Dual relief oiling system. How it works.

[redhot]

Regarding the Mexico oil pump, two issues comes to mind.

1) The filter, probably a large restriction and therefore the testing done without filter won`t give the correct data, and extra oil passage length and direction changes should represent a pressure drop themselves.

How large pressure drop is the key issure. If the outlet pressure of the pump is no higher or just slightly higher than the 26mm standard pump no modifications to the case should be necessary.

ps: does the OEM mexico pump have a integral bypass, and how does it operate?

2) In all engines, with all oilpumps, high RPM would increase the pressure, and thereby bypassing the oilcooler IF the control valve doesn`t flow enough oil.

[udidwht]

How would the test/s fair today using todays superior oils instead of yester years inferior oils?

[Jimmy111]

Todays oils are not necessarly more superior than yesterdays oils.
multigrade oils are prepared the same way today as they were 30 years ago so the tests would probably be the same. In my opinion 20-50 is not a good choice for todays VW motors.

Your statement on the other post did not make much sense to me either.
Perhaps you should take a good look at it and rewrite it in a maner that everyone can understand it.

[udidwht]

Udidwht wrote:

"Not entirely correct. It bypasses the oil cooler until the relief valve returns. Remember, the relief valve relieves pressure. Hence the word relief. Oil will always be at the bearing surface/s. The pressure will be relieved by the relief valve should it come into play."


Marv [UK] wrote:

"Absolutely. It is not an "on / off" switch. It is there to prevent damage to the cooler from too much pressure, not to prevent oil from getting anywhere. The oil still passes through to the lifters and bearings.

At higher temperatures, the oil thins out and reduces in pressure and then passes through the cooler.

the oil control valve performs a similar function in returning excess oil to the case. Look at the oil sticky for the diagrams. The oil control valve is in operation quite a lot more than people think.

The oil galleys can only cope with so much oil as they are so narrow. chucking huge flows of oil through bearings means that it's going to find the easy way out a lot faster IMHO. Super slippy thin oil [tm] won't necessarily coat things as it should. The bearings are designed to "float" the crank on a thin layer of oil. This ability to coat under pressure is called the film strength or lubricity (apparently)

I'm no oil expert. VW designed the original engine with remarkably close tolerances given the time. The rod bearings etc were designed with an SAE 30 oil in mind. I don't believe that the tolerances have been tightened up since the 70's.

At 210*F, it has a viscosity of index of 30 and a film strength to deal with the forces in a STOCK engine. Over the years they have changed things about with increasing technology of lubrication and have recommended 15W40 amongst others. Either way the statement below applies

If you're putting more force and stress through your bearings, it doesn't matter what the flow is if the film strength won't stop your bearings and journals grinding.

Performance engine requires an oil with a greater film strength than SAE30. It's viscosity depends entirely on your general atmospheric conditions.

This is an extract from an AMSOIL website, OK so some if it is advertising so automatically some people are goint to instantly disregard it but it's a pretty good rule of thumb guide."




Odd that Marv understands...(His first sentence in his post). There are THOSE who would also disagree that todays oils are the same. Back to topic.

[Jimmy111]

What marv wrote was correct. What you wrote was not. That was Buginva's gripe.

But the relief valve IS a on off switch. It does not vary the oil thru the cooler. If the valve is open at all, little to no oil will flow thru the cooler.

ALL high performance factory motors call for either 0W30 or 5W30 today. The engines are not tighter than a VW motor. When you build a motor for proformance you will increase the oilflow thru the bearings by decreasing the journal diameter of the crank. Not increasing it.

When VW's were designed, bearing material was a Babbitt which is a mix of 80% lead 15% antimony and 5% tin. In the late 1970's they went to a babbitt of 89% tin 7% antimony and 4% copper to keep the Cat converters from fouling. The Lead based babbitt worked very well with straight 30W oil. It did not work well with the tin based babbitt so VW experimented with other oils. 74 and later VW motors were known for spinning bearings.
If you buy a Crank bearing for your VW today it is made from Aluminum with a very thin film of Tin Based babbit on it. The aluminum bearings require a light oil with high flow. They are not the bearings that VW supplied or even recomend. 5w30 is what is recomended by almost every major gasoline engine manufactruer. Cars these days go 200-300,000 miles with little bearing wear using aluminum bearings and 5W-30 oil.

[bugninva]

[miniman82]

You'd think that would be a simple thing to understand....
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[udidwht]

Our two statements are the same aside from not being word for word. Not hard at all, a no brainer. He even agrees with, "Absolutely..."

You'll always have oil to the bearings. Nothing is shut off. What amount will depend on temperature, pressure, oil viscosity...

Then you say Marv is correct but then turn right around and say, "But the relief valve IS a on off switch." ...You'd think that would be a simple thing to understand. Apparently not since Marv said,"It is NOT an on/off switch."


The engine tolerances of 'todays' vehicles are not of the same tolerances of ACVW's. High performance motors aside. The vast majority on this forum probably fall within the 'Stock-mild' range. ACVW's expand/contract far more due to the operating temperatures they operate at. Vehicles of today don't see the expansion rates or temps ACVW's see.

For most of 'Todays' vehicles the following does hold true as you stated:

"5w30 is what is recommended by almost every major gasoline engine manufacturer. Cars these days go 200-300,000 miles with little bearing wear using aluminum bearings and 5W-30 oil."

This holds true for my Highlander but it also isn't Air-cooled.

The catch is for 'Todays' vehicles.


Bottom line is the builder of the motor will know what's best. There is no one size fits all as some suggest.

[miniman82]

No, there isn't a one size fits all but if there were, it sure as h-e-double-hockey-sticks wouldn't be 20W-50! All babble aside, one thing always remains true- oil has to flow to lubricate. 5W-30 flows better than 20W-50 at all temperatures, which is why I run it. I'd rather know a failure I have was caused by my own doing, not ignorance of oil viscosities...
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[udidwht]

[miniman82]

If your engine gets hot enough to need more than 30 weight oil you need a better oil cooling system, not heavier oil.
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[udidwht]

[bugninva]

[miniman82]

How many of today's cars come equipped from the factory with oil coolers?
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[bugninva]

[Jimmy111]

Most people are under the impression that ACVW's have hotter oil temps than water cooled motors. But this is not the case. 200-220 is the norm for a ACVW. However most Water cooled cars see normal oil temps in the 300F range. This temp would turn your Mag case into a piece of jello.

Udidwht. Now you are saying 30w would be good. That is fine. Its the 20w50 that you need to stay away from.

[bugninva]

[udidwht]

[bugninva]

[udidwht]

Got a bit ahead of myself there.