IO550 Backfire

[Alan Maurer]

Hello everyone, I have a question. Starting Ovation today, on start up while cranking the engine has a backfire.....pretty loud. Then it started in a normal fashion

and CHTs and EGTs were all normal. In recents starts this has never happened. Could mag timing be off? Any thoughts?

Thanks

Alan...N913ND  Ovation M20R

[PT20J]

A true backfire (through the induction system) usually means that there wasn't enough prime and the mixture was so lean that there was still some fire in a cylinder when an intake valve opened and that lit off the charge in the intake manifold. Another form or backfire (technically an afterfire) happens when there is too much prime and raw fuel ends up in the exhaust system and it gets lit off when the exhaust valve opens expelling hot gasses.

[kortopates]

you merely over primed, flooding it sufficiently to pump some fuel into the exhaust from cranking. then upon starting the fuel in the exhaust ignited. technically it’s called after fire.


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[Fly Boomer]

39 minutes ago, Alan Maurer said:

on start up while cranking the engine has a backfire.....pretty loud

I think Mike Busch wrote "in warm weather people generally over prime; in cold weather, they usually under prime".  Probably can't use the same technique winter and summer.

[BDPetersen]

Some concern for damage to muffler/exhaust system. 

[Alan Maurer]

thanks everyone...annual coming up ...will get exhaust system and muffler checked

Alan

[PT20J]

4 minutes ago, Alan Maurer said:

thanks everyone...annual coming up ...will get exhaust system and muffler checked

Alan

Unlikely a problem unless it was a huge boom. They are designed to take that as backfires happen.

[carusoam]

Really Old / worn systems can be sensitive to exploding fuel in the exhaust system….

If you have a good CO monitor…. Use it….

If you don’t have a good CO monitor…. Get one….

Some people have dental cameras they have sent up the exhaust pipe to inspect the internal bits of the muffler….

The annual inspection normally covers exhaust system health…. Pretty well….

If you get any strange rattling sounds while taxiing that could be a sign of something broken loose in the exhaust system…

If the system has many thousands of hours on it…. Some of the welds may be weakened over time…. This could lead to CO getting into the heating system…

 

If you have a worn or broken muffler… it may be the first recorded for an Ovation on MS….

Not a very common problem for Long bodies…. Yet.

Best regards,

-a-