Oil Pressure or Oil Flow - which is more important?

[Guest]

[Fordota]

10w-30 conventional

[Fordota]

So I could be thinking about this wrong, but bare with me here.

I believe the oil pressure in an engine would be a dynamic pressure since it is not a sealed system. So by removing, radiusing, blending, and chamfering you make less of a restriction in the oils path. This wouldn't effect a closed system (static pressure) but I think it would make the dynamic pressure go down. This is a good thing because your pump can output more oil before it reaches it's bypass level (say 60#) where its not actually pushing anymore oil just dumping it back into the oil pan.

[Joel5.0]

I always look at it as...... you have oil flowing and a "backup" pressure of 15 psi under those engine idling conditions.... besides, you are not "pressure washing" with oil the internal components, you need a constant flow of oil to ensure lubrication and cooling. ..... would oil cool effectively the valve springs if it gets overshot from the rocker oil hole? 

[ranchopower]

At 70 mph
At Hot Idle using 10W40 synthetic oil  
This was low at that time cause the radiator was half clogged and the temp was at 240F when I took those pics, yet the engine oil survies during these times due to the nature of synthetic oils.

I learned from years of watching thousands of people building engines, they all want to force more oil through a engine.
This I believe is because the available POPULAR OILS are of poor quality, and the more flow the cooler the equiptment.
So I find it rather amusing the great lengths people go through to shove oil through the engine to prevent starvation or metel to metal contact.

I think outside the box only cause when I watch people grenade engines the same way over and over again, you learn why they fail.

Engine oil is the single most important product you can purchase. Ronnie Crawford has a saying
"ENGINES DO NOT BREAK, PEOPLE BREAK ENGINES"

I believe that to be a fact. A finished engine is perfect, lets just say.

We put into the engine our choice of coolant and engine oil, right there you have either doomed the engine or keep it as if it was new.
Some oils will allow metal to metal contact and some will allow less.

Here at SBFTECH we are known to take things to the limit so the oil we choose may be more suited to this enviroment.

To determine wich oil will work for you or not you need DATA.

I will leave you with this article wich was just published and I promise you there is no mention of any oil manufacture, just some well known facts from the lubricant world
http://www.enginebuildermag.com/Article/81903/breakdowns_flashpoints_and_other_reasons_to_change_oil__part_1.aspx

Javier

[liljoe07]

I haven't received my latest Engine Builder magazine!

Anyways, I know you do a lot oil testing and research Javier.
So what determines the film strength of the oil?

[David Claflin]

My 418 from woody runs at 750 rpm and 15psi hot idle. Made me pretty nervous because its not what you normally see, but the flow vs pressure (restriction) theory makes perfect sense to me. Once I unscrewed my large oil fill cap and took a peek with a flashlight I could see TONS of oil everywhere! 

I should have asked if they do any mods to the oiling sytem of the block as part of the prep. I did the emlarging of the oil passage between the block and filter on my 302. Also figured out a trick for drilling the bearings, will have pics tomorrow night of that.

[ranchopower]

I haven't received my latest Engine Builder magazine!

Anyways, I know you do a lot oil testing and research Javier.
So what determines the film strength of the oil?

High-Temperature/High-Shear

This test is a simulation of the shearing effects that would occur within an engine. In fact, it's actually designed to simulate motor oil viscosity in operating crankshaft bearings.

Under high stress conditions where shearing can occur, the VI Improvers (polymers) break down. As they do, the viscosity of the oil decreases. This is what the High Temperature/High Shear test checks for.
The HT/HS test is measured in Centipoise (cP) as the Cold Crank Simulator test is. However, in this case, because you're hoping for the least loss of viscosity with an increase in heat and stress, you want the cP value to remain high.

Each SAE multi-viscosity grade has a specific lower limit for the HT/HS cP value. If a multi-viscosity oil cannot achieve a cP value above that limit, it cannot be classified under that viscosity grade. For instance, according to the SAE specifications, an oil must achieve an HT/HS cP value of 3.7 or higher in order to be classified at the 15w40 viscosity grade. The thinner the oil the lower the number.

So, whether this data appears on a manufacturer's tech spec sheets or not, the company always has the data and it should be available on request.


I use AMSOIL 10W40 in my engine
High Temperature/High Shear @ 150°C and 1.0 X 106 s-1, cP (ASTM D 4683), cP 4.3
AMSOIL 20W50 High Temperature/High Shear @ 150°C and 1.0 X 106 s-1, cP (ASTM D 4683), cP 5.0

Javier

[cheese_05_70]

David,
    Where is these pics that you were supposed to have tommorrow night? Just curious how you did it?

Thanks
Colby

[David Claflin]

I know, I didn't produce, the block is at the machine shop getting new cam bearings, I have the main bearings, and the "fixture" ready, just waiting for the block to come back.

[cheese_05_70]

Well when you can post pictures i get my block back this weekend. 
 Can you explain how your doing it? then post pictures when you can 

thanks
Colby

[OVERKILL]

There is an extremely in depth and informative article on this, written up by a auto enthusiast, and surgeon who specialized in blood flow through arteries.    I wont bother anyone by posting it here.

One thing ive always seen though, is that 10 psi  per 1,000 rpm of loaded engine operation is usually a good base.  Indicated by your referenced 18 psi at 2,000 rpm for a variety of motors. 

For example,  Ferrari on some cars does not recommend a specific weight of oil, only a desired pressure achieved during operation.

Ive always done the same thing on my motors,  looking for the right weights to give me around 60 psi @ 6,000 rpm   at 70 degrees celsius or better oil temperature.

Its a tough topic to really corner into one answer.

If you are thinking of AEHaas, he is a plastic surgeon. He has a deep interest in oil and lubrication and participates semi-regularly on BITOG. He is not a lubrication engineer however, and a lot of his theories are just that.... theories. Albeit many of them good ones.

[OVERKILL]

This is a topic I've got a great deal of interest in. I actually am a member of an oil-enthusiast website, LOL! Bob Is the Oil Guy, otherwise referred to as BITOG.

Bearing lubrication is hydrodynamic. The pressure at the bearings creates as "wedge" of oil that the crankshaft rides on. As long as there is adequate pressure to maintain that hydrodynamic wedge, you aren't going to have problems.

Now, the faster you spin an engine, the greater the loads on this wedge. The crankshaft and rods, spinning around create centrifugal force as well, which will work to "spin" the oil out of the bearings as well. This is why adequate volume and pressure are necessary. This is also why HTHS is important, as an oil's capabilities to maintain the required viscosity and the hydrodynamic lubrication wedge is very much what the HT/HS represents.

Many European engine families spec a specific minimum HT/HS value. This is not the case with North American cars. The reason of course is the relatively high power density of power plants from companies like Mercedes and BMW and long-term high-speed use like driving on the  Autobahn will elevate oil temperatures significantly. Much hotter than the car would ever see in road use in North America unless they are being driven on a track/road course. This is why oils like Mobil 1 0w40 exist. As most of the Euro cars spec a 0w40 or 5w40 synthetic because of the long drain capability as well as the high HT/HS to handle the high oil temperatures.

That being said, it all comes down to temperature. Elevated oil temperatures create a need for a heavier oil. One that has a higher film strength and will be able to maintain lubrication as it is sheared and thinned from heat.

If you run an oil cooler and are able to control your oil temperatures, you can get away with running a thinner oil and getting the same degree of protection.  And engines with lower power densities will also heat the oil less. Oil with higher power densities, like the Modular engines in the Ford GT, GT500...etc spec a 5w50 because of how hot they can potentially make the oil under hard use. And so in order to maintain adequate protection under those extremes, Ford requires a much heavier oil than their "regular" Modular siblings. Ones without a blower and much higher power output.

If you KNOW your engine is healthy, and the oil pressure is somewhere within the manufacturer's spec'd range, then I wouldn't be concerned. Oil pumps are positive-displacement. So a stock pump on a 302 moves adequate volume to properly lubricate a 302 regardless if the gauge reads 20 or 40psi hot at idle. As long as both engines are healthy and everything is in good shape, the differences in bearing clearances alone can give you two identical yet different engines with a rather large spread in hot idle oil pressure. Now if you have an engine that USED to have 38psi and now has 12, well I'd say that's an indication of a problem, LOL

[David Claflin]

Well when you can post pictures i get my block back this weekend. 
 Can you explain how your doing it? then post pictures when you can 

thanks
Colby

I had a couple of strips of aluminum about 1/2" wide I thought I could bolt down to hold the bearings down while drilling the holes. Turns out I didn't need the strips at all, just the bolts with good sized washers under them do a good job of holding the bearing shell down in the saddle without letting it move around. THe only issue is the oil hole in the block is not directly under the factory hole in the bearing shell, and the oil hole in the block, does not go straight down. So making a neat hole is a little tough, but I did start out with a smaller drill bit then moved up to the larger size I needed. I marked the bearings in the position they were drilled for 1-5 so they would go back into the same spot.  I've just got to file the edges of the hole in the bearing to make a nice smooth contour. Also, something I noticed, make sure to check the back of the bearing shell for burrs after drilling too, the front is not the only place. Sorry no pics my little camera shit the bed 

[David Claflin]

I don't know if this has been brought up before, but this article is pretty interesting.
http://www.bobistheoilguy.com/cms/index.php?option=com_content&view=article&id=75

[ranchopower]

read the linky from BITOG
and all the way at the end the OP writes this

If you have absorbed and digested the information here you should be able to pick out the proper operating oil grade for your car, be it a 30, 40, 50 or even 20 grade oil. I have always used oils that were a grade thinner than recommended even though many use a grade thicker than recommended. I showed evidence that the starting grade should always be 0 or 5 (0W-XX or 5W-XX for thicker oils). If you want the best protection and highest output from your motor use a synthetic based oil.

I have been banned multiple times from BITOG for many reasons, same reasons JAY would get banned from sites.

They have Mods that cant answer questions so they silence you instead.

I dont even bother with BITOG anymore, the user name there BILLinUTAH is the MOD that cant answer questions with any personal experience so he closes the door and end of discussion.

Yet he can tell me that what I am doing is all wrong, but never tried it himself...


Javier