Based on this thread I ordered a Killer B pickup tube. Worst that happens is it does nothing, best case that happens is it's a simple change that improves the oiling situation when I'm on track.

The erosion in cavitation happens in the intake (low) side, where negative pressure takes gas out of solution in the fluid, bubbles form and immediately implode eroding the material in the process. In ship propellers or fire truck pump impellers this is in the trailing edge of the blade, for example.

@CSG Mike


Maybe Mike can chime in. Pretty sure he is on a stock engine with decent turbo'd boost/power, and he is probably tracking the car more than most on here. Pretty sure he is running 0w20 oil too, if I remember correctly from other threads.


Poiseuille's equation shows that the resistance to flow will be inversely proportional of the radius to the power of four, meaning a small change in diameter should result in a huge change to flow, so increasing the diameter of the oil pickup and oil galleys should result in a large increase in flow, but there is an assumption that oil starvation was a feed problem. Let's say it was then what would happen if the feed diameter in a system is enlarged everywhere except to the bearings or in multiple other locations? In other words, will increasing only part of the system's diameter be enough, or would the system still be limited by the smallest diameter? I believe the weakest link in the system will restrict flow, or in this case, the smallest diameter pipe will still restrict flow. This is like trying to attach a larger straw to the end of a smaller straw and expecting to suck fluid out of your drink faster. He clearly enlarged many pipes in the system, even the clearance of the bearings, but were the feed holes to the bearings all enlarged, specifically at the delivery end? I don't think so.


The other thing that can effect resistance is viscosity, which will change with temperature of course, but it is proportional to resistance, so the greater the viscosity the greater the resistance. Other factors not mentioned in the equation is turbulence, or other phenomenon like cavitation. The big thing to mention with the viscosity is, if the diameter of the feed is constant because the oil channels at the bearings are fixed, or the bearing itself has a feed diameter that is fixed, then viscosity will be the greatest influence to resistance in the system, which is why I mentioned it above.


The flow rate is also fixed and is proportional to resistance, but this would be good resistance, or rather pressure. Like sucking harder on the straw, or like increasing stroke rate or heart rate on a heart, more flow rate would be better for delivery. There is the Reimax solutions to replacing or increasing the pump volume rate, so this could be a solution, but the problem with increasing pressure or volume/flow rate is that the new volume could go to the path of least resistance, which could be away from the bearings. I have read before that improvements to delivery just results in more flow to the head and not the block


https://en.wikipedia.org/wiki/Hagen%...uille_equation


https://www.counterspacegarage.com/reimax-oil-pump-fa20


https://www.counterspacegarage.com/r...-oil-pump-fa20


Sorry this is long winded, but the other thing that could be mentioned is that there is an assumption like I mentioned above that oil starvation is the issue. Perhaps there is just an inadequacy in bearing size for the forces of FI or the forces from high piston speeds. A larger surface for supporting the loads and dissipating the heat might be advantageous instead of increasing viscosity.


http://www.ft86speedfactory.com/king...l#.XOgeS1iWymw

I would absolutely recommend to get the Killer B oil pickup!

I was going to use the one I ordered straight up, but then I noticed I couldn't because length and orientation where different in the GT86 FA20 and the WRX FA20DIT. At the time I ordered, Killer B didn't have a GT86 option. From the pictures I thought there were the same but go figure :bonk:.

As I had to modify Killer B's pickup anyway, I chose to go with the 1" tube that gave me an inner diameter that better matched the rest of the intake galleries I had improved.

If there's a real improvement between a 3/4" or 1" tube is up for discussion.
Even if it existed, it'd be far less of an improvement than going from stock (18mm, bent, restrictive mesh) to Killer B (3/4", straight, much better mesh).

I've contacted Killer B and Chris has been kind enough to offer to send me one of their new GT86 FA20 oil pickups to make a test in my car: stock vs 3/4" (Killer B) vs 1" (Killer B modified by us). We'll see how it goes, but I'd recommend to anyone with the stock pickup to get Killer B's asap.

The 3/4" vs 1" discussion is better suited to rebuilt engines with looser tolerances and higher flow, so even the objective results from the test we'll do will have to be interpreted correctly and probably won't apply to a stock engine.

OK, who will be the first to go into a parts department and take and post a picture of a NEW oil pump - :iono:


humfrz

I think thinner oil will have less problems with cavitation because it has less resistance to flow which results in more pressure on the inlet (or less vacuum). Interestingly enough, higher viscosity does seem to reduce damage done by cavitation: http://www.aun.edu.eg/journal_files/80_J_7365.pdf

I think the most important factor here for cavitation is the inlet pressure which is caused by major and minor hydrodynamic losses. Major being mostly friction, minor being mostly changes in direction of the fluid. So a thick fluid running through bendy pipe and small diameters is going to cause more vacuum on the inlet. A thin fluid running through straight large diameters is going to cause less vacuum on the inlet.

This is just examining the inlet side of the pump though with the purpose of reducing or eliminating cavitation and increasing flow rate.

You make good points about whether or not this is actually significantly helping on the other side of the pump. Even if most of the increased flow is going to the head and not the block, there should be some small amount of increased flow even through a bottleneck. Again, whether it's significant or not, or even the correct solution, is another question.

Edit: Removed a possibly incorrect statement about oil viscosity and its relation to cavitation.

I'm running a 100% stock engine.

Increased flow isn't always a good thing, when your return system/mechanism is unable to keep up under cornering.

I'm also tuned for 7800 RPM, but I don't make it a habit to stay up there.

I never actually expected a stock engine to last this long, but I also have more supporting mods than most, and probably more tuning hours (2 days with Bill and 80+ with Zach at @DeliciousTuning on the turbo tune alone) than most too.

So cavitation will be reduced by higher viscosity, but the vacuum will be increased on the inlet side due to increased friction losses. I think the question is which of the two effects is stronger. I think it doesn't matter either way, increasing the diameter of the inlet to accommodate the viscosity that will work best for the engine is what's important.

Dude this is a discussion that has existed for ages and will probably never be settled, you can read for hours arguments for both on BITOG from very reputable persons.

I think in the particular case of an inlet restricted oil pump, higher viscosity is worse because it will cause cavitation sooner with the same flow. High viscositý will have lower intlet pressure than low viscosity because it creates a bigger pressure drop with the same flow. Once the pump is cavitating heavily, the thicker oil film the high viscosity gives you (it's only advantage, actually), doesn't matter because the oil just doesn't get to the bearings. This also depends on the PRV on that particular engine, so it becomes a complicated discussion. One of my engine failures was using Motul 10W60 oil, I used it thinking of the same reasons you describe.

I recommend you pursue a solution, rather than keep trying to fix the symptoms.

Thanks. That paper helped my understanding.


I think the data he posted is clear that increasing the diameter of the inlet should raise pressures, and the evidence suggests that this should decrease cavitation. If that translates to a reduction in the occurrence of oil starvation is still up for interpretation, and really, is yet to be seen, but regardless, it is definitely a solution to a potential inadequacy.


I'm still bugged by the fact that the output side didn't show an equally dramatic improvement in pressure. Here is an analogy:


--Imagine we had a water wheel in a river, and instead of being driven by the flow of the river like they typically area, it was being driven by a machine spinning the wheel in order to pass the water into an output pipe. Now, say the river level was variable and inadequate (maybe a beaver was clogging it upstream) then the wheel's fins or buckets were never getting filled completely. This would cause low flow to the output pipe.
--Farmers decided to remove the dam and the river's levels rose. Now the buckets are getting filled completely, and the output pressure/flow rate increases.
--Now say the output needs to be increased, so the farmers turn up the machine to spin the wheel faster and when they do they get more output.
--Now say the output needs to be increased more, so the farmers turn up the machine more, but there isn't more output. Why? As the bucket is spinning, it is spinning so fast that the bucket doesn't have time to fill (I'm a hospital worker, and we see this in the hospital with high heart rates when there is inadequate time to fill the chambers, ie, preload drops).
--The next day it rains and suddenly the river is flowing faster, so the buckets are able to fill completely once more, even at the fast speed, so pressure/flow increases at the output pipe (this is analogous to having the body respond with better vascular tone and muscle pump to increase preload, just to continue that analogy of this analogy lol).


So, where am I going with this? If the output pressure isn't increasing with an increase in inlet pressure then perhaps the scoops or buckets of the pump are already picking up all they can; ie, there isn't an inlet inadequacy. Perhaps the inlet inadequacy could decrease cavitation, but maybe the pump is already scooping up all the oil it can fit in the space of the pump.

I think the output will always be limited. You can only squeeze so much oil out of the rod and main bearings. From what I have understood previously, and maybe I misunderstood, the FA doesn't prioritize feeding the mains.

Off of Element Tuning's page.

Unlike the EJ series of Subaru motors this engine does not have a “main priority” oiling system and therefore critical oil pressure isn’t directed to the engine bearings first.