soot buildup in exhaust pipe tips

[alpinelakespilot2000]

I've got just over 40 hours now on my O-320 and have noticed a little bit of soot buildup in my exhaust pipes. Not a ton, just enough to be visible and felt. It's gray in color. I'm not exactly sure when during the first 40 hours it built up, whether it was during the first 15-20 hours when I wasn't leaning very much for break in, or whether it's continued since then. I couldn't find much about this in the archives. What causes this and should it be something I am concerned about?

Left pipe:


Right pipe:


Thanks.

[danP]

My pipes looked just like yours. I think it was from what you were thinking. I did not lean at all for the first 20 hrs also.
Dan P

[Mark Burns]

Guys,
Gray is good. Black is bad.

Looks perfectly normal to me.

Mark

[MNAv8or]

100% agree. Looks normal.

Originally Posted by Mark Burns

Guys,
Gray is good. Black is bad.

Looks perfectly normal to me.

Mark

[aussieflyer1]

I have the gray soot in my left exhaust a little more that the Right also with 6hrs on a New 0360 as well as on the bottom of the belly of the plane same side. I'm going to start leaning at about 25 hrs and see if it goes away or the nature of the engine.

Originally Posted by MNAv8or

100% agree. Looks normal.

[plehrke]

Mine have looked like that from hour 1 to now at hour 550+.

[miyu1975]

If black is bad, why? What does it indicate?

[MNAv8or]

Originally Posted by aussieflyer1

I have the gray soot in my left exhaust a little more that the Right also with 6hrs on a New 0360 as well as on the bottom of the belly of the plane same side. I'm going to start leaning at about 25 hrs and see if it goes away or the nature of the engine.

Agreed. On a new engine you don't really have a good baseline to compare to. Break in the engine per manufacturers instructions and then lean as you require (some people prefer LOP and some prefer ROP). The way the aerodynamics of your aircraft may cause exhaust build up on one side more than the other. I have seen Malibu's that output more exhaust residue on the pilots side of the aircraft. I guess I always attributed this to the prop vortex going in a clockwise fashion if your we're sitting in the seat. Makes sense in my mind anyways

As with jet aircraft that you can see a soot trail on take off and diesels in trucks, black soot or exhaust indicates unburnt fuel. Running to rich, leaking fuel nozzles, leaking carb to set up a rich condition all can be causes of black soot. Try to avoid if you can. A properly running engine should produce a nice gray look to your pipes as shown above. Just be sure to clean it off the belly every so often. It's nasty stuff. I have seen it eat through the paint, belly of a Malibu cuz the guy never washed the belly.

[M McGraw]

Originally Posted by miyu1975

If black is bad, why? What does it indicate?

Ryan,
Black on your exhaust and sparkplugs means you are running too rich and running excess unburnt fuel through the system. That will eventually build up carbon and lead inside your engine and exhaust system. Your plugs and exhaust should have a dry light brown/gray color. Next time you go to OSH go to one of the vendors and ask for the Champion Sparkplug Chart. It will have pictures of sparkplugs with different problems and what a proper plug should look like. Very helpful and sometimes free! Now, black on your plugs/exhaust shortly after starting or doing groud runs may be normal. The pictures discussed in this thread are for an engine that has been run after a normal flight. One last note, white can be bad also, it would mean your mixture is too lean. Who knew you could diagnose your engine with color

[RV6_flyer]

Originally Posted by plehrke

Mine have looked like that from hour 1 to now at hour 550+.

Normal. If the engine is running correctly, they will like that way when you have 2,600+ hours like mine do.

Originally Posted by miyu1975

If black is bad, why? What does it indicate?

The two questions can be answered with one answer.
Incomplete combustion.