FA20 oiling problems, study and solution

[Capt Spaulding]

Fascinating stuff. I have a number of questions I'mm still trying to formulate. Thanks to the OP for the work and the willingness to publish it.

[Horrid_Funk]

Originally Posted by Irace86.2.0

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.

The inlet and outlet pressures of the pump go up approximately the same amount in his data. At 5000 RPM it looks to be approximately 0.1 bar.

[Irace86.2.0]

Originally Posted by Horrid_Funk

The inlet and outlet pressures of the pump go up approximately the same amount in his data. At 5000 RPM it looks to be approximately 0.1 bar.

Lol Thanks. I read this after looking at the graphs:

Big difference in inlet pressure but small difference in outlet pressure (which ilustrates how oil pressure in the outlet doesn't tell you 100% of the story).

And incorrectly assumed one was a big change like he said and like it looks. I should have looked at the numbers more closely. Thanks.

[ETM_Shaman]

Originally Posted by CSG Mike

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

Please do elaborate!

[Capt Spaulding]

Originally Posted by CSG Mike

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

I have to confess Mike, that I don't quite understand your point. It seems to me that addressing the symptoms would be using thicker oil, weird additives or something of that sort. It seems the OP is exploring the structural/design causes of the oiling problem itself and proposing/testing solutions. Am I missing something?

[ermax]

Originally Posted by Capt Spaulding

I have to confess Mike, that I don't quite understand your point. It seems to me that addressing the symptoms would be using thicker oil, weird additives or something of that sort. It seems to OP is exploring the structural/design causes of the oiling problem itself and proposing/testing solutions. Am I missing something?

Maybe he didn’t read the whole thread?

[ETM_Shaman]

Originally Posted by solidsnake11

https://www.crossco.com/blog/prevent...ing-pump-inlet

https://www.machinerylubrication.com...avitation-wear

Very interesting read, thanks!

I think those links don't apply fully to our pump because those are gear pumps whereas ours is a gerotor pump with bilateral charge and discharge.
The oil flow to the pump pockets is very different. To tell you the truth we would need a pressure model showing how the oil's instantaneous pressure changes in our pump while it passes through our pump.
My main reason to sustain that in our pump cavitation is happening in the inlet side is that the erosion marks we've found (yours looks a lot like mine) in our pump are very typical of cavitation erotion and I can't think of what else could cause this. This together with my low inlet pressure measurements convinced me.

@Horrid_Funk's post about higher viscosity protecting from cavitation is also very interesting, although I think it's more related to cavitation damage itself (the erosion) than the starvation damage due to the pump's oil flow deteriorating when cavitation happens.

All in all I think there's still a lot to learn (at least for me) and the insight of someone with expert knowledge and experience in this particular matter would be greatly appreciated.

[CSG Mike]

Originally Posted by Capt Spaulding

I have to confess Mike, that I don't quite understand your point. It seems to me that addressing the symptoms would be using thicker oil, weird additives or something of that sort. It seems the OP is exploring the structural/design causes of the oiling problem itself and proposing/testing solutions. Am I missing something?

Originally Posted by ETM_Shaman

Please do elaborate!

The thicker weights are band-aid fixes for a symptom (cavitation). What is causing the cavitation? The increased pressure differential from the enlarged passages.

Are the enlarged passages even necessary? While my engine is only one data point, it is a very strong data point, given the number of hours on my engine, as well as the power level which may be comparable to the OP.

I've intentionally been running this until it fails, to see what ACTUALLY fails, when prepped to the best of my ability.

I don't have any of the issues the OP is having, and I believe many of the issues are self induced.

I run 0W20 and 5W30, depending on ambient temps, and my oil temps never exceed 230F. My turbo is oil cooled.


A flat 4 struggles with oil return; without a dry sump, I don't think increasing oil flow volume is a good idea; you'll just drain your pan faster without refilling it under cornering.

[Calum]

Originally Posted by ETM_Shaman

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 .

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.

3/4" is almost exactly 19mm. Just an FYI for anyone reading this.

[ETM_Shaman]

@Irace86.2.0Irace86.2.0 I've inspected and measured almost every oil gallery in this engine. I've also used the Hagen–Poiseuille equation to estimate and compare flow characteristics in the different galleries. Like you say, the most important variable is the radius of the gallery.

From all the galleries, I found that there are some drillings that seem to be used to control the proportion of flow that each part gets:

- Both heads have 8.0 mm drillings on their entrance
- Main bearing galleries 1,2,3,4,5 have: 5.5, 3.5, 6.5, 3.5, 5.5 mm drillings.

I think all galleries before this drillings should provide as low a pressure drop as possible to improve system efficiency: more overall flow, less pressure at the pump's outlet (which makes the PRV recirculate less oil), less friction losses, same or less power cost to drive the pump. For the inlet, to keep the pressure as high as possible (atmosphere in our case) is the objective in my opinion.

[Capt Spaulding]

Originally Posted by CSG Mike

The thicker weights are band-aid fixes for a symptom (cavitation). What is causing the cavitation? The increased pressure differential from the enlarged passages.

There seems to be a consensus that these engines have crank oiling problems. Element Tuning has apparently spent a bit of time and money developing a solution to it and are, rightfully, keeping it close. Looking at the pictures the OP posted I get the impression the cavitation had been going on for a while. If the inlet side of the pump was restricting the flow to the impeller and cavitation was resulting all the while and, in turn restricting pressure and raising temps. Some other posters have confirmed the cavitation problem in engines that have not been modified suggesting opening the outlet side is probably not responsible for it.


Are the enlarged passages even necessary? While my engine is only one data point, it is a very strong data point, given the number of hours on my engine, as well as the power level which may be comparable to the OP.

The necessity of enlarging/de-restricting the oil passages is not clear. If I recall my undergrad physics restricting flow reduces pressure on the downstream side of the restriction. In some situations that may be desirable. Again, a lot of people have problems with these engines grenading. The culprit seems to have something to do with low oil pressure to the crank. If removing or reducing restrictions increases pressure at the crank that goes some distance toward addressing that particular problem.

I've intentionally been running this until it fails, to see what ACTUALLY fails, when prepped to the best of my ability.

I don't have any of the issues the OP is having, and I believe many of the issues are self induced.

This is certainly possible, but the OP's problems appear to predate his modifications.


I run 0W20 and 5W30, depending on ambient temps, and my oil temps never exceed 230F. My turbo is oil cooled.



A flat 4 struggles with oil return; without a dry sump, I don't think increasing oil flow volume is a good idea; you'll just drain your pan faster without refilling it under cornering.

I'm not convinced that a global increase in oil flow is what he's shooting for or getting. He restricts flow to the driver side head to what appears to be the same orifice as the passenger side. If the overall flow in the system is increased, it will still face the restriction going to heads, increasing pressure on the upstream side which may pay dividends in the form of crank bearing survival.

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).

[solidsnake11]

Some useful data now would be a comparison of oils under vacuum and heat until they cavitate.

[solidsnake11]

Originally Posted by CSG Mike

The thicker weights are band-aid fixes for a symptom (cavitation). What is causing the cavitation? The increased pressure differential from the enlarged passages.

Are the enlarged passages even necessary? While my engine is only one data point, it is a very strong data point, given the number of hours on my engine, as well as the power level which may be comparable to the OP.

I've intentionally been running this until it fails, to see what ACTUALLY fails, when prepped to the best of my ability.

I don't have any of the issues the OP is having, and I believe many of the issues are self induced.

I run 0W20 and 5W30, depending on ambient temps, and my oil temps never exceed 230F. My turbo is oil cooled.


A flat 4 struggles with oil return; without a dry sump, I don't think increasing oil flow volume is a good idea; you'll just drain your pan faster without refilling it under cornering.

Originally Posted by CSG Mike

I run a stock radiator, with a fully ducted cooling stack, upgraded intercooler from JDL using a Garrett core, a GReddy (ducted, divorced) oil cooler, and Trackspec hood vents, along with a CSG fan shroud with SPAL fans and relays.

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.

[CSG Mike]

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.

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.