Very high oil pressure

[Jamo]

Here we go...from when the motor was going together. The unconnected line hanging from the back with the heat resistant cover plugs into the back of the block, and then attaches to the fitting at the top of the front side of the pan. You can see the inline pressure valve.

[BOURRET]

With FE 489 cu.in.(alu block) running steady :
my normal oil pressure is 75PSI at 2850rpm
with oil temperature of 125°F
and 72 mph (130km/hr)
with an outside air temperature of 60°F .
Oil is synthesis 5W40.

When I start the engine, the initial oil pressure goes up to 120 PSI at 800 rpm and I let it warm up and drop until it reaches less than 100 PSI and a minimum temperature of 110° before moving the car.
At steady idle, in traffic, the values are:
800rpm
125°F (oil)
30 PSI.

[Jamo]

Here's the only pic I have of the line going into the back of the block...you can see it towards the bottom below the oil separator tank at the back of the manifold...



BTW, my FE runs at about 70-75lbs when hot at 2500rpm/30-35lbs at a fairly fast idle (lumpy cam...about 1200rpm). Higher, of course, when cold.

My C6 Vette....using Moble 1, it runs at about 20lbs idle and never higher than 45lbs even at 6,000rpm. Doesn't burn a drop between changes and has 60k on the OD.

Go figure...

[Excaliber]

I'm about the same pressure as Jamo, 40 at idle (1000 rpm), 20-50.

[troll]

what does it do @ 6000 or 7000 rpms ?At that point who wants to look at that.
does anyone know what kind of oil pressure those new 2.4 liter v8 F1 engines have @19,000 rpms?

[PatBuckley]

Cosworth DFV V8- about 80/90 psi at normal running speeds - 8-11,000 rpm.

[troll]

I guess this one is solved 100 is to much @ idle.

[Excaliber]

Come to think of it, many oil FILTERS have a bypass built into them. When the pressure gets to high the oil isn't being filtered, it's being bypassed.

Anybody know what a typical oil pressure bypass setpoint is?

[patrickt]

Originally Posted by Excaliber

Anybody know what a typical oil pressure bypass setpoint is?

It's very low, like around 10 to 15 psi. But that's differential pressure, not absolute.

[Excaliber]

Oh, differential pressue, sensing a 'plugged up filter' element, not a problem then.

[Jerry Clayton]

I'll give you something to think about---We run some 500 inch drysumped engines that have about 20-25 inches crankcase vacume thru out the rpm range all the way to 10,000+ rpm.
If we removed the pressure pump COMPLETELY out of the system, the engine would run just fine with the vacume sucking the oil out of the tank and thru the bearings---THINK ABOUT IT--- just like drinking a malt threw a straw

Jerry

[patrickt]

Originally Posted by Jerry Clayton

If we removed the pressure pump COMPLETELY out of the system, the engine would run just fine with the vaccum sucking the oil out of the tank and thru the bearings...

You could then say that you just decided to eliminate the only major component of the engine that was forced to receive unfiltered oil.

[Jerry Clayton]

I always try to plumb the filter into the return lines to the tank, thus keeping the tank clean and running unrestricted to the engine--yes a pump failure will contaminate the engine but if you kill a pump you will probably kill the filter and it will then bypass into the engine anyway---

We used to not run filters on our top fuelers to save weight, but then got a sponsership by a company that bought a filter company---

Jerry

[Anthony]

Some thoughts.

Originally Posted by PatBuckley

As for the oil pressure, I have always gone with 10 psi per 1000 rpm.

Yes, I have heard that many times too. I've also been told that it is the bearing clearence that truly determines PSI and weight of oil needed, not what the oil pressure gauge says.

Originally Posted by PatBuckley

Excessive pressure costs power and you run the risk of breaking things. It takes a lot of twist to generate all that pressure and in any case it's the lubricating properties of the oil that keeps things going not the pressure of the oil.

Absolutely. I've heard about shaft and gear failures, and obviously, the more pressure and flow you generate, the more HP it's going to cost you. But, the higher pressure will likely give higher oil flow, cooling the bearings and other engine components to a greater degree.

What you can't measure is the oil pressure at the rod bearings. I've read somewhere that chamfering only the leading edge on the main journal, and only the trailing edge on the rod journal will significantly increase pressure and flow of oil to the rod bearings, which I have done on my crank.

[double ugly]

WOW..... way over my head, but incredibly entertaining. We just had a couple neighbors who have PHDs at the house for dinner and I'm feeling exceptionally inadequate.
John

[Jerry Clayton]

Double---I've been wondering---is there any such thing as an average fighter pilot?

[double ugly]

Yup, that be me.....

[Jac Mac]

Dont want to get off track here but,think about the old splash fed big ends on the old six cyl chevy for a minute. With a scoop on the rod cap to grab some oil out of the trough for about 45° of rotation then nothing for the remaining 315°- add to that the oil is introduced at the bottom of the stroke.
When you start to think along these lines you only need enough pressure/volume to get the oil past the centerline of main journals ( in the main to rod journal feed ) after that centrifugal force takes over to deliver the oil to the rod journals. As long as the bearing clearance is tight enough and the drilling contains enough oil to last until it gets replenished next time around all should be ok, admittedly a bit of pressure will help, but its what they refer to as the hydrodynamic wedge that really does the 'work'. A lot of the 'High' pressure's touted by builders are at the gauge which is usually mounted on the exterior of the block, however the 'actual' pressure at the entry to the main bearing can be a lot lower- I seem to remember that for every 90° bend in hose fittings ( as opposed to 'sweeps or radius bends ) that a 5lb drop in flow pressure can be expected.
Now on that basis an FE has -70°,90°,90°,90° going from pump to filter ( no Cooler ) then 90,90,110,110 to the front main and a further 90,110 to each main in a side oiler & or about the same on a center oiler plus the trip around the cam bearings. Now if the 5lb pressure drop per 90° theory is correct we have about 50lb of pressure drop from the gallery system.
This a large part of the reason we now see oiling to both ends of the main gallery as on the alloy block pic's earlier in this thread.

Jac Mac

[elric]

On my Cammer I see a 40lb difference from the base of the filter to the furthest point I can measure in the system(back of pass. side cyl head). There is a significant loss from all the bends in the system.

[Jerry Clayton]

The hollow from front to back on the ford cranks was supposed to pump oil thru the engine at 7000rpm and above
The billet cranks we had made for out top fuelers in the early 70s were drilled with interconnecting oil passages to balance/insure oil flow to all the bearings

The bearing clearances determine what the oil flow is not the pump and plumbing--the supply just has to be adequet to supply that volume

Jerry