oil pressure

[NoHaveMSG]

Originally Posted by JIM THEO

I see, it's a designation of oil suction problem and oil path, what about something like this:

Comparison between OEM and aftermarket oil suction:

Yeah, it seems to have more to do with the oil system. I think as long as you are not doing long sustained redline it is fine even at 250+f oil temps I was still getting around 58psi at 7800rpm with 5w30. At around 230-240f it was 60psi. Was peaking at 5800 at over 70psi. Depending on oil temp my peak pressure would shift a couple hundred rpm either way.

That would help in turns more then an oil baffle. I do notice that if the dipstick is not right at the full mark it drops oil pressure in high g turns. I plan on buying one.

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[JIM THEO]

Usually 0W20 gives lower pressure at high rpms which is exactly the opposite from your findings!
Do you know if OEM oil pump can cope with the increased volume of oil, they are designed as a whole system and I don't think is coincidence the oil pickup shape/size.

[NoHaveMSG]

Originally Posted by JIM THEO

Usually 0W20 gives lower pressure at high rpms which is exactly the opposite from your findings!
Do you know if OEM oil pump can cope with the increased volume of oil, they are designed as a whole system and I don't think is coincidence the oil pickup shape/size.

I was getting lower peak pressure with 0-20 at temp but I don't remember the oil pressure dropping off like this. I do remember it still wasn't severe enough that I was overly concerned about it. It's been a year since I ran 0-20 and I was not making a good habit of documenting then.

I am going to try some of the mods in the other thread on my spare motor and see if it helps. It won't be exact since it will be a different motor but it will at least give me an idea.

Either way in NA form I wouldn't be afraid to thrash the car on either weight oil as long as I have a cooler and I'm running quality oil.

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[JIM THEO]

It would be interesting to see oil pressures in a motor with the upgraded Killer-B oil pick up and compare.

[PuslarBrrrz]

[ame]https://www.youtube.com/watch?v=cDfFJ5s6IDg[/ame]

[NoHaveMSG]

Originally Posted by PuslarBrrrz

Weird that I see a drop at high rpm on my gauge and they show an increase. Wonder if there is something in my setup that is causing it.

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[Legend@wheels]

Originally Posted by JIM THEO

It would be interesting to see oil pressures in a motor with the upgraded Killer-B oil pick up and compare.

brz's owners also use pickup tube?(thought only sti's does that!).
thought the brz's engines are fair more reliable .
and back to subject-
i think 0w30 might be better and a good solution of 020 and 530 .
cuz its thicker when needed(high temps)and its thinner when needed(cold starting)better oil pressure and flow thru the system.
im really considering to use 0w30 oil next time i service my car!(hopefully to find some decent 0w30 oil)

[JIM THEO]

Originally Posted by Legend@wheels

brz's owners also use pickup tube?(thought only sti's does that!).
thought the brz's engines are fair more reliable .
and back to subject-
i think 0w30 might be better and a good solution of 020 and 530 .
cuz its thicker when needed(high temps)and its thinner when needed(cold starting)better oil pressure and flow thru the system.
im really considering to use 0w30 oil next time i service my car!(hopefully to find some decent 0w30 oil)

STI owners use aftermarket oil pick up as the factory one tends to crack in the welding or when they upgrade oil pumps etc for high power applications.

Imho 0W30 is the worst choice between the two for the twins especially for your climate conditions, the wider viscosity means more additives in the oil and you know what suffers first at high temps?
Just to give you an example, compare the two oils from Redline, 0W30 is worst in every aspect except the tiny difference in cold start expressed by Vis @ 40C but in critical indexes HTHS, Noack volatility and TBN (not mentioned in tech specs) is worst:
https://www.redlineoil.com/0w30-motor-oil
https://www.redlineoil.com/5w30-motor-oil
The same applies to Motul V300 5W40 and 0W40:
https://s3-eu-west-1.amazonaws.com/m...pdf?1492017370
https://cdn.opieoils.co.uk/pdfs/motu...ophy-0W-40.pdf
In every case you are covered with 0W30 V300 for track use, personally as we also face very high summer temps (sometimes >40C) I'll stay with Redline 5W30 and see if I can log oil pressure in my service with a temporary fitted sensor they have.

[7 skulls]

https://forums.nasioc.com/forums/sho....php?t=2714154

This oil selection thread on NASIOC has lots of great info. See section 9 for info on the Stribeck Curve and Temp/Viscosity graph.

"Extrapolating from Subaru's recommendations
So, Subaru makes recommendations for “normal” use, but what are your usage conditions? How are they different from Subaru's baseline? How do those conditions affect oil choice? Answering those questions will require some informed speculation and will leave substantial ambiguity. If you're towing a trailer into the mountains of Denali National Park in January or track driving at Road Atlanta in the summer, the “best” oil is likely different from what's in the manual. Ideally, we could measure oil temperature under various conditions to inform our choice, but until now most Subarus were not equipped with oil temperature sensors, and most owners didn't invest in aftermarket ones. Luckily, newer FA series engines (FB too?) are equipped with an oil temperature sensor which can be read using a scan tool, owners of such cars who are truly interested can monitor their oil temperatures and make a more informed choice. Most owners though will have to make due with generalizations about how the car is used.

What can we assume about how Subaru designed the hydrodynamic interfaces of the engine? Well, we can assume they used the Stribeck curve, remember that? Remember point 'a' the transition between mixed-film and hydrodynamic lubrication which happens at a certain viscosity? Notice how the friction increases quickly as we move into mixed-film lubrication and much more slowly as we move farther into the hydrodynamic regime? Being mixed-film lubrication, increased friction also indicates increased wear, while increased friction in the hydrodynamic regime reflects only increased hydrodynamic drag without increased wear. It is therefore much preferred to stay in the hydrodynamic regime even if it means slightly increased friction, and Subaru's engineers know that. We can therefore assume that Subaru designed the engine so under “worst-case” conditions the operating point of the engine will be at point 'a' and all other times will be to the right. We can further assume that this condition will be at maximum oil temperature, which in terms of piston cooling will be sub-optimal. The engine will be designed to survive these conditions, but not thrive under them. This is a simplistic, but instructive view.

This image has been resized. Click this bar to view the full image. The original image is sized 816x576.

Figure 7 – The Stribeck Curve
1 – Boundary lubrication
2 – Mixed film lubrication
3 – Hydrodynamic lubrication

So what exactly is “worst-case” operation? Subaru has given us some clues in the owners manuals by indicating that thicker oils are recommended for heavy use and high temperatures. From that clue we can infer that the viscosity of the oil recommended for the car at the temperatures seen during moderately heavy street use puts us a bit to the right of point 'a' on the Stribeck curve, for a little bit of safety margin. Such use would be twisty-road carving on a hot day (say 90° F) in a car that is not heavily loaded and not climbing a mountain. Any decrease in viscosity, either through shearing or higher oil temperatures, risks using up the safety margin and moving toward mixed-film lubrication.

In reality it's not quite as bad as it seems. Notice the dashed line to the left of point 'a'? That's the actual friction curve of real motor oil. The idealized Stribeck curve is for a pure hydrodynamic lubricant, one without anti-wear or friction modification additives, an actual oil will not see the large increase in friction in the transition to mixed-film lubrication because it contains anti-wear and friction modification additives. So a small amount of mixed-film operation will not result in bearing death, but being diligent owners we want to avoid the situation any way.

So, if you use your car only moderately hard, the oil recommended in the owner's manual should provide good service, but the definition of “moderately hard” is ambiguous, and the consequences of poor selection are asymmetric; an oil which is too thick costs you a little fuel economy and a couple horsepower, an oil which is too thin causes bearing wear or possibly a spun bearing. Given that, selecting an oil which is slightly thicker than we really need is entirely rational in pursuit of a bit of safety margin, but there's a problem.

At the same temperature, a thicker oil will provide a stronger hydrodynamic film, but it will also run hotter under the same operating conditions. The additional work done by the engine to move the thicker oil and spin rotating parts through it ends up as heat in the oil. A 40 grade oil won't run so much hotter that it's operating viscosity is lower than a 30 grade, but we can't simply compare KV100 values and assume they represent operating viscosity. There's a delicate balancing act here, oil that's too thin risks bearing wear, oil that's to thick promotes detonation by keeping the pistons hotter.

That means the range of optimum oil temperature is quite narrow, while the range of acceptable oil temperature is much wider. To keep water and fuel out of the oil we want the oil temperature above 212°F (the boiling point of water), but we want the pistons as cool as possible, so optimum oil temperature is in the range of 215-230°F. Operating temperatures down to 170°F or so occur in low load running in cold weather and generally aren't a problem. Temperatures up to 270°F occur in heavy use in high temperatures and usually aren't a problem either. This thread from FT86 club takes advantage of the oil temperature sensor in the 86 twins to give us some decent information on typical oil temperatures: http://www.ft86club.com/forums/showthread.php?t=29965

Taken together, these factors indicate that wise oil selection will be at most two categories thicker than recommended by Subaru. For engines which recommend 0w20, a HD 30 grade is about the thickest wise choice, for 5w30 engines, a 40 grade is about the thickest wise choice. 40 grade oil in a 0w20 car or 50 grade in a 5w30 car could be used in the event of infrequent very heavy use, but is definitely sub-optimal. An examination of viscosity-temperature behavior will show us why.

Here's a viscosity chart with typical oils from the relevant categories zoomed in on the normal operating temperature range. We can see that stepping up one category results in an oil which has the same viscosity about 20°F (~10°C) warmer.


Figure 8 – Operating Temperature Viscosities

If Subaru recommends 0w20 for your engine, the bearings should be very happy with 7.5 cSt oil, if we put RC 5w30 into the engine, the oil temperature can rise to 240°F before the oil viscosity drops below 7.5 cSt, now we're at the upper limit of optimal oil temperature. With HD 5w30 the 7.5 cSt temperature rises to 260°F, basically the upper limit of acceptable. In other words, using a 40 grade oil implies we will be operating the engine at unacceptably high oil temperatures. And since using a heavier oil encourages higher operating temperatures, we're compounding the problem. So, if you think you need 5w40 in your car that calls for 0w20, what you really need is an oil cooler, possibly a big one. "

[ZDan]

Originally Posted by PuslarBrrrz

From the linked video:

"OK, so we've already established the fact that if you track this car, stock, with or without forced induction, you need an oil cooler on the car, there's no way around it."

Stating the same thing again and again does not establish it as a fact.
I have yet to see any evidence or analysis suggesting that an oil cooler is required for tracking these cars. If it's out there, somebody provide a link with more substantial evidence than the same old "you must have an oil cooler" mantra repeated ad infinitum.


http://garage.grumpysperformance.com...iscosity.1334/
According to this source, at 220°F 0w20 viscosity is ~8 cSt, figure that is what the engine tolerances are designed for.
At 270°F:
0w20 viscosity has dropped to ~4 cSt,
Xw30 ~5-5.5 cSt,
Xw40 ~6.5-7 cSt,
15w50 ~8 cSt or about the same as 0w20 at 220°F.

I ran 5w30 for 10 out of 13 track days this year. For the other 3 track days I ran 0w20 because of poor planning/preparation on my part...

Next year I'll run 30- or 40-weight at every track day. Given the relatively limited number of track events, shortish duration of stints, and daily-driver status of the car, I don't think 15w50 is warranted in my case. I still have no plans to get an oil cooler...