Glazed cylinder walls

[Tom-D]

Edit://
Found a article that explains ashless dispersant mineral oil.
http://www.aviationtoday.com/am/repairstations/The-Mineral-Oil-Myth_564.html

Who ever wrote that article is under the impression that "A" ashless is a part of the additive package, which it is not, ashless is a characteristic of the oil stock that is used in aviation oils.

and simply put, it means the oil will burn and not leave a metallic ash.. All oil stocks that contain Sulpher will when burned, leave a metallic ash and cause preignition

the rest of the article is right on.

 

[dell30rb]

My break in philosophy for the motocross bikes I used to work with was always - use dino oil with no friction modifier additives, get the motor warm and then ride it hard. Change oil after every ride for the first 5 rides, then use full synthetic oil and change after every 5 gallons of fuel burned.

My stuff always lasted much longer than anyone else's. I largely credit my break-in for this. The manual says not to go over 1/4 throttle for the first hour of operation. They can't tell you to run it WFO for break in (even though this is sold as a closed course competition bike) because some kid will crash and sue the manufacturer for telling him to ride it hard for break in and ring sealing. These bikes had a tbo of about 50-100 hours. Not bad for a single cylinder 250cc motor with 5 titanium valves that redlines at 13,500 rpm and produces 40hp

 

[dell30rb]

if the cylinder is glazed can't you just pull em and hone them? not always an option with electroplated cylinders but I am assuming they are sleeved

 

[Dan Thomas]

if the cylinder is glazed can't you just pull em and hone them? not always an option with electroplated cylinders but I am assuming they are sleeved

If you hone them you need new rings, too. Rings are machined either with a small angle on the cylinder mating face so that an edge is in initial contact to force rapid seating, or the ring will have a chamfer around one inside edge to make the ring twist in the groove a bit to make a better seal in the groove and put the lower (usually) mating edge in contact with the cylinder. Often, rings will have both an angled face and a chamfer.

Honing a cylinder won't do much for reseating against used rings.

Dan

 

[TripleZ]

Do you understand what an EP oil is ?

Remember the oils we use are all from the same base stock, and all have the same lubrication properties except the EP oils which are fortified to a higher film strength than the regular AD oils by the additive package.

If by EP, you mean extreme pressure oil, then yes. Those oils will have a heavy additive package with friction and shear modifiers. Phos, Molly, etc.

And agreed, the article was off on the ashless base stock, although there are sulphate additive packages in automotive oils that will leave deposites. My background is again in marine engines (heavy friction and corrosion additives) so I'm learning the ins and outs of aircraft oils.

 

[dell30rb]

If you hone them you need new rings, too. Rings are machined either with a small angle on the cylinder mating face so that an edge is in initial contact to force rapid seating, or the ring will have a chamfer around one inside edge to make the ring twist in the groove a bit to make a better seal in the groove and put the lower (usually) mating edge in contact with the cylinder. Often, rings will have both an angled face and a chamfer.

Honing a cylinder won't do much for reseating against used rings.

Dan

True it won't be like new but I wasn't suggesting he not replace the rings - they're relatively cheap and if you're pulling the cylinder you may as well replace them.

The old rings should seat however, the honing provides a sharp, fresh cross hatch on the cylinder wall which will bite into the rings and encourage them to seat.

My uncle honed an old outboard motor and left the old rings in there... just popped the head off, put the piston at BDC and ran the hone. Compression went from about 75 psi in one cylinder to 115 and the thing ran great after that. Not the type of shadetree work i'd be doing on an airplane but the motor was obsolete and not worth putting any real $$ into.

 

[Skylane81E]

Yes, rehone rering is the solution to a glazed cylinder. It's not hard other than yanking the jugs off.

 

[Tom-D]

If by EP, you mean extreme pressure oil, then yes. Those oils will have a heavy additive package with friction and shear modifiers. Phos, Molly, etc.

And agreed, the article was off on the ashless base stock, although there are sulphate additive packages in automotive oils that will leave deposites. My background is again in marine engines (heavy friction and corrosion additives) so I'm learning the ins and outs of aircraft oils.

Water cooled engines never run cylinder head temps high enough to cause pre-ignition so they are OK with sulfur based additives. some aircraft engine are ok with it too but some aren't, so we go to the safe side and go with oils that are ashless.

 

[Tom-D]

True it won't be like new but I wasn't suggesting he not replace the rings - they're relatively cheap and if you're pulling the cylinder you may as well replace them.

Not always, you must evaluate what you have and decide the best repair. throwing money at the problem isn't the best way.

The old rings should seat however, the honing provides a sharp, fresh cross hatch on the cylinder wall which will bite into the rings and encourage them to seat.

The rehone you use a fine grit ball hone and remove as little material as possible.

My uncle honed an old outboard motor and left the old rings in there... just popped the head off, put the piston at BDC and ran the hone. Compression went from about 75 psi in one cylinder to 115 and the thing ran great after that. Not the type of shadetree work i'd be doing on an airplane but the motor was obsolete and not worth putting any real $$ into.

All after market and new OEM cylinders are now coming out of the factories with a fine hone marks with a 30 degree cross hatch. and all recommend the use of a 20W50 AD oil. we are moving away from the use of single weight non D oils for break in, 20W50 from day 1 to TBO is the way to go.

 

[Lance F]

I carefully tracked oil consumption from hour 1. Until Feb it was consistently 12 to 13 hous per quart. Then over the course of one oil change (~2 months) it dropped to about 7 hours per qt. Compressions have always been and are now in the mid 70s.

How did I make my diagnosis? I put a piece of tubing on the vent and ran the tubing into a bucket of water. Using a standard compression tester set at 40 psi my A&P and I checked each cylinder at TDC. #1 & 3 generated almost no bubbles. #2&4 bubbled A LOT. This test is not in the Lycoming manual. I made it up on the spot. But no one offered me any way to isolate the source. I was hoping it would only be one cylinder, but it appears to be two of them.

To pull and IRAN the two cylinders will cost about 2Gs and take the plane down a week or two. I just have to decide if it's worth it.

 

[Skylane81E]

I carefully tracked oil consumption from hour 1. Until Feb it was consistently 12 to 13 hous per quart. Then over the course of one oil change (~2 months) it dropped to about 7 hours per qt. Compressions have always been and are now in the mid 70s.

How did I make my diagnosis? I put a piece of tubing on the vent and ran the tubing into a bucket of water. Using a standard compression tester set at 40 psi my A&P and I checked each cylinder at TDC. #1 & 3 generated almost no bubbles. #2&4 bubbled A LOT. This test is not in the Lycoming manual. I made it up on the spot. But no one offered me any way to isolate the source. I was hoping it would only be one cylinder, but it appears to be two of them.

To pull and IRAN the two cylinders will cost about 2Gs and take the plane down a week or two. I just have to decide if it's worth it.

FWIW I just pop the oil cap off and listen for air when checking for ring leakage.

 

[Cap'n Jack]

and simply put, it means the oil will burn and not leave a metallic ash.. All oil stocks that contain Sulpher will when burned, leave a metallic ash and cause preignition

the rest of the article is right on.

Tom- why do you consider sulfur to be metallic?

(if you are using the English spelling, it's "sulphur")

 

[Tom-D]

Tom- why do you consider sulfur to be metallic?

(if you are using the English spelling, it's "sulphur")

I'm using auto correct that came on the Mac.

 

[bbchien]

To pull and IRAN the two cylinders will cost about 2Gs and take the plane down a week or two. I just have to decide if it's worth it.

Lance, if you don't pull the cyls, they will get out of round, the choke will erode and then you will not be able to send them useably to G&N to have a stock spare made. You'll actually potentially save $1,300 per cyl by pulling them and spending $500 on a rework, get yellow tagged, and then have the stuff IN STOCK and ready.

You'll be stuck buying Lyc Cyl kits and have not gained a spare.
Or two.

At least, that's how I view it.

 

[Tom-D]

Tom- why do you consider sulfur to be metallic?

I don't know that is, until it is burned.

(if you are using the English spelling, it's "sulphur")

there two spellings that pass the spell checker sulfur, sulphur

do you have another substance that can cause a metallic ash ? other than detergent additives?

 

[charlie]

I carefully tracked oil consumption from hour 1. Until Feb it was consistently 12 to 13 hous per quart. Then over the course of one oil change (~2 months) it dropped to about 7 hours per qt. Compressions have always been and are now in the mid 70s.

How did I make my diagnosis? I put a piece of tubing on the vent and ran the tubing into a bucket of water. Using a standard compression tester set at 40 psi my A&P and I checked each cylinder at TDC. #1 & 3 generated almost no bubbles. #2&4 bubbled A LOT. This test is not in the Lycoming manual. I made it up on the spot. But no one offered me any way to isolate the source. I was hoping it would only be one cylinder, but it appears to be two of them.

To pull and IRAN the two cylinders will cost about 2Gs and take the plane down a week or two. I just have to decide if it's worth it.

We are next day UPS from most of GA and have a real hone! Charlie Melot
Zephyr Engines

 

[Lance F]

FWIW I just pop the oil cap off and listen for air when checking for ring leakage.

We did that too at first, but it was very inconclusive. The water bubble test is actually somewhat quantitative.

 

[Cap'n Jack]

there two spellings that pass the spell checker sulfur, sulphur

you may want your Mac autocorrect checked as the word showed up spelled with an 'e' in the post I questioned (post # 41 in this thread).

do you have another substance that can cause a metallic ash ? other than detergent additives?

Actually, sulfur isn't a metal- so it can't make a "metallic ash"

As for another sustance that can make ash, one additive, used by Castrol, at least in some of their oils, is zinc dithiophosphate. (http://www.msds.exxonmobil.com/psim...rand=XOM&DocumentID=629143&DocumentFormat=RTF appears as an MS word file). This is not a detergent- it is used as an antiwear additive and an anti-oxidant ( http://en.wikipedia.org/wiki/Zinc_dithiophosphate ).

Zinc and sulfur will be in the ash; they call this "sulphated ash".
( http://www.swri.org/4org/d08/global/SulfAsh/default.htm ).

I'm not saying there's no such thing as "metallic ash", merely that they class the ash from sulfur differently.

 

[Tom-D]

you may want your Mac autocorrect checked as the word showed up spelled with an 'e' in the post I questioned (post # 41 in this thread).

Actually, sulfur isn't a metal- so it can't make a "metallic ash"

As for another sustance that can make ash, one additive, used by Castrol, at least in some of their oils, is zinc dithiophosphate. (http://www.msds.exxonmobil.com/psim...rand=XOM&DocumentID=629143&DocumentFormat=RTF appears as an MS word file). This is not a detergent- it is used as an antiwear additive and an anti-oxidant ( http://en.wikipedia.org/wiki/Zinc_dithiophosphate ).

Zinc and sulfur will be in the ash; they call this "sulphated ash".
( http://www.swri.org/4org/d08/global/SulfAsh/default.htm ).

I'm not saying there's no such thing as "metallic ash", merely that they class the ash from sulfur differently.

I'm happy that you read me close enough to pic those nits.

Castrol aviation oils are ashless and a semi synthetic. (from what I can read from their home page.)

 

[Cap'n Jack]

I'm happy that you read me close enough to pic those nits.

Castrol aviation oils are ashless and a semi synthetic. (from what I can read from their home page.)

Just making sure I fully understand your pearls of wisdom

I don't know of any aviation oil that isn't "ashless". You specified non-detergent compounds, but not the type of oil.

 

[Tom-D]

We are next day UPS from most of GA and have a real hone! Charlie Melot
Zephyr Engines

And you do a fine job with it. The 4 we got from you are coming up on 1200 hours and still 76/80. they now belong to a Canadian on VanCouver Island.

 

[Tom-D]

Just making sure I fully understand your pearls of wisdom

I don't know of any aviation oil that isn't "ashless". You specified non-detergent compounds, but not the type of oil.

Heres a little E-mail gem

Mr. Downey,

Thank you for your inquiry. The ashless dispersant aviation engine oil specification is SAE J1899 and it has an established limit for sulfur content which varies depending on the viscosity grade. The multigrade aviation engine oil sulfur mass % maximum is 0.6%. Multigrade oils have the same allowed sulfur content as SAE 30 straight grades. Other heavier straight grades have a little higher max sulfur specification per SAE J1899. The typical sulfur content in Phillips 66 aviation oils is well below that allowed by the SAE Aviation Engine Oil specifications. The total ash content is also specified by SAE J1899 and our oils are well within that specification. Aviation engine oils are formulated with ashless additives and utilize very low ash base oils in order to satisfy the specifications for aviation engine oils.

Best regards,

Harold Tucker
Director, Lubricants Technical Services
ConocoPhillips Company

and

Tom, sorry I fell short of a complete answer. The limit on sulfur content in the finished lubricant is related to controlling corrosion of copper and bearing materials rather than combustion chamber deposits. Sulfur compounds can and frequently are used in additives used in automotive and industrial lubricants but they are not desirable in aviation engine oils.

Regards,
Harold


When we ask the right people we can get right answers and we all learn.

I still have one question in his in box. probable won't get an answer till monday.

 

[Cap'n Jack]

When we ask the right people we can get right answers and we all learn.

I still have one question in his in box. probable won't get an answer till monday.

Yep. Glad you're doing some research.

So far, Harold said nothing that contradicted anything I posted.

 

[Tom-D]

Yep. Glad you're doing some research.

So far, Harold said nothing that contradicted anything I posted.

Where did I say it would?

 

[Cap'n Jack]

Where did I say it would?

You didn't-- I was checking on myself. There's always a chance that I question you about something that is named due to historical reasons, rather with the "correct" label based on more modern knowledge.

 

[Tom-D]

You didn't-- I was checking on myself. There's always a chance that I question you about something that is named due to historical reasons, rather with the "correct" label based on more modern knowledge.

understand,, it's contagious on the net..

 

[Tom-D]

More from Harold at Phillips
Tom,

The sulfur doesn't contribute to ash. The ashless specification is to eliminate the use of chemistry like calcium, magnesium, and zinc which are common to automotive engine oils. Aviation engines consume more oil per hour of operation than their automotive counter parts so the ash allowed in aviation is restricted in order to prevent combustion chamber deposits that may form as a result of the metallic residue. Ash deposits may contribute to pre-ignition which can damage pistons and valves. The allowable ash is so low that the intentional inclusion of ash bearing chemistry is forbidden by the aviation engine oil specification SAE J1899.

Happy Thanksgiving,
Harold

 

[Cap'n Jack]

Can you see the crosshatch?[/QUOTE]

If your two opinions were suggested without seeing what you saw through the bore scope, then it seems your inspection debunked their theory and Doc has a better diagnosis. If they did, I'd be curious too.

You might ask on the Yahoo Lycoming Groups forum, some good engine advice there.

Glazing looks like glazing.....the cross hatch clearly won't be the surface your rings are running on.

What is the "cross hatch"? I thought cylinders were smooth.

 

[Tom-D]

Can you see the crosshatch?[/QUOTE]



What is the "cross hatch"? I thought cylinders were smooth.

http://www.hastingsmfg.com/ServiceTips/cylinder_bore_refinishing.htm

 

[Ted]

Water cooled engines never run cylinder head temps high enough to cause pre-ignition so they are OK with sulfur based additives. some aircraft engine are ok with it too but some aren't, so we go to the safe side and go with oils that are ashless.

Actually, that is not true. Water-cooled engines can still get pre-ignition. I have seen that happen in a number of cases. Many factors go into detonation and pre-ignition.

 

[Tom-D]

Actually, that is not true. Water-cooled engines can still get pre-ignition. I have seen that happen in a number of cases. Many factors go into detonation and pre-ignition.

Water boils at 212 degrees, and yes I've seen the steam getting out too.

but what is your normal CHT?

WE must remember in all of this, some of these rules were set when we were running large radial engines which had huge oil consumption and the lower cylinders would collect large amounts of carbon from oil in the combustion chambers.

I've often wondered why the airboat operators can run automotive oils in the aviation engines and never have a problem. I truly believe the flat engines don't burn enough oil to have a problem.

 

[Gmaper]

This is a bit off topic but I think it makes a point. Several posts reference "aviation engine oil specification SAE J1899" as being the basis for what the limits are for various aspects of aviation oil. Sounds good to me.

But, in today's society, and in many posts, we hear about "regulations are bad and the government ought to get out of our business and the high cost of aviation is in part because of said regulations, etc. etc.". So, would aviation oil be as good as it is today if we did not have "aviation engine oil specification SAE J1899"?

 

[Tom-D]

This is a bit off topic but I think it makes a point. Several posts reference "aviation engine oil specification SAE J1899" as being the basis for what the limits are for various aspects of aviation oil. Sounds good to me.

But, in today's society, and in many posts, we hear about "regulations are bad and the government ought to get out of our business and the high cost of aviation is in part because of said regulations, etc. etc.". So, would aviation oil be as good as it is today if we did not have "aviation engine oil specification SAE J1899"?

Yer probably right, but how would you like to have had mobile 1 in your aircraft? you could be used as a ginny pig

 

[Capt. Geoffrey Thorpe]

This is a bit off topic but I think it makes a point. Several posts reference "aviation engine oil specification SAE J1899" as being the basis for what the limits are for various aspects of aviation oil. Sounds good to me.

But, in today's society, and in many posts, we hear about "regulations are bad and the government ought to get out of our business and the high cost of aviation is in part because of said regulations, etc. etc.". So, would aviation oil be as good as it is today if we did not have "aviation engine oil specification SAE J1899"?

SAE is not the government.

 

[Gmaper]

SAE is not the government.

So there is no requirement to comply with the standard?

 

[Ted]

Water boils at 212 degrees, and yes I've seen the steam getting out too.

Water boils at 100C at standard atmospheric pressure. It will boil at a colder temperature in Denver, and it will boil at a hotter temperature with the pressurized systems that most liquid-cooled engines. But we all know most of our coolant systems are typically in the 180-210F range.

but what is your normal CHT?

380F, but that's not actually the point. You said that liquid cooled engines never have cylinder head temps high enough for pre-ignition. That is not true.

Liquid-cooled engines, in spite of their lower head temperatures, can quite easily have detonation and pre-ignition. All I have to do to get detonation on my Mitsubishi is turn the boost up to 25 psi, or put in regular unleaded. It will detonate very well, and then get pre-ignition. Even my '69 Cadillac got pre-ignition in its 472 and blew a hole in the piston.

 

[Tom-D]

Water boils at 100C at standard atmospheric pressure. It will boil at a colder temperature in Denver, and it will boil at a hotter temperature with the pressurized systems that most liquid-cooled engines. But we all know most of our coolant systems are typically in the 180-210F range.

380F, but that's not actually the point. You said that liquid cooled engines never have cylinder head temps high enough for pre-ignition. That is not true.

Liquid-cooled engines, in spite of their lower head temperatures, can quite easily have detonation and pre-ignition. All I have to do to get detonation on my Mitsubishi is turn the boost up to 25 psi, or put in regular unleaded. It will detonate very well, and then get pre-ignition. Even my '69 Cadillac got pre-ignition in its 472 and blew a hole in the piston.

I believe you are off on a tangent again, Detonation is a totally different phenomenon than pre-ignition caused by a metallic ash.

and its known that auto engines do not operate hot enough to create a problem with ash glowing in the combustion chamber causing the gas to ignite before it should.

 

[Ted]

and its known that auto engines do not operate hot enough to create a problem with ash glowing in the combustion chamber causing the gas to ignite before it should.

Tom, that's simply not true. A typical automotive engine (especially from the factory) won't have this issue. However, when you look in the modified world, it's a whole other affair.

But you do have your definition of pre-ignition correct.

 

[N801BH]

Water boils at 100C at standard atmospheric pressure. It will boil at a colder temperature in Denver, and it will boil at a hotter temperature with the pressurized systems that most liquid-cooled engines. But we all know most of our coolant systems are typically in the 180-210F range.

380F, but that's not actually the point. You said that liquid cooled engines never have cylinder head temps high enough for pre-ignition. That is not true.

Liquid-cooled engines, in spite of their lower head temperatures, can quite easily have detonation and pre-ignition. All I have to do to get detonation on my Mitsubishi is turn the boost up to 25 psi, or put in regular unleaded. It will detonate very well, and then get pre-ignition. Even my '69 Cadillac got pre-ignition in its 472 and blew a hole in the piston.

You mean like this......

 

[Tom-D]

Tom, that's simply not true. A typical automotive engine (especially from the factory) won't have this issue. However, when you look in the modified world, it's a whole other affair.

But you do have your definition of pre-ignition correct.

We aren't, we were talking simple old aircraft engines and ash less oil. and the use of auto oils in aviation engines. and why it will or will not work.