Another Oil Pressure data point

#21

Oil capacity has nothing to do with oil pressure (assuming stock pan vs. Paul’s) The pan could be 4 feet deep and the dipstick would still indicate the FACTORY recommended oil level.

The reason more oil will help maintain OP is there is more available before uncovering the pump. Now, the best case is when we have a sump within the pan with trap doors to keep oil around the pump at all times. That, in addition with the windage tray, work together to keep the pump in oil on high G left hand corners.

Paul, if you aren’t completely overwhelmed, post a picture of your pan. CB

#22

Oil capacity has alot to do with oil pressure when going around a long right or left hand corners. That’s what you guys are talking about, right? Like Chuck said, we’re talking about maintaining oil pressure, not increasing it at idle.

I’d agree about the dipstick, it just shows oil level relative to the bottom of the engine/oil pump, not bottom of the pan.

#23

For god’s sake people, quit talking about different oil pans increasing OP. It’s just confusing people. We’re not talking about some meaningless “average OP”. We’re talking about keeping the pickup covered.

#24

Which is exactly what a larger oil pan with baffles will do.

#25

Chuck here is a picture. I will be running this pan next season as well with no crank scraper. I don’t think it will be necessary based on this pans design. You can make your own call on that.

Jason

#26

Second shot.

#27

Chuck can fill us in the the minor differences between these shots and the pan he received. This was a preproduction version but the final design should be real close to this. I will get mine in a few weeks.

Jason

#28

That is the configuration of my pan. I still, however, feel a windage tray is necessary since it prevents oil from escaping the pan to the right side of the motor. CB

#29

When you refer to windage tray is that the same as a crank scraper most run today?

#30

Yes, meant the IJ crank scraper. CB

#31

drumbeater wrote:

Steve (Gasman) is apparently talking about bigger oil pans that old more oil increasing OP. And he doesn’t seem to be talking about uncovering the pickup. Therefore in this thread you have to be specific.

Lots of factors contribute to average OP. Here we’re talking about only one factor.

#32

Scott, The point I was trying to make is this. The hash mark on the dip stick is a visual reference for the oil level with a stock pan. The more oil you have in a confined space, the greater the oil pressure will be.

The oil pickup isn’t relevant to my point, but I can understand how adding baffles to the pan could possibly help. To me, it’s like putting swimmy’s on your child that is wearing a life jacket. If it makes them feel better, so be it.

#33

Gasman wrote:

I believe this is only true in a pressurized, closed system. My understanding is that the oil in our motors is under pressure from the pump to the bearings, but after the bearings it is at atmospheric pressure only.

I may be wrong, though. :huh:

#34

Ranger wrote:Lots of factors contribute to average OP. Here we’re talking about only one factor.[/quote]

What are the factors? I’m just curious, assuming filter’s clean and engine seals/rings/etc are tight.

Viscosity
Covered oil intake/external forces

Steve D, I agree I think its just gravity at that point.

#35

Gasman wrote:

[quote]Scott, The point I was trying to make is this. The hash mark on the dip stick is a visual reference for the oil level with a stock pan. The more oil you have in a confined space, the greater the oil pressure will be.

The oil pickup isn’t relevant to my point, but I can understand how adding baffles to the pan could possibly help. To me, it’s like putting swimmy’s on your child that is wearing a life jacket. If it makes them feel better, so be it.[/quote]

The example of the oil pickup 2" deep in a pool or lake is accurate. OP in both cases are the same.

John is right, the key is gravity. Air pressure doesn’t play. In both cases there is the weight of 2" of oil above the pickup. That’s the static pressure that the pickup feels, but isn’t enough to matter.

Re. oil in a confined space. If you measure the OP of oil 2" deep in multiple different containers, they will all measure the same static pressure. The shape and size of the container don’t matter.

On the otherhand, if you poured oil into a hydraulic piston and then compressed it, then in that example there’d be an increase in pressure. But the oil in our pans is neither confined nor compressed.

The picture that I was presented of the oil in the pan and around the crank in a race car is one of a violently whirling sloshing maelstrom. The challenge for the folks baffling oilpans is to create a “still volume” of oil around the oil pickup. That’s what the trap doors and walls around the pickup are are about in the baffles. Make it easy for oil to get near the pickup, but harder for it to move away.

Adding a qt over full does nothing to create that “still volume”, it just adds some oil to the whirling, sloshing maelstrom. Certainly adding a qt is a step in the right direction, but it’s still a bandaid. Our crankscraper isn’t so hot either, in that it sits below the crank so isn’t nearly as effective (so I’m told) as scrapers for different engines where the scraper is at a tangent to the crank. Apparently it’s a better baffle for left turns then it is a scraper.

5yrs from now we may have enough data to say that engines without scrapers and not run a qt high tend to last <50 events. Engines with scrapers and run a qt high tend to last several hundred events. And engine with custom oil pans or sumps seem to avoid bearing problems. But right now all we have is anecdotes and opinions.

#36

I am just a spec E30 wannabe, but I do know a bit about race engine oiling problems. I find this topic interesting, so please accept some comments from an outsider.

Oil presssure is normally controlled by a pressure relief valve. Sometimes the pump cannot provide enough flow to reach the relief pressure. This is the case at idle.

The inside of a crankcase at 5000 rpm looks like the inside of your kitchen blender at full tilt. There is more foam and froth than liquid, like a cappuchino. Since the oil pump is a lousy air pump, flow and pressure will drop if the pump is exposed to froth as opposed to liquid oil. Both the steady. regulated pressure and the momentary dips due to exposure to aerated oil can clearly be seen in that great piece of data posted earlier.

The frothy oil lies on top of the liquid oil. Adding a quart ot two increases the thickness of the liquid layer at the risk of raising the oil level up into the spinning crank (the creator of the froth).

Some race engine builders go to great lengths to reduce the oil flow to the head and valvetrain. This helps by reducing the amount of oil that falls on the spinning crank, reducing pump flow requirements for a given pressure, and by keeping more of the oil down in the pan.

Accusumps work well to fill in those momentary dips in pressure, but if the pressure loss is too great or lasts too long, you will drain the cannister, and you are then well and truely screwed. Ask me how I know. :frowning:

As I modified my car over the years from stock to slick-tired race car, I found that the oiling system that worked one year was inadequate the next. I went from baffled pan to Accusump and ultimately, to a complete dry sump system.

#37

Dyno wrote:

[quote]Adding a quart ot two increases the thickness of the liquid layer at the risk of raising the oil level up into the spinning crank (the creator of the froth).
[/quote]

Would it be safe to say that this could lead to bearing failure and not prevent it as some have thought?

#38

Gasman wrote:

[quote]Dyno wrote:

[quote]Adding a quart ot two increases the thickness of the liquid layer at the risk of raising the oil level up into the spinning crank (the creator of the froth).
[/quote]

Would it be safe to say that this could lead to bearing failure and not prevent it as some have thought?[/quote]
The rule of thumb is that you need at least 10 psi per 1000 rpm. So, if you have less than 50 psi your are definately at risk of bearing failure. That is not to say you engine will blow up if you hit 49 psi for a millisecond. Being a chain smoker does not automatically guarantee you will get lung cancer, but…

I lost oil pressure somewhere in the carousel at Indianapolis Raceway Park. Lost the rod bearings, which ruined the crank. Bits of bearing material got caught betweeen piston skirts and cylinder wall, requiring an overbore and new pistons. $$.

#39

Sorry, but I think I mis-read your question.

Regarding adding oil, this is common practice in some cars. I’d think adding one quart would probably be safe and beneficial. Adding three quarts would probably make things worse.

Gotta run the experiment yourself. Don’t do what I did and assume your oil pressure gage is responsive enough to see those momentary dips. Only after I swapped out the stock gage with a race-quality gage AND some large-diameter oil line did I actually see what was happening.

The oil pressure plot shown earlier is incredibly telling and valuable. That is the ultimate picture of the problem. Now, we just need to see before/after comparisons!

#40

Dyno wrote:

[quote]The rule of thumb is that you need at least 10 psi per 1000 rpm. So, if you have less than 50 psi your are definately at risk of bearing failure. That is not to say you engine will blow up if you hit 49 psi for a millisecond. Being a chain smoker does not automatically guarantee you will get lung cancer, but…
[/quote]

Last year I was trying to better understand the relationship between OP and oil viscosity. I latched on to the 10psi/1000rpm rule of thumb and thought that all I had to do next was chart the pressures of different oils. But when I talked to the oil geeks at www.BobIsTheOilGuy.com, the center of all oil knowledge, they pretty much beat the crap out of me for getting too wrapped up into 10psi/1000rpm.

A link to that thread is on my oil debate page:
http://www.gress.org/Home/Cars/TrackTales/DIY/OilingSystem%20Improvements/Oil%20Debate/The%20Great%20Oil%20Debate.htm

My tow vehicle, w/ a POS Chrysler 5.9l, has ~80psi at 1500rpm.