Ash content corrolations to Pre-Ignition

[joff]

Very interesting thread.

Any speculation as to why oil ash content causes higher preignition? Is it because of the ash in the exhaust->intake carry-over volume due to the burning oil in the expansion/exhuast strokes?

Compare that to oils that have relatively high ash contents (1.2, 0.9) which experienced their first pre-ignition event within 8 cycles.

Preignition within 8 cycles??!! I doubt many people have paid that much attention to oil ash content in the past -- how can there not be more blown motors because of this?

[vex]

Originally Posted by joff

Very interesting thread.

Any speculation as to why oil ash content causes higher preignition? Is it because of the ash in the exhaust->intake carry-over volume due to the burning oil in the expansion/exhuast strokes?




Preignition within 8 cycles??!! I doubt many people have paid that much attention to oil ash content in the past -- how can there not be more blown motors because of this?

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.

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.

[Barry Bordes]

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.

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.

Vex and Joff,

In the NSU paper linked above, the engineers were finding engines being destroyed after high speed runs on the Autobahn. Their conclusion was preignition for metal ash deposits on the rotors.

The good news on the Valvoline VR1 is that I found it a O'Reilly's so it may be a other automotive stores also. They only had it in 50W and 20W50. It comes in 10W30 and 10W40 also.

Barry

[vex]

Originally Posted by Barry Bordes

Vex and Joff,

In the NSU paper linked above, the engineers were finding engines being destroyed after high speed runs on the Autobahn. Their conclusion was preignition for metal ash deposits on the rotors.

It's been a while since I've looked at the NSU papers, do you have a page to the conclusion that declares the ash deposits on the rotors as being the cause? I was thinking it would have been a combined effect of the plugs and combustion surface.

The good news on the Valvoline VR1 is that I found it a O'Reilly's so it may be a other automotive stores also. They only had it in 50W and 20W50. It comes in 10W30 and 10W40 also.

Barry

Is it classified as fully synthetic, or is it a highly refined conventional?

[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?

[vex]

Originally Posted by joff

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



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?

That presumption would be correct (however the carbon instantly vanishing is not necessarily true. It will still need to be burned off, or dieseled to remove the built up carbon, which in and of itself may cause issues with the cars setup). NSU papers did multiple tests. The problem comes with the oil not containing ash, but impurities that produce ash when burned. Hence the high PPM of Calcium causing more sulphated ash, and the respected correlations. VOA and UOA are helpful in narrowing it down to oils that would work stellar in our engines. The problem comes in that a majority of "high end" oils contain low calcium numbers, but those numbers are still too high for our engines (remember the lower the sulphated ash the better; <500ppm of Calcium). Running a pure base, or synthetic that has <<<500ppm of Calcium is the better.

On that note; I did not find VR1 oils at Pepboys in Alexandria, VA. Next time I go to an autoparts store I'll check for it.