Viscosity Affects Piston Rings

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Very interesting. All these years, I figured I was reducing blowby by running 10W-40 / 20W-50 in my old carbureted Small Block Chevies.

This brings me to another question: When an engine need re-ringed, is it more often because the rings wear, or because the ring packs become sludged up, and the gasses can no longer get behind the rings to let them do thier job?

I'm sure it is a combination of both, but I had always assumed that combustion pressures were high enough that some deposits were not a big issue. Since visiting BITOG, I have begun to change my mind.
 
Visions of the Saturday Night Live character Roseann Rosannadanna. "If it's not one thing, it's another."
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Vis in a engine is like shoes on the feet, too tight and it rubs you sore, too loose and you slop around all over the place.

Both hurt a racing engine really bad...
 
quote:
Vis in a engine is like shoes on the feet, too tight and it rubs you sore, too loose and you slop around all over the place.
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Thats a great analogy and great article. Goes to show you it's just not that simple in terms of viscosity.
 
Holy crap- Just change your oil at 3000 intervals with a good dino and forget about all the over the head language by shell. My goodness all they are saying is just change the oil as suited to your needs.
 
That's an interesting paper, Motorbike. It would have been even more informative to sit in on the lecture to go along with the slides.

The Shell researchers found that there's a good amount of Si in ring deposits. Mobil researchers found the same thing, and were surprised at the amount of Si. The upshot, I would think, is that if you want to keep ring deposits down, make sure your air filtration is as good as it can be.
 
Jay said " The Shell researchers found that there's a good amount of Si in ring deposits. Mobil researchers found the same thing, and were surprised at the amount of Si. "

I'm not surprised after looking at many of BITOG'R's UOA's !
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Air filtration is important but what about that microscopic trash embedded in the rings ?

Auto-RX or Cycle-RX might be a safe and easy way to clean annually.
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Note that the higher top ring film thickness is under the ring, not mentioned in ring to bore thickness.

either way indicates higher oil consumption with the lighter oils.

Interesting about more blowby with thicker oils due to ring tilting...makes some sense.
 
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Interesting about more blowby with thicker oils due to ring tilting...makes some sense.
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One person I know has mentioned the same thing before. His oil consumption was much lower with a thinner oil. In my case it's the other way around.
 
My Ferrari 575 Maranello used a qt. of the manual specified Shell Helix Ultra 5W-30 in 500 miles. It used no oil when I switched to Mobil One 0W-30 for the next 500 miles and no oil was consumed after 3,500 miles of using Mobil One 0W-20, my current oil.

aehaas
 
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The upshot, I would think, is that if you want to keep ring deposits down, make sure your air filtration is as good as it can be.
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Hmmm, what about a pre-air filter? Like sticking a K&N cone filter onto the air scoop.

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You could also use a coarse mechanical filter followed by an electrostatic precipitator, and have very low airflow resistance. You'd have to mix in some warm air, to keep the humidity below 100%.
 
quote:
Originally posted by AEHaas:
My Ferrari 575 Maranello used a qt. of the manual specified Shell Helix Ultra 5W-30 in 500 miles. It used no oil when I switched to Mobil One 0W-30 for the next 500 miles and no oil was consumed after 3,500 miles of using Mobil One 0W-20, my current oil.

aehaas
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Your running 0w-20 in your Maranello?
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Is this the specified viscosity?
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No matter what Ferrari stipulates, 0W-20 would murder the engine in stop and go 40c+ temps, no way can any thin oil keep the film strength up at that temps.
 
This paper did not really give us a lot of data that can be applied directly to field type work. The ring area is not the main are of concern in wear prevention either. It is clear to most that keeping the ring pack clean is of great importance. CI-4 oils already do a good job of this. The 5W20 while being ok for the ring area due to enhanced flow chartristics would probably fair poorly in the cam,injectors and conecting rod bearing. Some of the information came from diesels and some from gasoline powered engines. They were very selective in which portions of each study they included and did not do a good job of pointing out when it was a gasolin engine or diesel engine for those that do not know.

I did like how they clearly and plainly made it clear that the piston and piston ring designs played a major role in ring area cleaness. It was of no suprise that viscosity could have an impact on this movemnet!!

I wish I still had access to SAE papers free of charge. I suspect their is a lot that they are not telling us in the pdf file. Not becasue they are trying to hide anyting.

Thanks for shareing though!
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I also thought it was odd that only the 5W30 pistons were shown in the photo's? CLearly it must not be a pro 5W20 study inspite of the percived results.
 
It also appeared that they were more concerned with oxidation control and oil flow. My only concern was that the ring area is not the most demanding load area. If we bias too much toward flow what happens to the conecting rod bearings? I did like that they seemed to be concerned about oxidation control!!!!!
 
Terry with aluminum being used more and more in engines and transmissions could some of the silicone be sloughing off of the case? Surely the polar nature of some fluids and or additives could cause silicone to migrate into the oil through non-wear means? Would this be a problem?

I am also woundering if LC would work well to stiffle this type of build up? I ask because I am a big fan of LC. WHat is truly needed to disolve these deposits? I have never tried to remove silicone from a surface before. I would imagine that so long as the silicone is not ebeded it would require some type of carbon to chemicly glue/bond it to the part?
 
quote:
Originally posted by Gurkha:
No matter what Ferrari stipulates, 0W-20 would murder the engine in stop and go 40c+ temps, no way can any thin oil keep the film strength up at that temps.
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What you are missing here is that the modern Ferraris have cooling systems (water, oil, and transaxel) designed for sustained use at 150+ MPH. At full chat his 515 HP engine disipates* about 1 MegaWatts of heat into the air; loafing through traffic, I doubt it disipates much more than 5 dozen kilowatts; chicken feed to a car with this kind of cooling systems.

As far as I can tell, as long as the oil stays below 250dF even these thin oils have sufficient viscocity and shear strength. Since the Ferraris have oil temp guages, Ali can keep close tabs on the instantaneous oil performance (and UOA don't hurt).

[*] extrapolated from the Wrigth book "Ferrari Formula 1 2000" states that the F1 engine disipates into the air 1.5 MW from its 830HP engine.
 
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