Dirty Exhaust

[Derek]

I got a 1994 M20J MSE last October and she's been flying great.

I put a GoPro on the tail tiedown last weekend to record a bit of footage and noticed when I got to our first destination that the lens was covered in crud.

I wiped it off and thought maybe some dust got kicked up landing or something.

I noticed the same crud on the camera after the next and final leg.

When I got home I scanned the video and noticed that not too long after takeoff and at cruise, the video gradually got cloudier and cloudier.

So I guess it's coming from the exhaust.

I had thought the airplane was running well, I have had to add about a quart of oil in the last 10 hours.

Should I be looking into my leaning procedure? Anything else I should be looking into before getting a shop involved?  Is this likely a sign of some big issue?

Im a relatively new pilot (sub 100 hours) and this is my first aircraft... So I'm learning a ton every time I fly and talk to you all.

Thanks for the help and suggestions!

[Hank]

Some exhaust residue is normal. How do you lean? That will affect the amount of residue. Should be light gray.

[Bob - S50]

How does the rest of the belly look? It could be the breather tube too?

[Derek]

8 minutes ago, Hank said:

Some exhaust residue is normal. How do you lean? That will affect the amount of residue. Should be light gray.

I lean until EGT peaks and richen 2 tick marks

[EricJ]

A clean belly on a single-engine reciprocating airplane is unnatural.   That's pretty normal for oil and exhaust residue to be doing that.   I worry about the ones that aren't spewing something out.

 

[Hank]

58 minutes ago, Derek said:

I lean until EGT peaks and richen 2 tick marks

50° Rich of Peak.

Folks will be along soon to tell you how wrong you're doing it, but it works fine and has for decades.

[carusoam]

So...

Leaning is one thing...

• We could write for hours about the merits of LOP vs. ROP... but that has been proven to get us nowhere...
• we might discuss what else could possibly be coming out the exhaust pipe... Put you finger in the pipe, you will know...
• How much oil do you have in the sump...?
• How long does it take for a quart of oil to disappear..?

My guess... something causes a quart of oil to disappear every 10hrs or so... often less...

• Either out the case vent tube.... find the tube see if the gunk matches the gunk on the lens...
• Or, out the exhaust... 

Somebody at Lycoming decided two quarts of oil is enough for the engine... six quarts is plenty... seven is more than enough...

The engine decides how much oil it is going to keep...

I believe, anything over six, has a tendency to find its way to the exit...   the higher the angle of climb the closer to the vent the oil goes...

Inside the engine is a real storm of moving parts, splashing oil, and some exhaust escaping from the cylinders past the rings...  the harder you run the engine... the more the oil gets misted...  high MP, high RPM, and hot piston crowns...

The case vent is an open tube... And work pretty good at allowing moisture and oil mist to escape...

The older the oil is... the faster it departs...

The more T/Os...and long climbs at VX... the faster it departs...

 

Many first time videographers use the tail tie down... it seems natural... a good choice.

realistically... if you look at the tail tie-down ring... it will have scars on it from being dragged on the surface...

The tail can get pretty close to the surface during certain phases of T/O and landing...   depending on your piloting skill and what you are trying to achieve...

Pull back on the yoke, just before Vx.... the Go Pro can probably get a lens full of tarmac...

 

Go fly 10 hrs... each hr. Measure the oil loss...  clean the case vent tube to see what is coming out...  open the dip stick cap and see what has gathered on the inside (hot & cold)...

expect that you put 100LL and oil in the engine... what comes out is the byproducts of burnt 100LL... and excess oil...
 

Sure you can clean up some of the byproducts of 100LL... LOP is one way... and keeping the CHTs warmed enough to get the lead out...

Or...

Consider some of the other locations for mounting the go pro....  

Find the thread for belly cleaners... anyone with a Lycoming will have a preferred cleaner...  Continental owners don’t lose nearly as much oil...
 

Keep in mind... 50 gallons of 100LL + Air.... turns into hundreds of pounds of water, CO₂, and a few other things... that get released in line with your tail tie-down...

Briefly,  Keep track of your oil... it has to go somewhere... when it loses a lot, it will drip off the tail tie-down...

PP thoughts only...

Best regards,

-a-

[Ragsf15e]

1 hour ago, EricJ said:

A clean belly on a single-engine reciprocating airplane is unnatural.   That's pretty normal for oil and exhaust residue to be doing that.   I worry about the ones that aren't spewing something out.

 

Yeah they are empty or they never fly.

[larryb]

I had a GoPro on the tail tie down on my J. I never had the lens get cloudy in a 1.5 hour flight. I burned about 1 qt in 6 hours typical. A bit more if doing approaches.