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BRZ Second-Gen (2022+) -- General Topics General topics for the second-gen BRZ


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Old 08-31-2021, 05:44 AM   #85
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When speaking of oil temps shouldn't we also be mentioning oil pressure as well?

Do you all mean that a good synthetic oil will be fine at high temps and still maintain good pressures?
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Old 08-31-2021, 07:28 AM   #86
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Originally Posted by Thefalls View Post
When speaking of oil temps shouldn't we also be mentioning oil pressure as well?

Do you all mean that a good synthetic oil will be fine at high temps and still maintain good pressures?
Should be fine if you run temperature-appropriate viscosity grade, known-good synthetic. I run 5w30 during track season.

From post #50:
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Originally Posted by ZDan View Post
I'll say it yet again, you should consider operating temps when selecting oil viscosity.

But even aside from that, we do have at least some evidence that running the same oil with and without an oil cooler results in the *same oil pressure*. I.e. the pressure drop due to the oil cooler is about what it is due to 275F oil being hotter than 250F oil:
https://www.ft86club.com/forums/showthread.php?t=91820

Last edited by ZDan; 08-31-2021 at 07:43 AM.
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Old 08-31-2021, 09:06 AM   #87
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Originally Posted by Kona61 View Post
I mean, color is a data point… For example, you can clearly tell burnt ATF vs new simply by the color, or old oil vs new.
Oh, are we running ATF in our engines now? Does it need a cooler for track use?

https://parts.olathetoyota.com/blog/...lors-represent

"Oil color doesn’t tell us everything, but there are things to watch for."
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Old 08-31-2021, 09:09 AM   #88
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Originally Posted by TommyW View Post
This "well the oil can handle it" narrative is almost comical. Heat is the enemy in almost all mechanical applications. Oil is not really even in the overall equation. Go to any track. The hoods are open to let heat out and never open because, well things are just too darn cool.
Not really. Look at the oil temps any modern performance cars run ON THE STREET.

The thermostat for the stock oil on my 135 wasn't even set to open until 240 degrees. And routinely ran 245-250 just in street driving.

Modern engines run much higher temps because they are more efficient at making power and produce less emissions. This is why you don't see people putting in lower temp thermostats for the radiator like the did in cars up until the early 2000s.
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Old 08-31-2021, 09:35 AM   #89
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If we're going to be talking oil pressures, then we've got to dispel what it is we are really looking for.

What you really want to know is if parts that need lubrication are getting lubrication. Which means oil needs to flow to and from said parts. What you really care about is oil FLOWRATE. However, oil flowmeters at various points in the lubrication system can be MASSIVELY costly so people tend to just measure pressure because it is cheaper and far less complex. A liquid pressure sensor is hella cheaper than any inline flowmeter. I've aided in the design of many HVAC systems for critical centers for over 16 years so I know the difference in costs.

This is why people tend to focus on PRESSURE and not the real thing, flowrate.

Now that the history lesson is over, if we're talking pressure, we gotta understand how pumps work.

The reason why most systems have a target pressure is because assuming you only have one fixed system (ie: no new routes for flow are suddenly added or taken away), for a specific flowrate, you have a specific pressure to overcome in order to hit said flowrate. This is the basic minimum resistance the system has to flowrate. All closed loops (ie: a self contained) have resistance to flow. What you are doing is saying if the system is perfectly normal, when I have X liters per second of oil flow, I see Y kilopascals of oil pressure out of the oil pump.

Now we fold in temperature and how that affects our fluid, the oil. When oil heats up, it thins out (viscosity drops). This means that it requires LESS power to pump said fluid. Unless your pump has fancy variable speed control, its only going to operate at a fixed speed and there's a pressure relief somewhere to prevent it from dead heading or over pressurizing the system. This means as viscosity drops (thins out), for the same speed of the pump, you will push out MORE flow. Depending on the system curve and the maximum power the pump can do (the system's known resistance to flow mapped out), you MIGHT be able get to the original pressure at a much higher flow. Most of the time, it is likely to just push out HIGHER flow BUT at lower pressure. I doubt the pump curve for the OEM oil pump is oversized enough to hit the original pressure setpoint at that much higher of a pump flow (not enough info to make this call).

The reason I got into this rant is because you can keep pressure high and STILL HAVE ZERO FLOW - this is called dead heading a pump. Also, higher pressure could also mean system is restricting flow. Too thick of an oil, your pump has to get overworked (ie: requires more hp to run than it has available) and you may not even get right pressure OR right flow.

The engineers have figured out a lot of details in designing this engine and oil flowrates are one of them. Unless you have full on data stating your facts, its all conjecture.

If you truly believe your oil temps are excessive (situation dependent), get a oil cooler but don't decry the OEM solution as garbage or a persisting problem. They did a LOT of work to get to where they are - your use scenario + environment might be an outlier.
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Old 08-31-2021, 10:04 AM   #90
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How much does your new oil cooler restrict flow? I bet no one knows that answer.
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Old 08-31-2021, 10:14 AM   #91
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Quote:
Originally Posted by Tokay444 View Post
How much does your new oil cooler restrict flow? I bet no one knows that answer.
THIS.

Any radiator will add pressure drop. Any additional lines will add pressure drop.

Higher pressure drops mean less flow at the same pump speed.

Slightly off topic buuuut here's a possible solution, you can always put a differential pressure sensor across the oil pump before you add the oil cooler and after to see where your oil pump performance point has shifted to.
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Old 08-31-2021, 10:43 AM   #92
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I'm NOT changing it just because of heat.

Then why are you changing it every track day?
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Old 08-31-2021, 12:45 PM   #93
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Then why are you changing it every track day?
So that I have fresh oil for daily driving.
Depending on how old the oil is, I've even changed it before and after a track day or two.
Heat cycles are not the oil measure of an oil's integrity.
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Old 08-31-2021, 01:01 PM   #94
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Originally Posted by Tokay444 View Post
How much does your new oil cooler restrict flow? I bet no one knows that answer.
Quote:
Originally Posted by Frost View Post
THIS.

Any radiator will add pressure drop. Any additional lines will add pressure drop.

Higher pressure drops mean less flow at the same pump speed.
See post #86 (& #50)^^^
Without oil cooler, ~7.5 psi/krpm at ~272F max oil temp,
Same 5w30 300v oil *with* oil cooler, ~7.5 psi/krpm at ~250F max oil temp.

So according to this data, it looks like pressure drop due to oil cooler is close to exactly the same as pressure drop due to hotter oil with no oil cooler...
https://www.ft86club.com/forums/showthread.php?t=91820
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Old 08-31-2021, 01:01 PM   #95
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@Frost, then are you matching the viscosity charts of your oil at 270 to the spec that Subaru has for the tolerances of the FA24 (and I am not sure if RPM is dictated in this spec)?

I honestly have no clue if that data is available.

It feels like if we are really talking about the main problem - maintaining a film between rotating metal pieces at a certain temperature and pressure to avoid wear while still having some overhead over the usable life of the oil in that condition.

I know this is a topic older than time, and I am more than happy to look into this more but I am not aware if general users are given the specifics to make a claim that 270*F is OK with Oil-X at weight Aw-B to maintain an appropriate film with C-hours and a max of D thermal cycles of the oil.

When in doubt, why not run cooler and conservative? Then the problem is no longer a min/max or limits issue?

Thanks for your insight.
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Old 08-31-2021, 01:12 PM   #96
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Originally Posted by dowroa View Post
@Frost, then are you matching the viscosity charts of your oil at 270 to the spec that Subaru has for the tolerances of the FA24 (and I am not sure if RPM is dictated in this spec)?

I honestly have no clue if that data is available.

It feels like if we are really talking about the main problem - maintaining a film between rotating metal pieces at a certain temperature and pressure to avoid wear while still having some overhead over the usable life of the oil in that condition.

I know this is a topic older than time, and I am more than happy to look into this more but I am not aware if general users are given the specifics to make a claim that 270*F is OK with Oil-X at weight Aw-B to maintain an appropriate film with C-hours and a max of D thermal cycles of the oil.

When in doubt, why not run cooler and conservative? Then the problem is no longer a min/max or limits issue?

Thanks for your insight.
I think the conversation is not so much about being in doubt and running an oil cooler, but simply whether someone NEEDS one or not based on their conditions. @Frost said himself to get an oil cooler if you feel that your oil temps are excessive.

I don't think anyone here is really trying to claim the specifics you speak of.
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Old 08-31-2021, 01:25 PM   #97
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Quote:
Originally Posted by dowroa View Post
@Frost, then are you matching the viscosity charts of your oil at 270 to the spec that Subaru has for the tolerances of the FA24 (and I am not sure if RPM is dictated in this spec)?

I honestly have no clue if that data is available.

It feels like if we are really talking about the main problem - maintaining a film between rotating metal pieces at a certain temperature and pressure to avoid wear while still having some overhead over the usable life of the oil in that condition.

I know this is a topic older than time, and I am more than happy to look into this more but I am not aware if general users are given the specifics to make a claim that 270*F is OK with Oil-X at weight Aw-B to maintain an appropriate film with C-hours and a max of D thermal cycles of the oil.

When in doubt, why not run cooler and conservative? Then the problem is no longer a min/max or limits issue?

Thanks for your insight.
There are disadvantages of running oil too cold (which I'm in an environment where it can legitamately happen). I don't trailer my cars to the track. This is why in my post, I said if your circumstances AND environment dictate it, get it. I'm not making general statements that the oil cooler is dumb. I am annoyed that people are calling the Subaru/Toyota team for failing at correcting a perceived problem, when it really isn't a problem for a majority of people.
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Old 08-31-2021, 01:30 PM   #98
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@Frost, gotcha sir.

Also, if I was an automotive engineer that isn't designing this as a track car, I think there are some assumptions the user isn't driving WoT for 20 mins as a time. I am not sure they design or test to that specification.

With that stated, thermostats are a good thing. Pressure drop is a real thing. Agree with understanding your variables, concerns and data before just `doing a thing`.

Thanks for your insight.
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