AE Haas recommends oil pressure to decide weight

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EXCELLENT point!

Glad someone said that. There are many things happening in the oiled areas that are not revealed by a simple gauge reading. That's why we have oil analysis.

Especially with higher output engines, bearings etc. can wear dramatically/severely while you still have proper pressure at the gauge.

And while many here have excellent educational resumes, I am STILL interested in what other people may say who come from the "school of extensive automotive experience" as I do!

SEAE Charter Member since 1970!!!
 
Originally Posted By: expat
Now, IF oil film strength was so low as to allow metal to metal contact at bearings or Cam (I have solid lifters), would I see it on the oil pressure gauge? IF I have 10 psi per thousand rpm can I be sure that, at some point, I don't have metal to metal contact?


1st question: No. If you are running an oil of such low viscosity that the film thickness that it produces between moving parts is less than the combined roughness of the surfaces, there will be metal to metal contact in localized spots. Tribologists call this "interaction of asperities", and it leads to higher friction and heat generation, which in turn causes the oil to heat more, making it lose more viscosity, and generate still lower film thickness and more metal to metal contact.

2nd question: No. Having X amount of oil pressure only has a secondary effect on oil film thickness in the bearing. Oil film thickness is governed by the diameter and clearance of the bearing, operating speed, and viscosity of the oil. Oil supply pressure becomes a problem when the amount of replacement oil being supplied to the bearing is insufficient to carry away the heat generated within the bearing.
 
Originally Posted By: expat
It may also be worth noting that the area of an engine where the oil is subjected to the highest temperatures, the piston, ring and ring cyl interface are not pressure fed.
I can imagine a situation where the oil in this area may easily be overstressed, but this would not be indicated by an OP reading or oil temp reading (taken at the oil pan).


This illustrates the point that different characteristics of an oil are required to properly lubricate different parts of an engine. Ring lubrication and wear is one of those areas where you are cursed if you do, and cursed if you don't. Because the piston stops at the top of the stroke, it is certain that hydrodynamic lubrication is lost as the piston slows and that the ring will be making metal to metal contact in a region where the temperature is the highest. It would be nice to flood the area with a lot of oil, but nobody would like the high oil consumption that results. Also, if oil makes it past the 2nd ring, all hope of it returning to the sump is lost, and it will be subjected to temperatures of ~550F, where it will boil or burn off and leave deposits. Hopefully, some of these deposits will be beneficial, as would be the case with zddp which would provide wear protection by breaking down an leaving a sacrificial coating on the wear surfaces. Unfortunately, some of the oil products of oil breakdown could be harmful; carbon and ash deposits over time could build up and lead to stuck rings. Conventional oils which have not been aggressively hydrocracked and dewaxed and/or contain high amounts of Viscosity Improvers are prone to this.

If I sit and think about this long enough, I might never buy another quart of conventional oil again...
 
This is where (I believe) an Upper cyl lubricant may pay a roll. But these days we have to live with Cats and oxygen sensors :-(

Often thought about rigging so I get UCL laced fuel for the start, warm up of an engine. But then, that's just when the cat is not yet up to temperature:-(
 
Originally Posted By: expat
It may also be worth noting that the area of an engine where the oil is subjected to the highest temperatures, the piston, ring and ring cyl interface are not pressure fed.
I can imagine a situation where the oil in this area may easily be overstressed, but this would not be indicated by an OP reading or oil temp reading (taken at the oil pan).

That's why determining the minimum OP spec' for an engine covers all the bases; there is no need to second guess.
In your rebuilt Triumph I'd much prefer to run a modern high VI oil like M1 0W-40. You'll have much better cold flow to the 10W-30 while retaining the higher hot OP of a 40wt. The higher phosphorus level of nominally 1,000 ppm should suit the engine well.
 
Originally Posted By: Doug Hillary
Hi,
SteveSRT8 - You're only a young Member, I joined up in the early 1950s!


Bravo! May you run well lubricated! May your filter remove all harmful pieces!

Thanks as well.
 
I would say that someone who was a chemical engineer and then moved on to plastic surgery probably has a pretty in depth knowledge of various substances, chemicals and their various properties under various temperatures and pressures.

I doubt you give a movie star "Angelina Jolie Lips" buy just grabbing a syringe of silicone and pumping it in there. I doubt there is anyone on this forum with the exception of "Charlie" who can comprehend plastic surgery.

Studying the various properties of engine oil would be quite simple for someone with the extensive schooling the above occupations required. As a matter of fact I think it would be pretty easy for someone who is a plastic surgeon without a chemical engineering degree.

Just think about doing "bodywork" on a real human being for a minute. It's not child's play. I doubt there are many on the planet that are REALY good at it regardless of their desire to be a plastic surgeon.

As we have all seen pics of his car collection I would surmise that he isn't just your "average" plastic surgeon which means he may very well be one of the best out there. I applaud him for his accomplishments.

I sense a slight bit of jealousy from some of the posts here. Some apply themselves to the fullest in life and there are others who don't. Dr. Haas obviously applied himself and used his time and his talents wisely when he was younger.

He deserves what he has and his opinions on oil viscosity and pressure are in line with numerous articles I have read on the subject over the years regardless of the age of the vehicle.
 
Time taken for oil to reach operating temperature is also related to sump catcity. The larger sump size the longer the time it will take to heat the engine oil. Its not just a function of oil grade/ viscosity.

Maybe is some advantage to a smaller sump in that it gets the oil to operating temperature quicker, and may require more frequent oil changes.

My 1996 3800 Holden V6 has a 4.3L capacity sump, compared to when Holden introduced their 1st attempt at longer drain in 2004 3800 V6 5.5L capacity sump. IE oil drain intervals were extended from 6mths to 9mths and from distance extended from 10000km to 15000km.

Ferrari sumps I think are double the Holden 3800 V6s.
 
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