Engine Vibration and Exhaust Noise at Low Power Settings

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pietromarx
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Re: Engine Vibration and Exhaust Noise at Low Power Settings

Post by pietromarx »

That is poor luck and you have our collective sympathies.

I have had a few airplanes, including two DA40s, and found that my sensitivity to roughness changed subjectively.

I did do a prop balance the other month and found that it made a big difference.

These airplanes (like all airplanes, including jet engines ... I worked for GE ...) are handmade. They're all different and idiosyncratic. A good set of ANC headphones help a lot.

I would suggest that you get quantitative about the vibrations, too. Get a seismograph app (they exist) on your smartphone. It will give you a sense of the "reality" of the vibrations.

I do the same with sound level app from NIOSH.
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mhoran
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Re: Engine Vibration and Exhaust Noise at Low Power Settings

Post by mhoran »

The source of my alternator issues ended up being a broken off terminal stud. The suspicion is that the roughness/vibrations broke it loose.
PXL_20210723_183026167.jpg
My plane is down at SouthTec now for some other work and the bill is adding up quickly. I added the engine issues to the list and they've rechecked everything discussed on this thread. Now the suspicion is that there is a fuel servo issue, as the roughness is less noticeable when running a lean mixture. I'm hesitant to go down that rabbit hole though, as I worry it'll be another potentially expensive replacement that goes nowhere. Also, I signed up for SavvyQA and they don't suspect a fuel issue based on everything I've reported to them. But who knows at this point.

I do hope I can get the engine issues sorted because SouthTec is doing a great job refurbishing my plane and taking care of some long deferred squawks. I just don't want to get back a great looking airplane that I'm not comfortable flying.

The head of maintenance down there shares my concerns about the current state of roughness and vibrations, so it seems not to just be my subjectivity.
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mhoran
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Re: Engine Vibration and Exhaust Noise at Low Power Settings

Post by mhoran »

Just to close the loop on this, I got my plane back from SouthTec this week and it's running just about as well as I remember. In the end I think my issues were due to a combination of issues. SouthTec replaced the flow divider, which addressed some of the roughness issues and backfiring at idle. They also dynamically balanced my prop. These two items seem to have addressed the concerning vibrations on downwind and final.

My right mag still drops more than the left during run-up, but it's within spec. I may invest in fine wire plugs at some point and see what that does for us. In the end I'm just happy to be up and flying again.
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Lance Murray
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Re: Engine Vibration and Exhaust Noise at Low Power Settings

Post by Lance Murray »

Since you have to replace the Alternator get rid of that heavy boat anchor and get a Plane Power alternator. They are much better and saves about 4 pounds if I remember correctly.
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