High CHT and EGT on one cylinder

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haykinson
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High CHT and EGT on one cylinder

Post by haykinson »

The new-to-me Diamond seems to have a consistently hot cylinder. During initial climb, temperatures climb into the 415-430° range, while the rest sit in the 380s or so. My typical procedure is to take off and within less than a minute to bring power back to 24-25 MP and 2400 RPM, and then continue my climb, but if I keep climbing below 85kts then the cylinder will continue to climb in temperature until it gets to mid-430s. In cruise, I have to go to 50-60% power or so in order to keep the cylinder below 400°. I tend to lean to 100° ROP The same cylinder is usually has the highest EGTs as well.

Here's a sample flight: https://www.diamondaviators.net/reports/flights/11539

The fact that this cylinder is running so hot means that I back off the power by quite a bit, but the engine should be able to run continuously at higher power. Has anyone seen this before, or have suggestions?
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krellis
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Re: High CHT and EGT on one cylinder

Post by krellis »

If you are running ROP and you have both high CHT and EGT, you might have a clogged injector.
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Rich
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Re: High CHT and EGT on one cylinder

Post by Rich »

I never see this kind of disparity. I'll offer an off-the-wall pair of suggestions:

1. Could you have GAMI injectors installed into the wrong cylinders?
2. If not (or you don't know), run a bottle test to see that the injectors are delivering fuel at the same rate to each cylinder.

When the throttle is full forward, there is an extra enrichment provided to all cylinders. Pulling back on the throttle cuts fuel flow. I just leave throttle full forward until I'm done climbing and sometimes leave it there, if I'm high enough. I monitor mixture during the climb to maintain ~1300 degF EGT. Cutting back RPM should help CHT's, so I note no obvious problem there.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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haykinson
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Re: High CHT and EGT on one cylinder

Post by haykinson »

krellis wrote:If you are running ROP and you have both high CHT and EGT, you might have a clogged injector.
That was our first idea as well, but cleaning produced no benefit.
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haykinson
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Re: High CHT and EGT on one cylinder

Post by haykinson »

Rich wrote:1. Could you have GAMI injectors installed into the wrong cylinders?
Looking at the logs, there's no record of GAMI injectors being used.
Rich wrote:2. If not (or you don't know), run a bottle test to see that the injectors are delivering fuel at the same rate to each cylinder.
I've got the 100hr fuel injector line check coming up in 20 hrs, I guess I can just move that up by a bit and have them run such a test.
Rich wrote:When the throttle is full forward, there is an extra enrichment provided to all cylinders. Pulling back on the throttle cuts fuel flow. I just leave throttle full forward until I'm done climbing and sometimes leave it there, if I'm high enough. I monitor mixture during the climb to maintain ~1300 degF EGT. Cutting back RPM should help CHT's, so I note no obvious problem there.
I think I still suffer from not wanting to go "over square", though nothing in the POH suggests that's a problem. I'll see what keeping the climb at full throttle but lower RPM does to the CHTs, though I suspect that if the problem exists in cruise as well then it's not a climb then it's not just throttle management that's at issue.
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astaib
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Re: High CHT and EGT on one cylinder

Post by astaib »

Hello,

I had exactly the same thing with mine since the engine was overhauled last year.

We have tried many actions to understand:
Injector cleaning
CHT probe swaping/changing to new
Fuel divider cleaning
Injectors tests
Contacting Diamond
The cylinder #1 has been returned for inspection
Oil analysis
...
=> No results

One day when I was looking into the engine compartment when the cowling was remove, I noticed that the rod retainer for the baffle were not there. It seems that they were lost during the overhaul. The workshop replace the rods and the difference between CHT #1 and the other fell down from 50°F to 20°F.
Then we continued to explore in this direction and we have inspected the baffle themselves and their seals.
Both of them (baffles and seals) were old, baffles cracked, seal not anymore sticking to the cowling...

We changed baffles and seals to new and the problem is gone.

Don't think that cylinder #1 should be the coolest one because he is in front position, when you look closer at the air flow inside the engine compartment, cylinder #1 is not the first to receive the fresh air.

Since that I heard from other Diamond owner that they have the same experience as me with the baffles/seals.

Try to change the seals only first because it can be enough, and because the baffles are expensive.

Have a good day.

Arnaud.
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Rich
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Re: High CHT and EGT on one cylinder

Post by Rich »

Because your EGT show a significant imbalance and you say your CHT's are following the EGT pattern, I still suspect mixture problems. I see #1&2 EGT's are pretty close and 3&4 are pretty close, but a persistent gap between the pairs. The 2 front cylinders are running higher EGT's than the rear. The injectors aren't the only thing that influence fuel flow. The distributor that sits on top of the engine might have a problem. These have been known to get AD's issued against them.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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astaib
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Re: High CHT and EGT on one cylinder

Post by astaib »

Hi Rich,

Which AD's are you talking about please?

Arnaud.
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Rich
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Re: High CHT and EGT on one cylinder

Post by Rich »

astaib wrote:Hi Rich,

Which AD's are you talking about please?

Arnaud.
I'd have to dig, but I remember getting one and having to check model/serial number for applicability (it didn't apply to my plane). I believe I have a record of it, but I'm sure it was 10 years ago or more.

My point is these things can malfunction, AD or not.
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Re: High CHT and EGT on one cylinder

Post by Antoine »

Arnaud did you post a report AFTER fixing?
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