FA20 oiling problems, study and solution

[Irace86.2.0]

Originally Posted by Joesurf79

Cavitation doesnt necessarily lead to a drop in outlet pressure, because (especially in a positive displacement pumps like an automotive oil pump) the drop in pressure that causes the inlet stream flow to drop below the vapor pressure of the entrained gasses (forming the micro bubbles that then collapse on the high pressure side - the resultant micro jets from which cause the characteristic grainey erosion on metal surfaces) is momentary and not representative of a large oil volume.

Remember that pumps - and this is ANY FLUID PUMP IN THE UNIVERSE - produce FLOW not PRESSURE! The pressure is a measure of the resistance the system presents to the flow the pump is producing. So if the pressure at the inlet of the oil pump drops due to the larger pickup tube allowing more FLOW, that is a good thing as long as the NPSH of the pump can be met through the larger tube with the pump's capacity. A larger PD pump doesnt produce more or less pressure - it moves a fixed volume for each rotation period.

The amount of metal removed in traditional cavitation is microscopic at these flow / pressure levels. It'd pass through bearing clearances, possibly even the filter media depending on brand. Conversely - it would show up on a UOA.

Pressure is monitored instead of flow in an engine because they are linked well with positive displacement pumps. Drop in pressure downstream of the pump means that flow rate has dropped. A flow meter is complicated and overkill for these applications.

Centrifugal pumps and gasses complicate things big time haha!

I was watching this video a few days ago when researching cavitation. I feel like this guy made an error in his words during the example of the water hose. He decreased the diameter of the water hose and said 'look water pressure increased', when in fact, water pressure decreases when the diameter decreases. What he should have said was velocity increases, but that wasn't what was interesting. He uses a 300k miles 1.8L Integra engine to show passages and illustrate his points. Go to 4:00, he pulls off the rod bearing and finds pits (cavitation, right, like what was linked by solidsnake11 earlier). I'm just curious how the motor made it to 300k with such pits, and I'm curious how much cavitation leads to engine failure when this motor didn't seem to have spun bearings with such pits.

[ame]https://www.youtube.com/watch?v=8f2fcbTh5yw[/ame]

[NoHaveMSG]

Originally Posted by ermax

Here is a picture of some of my bearings. 86k miles, all stock running 5-w30. Spun #3 (pictured on the left) but all the others looked like the one on the right. Very clear signs of starvation.

If you reference Element Tuning's FA20 build page they talk about this. The oil port for the #3 main feeds two rod journals. So they are more susceptible to starvation.

[Ultramaroon]

Originally Posted by Irace86.2.0

The fluid dynamics isn't easy to understand, nor is it easy to see how the system is set up just looking at the parts from pictures on the internet. I feel like we would need to see a flow diagram with the size of the tubes. Even then I don't know if I am up to the task.

There's enough info here for a first-pass discussion. I argue that:

• the bank-2 head tap is upstream of the factory pressure tap.
• the front main tap is the very next spot downstream.
• head loss in that short distance along the timing cover is negligible.

Unless that o-ring between the cover and block is blown out, it would be difficult to measure the difference. I am going out now to do this test.

GENERAL; 2013 MY FR-S [03/2012 - �������]
SYSTEM DIAGRAM; 2013 MY FR-S [03/2012 - �������]
DETAILS; 2013 MY FR-S [03/2012 - �������]

[Joesurf79]

Originally Posted by solidsnake11

Bubbles take up volume so if your pumping gas bubbles and oil then you collapse the bubbles you have lost volume.(pressure). Somewhat like air in your brake system.

You haven't lost volume though - the volume of gas (air for arguments sake) entrained in the fluid doesn't change - it was always there, always being pumped, down the line, evenly distributed. Nor does the volume of liquid in the system change. It's the drop below vapor pressure for the liquid that allows the gas to dissociate from the liquid into clumps (bubbles) that collapse as soon as the pressure on the fluid rises back above vapor pressure. That bubble collapse causes the damage to adjacent surfaces.

You'll see more of an effect on discharge pressure from a centrifugal pump due to cavitation than you will from a PD type pump due to the fixed relationship between RPM to volume moved in a PD (reciprocating piston, gear, lobe vane, peristaltic, etc) pump.

[Joesurf79]

Originally Posted by Irace86.2.0

...I feel like this guy made an error in his words during the example of the water hose. He decreased the diameter of the water hose and said 'look water pressure increased', when in fact, water pressure decreases when the diameter decreases. What he should have said was velocity increases...

He is correct, in that upstream of his thumb restriction, the pressure increased. The system's resistance to its flow rate increased. That resistance is pressure. Downstream of the restriction his thumb created, the pressure in fact decreases. This is how a control valve works in a pipeline or refinery.

The flow rate necessarily increases through a smaller orifice, which is also correct.

A flowing fuid's pressure at a given flow rate increases as the passage through which it passes decreases in diameter.

[Irace86.2.0]

@ETM_Shaman

Have you considered testing the stock pickup tube pressure or inlet pressure with 0w20 or even 5w30 instead of your 10W40? Perhaps the heavy grade oil was the problem all along.

Skip to 1:20. If the cavitation you are trying to resolve is from starving the pump then couldn't higher viscosity oil be the problem?

[ame]https://www.youtube.com/watch?v=iau3DuphVqY[/ame]

[churchx]

Joesurf79: Flow rate or fluid speed, that increases through narrower tube? I believe in closed loop portion first is constant, and 2nd varies, by Bernoulli principle, no?

[Irace86.2.0]

Originally Posted by Joesurf79

He is correct, in that upstream of his thumb restriction, the pressure increased. The system's resistance to its flow rate increased. That resistance is pressure. Downstream of the restriction his thumb created, the pressure in fact decreases. This is how a control valve works in a pipeline or refinery.

The flow rate necessarily increases through a smaller orifice, which is also correct.

A flowing fuid's pressure at a given flow rate increases as the passage through which it passes decreases in diameter.

Except the pump is probably governed by a pressure regulator, right, just like a fuel pressure regulator, in that it allows bypass of the flow from the pump when a given pressure is achieved, so the pump doesn't overwork or simply fail from extreme pressure buildup when resistance is high like when fuel injectors aren't opened much? In that case, the feed pressure is constant.

Fluid flowing in a tube will drop in pressure and increase in velocity when the radius decreases. If the feed pressure is constant (as explained above) then as he squeezes the end, reducing the radius, there must be conservation of forces (Bernoulli's Principles) the pressure of the fluid in the section of the pipe drops and the fluid will dramatically increase in velocity. There only needs to be a difference in pressure for it to flow in a direction (that is the force).

[ame]https://www.youtube.com/watch?v=VA03j6t5F-8[/ame]

[Irace86.2.0]

Originally Posted by Ultramaroon

There's enough info here for a first-pass discussion. I argue that:

• the bank-2 head tap is upstream of the factory pressure tap.
• the front main tap is the very next spot downstream.
• head loss in that short distance along the timing cover is negligible.

Unless that o-ring between the cover and block is blown out, it would be difficult to measure the difference. I am going out now to do this test.

GENERAL; 2013 MY FR-S [03/2012 - �������]
SYSTEM DIAGRAM; 2013 MY FR-S [03/2012 - �������]
DETAILS; 2013 MY FR-S [03/2012 - �������]

Excellent find sir!


Doesn't the system diagram seem off?

I don't know about you, but it looks to me like the oil goes from the oil pump to the oil filter then part of it goes to the left/driver's side of the motor (camshaft journals) then the rest goes to the middle then it branches again, right? Then part of the oil goes to the crank area and the other part goes to the right/passenger's side of the motor (again, camshaft journals). Is that what you see? I see a return line from the right; I see a pickup tube; I don't see a return line from the left, so maybe they left it off the diagram. What do you think?



Also, when looking at the picture bellow of the cover, it seems like there is three outlets and one inlet. One to the right and left and one to the middle with a single return. Supporting my point, it also seems like the oil is diverted after the filter to the left/driver's side of the motor, and the rest goes to the middle, where it then diverges to the crank and right/passenger's side.



I can't tell where the stock oil pressure sensor location measures from. It looks like it is on the top return channel from the filter, meaning the channel that is returning to the center (possibly after diverting oil to the driver's side section), and I can't tell where the front/top oil galley plug is situated, but it could be after more oil has been diverted to the right/passenger's side of the motor, right? What do you think? If it has then couldn't there be a significant drop?

[Irace86.2.0]

@Ultramaroon

I also found this:

To answer the OP, an oil pressure sender can go in either the galley plug or the front of the block. The oil pressure range specified in the manual is taken from the port at the front. That being said, the oil galley will apparently give a better idea of the oil pressure as seen by bearings, and that's where I'll be mounting mine (due in large part to packaging simplicity). Pressure measured at the oil galley will be up to 10 PSI lower than pressure at the port on the front of the engine.

https://www.ft86club.com/forums/show...91&postcount=7

[Joesurf79]

Originally Posted by churchx

Joesurf79: Flow rate or fluid speed, that increases through narrower tube? I believe in closed loop portion first is constant, and 2nd varies, by Bernoulli principle, no?

You're right, typing too fast. Fluid speed.

[Ultramaroon]

Originally Posted by Irace86.2.0

@Ultramaroon
I also found this:
https://www.ft86club.com/forums/show...91&postcount=7

He's the friend.

[Irace86.2.0]

Originally Posted by Ultramaroon

He's the friend.

Oh I see

Let us know what you find if you make the switch. I'm curious.

[Ultramaroon]

Originally Posted by Irace86.2.0

What do you think? If it has then couldn't there be a significant drop?

I've looked at these diagrams fifty times and for the first time I just realized that the branch for the bank-1 head is in between the two points.


There indeed could be a significant drop. Very interesting. That being said, note the initial bullshit offset on my test gauge which is connected to the pressure switch port. If the static offset is taken into account, the two gauges are pretty close. Otherwise, they disagree in the wrong direction.








I'll warm up the engine and take some more readings.