FA20 oiling problems, study and solution

[CSG Mike]

Originally Posted by Capt Spaulding

In the end, what he's doing is an experiment. Several other members have had similar ideas and implemented some of them. They may all go "kerblamo," but it's also possible they've hit on what the guys at ET are doing. I don't mean to offend, but this sort of engineering/experimentation is interesting (particularly when somebody else is doing the work and footing the bill). [/COLOR]

100% agree, that whether it works or doesn't work, it's awesome to see someone doing data collection of this caliber. Success or fail, real world results are what truly matter at the end of the day!

[solidsnake11]

https://www.waukbearing.com/en/techn...ation-erosion/

https://www.google.com/url?sa=t&sour...=1558758736897

Assessment
Pressure surges caused by the implosion
of gas and vapour bubbles near to the
surface of the bearing result in material
nicks (see chapter: "Erosion and
cavitation – introduction"). Cavitation often
comes hand-in-hand with erosion and
corrosion and can cause fine scoring in the
same or adjacent bearings.
Possible causes
High temperatures and low-boiling
impurities may advance cavitation.
• Impurities in the oil: water, fuel or
deposits from abrasion and dirt
• Oil pressure that is too low: unforeseen
loss of pressure (for example due to
defective oil pump) is present or the oil
pressure is set too low
• The vapour pressure of the oil used is too
low
• Increase in temperature in the bearing
(for example due to a lack of oil)
• Oils with low viscosity increase the risk
of cavitation

[Irace86.2.0]

Originally Posted by solidsnake11

Please inform people why you never exceed 230f.
Because when I first read it I was like wow but then I found this. You are also running a higher cst than a thicker oil at higher tempatures.

Originally Posted by CSG Mike

Key data point there, although the differences may not be THAT big, depending on how hot the OP's oil is inside the engine and on surfaces the need lubrication

For those reading, My 5W30's viscosity at ~225F is approximately equal to 40 weight oil at ~245F, or a 50 weight oil at ~280F. This is also ~~0W20 at ~210F. For reference, I use Motul 300V.

Wouldn’t fans limit flow/cooling at speed? Is there a lot of hot idling time during track days?

[Irace86.2.0]

Originally Posted by solidsnake11

https://www.waukbearing.com/en/techn...ation-erosion/

It would be cool to see some pictures of cavitation on bearings from 86’s. I’m curious if the OP has some pictures of his spun rods? He mentioned them showing signs of oil starvation.

[ermax]

Originally Posted by Irace86.2.0

It would be cool to see some pictures of cavitation on bearings from 86’s. I’m curious if the OP has some pictures of his spun rods? He mentioned them showing signs of oil starvation.

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.

[Irace86.2.0]

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.

Any signs of cavitation like in the links above?

[ETM_Shaman]

I don't think cavitation at the bearings is causing damage or even happening (I don't know really).

I think this is the chain of effects:

restrictive pump inlet -> low inlet pressure -> cavitation at the pump -> decreased oil mass output from the pump + huge pressure oscillations -> decreased oil pressure / flow in the main gallery -> oil starvation at the bearings (rod bearings 2 +3 are the most damaged usually because of the shared oiling)

Now there's another big variable that complicates things which is the PRV. Exactly how much it contributes to the above conditions in the FA20 engine is unknown to me, but it's easy to see that when it opens it creates turbulent flow right at the pump's inlet so it can only make things worse. Chris from Killer B has studied this deeply in the EJ engine and thinks it contributes a LOT.

Reducing the pressure drop between the pump's outlet and the main gallery (by doing the modifications I did) can only contribute to keep the PRV shut more and help with this. Adding shims to increase the PRV opening pressure also helps.

The way to study the PRV's behavior is simple (but I don't think I'll be the one to do it): tap the pump's outlet as close to the PRV opening as possible and install a pressure sensor the way I did in the inlet. Analysing that pressure in relation to the pressure in the main gallery and the pump's inlet would allow us to get a very deep insight on the PRV and the lubrication system for this engine in general (doing this in a bone stock engine would also be very interesting).

With my 2.0 mm shims I've measured a 17.0 kg opening force for the PRV which means 8.3 bar (16.0 mm PRV piston diameter). You would think it's not opening if my oil pressure sensor indicates 4.0 bar, but if there's enough pressure increase from the main gallery (where I measure oil pressure) to the pump's outlet (where the PRV is) it might very well be dancing around.
Measuring the pressure right at the PRV would tell us exactly.

Just as an example:





You can see the big (~ 1.0 bar) pressure drop between both measuring points. It's almost double than what my complete JDL oil cooler creates. Only after seeing this is that I decided to make more extreme modifications (like modifying the block's entrance for a bigger oring) to the galleries that take the oil from the pump to the main gallery in the block.

Please remember all this is to increase oil flow TO THE CRANK. The heads have different entrances (although some parts are shared) and I haven't touched them. Increasing oil flow to the crank will not create oil return problems in a boxer engine because the oil drops directly to the pan.

Having said this, I have ALSO ported and improved the head oil return ducts to the pan (many obvious spots that can me improved) and installed a Bluemoon Performance baffled oil plate to help get the oil to the pan more efficiently and keep it there.

And just to make it clear, I embarked in all this craziness only AFTER having oil starvation engine failures with a stock lubrication system. If my engine would have survived without problems, I probably would've never even disassembled the oil pump in the first place and would've spent all my time tuning, trying to make more power and enjoying the car at the track.

[Ultramaroon]

Originally Posted by ETM_Shaman

You can see the big (~ 1.0 bar) pressure drop between both measuring points.

This blows my mind. I have argued with a friend, insisting to him that the difference in pressure between those two points must be insignificant. You've tested those gauges against each other to verify agreement?

Now I'm motivated to look at this myself. Unbelievable!

[solidsnake11]

I have a solution to the oil cooler pressure drop. WRX scavenge pump modified to pump oil through the cooler.

[Irace86.2.0]

Originally Posted by Ultramaroon

This blows my mind. I have argued with a friend, insisting to him that the difference in pressure between those two points must be insignificant. You've tested those gauges against each other to verify agreement?

Now I'm motivated to look at this myself. Unbelievable!

The oil system isn't a closed system, right, so the oil pressure at the gauge will never be a reflection of the whole system? It doesn't tell us what is happening at the bearings, or the crank, or the heads. It isn't an average of the system or anything. Ideally, we want to know what the max pressure is, right, because the minimum pressure will always be zero in an open system, so knowing the max means we know what we have to work with? Obviously we can't know everywhere in an engine.

Doesn't the pressure drop have to be somewhat significant for oil to flow in a given direction fast enough? The difference in oil pressure will determine the flow. The closer the pressures are to each other then the slower the flow will be.

I'm pretty sure my Greddy oil pressure sensor is attached to the stock location on the front of the cover, closest to the pump, right? My Greddy oil temp sensor is attached to the main oil galley on top of the block, closest to the core of the motor, right?

How is your set up?

[Ultramaroon]

Originally Posted by Irace86.2.0

The oil system isn't a closed system, right, so the oil pressure at the gauge will never be a reflection of the whole system? It doesn't tell us what is happening at the bearings, or the crank, or the heads. It isn't an average of the system or anything. Ideally, we want to know what the max pressure is, right, because the minimum pressure will always be zero in an open system, so knowing the max means we know what we have to work with? Obviously we can't know everywhere in an engine.

Doesn't the pressures have to be somewhat significant for oil to flow in a given direction fast enough? The difference in oil pressure will determine the flow rate. The closer the pressures are to each other then the slower the flow will be.

I'm pretty sure my Greddy oil pressure sensor is attached to the stock location on the front of the cover, closest to the pump, right? My Greddy oil temp sensor is attached to the main oil galley on top of the block, closest to the core of the motor, right?

How is your set up?

I monitor at the front-side main oil gallery. It's just downstream of the stock pressure tap - like 8 inches downstream. I think he only split is for the bank-2 chain tensioner, hence my amazement. It's where most people tap for their turbo.

[Joesurf79]

Originally Posted by Irace86.2.0

So what you have found is that the inlet is inadequate because sustained rpms leads to a drop in inlet pressure, and that leads to cavitation, right?

A few points of confusion:

--Shouldn't cavitation lead to a more significant drop in outlet pressure if that is the cause of the oil starvation, and you showed only a small difference in outlet pressures?

--If cavitation is happening then couldn't that metal debris be a cause of bearing failure? Moreover, shouldn't it show up in an engine oil test as metal in the oil?

--If this is the cause of oil starvation then couldn't this be replicated on a dyno or something, meaning, if it is just sustained rpms, and not sustained lateral g's or something else commonly related to track oil starvation, then couldn't it be replicated in a static environment? Is it common for oil starvation failure to happen, for instance, during a top speed run (ie long sustained rpms)?

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!

[Irace86.2.0]

Originally Posted by Ultramaroon

I monitor at the front-side main oil gallery. It's just downstream of the stock pressure tap - like 8 inches downstream. I think he only split is for the bank-2 chain tensioner, hence my amazement. It's where most people tap for their turbo.

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.

[solidsnake11]

Originally Posted by Joesurf79

Cavitation doesnt necessarily lead to a drop in outlet pressure

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.