HIO-360_D1A HIGH EGTs

[Trigga]

Hello folks, I am hoping to get some help here after a frightening flight in a Schweizer 300c with a HIO-360_D1A fuel injected Lycoming engine

I recently installed a JPI EDM-730 to monitor engine conditions. After a few flights CHT are around 300F and EGTs have been good at an average of 1350. Then, the other night (dark) lifting off at 3000ft and a little below freezing, about OAT 28F. I climbed out and leveled off and reduced power to around 20" Manifold pressure. I looked over at the JPI and saw EGTs through the roof! average around 1650 and one cylinder peaked at 1730. I reduced the power to descend and land but had nowhere to land, so I pulled power up to 26" to climb out. With a careful eye on the JPI I saw the EGTs lower to a reasonable number like 1500F. I kept climbing and the EGTs remained about 1500F. I climbed out and flew to 7500ft to return to base. I noticed when I reduced power the EGT climbed significantly. Descending to land I had super high EGTs again. Well, I made it but did not enjoy that flight as those EGTs are frightening. The next day I went for a test flight. Lifting off at 3000ft but this time at an OAT temp of 65F. The EGTs were stable at 1350. Everything looked better. But when reducing power EGT climbed, not dangerously but enough to show a trend. EGT at lower power of 18" went to 1500F.

Any ideas?

 

[Mikey52]

It's running lean when cold. Cold air more dense. I don't think the fuel injection system is temp compensated.

 

[Trigga]

Yeah, I wonder if there is an adjustment to be made. Surely a EGT of 1730 can not be considered normal.

 

[Tarheelpilot]

What is the maximum egt in the maintenance manual?

 

[Stewartb]

Where did you install the temp probes?

Do you have a mixture control? When you reduced MP did you leave it full rich? Temps that high would make me think you were exhausting burning fuel. My first action would have been to adjust mixture to see if the temps changed.

 

[Trigga]

Where did you install the temp probes?

Do you have a mixture control? When you reduced MP did you leave it full rich? Temps that high would make me think you were exhausting burning fuel. My first action would have been to adjust mixture to see if the temps changed.

the Schweizer 300c does have a mixture control. On this helicopter we always run this full rich. It was full rich at the time of these high EGTs.

 

[Trigga]

What is the maximum egt in the maintenance manual?

The POH doesn't mention EGTs as there is no monitoring system in the original equipment. But after researching the internet I have seen the mention that the maximum EGT is 1650.

 

[Trigga]

Where did you install the temp probes?

Do you have a mixture control? When you reduced MP did you leave it full rich? Temps that high would make me think you were exhausting burning fuel. My first action would have been to adjust mixture to see if the temps changed.

The EGT probs are in the header about 2" from the cylinder head. i.e. as close as practical to the port but in the pipe.

 

[Tarheelpilot]

The POH doesn't mention EGTs as there is no monitoring system in the original equipment. But after researching the internet I have seen the mention that the maximum EGT is 1650.

Well.

You’re asking for opinions from the collective so here’s mine.

The original equipment had no monitoring, you were full rich and all other indications were in the normal range.

If you want to have the fuel setup verified to ease your mind go for it but there is no limit for egt. Probe placement has a significant impact on readings. So you could just move those probes a little further away from the exhaust port to make yourself feel better.

Furthermore having egt on each cylinder is mostly useful for temperature relative to peak in LOP ops.

One snippet I read years ago by a senior A&P was that the worst thing anyone did to engine monitoring systems on piston engines was put numbers on the egt data.

TLDR: There is nothing wrong with your engine.

 

[Stewartb]

I disagree with any statement that EGT monitoring is bad or unnecessary. EGTs are indicative of conditions. Why these EGTs rose differently than usual on that occasion is curious. In a similar RPM/MP ground run I doubt full leaning would duplicate those temps. It’s a head scratcher.

At full power the servo is adding fuel for cooling. I’d expect EGTs to rise a little with reduction of throttle.

It is interesting that full rich is used for 65° and 28°. I run full rich at takeoff but lean at least 100° for cruise. More like 125-150° in 70° temps.

 

[Hang 4]

About 2" or less than 2"? JPI recommends 2 - 4 inches and I'm betting that one at 2 and one at 4 have a pretty different reading. The main thing with EGT is not the absolute value, but the value relative to peak and from cylinder to cylinder. They do say to mount the same distance on each pipe.

 

[Tarheelpilot]

I disagree with any statement that EGT monitoring is bad or unnecessary. EGTs are indicative of conditions. Why these EGTs rose differently than usual on that occasion is curious. In a similar RPM/MP ground run I doubt full leaning would duplicate those temps. It’s a head scratcher.

At full power the servo is adding fuel for cooling. I’d expect EGTs to rise a little with reduction of throttle.

It is interesting that full rich is used for 65° and 28°. I run full rich at takeoff but lean at least 100° for cruise. More like 125-150° in 70° temps.

he has no idea what’s usual for these conditions. The egt monitoring system is brand new and he stated this was the first operation in the reported conditions, it very likely a normal condition for the aircraft.

And to be clear. I never said it was “bad.” So do not associate that with my post.

Im merely highlighting this particular aircraft is now establishing its baseline indications for its normal and there is no maximum.