Oil weight for track only car with a lot of cooling?

[ZDan]

Originally Posted by RT-BRZ

I don't disagree at all. These same teams also run their cars for much longer periods of time and at much higher average RPM as well. The point is that they don't just expect to run thicker oil to compensate for those conditions.

The point is that they don't mind running 280F sump, 355F max oil temps for hours on end at 9000+ rpm. While reportedly running 0w20...

So, the answer to the basic question of thicker oil versus a cooler seems relatively straightforward. An oil cooler is the better way to address the issue.

I have a different conclusion: 275F indicated, ~255F sump oil temps are likely not a problem even for good synth 0w20, but I run 5w30 with high HTHS (3.5) anyway. IMO there is no issue here to begin with.

[CSG Mike]

Originally Posted by ZDan

The point is that they don't mind running 280F sump, 355F max oil temps for hours on end at 9000+ rpm. While reportedly running 0w20...



I have a different conclusion: 275F indicated, ~255F sump oil temps are likely not a problem even for good synth 0w20, but I run 5w30 with high HTHS (3.5) anyway. IMO there is no issue here to begin with.

At those temps, how much flow do you think they have, vs what we have in a FA20/FA24?

Food for thought, as if you want to look at the data, you should consider ALL the data, rather than just a few.

[Ultramaroon]

Originally Posted by CSG Mike

At those temps, how much flow do you think they have, vs what we have in a FA20/FA24?

Food for thought, as if you want to look at the data, you should consider ALL the data, rather than just a few.

Care to spoon feed me a bit?

[CSG Mike]

Originally Posted by Ultramaroon

Care to spoon feed me a bit?

NASCAR teams want power. FA2x guys want to make sure the engines don't blow up.

That hotter/thinner oil nets them a few more ponies; lubrication isn't the issue for them.

On the other hand, FA's aren't exactly looking for a few more ponies in an engine that's being replaced regularly.

[ZDan]

Originally Posted by CSG Mike

At those temps, how much flow do you think they have, vs what we have in a FA20/FA24?

Food for thought, as if you want to look at the data, you should consider ALL the data, rather than just a few.

There's no reason to think you'll get "more flow" running an oil cooler. You'll get less in fact due to greater restriction (minimal with a decent cooler but still).

Anyway, yeah, *flow* is the most important thing, and a lack of it due to RTV blockages and loss of pickup during cornering have been identified as issues. I wouldn't think running oil temps of 275F indicated, 255F sump should hurt or reduce "flow".

[blsfrs]

Originally Posted by ZDan

There's no reason to think you'll get "more flow" running an oil cooler. You'll get less in fact due to greater restriction (minimal with a decent cooler but still).

Anyway, yeah, *flow* is the most important thing, and a lack of it due to RTV blockages and loss of pickup during cornering have been identified as issues. I wouldn't think running oil temps of 275F indicated, 255F sump should hurt or reduce "flow".

All of this discussion makes me curious about oil flow.

Say at 5000 rpm, what is the difference in flow of oil at 200*f and 60psi versus flow at 260*f at 30psi?

[GrandSport]

Originally Posted by autoracer86

This video should help answer that. There is a few forum posts on the topic as well

STREET TEMPS
0W20 Redline

0w20 Redline 185F @ 800RPM 10PSI Oil Pressure
0w20 Redline 185F @ 2000RPM 35PSI Oil Pressure
0w20 Redline 185F @ 4000RPM 54PSI Oil Pressure
0w20 Redline 185F @ 7000RPM 65PSI Oil Pressure

10W30 Redline

10w30 Redline 185F @ 800RPM 19PSI Oil Pressure
10w30 Redline 185F @ 2000RPM 51PSI Oil Pressure
10w30 Redline 185F @ 4000RPM 65PSI Oil Pressure
10w30 Redline 185F @ 7000RPM 83PSI Oil Pressure

10W40 Redline

10w40 Redline 185F @ 800RPM 25PSI Oil Pressure
10w40 Redline 185F @ 2000RPM 64PSI Oil Pressure
10w40 Redline 185F @ 4000RPM 78PSI Oil Pressure
10w40 Redline 185F @ 7000RPM 91PSI Oil Pressure


TRACK TEMPS AFTER 9 LAPS @ 1 Minute 15 Seconds Per Lap
0W20 Redline

0w20 Redline 225F @ 800RPM 7PSI Oil Pressure
0w20 Redline 225F @ 2000RPM 30PSI Oil Pressure
0w20 Redline 225F @ 4000RPM 48PSI Oil Pressure
0w20 Redline 225F @ 7000RPM 43PSI Oil Pressure


10W30 Redline

10w30 Redline 245F @ 800RPM 7PSI Oil Pressure
10w30 Redline 245F @ 2000RPM 35PSI Oil Pressure
10w30 Redline 245F @ 4000RPM 52PSI Oil Pressure
10w30 Redline 245F @ 7000RPM 46PSI Oil Pressure

10W40 Redline (12 Laps)

10w40 Redline 265F @ 800RPM 8PSI Oil Pressure
10w40 Redline 265F @ 2000RPM 31PSI Oil Pressure
10w40 Redline 265F @ 4000RPM 55PSI Oil Pressure
10w40 Redline 265F @ 7000RPM 45PSI Oil Pressure





This is why I started to log my oil pressure so I could gather my own data and do what works for me.

It has always been clear to me that as the oil gets hotter the flow starts to drop in our cars. My own data logging backs this up as well.

Now if I ever do add an oil cooler to my setup beyond the OEM heat exchanger I can clearly see how much pressure drop the cooler itself caused. A good cooler should be less than 5PSI drop from what I am lead to believe. I know some setups can cause double digit drops but that's not the norm. Again do your own testing

So far for my use case I am able to keep temps and oil flow in a place on track I am happy with and the UOA have been good. But if my logs say otherwise I plan to add a proper oil cooler and go from there.

Without data you're just guessing...

Not to get into semantics again, but flow isn't pressure. Pressure is resistance. Flow is mass/volume per second.

[autoracer86]

Originally Posted by GrandSport

Not to get into semantics again, but flow isn't pressure. Pressure is resistance. Flow is mass/volume per second.

okay thanks

[ZDan]

Originally Posted by blsfrs

All of this discussion makes me curious about oil flow.

Say at 5000 rpm, what is the difference in flow of oil at 200*f and 60psi versus flow at 260*f at 30psi?

Difficult to know, as oil at 200F will be much thicker than oil at 260F. As @GrandSport notes above, pressure isn't *flow*.

But anyway, as always, if you are worried about low oil pressure at higher temps, easy enough to go up in viscosity. From what I've seen, people are not seeing oil pressure as low 30psi even running 0w20 at 270F indicated.

[GrandSport]

Originally Posted by ZDan

Difficult to know, as oil at 200F will be much thicker than oil at 260F. As @GrandSport notes above, pressure isn't *flow*.

But anyway, as always, if you are worried about low oil pressure at higher temps, easy enough to go up in viscosity. From what I've seen, people are not seeing oil pressure as low 30psi even running 0w20 at 270F indicated.

Yeah a lot of stuff starts happening with reduced thickness and lower density and viscosity of an incompressible fluid through an oil pump based on rpm.

The auto world has a weird way describing flow with the resistance to flow. Think forced induction. "I'm running 20psi." No one says "It's pushing X g/sec of airflow." 20PSI is an insane amount of airflow in my Viper. It's nothing in my NB Miata that is running a restrictor plate. It tells us absolutely nothing unless they are nearly identical engines.

Then again, the diameter of a tire is expressed as a function of half the width of the mm plus the wheel size in inches. I really cant even think of a dumber way to do it. Why is not just width/height/wheel size (like old school trucks) in the same units. 750/245/17. Then you'd have standardized heights instead of 748.27mm. But I digress...

[blsfrs]

Originally Posted by GrandSport

Yeah a lot of stuff starts happening with reduced thickness and lower density and viscosity of an incompressible fluid through an oil pump based on rpm.

The auto world has a weird way describing flow with the resistance to flow. Think forced induction. "I'm running 20psi." No one says "It's pushing X g/sec of airflow." 20PSI is an insane amount of airflow in my Viper. It's nothing in my NB Miata that is running a restrictor plate. It tells us absolutely nothing unless they are nearly identical engines.

Then again, the diameter of a tire is expressed as a function of half the width of the mm plus the wheel size in inches. I really cant even think of a dumber way to do it. Why is not just width/height/wheel size (like old school trucks) in the same units. 750/245/17. Then you'd have standardized heights instead of 748.27mm. But I digress...

It's interesting to see that your logs, at higher temperatures, show a decrease in pressure from 4k-7k. Why is that?

Is there a way that Bernoulli's principles are at work here? My basic understanding is that the higher flow rate of a fluid, the lower the pressure. I would try the math but I don't have the right crayons.

[GrandSport]

Originally Posted by blsfrs

It's interesting to see that your logs, at higher temperatures, show a decrease in pressure from 4k-7k. Why is that?

Is there a way that Bernoulli's principles are at work here? My basic understanding is that the higher flow rate of a fluid, the lower the pressure. I would try the math but I don't have the right crayons.

No crayons needed. You're overthinking it. It's just thinner fluid / less resistance. In general, you'd expect lower pressure with a hotter/thinner fluid.

[blsfrs]

Originally Posted by GrandSport

No crayons needed. You're overthinking it. It's just thinner fluid / less resistance. In general, you'd expect lower pressure with a hotter/thinner fluid.

Don't put your crayons away just yet.

I understand that with higher temperatures there is a decrease in pressure due to the decrease in viscosity.

Is there a corresponding increase in flow?

And, I'd still like to understand the drop in pressure from 4k to 7k rpm with higher temperatures.

[GrandSport]

Originally Posted by blsfrs

Don't put your crayons away just yet.

I understand that with higher temperatures there is a decrease in pressure due to the decrease in viscosity.

Is there a corresponding increase in flow?

And, I'd still like to understand the drop in pressure from 4k to 7k rpm with higher temperatures.

You're going to hit mechanical limits of the oil pump at a certain point (rpm), is my guess. It's going to be "volume flow limited." Same volume, lower viscosity, lower pressure, lower mass flow. The volume flow will certainly be constant for a given RPM across each "test."

BTW: with all this said, PRESSURE and not mass flow is important for oil because its oil pressure that keeps the rod bearings from rubbing on the crank. Flow and pressure are obviously related (Pressure = flow * resistance), but you can pump as much oil as you want- if there isn't pressure (force) to push back on the rod bearings, you'll have contact.

Oil doesn't so much "lubricate" rod bearings as it does keep the separate. It lubricates contact surfaces like rings/walls, camshaft lobes, etc.

Using fluids is a buffer, the same but different, is used in after burners. They burn at 4000 degrees. You know what doesn't burn/melt at 4000 degrees? absolutely nothing useful. But air still has to be ducted (and in the case of the F22, trust vectored). Imagine 4000 degree exhaust gas temps. What the hell do you do?
They push a layer of cold bypass air through thin little holes (that some super smart dude figured out where to put and how many to put in) so they get a near perfect laminar sublayer of air between the exhaust flap and the hot air. Effectively, it creates a buffer between the hot air and the exhaust flap. You can see the little holes and slits in the hot side of the convergent/divergent flaps
https://qph.cf2.quoracdn.net/main-qi...2dcc0148b17255