Strange and fleeting vibration

[DaveMC]

Hello all,  Question for bravo owners.

Yesterday I made a 3.5 hr flight from Cheyenne wy to Boise Idaho.  I was at gross on takeoff. My final altitude was 20K.  My climb out setting are 34/24 and lean TIT to 1410 seeing CHT <380,  Cowl flaps open and cruse climb at 120kts.  I was climbing through 12k when I felt a vibration which felt like it was coming from forward.  it was fleeting and only lasted a second or less.  needless to say my pulse rate went up over 100 instantly . I immediatly gave the red knob a good twist to the right cooling TIT to 1350 and my eyeballs were fixed on the JPI900. The engine numbers didn't move  at all and every single number was in the green.  the reminder of the climb out and flight was completely uneventful. I ran at 28-29/24 and 150 ROP.  

WTF

 

I have had this happen one other time about 6 months ago I was in Cruse at 21K trailing about half cowl flaps   At about an hour into a flight from boise to Missouri.  again it lasted less that a second and not a peep from the engine monitor.  

 

anybody ever had this happen ?

 

Thanks in advance

[N201MKTurbo]

Usually a fouled plug. Could be one of those lead balls you see when cleaning the plugs.

[DaveMC]

15 minutes ago, N201MKTurbo said:

Usually a fouled plug. Could be one of those lead balls you see when cleaning the plugs.

So lean more on climb out?

[N201MKTurbo]

1 hour ago, DaveMC said:

So lean more on climb out?

I usually don't lean on climbout, I can't keep the temps down. I go LOP in cruise.

My theory is that lead balls (lead oxide) form in an oxidizing atmosphere (LOP). They will be consumed in a reducing atmosphere (ROP).

Conversely, carbon is formed when ROP and consumed while LOP.

You might want to run a bit richer in climb. I don't have any data to prove any of this. 

 

[ArtVandelay]

I usually don't lean on climbout, I can't keep the temps down. I go LOP in cruise.
My theory is that lead balls (lead oxide) form in an oxidizing atmosphere (LOP). They will be consumed in a reducing atmosphere (ROP).
Conversely, carbon is formed when ROP and consumed while LOP.
You might want to run a bit richer in climb. I don't have any data to prove any of this. 
 

Less fuel, less lead...

[LANCECASPER]

Leaning on the ground in the Bravo is a must.

[carusoam]

Show us your engine monitor data...

Some data is better than no data...

Post it on savvy...

Click the share button...

Post link here...

Things like these are interesting... they always leave finger prints...
 

Fear not the sharing of the data...  

You might learn something about your engine’s behavior...

You might find it is always the same cylinder...

Maybe it is a lower plug...

Maybe the valve wants to have its picture taken...

PP thoughts only, not a mechanic...

Best regards,

-a-

[LANCECASPER]

15 hours ago, DaveMC said:

So lean more on climb out?

The M20M POH says in all three climb scenarios you should be at FULL RICH - not to lean.

If your cooling is set up properly (Full Rich and good engine baffles) I've never seen any advantage to pull power back for the climb. Your climbs end up being longer and you don't really save any fuel since it's taking you longer to get to where it operates more efficiently. I like Best Rate Climbs in the Bravo.

If it's a 2 hour or more flight the mission profile with the Bravo (depending on winds) is climb as high as you can, as fast as you can and stay there as long as you can.

Since you pulled back power your episode could be the fuel fluctuation as described in the POH.

 

[DaveMC]

So is the concensus that my vibration was from a fouled plug and not say the cowl flaps?  Ill try and pull the data.

[Marauder]

59 minutes ago, DaveMC said:

So is the concensus that my vibration was from a fouled plug and not say the cowl flaps?  Ill try and pull the data.

I have had a few episodes of momentary vibration over the years. Most last only a few seconds if that. In all cases, it has been a plug issue. Didn't read through the whole thread but if you have a JPI, you will need to make sure the unit is catching in 1 second intervals. Otherwise, it may be missed. I think the JPI default is 6 seconds.

[Danb]

It happens to all of us, either a fouled plug or a little crap got in one of the fuel injectors. My first thought would be a little crap in the fuel injector.

 

[Rick Junkin]

9 hours ago, DaveMC said:

So is the concensus that my vibration was from a fouled plug and not say the cowl flaps?  Ill try and pull the data.

I have an occasional vibration on climb out that I THINK I've isolated to a momentary increase in AOA and may be coming from my nose gear doors. I notice it when I'm climbing through turbulent air that requires a pitch adjustment - I hand fly my airplane in the climb. Does that ring any bells similar to your situation? I religiously review my engine data and have a Savvy subscription and no engine anomalies have been seen.

I'm annualing at an MSC @AGL Aviation in October and will be asking for a good check on the gear door rigging. I'll report what I find out from Lynn.

Cheers,
Rick

[DaveMC]

On 6/28/2020 at 9:57 PM, carusoam said:

Show us your engine monitor data...

Some data is better than no data...

Post it on savvy...

Click the share button...

Post link here...

Things like these are interesting... they always leave finger prints...
 

Fear not the sharing of the data...  

You might learn something about your engine’s behavior...

You might find it is always the same cylinder...

Maybe it is a lower plug...

Maybe the valve wants to have its picture taken...

PP thoughts only, not a mechanic...

Best regards,

-a-

https://apps.savvyaviation.com/my-flights/22487/67db0695-cbca-4e53-abd4-37bdef62b88a

 

Here is the link. the flight is CYS - BOI on 6-27-202

 

yesterday I did a  GAMI lean test and a inflight LOP mag test.  I notice a few things but not sure what they mean like #3 EGT off the hook high on the left mag