I finally (reluctantly) landed, I sat down and just marveled at what we built.

Old men aren't supposed to have this much fun but any ideas on low egt will be appreciated.

Barry
Tucson

MrNomad said:

egt (1 thru 4) 1236 938 1325 1329
cht (1 thru 4) 347 385 385 408
What could be causing this?

Click to expand...

Barry,

It could be that they are still breaking in and will come around in a few more hours.

Try getting some Aluminum duct tape from any hardware store and put it on the front two cylinders. I did this with mine and blocked off about a 1/2" of the cylinder head and barrel face. This forces air up over the front cylinders and down between the two. The net result for me was cylinders that are now within four degrees in cruise. YMMV.

LOW EGT - help requested

N941WR said:

Barry,

It could be that they are still breaking in and will come around in a few more hours.

Try getting some Aluminum duct tape from any hardware store and put it on the front two cylinders. I did this with mine and blocked off about a 1/2" of the cylinder head and barrel face. This forces air up over the front cylinders and down between the two. The net result for me was cylinders that are now within four degrees in cruise. YMMV.

Click to expand...

My good friend Chet suggested I add alum duct tape to the front of cyl 1 and that increased cht on 1 and reduced cht it on cyl 3. It did not occur to me that adding alum duct tape to the front of cyl 2 could raise egt on cyl 2.

Is that what you're suggesting? Test EGT after adding alum tape to the front of cyl 2 in an effort to get it to equalize the rest?

Another idea I've heard is that the probe is inserted on an angle but it sure looks centered to me.

Yet another was a crack in the mag cap causing a slight misfire but the plugs looked great after flight #1.

Thanks again.

Barry
Tucson

N941WR said:

Try getting some Aluminum duct tape from any hardware store and put it on the front two cylinders. I did this with mine and blocked off about a 1/2" of the cylinder head and barrel face. This forces air up over the front cylinders and down between the two. The net result for me was cylinders that are now within four degrees in cruise. YMMV.

Click to expand...

This is too true. During my phase I nearly every flight I was reaching in through the front inlets to slightly adjust the position of this tape - to gett CHTs uniform across all cyls. Once I was happy, I used tin snips to make couple of appropriate angled walls out of .020 and pop riveted in place.

If your CHT on #2 is 385, you do not need the tape to raise it any more.

How does the exhaust look? Did it turn that copper/brown color or is it still "shiny?" If it's shiny then you do have low EGT and it's not a bad probe...

I had low EGT on #1, but that was "fixed" by the tape as Bill mentioned.. however, my CHT was below 300 s there was a lot of room for adjustment..

Low EGT - Response from Superior

Radomir said:

If your CHT on #2 is 385, you do not need the tape to raise it any more.

How does the exhaust look? Did it turn that copper/brown color or is it still "shiny?" If it's shiny then you do have low EGT and it's not a bad probe...

Click to expand...

I'll check on the color tomorrow. After several emails to Superior, I agreed to swap sensors and leads (again) and take readings using an external heat sensitive gun (again). Turns out that they have seen lifters that fail to maintain adequate pressure and lift causing a diminished "filling" of the cylinder (assuming it's intake). We also discussed a pushrod that might be too short which would open late and close early. Assuming all probe/lead/external readings come up with the same results as last time (no change), their advice is to continue to run the engine for a few more hours and wait for the lifter to respond. They also offered to send me a procedure to check the height of the existing lifter.

Thanks to all who responded. This truly is a helpful community. Kudos to Doug once more.

Barry
Tucson

Low EGT - Problem solved

MrNomad said:

After several emails to Superior, I agreed to swap sensors and leads (again) and take readings using an external heat sensitive gun (again).

Click to expand...

Yes, it was a probe after all. Thanks to Dynon's warranty, problem solved.

I have 8 hours on the 9A. Old men like me are not supposed to have this much fun and excitement. The 18 months of build, build, build was worth it.

Barry
Tucson