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IO-540-D4A5 Whine??

BillL

Well Known Member
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
 
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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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
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.

That's interesting, as the oil pump body and gears are almost identical to those used on the 4 bangers, with the same drive mechanism. I would be more inclined to speculate on the mag drive idlers/gears. The 540 is known to have serious resonance issues in those gears, hence the rubber couplers and the shorter inspection intervals on the 6 cyl mags, compared to their 4 cyl counter parts. Any resonance in that area would like works it way to the F/W via the cooler lines.

Larry
 
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I also have the whine after cooler starts (40-60F).
I preheat when it gets cooler than that.

Larry - can you expand on the "shorter inspection intervals on the 6 cyl mags"?

Thanks
Thomas
 
I also have the whine after cooler starts (40-60F).
I preheat when it gets cooler than that.

Larry - can you expand on the "shorter inspection intervals on the 6 cyl mags"?

Thanks
Thomas

The slick mags have long had a recommended inspection interval of 500 hours. I read something a while ago, where slick had reduced the recommended inspection interval on the 6 cyl version of their mags to something less than 500 (300 vaguely rings a bell). The reason cited was increased failure rates due to the difficulty of these devices in dealing with the unfavorable harmonics that exist under the accy case of 540's. I presumed that these harmonics came directly from the mag gear/idler but can't make that a statement of fact.

I have dual EI's, so didn't pay a lot of attention to the details of the SB. It was, however, enough to scare me away from a mag hole based EI timing pickup device like I built for my 320.

Larry.
 
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Can you hear this whine in the airplane? In my Comanche with the same engine its quiet and smooth.
 
Thanks, Larry. A brief google search didn’t bring anything up for me.

I am nearing 300h on my original mags, was planning a 500h service but will look into this more.

Bob- on mine, when started in cool conditions, it is audible in the cockpit but goes away when the engine warms up. Always gone well before takeoff.
 
Thanks.

I pulled the impulse coupling and installed a Slickstart module ... the way I read that, I am back to the usual 500hr inspection?

Thomas

Hopefully you meant "pulled the impulse coupled mag and replaced it with a retard mag". Starting without retarded timing is asking for trouble.
 
Can you hear this whine in the airplane? In my Comanche with the same engine its quiet and smooth.

Apparently barely. I have been in there for hours and never noted anything odd. I downloaded a spectrum analyzer app and will make a recording to see if anything pops.

The crank gear is apparently 13 teeth. I had the owner go to a tone generator on the net and he closed his eyes and stopped the slider at around 513 hz which translated to 2367 rpm, he typically runs 2350-2360. I don't think anything is wrong, just making sure.
 
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Mystery Solved

Solving things in real life is a lot easier as evidence presents itself without query.

The cause of the vibration was a trim plate covering the aft door hinge on the passenger side. I was sitting there and about 100kts it started screaming. I thought it was an alarm at first and asked the pilot, he did not hear it. Taking off the Bose headset and listening quickly found it. It was sucking air through it and vibrating like a reed on a wind instrument. VERY LOUD too and VERY irritating. Definitely not there before the paint shop. (no daggers at them)

It took all of 30 seconds to locate it. A lucky day:), unlike the stock portfolio today.:mad:

Picture is attached, we removed the screws, bent to tighten the gap to zero, and now it should be history.

Thanks to all who contributed, I am sure the gear sound is still there but all quiet in the cockpit now.
 

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