White smoke on a Wright R1820-56

Discussion in 'Engines' started by lolo67, Oct 5, 2009.

  1. lolo67

    lolo67 New Member

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    Hello,

    A friend (but not terribly keyboard/internet expert) operates a T28 with a Wright Cyclone R1820-56 and experiences white smoke coming from the exhaust pipe of the two lower cylinders.

    The engine has the clean kit. He replaced the two cylinders with two overhauled (albeit some time ago) cylinders but the problem is still there. This is only happening at idle.

    Any guru on Cyclone engines around here, to give us a few hints ?

    Many thanks and by the way, great forum !

    Henri.
     
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Has he done a compression check on those 2 cylinders? What's his oil consumption? At landing does the engine backfire when the throttle is pulled back quickly? Dose this happen at idle when the engine is hot?

    For the most part it sounds like he's got some problems with exhaust valves or valve guides.
     
  3. lolo67

    lolo67 New Member

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    Thankyou FlyboyJ !

    Well the engine does it ONLY when hot and at idle. With power on, it doesn't smoke white any more. And when the engine is cold, it does not either. As for your other question, he never pulls back quickly the throttle so he can't say, but he will do so this afternoon during a flight test and will report.

    One thing is, when he replaced the two cylinders, he kept one oil-scraper ring from the old cylinders because he did not have a replacement of the same type. I believe that the tightness of the rings is better when the engine is delivering power than at idle, is that correct ? That could be an explanation then. But why only when the engine is hot ?

    This afternoon he will take momentarily the clean kit off, to see what happens.

    Many thanks for your informed comments, FlyboyJ, and blue skies !

    Kind regards,

    Henri.
     
  4. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    My Pleasure Henri.

    The oil scraper ring "may" be part of the problem. It does sound like valuve guides. After today's test flight I'd recommend a compression check.
     
  5. lolo67

    lolo67 New Member

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    Hello FlyBoyJ again !

    Problem still not solved. He did a flight recently, did not notice any change in behavior when he pulls back quickly or not the throttle, the engine always rattles a bit but no different as before. Like said, this is only happening at idle, engine hot. He is now in the process of looking at the two scavenge pumps, the one in front is fine and he will be looking at the one on the back side of the engine, fact is when he activates the clean kit electric pump after a flight he pumps a lot of oil back in the oil tank, which would suggest that the mechanical pumps do not scavenge well the oil during or just after the flight.

    Compressions are all OK. Also, the harness was changed after the problem appeared, to no avail.

    I have also suggested to look at the surface of various cylinders after a flight, by taking the plugs off, the two down cylinders but also others, for comparison, if the surface is oily then that should indicate a worn scraper ring, shouldn't it ? (I'm no wizard in radial engines).

    I've also heard, on a Franklin engine (flat-six), of a cracked boss in the cylinder where the valve guide is inserted, the crack was minor and only visible with a magnifying glass, but obviously oil could then flow by. But that required taking the jugs off, this is only for the next step of problem solving.

    This problem is actually quite puzzling.

    Many thanks for your help,

    Henri.
     
  6. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Hi Henri;

    Sounds like you're right on track on what I would do and yes "if the surface is oily then that should indicate a worn scraper ring."

    Pulling the lower jugs may be the last resort and aagin you could replace valve guides as a precaution.

    What's his oil consumption like? Is he burning a lot of oil?
     
  7. vintage radials

    vintage radials New Member

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    your superchager oil seal rings are worn, the suction in the induction pipes is pulling oil into the housing ond out through the lower pipes. goes away when the throttle is opened and boost is up.
     
  8. velox

    velox New Member

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    I am not an radial engine expert, but from your description your problem, while oil, is not due to cylinders, since you already have replaced them.
    As the previous poster made a suggestion about oil through the supercharger, it it probably something like that, The bottom cylinders suffer because of gravity.
     
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