Ash content corrolations to Pre-Ignition

[joff]

Originally Posted by vex

8 cycles on a single rotor test bed. Just because you have a pre-ignition event does not mean you'd have a catastrophic pre-ignition event.

Yeah, I missed the part where 1 cycle = 2.5 hours and thought it was meant 8 rotations of the rotor which sounded absurd.

Originally Posted by vex

As for speculation on why the ash causes pre-ignition events it's nothing more than a few ideas being passed around. As it stands right now the Pre-ignition is a direct result of ash because of carbon build up on the combustion surfaces. The carbon build up carries over heat causing the pre-ignition event where the gas reaches its flash point with contact to the surface. But that's just a theory.

This theory could be tested by replacing oil with ashless oil and seeing if a high preignition rate continued. I presume carbon build-up accumulated would not instantly vanish?