ET: Engine (Twin) Foreign Object

[Vincent Brake]

Running on the rich side??? or?

 

[davidd]

Testing at TDC is the best because that is where the explosion takes place. However, as a general check, you can simply remove the two pushrods and then do the check on that cylinder. When the air is turned on the piston will automatically move to BDC, but the reading should tell you what you want to know, which is how much air is passing by the rings or the exhaust and intake valves. It is often difficult to hold the engine at TDC with 100 lb pressure in the cylinder.

When you are done, you can just install the pushrods and check the clearance at TDC as usual.

David

 

[nigsey]

Running on the rich side??? or?

Definitely Vincent, but mostly before I bought it.

 

[nigsey]

Testing at TDC is the best because that is where the explosion takes place. However, as a general check, you can simply remove the two pushrods and then do the check on that cylinder. When the air is turned on the piston will automatically move to BDC, but the reading should tell you what you want to know, which is how much air is passing by the rings or the exhaust and intake valves. It is often difficult to hold the engine at TDC with 100 lb pressure in the cylinder.

When you are done, you can just install the pushrods and check the clearance at TDC as usual.

David

Thanks David, that sounds like like really good advice.

 

[rapide049]

Testing at TDC is the best because that is where the explosion takes place. However, as a general check, you can simply remove the two pushrods and then do the check on that cylinder. When the air is turned on the piston will automatically move to BDC, but the reading should tell you what you want to know, which is how much air is passing by the rings or the exhaust and intake valves. It is often difficult to hold the engine at TDC with 100 lb pressure in the cylinder.

When you are done, you can just install the pushrods and check the clearance at TDC as usual.

David

Select Top Gear -Apply the Brake

 

[nigsey]

Select Top Gear -Apply the Brake

Many thanks for your suggestion, which worked! A common sense solution

Select Top Gear -Apply the Brake

I did as you suggested, it worked, thank you.

 

[nigsey]

I’m

Carbon is not magnetic. If there are some iron filings mixed up in the carbon then it might seem to be magnetic.

Broken rings usually stay in place. Over time the bits of ring widen the ring groove, but they still remain trapped in the piston.

View attachment 60851
I suppose it could be a small shard that made it by the piston. The best thing to do is a leak-down test, but you probably don't own a tester. A compression test should tell. When I did a leak-down test on the above cylinder it showed 60% of the air passing by the rings.

Fortunately, I had a Nicasil aluminum cylinder liner in the muff and it is still running today 13 years later.

David

Leak down test completed, 12% loss from front cylinder and 14% loss from the other, so it’s looking good there I think.

 

[Alyson]

I’m


Leak down test completed, 12% loss from front cylinder and 14% loss from the other, so it’s looking good there I think.

Where did you loose it from ? Intake, exhaust, rings ? Over how long did you do your leak down test ? Might need to lap your valves and/or re ring.

 

[oexing]

Leak tests are done latest at each annual check with aero engines - a bit questionable as there may be just a bit of crap on valve seats spoiling the test. So advice is to do another hour of decent flight and test again. Mostly that does it.
For knowing the point of leak have the air connected to the plug. Then open some inspection cap on the engine and listen to any hiss from inside. That would tell you the piston rings leak a bit.
Then take off the exhaust pipe and listen into head exhaust port, that would tell the ex valve is leaking.
Next listen into carb mouth for hiss, that means the intake valve leaks a bit. Then do your conclusions . . . .

Vic

 

[nigsey]

Where did you loose it from ? Intake, exhaust, rings ? Over how long did you do your leak down test ? Might need to lap your valves and/or re ring.

Air loss was past the rings, no loss detected past the valves. Test duration was about 5 mins