pbeck39

I have an Aeroworks Extra 300 powered with a DLE 30cc engine running on a 40:1 petrol / redline oil mix. After flying there is a noticeable amount of soot on the aircraft, just aft of the exhaust, on the leading edge of the wing and on the stabiliser. Is that normal or should there be virtually no residue left. Could be that the engine is running a little rich perhaps or is it ok as is. It runs well though if pulled up into a hover manoevre there is a tendancy for the engine to momentarily pause but only very slightly. Any expert advice here would be much appreciated.

Charlie P.

Some exhaust soot is normal. Carbon is an exhaust product of burning hydrocarbon fuel. Most gasoline models can accomplish a run with minimal exhaust residue.

But without seeing it and your exhaust set-up it's hard to say. Someone coming from glow fuel is usually happy while someone coming from electric is upset with the mess.

jester_s1

I'd try to fix that slight hesitation you mentioned. How is the setting on your high speed needle? Do you get much of an RPM rise when you pinch the fuel line? Gassers don't need to be set up as rich as glow engines do. 100-200 rpm is enough, and that's barely perceptible to your ear when you pinch test.

j.duncker

My Feedback: (2)

Are you sure it is soot? Black stuff is much more likely to be something metallic loose and vibrating. I would check exhaust and engine mounts.

bbbair

Soot? No it is carbon mixed with oil.

Not enough oil. You mentioned that you are running a 40:1 oil mix - it should be 30:1
See the Tech details here;

http://www.dle-engines.com/dleg0031.html

Regardless, it sounds to me like you need to tune the engine as it is not burning the fuel properly which is causing 'Soot' which is sticking to your plane compliments of the oil mix.

Lean the engine a bit and confirm the engine speeds with a tach.

Happy Landings!

pbeck39

Thanks to all for the advice. Its certainly not a metallic residue as it wipes off quite easily with simple green or alcohol cleaner. More as someone said, carbon with a bit of oil. We will run a few more tests I think with respect to the mixture setting. Overall though the thing runs very well, far more reliably than my glow plug motors ever did.