Oil Cooler/Reliability Mods

[ZDan]

Originally Posted by Dzmitry

That's really all that freaks people out with this platform, is this drop in oil pressure right near the peak RPM range unexpectedly. I am sure if pressures were fairly linear, this subject would probably lack much existence with these cars, regardless of higher temperatures. So to fix the problem, most people decided an oil cooler is the way (contrary to my belief, but who knows).

Well there's this:
https://www.ft86club.com/forums/showthread.php?t=134863

Suggests that restriction on the pickup side might cause oil delivery issues at high rpm. But also says stock engines fine up to 7600rpm. So I'm stickin with stock pickup tube for now...

[rice_classic]

Y’all should build race cars, then we can discuss this over beers on the paddock.

[ZDan]

Originally Posted by rice_classic

Y’all should build race cars, then we can discuss this over beers on the paddock.

If I was to race a car, it'd prolly be something like an F500!

More likely I'll go back to racing FZR400 and keep time-trialing the BRZ :P

[Dzmitry]

Originally Posted by ZDan

Well there's this:
https://www.ft86club.com/forums/showthread.php?t=134863

Suggests that restriction on the pickup side might cause oil delivery issues at high rpm. But also says stock engines fine up to 7600rpm. So I'm stickin with stock pickup tube for now...

Still have some reading to do there, haven't finished the full thread. But yes, stock pickup should be alright for your use. I mean there's no real solid solution to this for sure. As we've agreed, there is plenty of missing information on our cars, even with all the data people have collected. It's all great stuff though and certainly helps us make better decisions on how we treat our cars... at least some of us

[Petah78]

Originally Posted by Petah78

3. To add to the complexity, we have not even discussed "oil flow" in this equation. Adequate pressure doesn't mean a whole lot without proper flow. You need an adequate supply of oil in order to provide proper lubrication. I remember coming across an article where it stated the FI version of the FA20 oil pump has a ridiculously high flow rate (though i can't remember the exact metric). However, i never found any specs for the NA version of the FA20. And our oil pumps are positive displacement meaning the flow is fixed.

For reference, I found the thread where I read about oil flow of the FA20. Again, this is for the DIT version of the FA20 (wrx engine) hence I am not sure if it’s applicable to our engines.

https://bobistheoilguy.com/forums/th...u-fa20.301595/

[Dzmitry]

Originally Posted by Petah78

For reference, I found the thread where I read about oil flow of the FA20. Again, this is for the DIT version of the FA20 (wrx engine) hence I am not sure if it’s applicable to our engines.

https://bobistheoilguy.com/forums/th...u-fa20.301595/

Unless I should be reading that forum to find it, I believe that is just the turbo oil flow data. Nothing that we can relate to.

[Petah78]

Originally Posted by Dzmitry

Unless I should be reading that forum to find it, I believe that is just the turbo oil flow data. Nothing that we can relate to.

Yes, this data is for only the DIT Turbo engine but I thought it will be an interesting datapoint, especially if you take a look at the spec’d oil pressure @ 120c, 46PSI. Mind you, I have never found the legitimacy of the source though.

[Dzmitry]

Originally Posted by Petah78

Yes, this data is for only the DIT Turbo engine but I thought it will be an interesting datapoint, especially if you take a look at the spec’d oil pressure @ 120c, 46PSI. Mind you, I have never found the legitimacy of the source though.

You're right, I slightly misread this as the TURBO oil specs, rather than the turbo ENGINE oil specs. So here's what is interesting to point out again, that I have mentioned earlier. IF this is legitimate, they are spec'ing for fairly linear oil pressure here again. About 5 psi at 600 RPM and a little under 50 psi at 6700 RPM. Notice they aren't rating at 6000 RPM, where it may actually require around 50 psi. This could relate to the linear specs for the FA20 at 80C of 7.3 psi at 600 RPM and 73 psi at 6000 RPM. Which, again, makes the hot temperature pressures of the FA20 look bad at peak RPM when you have a sudden drop in pressure.

OR... might not relate at all and this could just be the characteristics for oil flow of a differently designed engine.

[ZDan]

Cushion at the bearings at rpm is largely from hydrodynamic wedge. Oil pressure needs to be sufficient to keep them and everything else fed with a continuous supply of oil.


http://www.kirbanperformance.com/pro...em-_pdf-44.pdf
https://www.substech.com/dokuwiki/do...ngine_bearings

[Dzmitry]

Originally Posted by ZDan

Cushion at the bearings at rpm is largely from hydrodynamic wedge. Oil pressure needs to be sufficient to keep them and everything else fed with a continuous supply of oil.


http://www.kirbanperformance.com/pro...em-_pdf-44.pdf
https://www.substech.com/dokuwiki/do...ngine_bearings

Yes, I believe this was lightly covered by rice_classic in the other thread you linked to earlier. These are nice reads, but they mostly back up information we have already covered. They certainly support the reason for wanting to use higher weight oil in high temperature/RPM applications.

[Autoxer62]

FWIW, after reading a lot of threads, I have settled on the following oil system mods for our intended STX build next year:

- Killer B oil pickup
- Moroso oil pan baffle
- Forester oil cooler
- Mobil 1 5w30

--Bryan

[rice_classic]

Pretty good video on hydrodynamic bearings. He briefly covers the sensitivity to wear at start up and shut down but does a great job explaining how the hydrodynamic wedge works. It helps visualize why maintaining proper viscosity is important when load is taken into account but also the importance of multi-viscosity oils to help minimize wear at start up.

[Dzmitry]

Originally Posted by rice_classic

Pretty good video on hydrodynamic bearings. He briefly covers the sensitivity to wear at start up and shut down but does a great job explaining how the hydrodynamic wedge works. It helps visualize why maintaining proper viscosity is important when load is taken into account but also the importance of multi-viscosity oils to help minimize wear at start up.

Just for the heck of it, here's a quick excel sheet I made some time ago to compare viscosities of various brands and oil weights back then when making my decision for oil choice. I live in SE PA, so climate varies from below freezing to sometimes over 100F in the summers. I'll sit down to watch this full video tonight, sounds like some good info.

[86league]

This didn't convert to google sheets seamlessly, but the data and basics of the graphs came through. For several 0w-20/5w-30 and I think an 0w-30 I took the quoted viscosity at 40/100C and did the Arrhenius Fit (v=A * exp(Ea/RT)) to get viscosity vs temperature.

https://docs.google.com/spreadsheets...it?usp=sharing

The 0w-20's are pretty tightly clustered, the 5w-30 oils have more variation.

I also did the same for the viscosity #'s blackstone labs gave me for my 0w-20 run and my 5w-30 run. The 5w-30 degraded more but stayed above the 0w-20 (naturally) and was close to fresh 0w-20 oils.

I also drew a horizontal line at 8cSt and a gray box from 210-220F on the excel file - that didn't make it to the google sheets graph. I can't remember why I put those in though...





The low temp graph shows how quickly things climb when temperatures get cold though. Thickest 5w-30 vs the thinnest 0w-20 is approaching 2x.



When things get hot the oil really thins out. My used 0w-20 is at about 3.5 at 266F, a new 5w-30 would be around 5. With a oil cooler pulling it back to 240ish F, you would be back to ~5 with the used 0w-20, and 7-8 for fresh 5w-30.

For my fair weather texas car I decided to run 5w-30 for a little more viscosity for high temps on track.