IO-540-D4A5 Whine??

[BillL]

Many aircraft engines have their own distinctive sound.

Does the IO-540-D4A5 have a distinctive whine, maybe a gear train sound?

I heard my friend's 10 fly over a couple of weeks ago and heard a whine. It was distinctive and thought it sounded like a gear sound.

He independently brought the subject up a week later and is now fixated on finding the cause after his wife asked about "that sound". I am just polling the braintrust to see if it is a known sound.

How many teeth are on the crank driver gear? That should help identify the frequency.

Final Edit: Problem solved: See post #22

[Electrogunner]

The only whine I ever have is in cold weather on start up for a couple minutes. Was told and read it's from cold oil going through the oil cooler.

[BobTurner]

I always thought mine had some sort of gear train sound. I thought it was just me.

[aturner]

Bill, I occasionally get a significant whine from my engine, as you describe, and it really bugged me for a long time. Heard at taxi power (but only occasionally) probably present at higher power settings but not loud enough to hear. Comes and goes. I chased all sorts of leads, with no luck, and then one day reached up with my foot and pressed it against the firewall. Whine stopped. Something from the engine (accessory case gears? Oil cooler?) is setting up a vibration that resonates with the firewall. The sound is unsettling, but I felt better once I understood that most of it was coming from the vibrating firewall. I also haven’t heard it much in the past year or two.

https://photos.app.goo.gl/H8bdyfkZbNjgVFp77

Like to hear the thoughts / experiences of others.

[AlpineYoda]

If it comes from a harmonic in the firewall, is it possible to attach some kind of foam or other material to reduce the vibration? If your foot can stop it, it seems like some kind of sound absorbing / vibration absorbing material should be able to take care of it.

[Bill.Peyton]

I too have a whine. Much worse when engine is hot. Occurs in the 900 to 1200 rpm range. It is amplified by the firewall and oil cooler. I bypassed the cooler and it disappears. I removed the oil cooler from the firewall and it disappears.

I replaced the vernatherm, the oil cooler and both hoses to the cooler and it temporarily went away, but 30 hours later it’s now back. I spoke with an old guy who used to own an engine shop and he told me that it was a common problem and it just a resonance set up by the spinning oil pump gears. He suggested changing the length of the oil cooler lines.

I’ve learned to ignore it.

[RV10inOz]

You would not hear the normal whine you get taxiing from a plane overhead. That is a different air noise you are hearing from the ground, and that is normal too.

[AIR HOG]

Does it sound like this? https://youtu.be/gOwIdAXlgPg?t=12

[kkmarshall]

I get a whine for a few minutes when starting in cooler/cold weather. Doesn’t happen when preheated.

[aturner]

Bill, thank-you for the good information. Same symptoms as my noise, and I’ve also been playing with the oil lines (though not to the extent you have!). It puts my mind at ease knowing it is a common issue and not likely a problem. Thanks.