Oil pressure drops on race track in S corners

[Blighty]

Originally Posted by KillerBMotorsport

Maybe. Consider this... The starvation issue is nearly always on breaking or steady right turns, and cresting right turns. Both have lite throttle applications if any. Loosing oil pressure at these times is not nearly as consequential and losing it under full load at corner exit when recharge occurs. You have to pick your poison here, but I will always choose lower oil pressure with no/low load over lower oil pressure under full load. Reassuring to see higher end sports cars with variable flow oil pumps doing the same; dropping pressure at throttle lift and no-to-light loads.

I would highly recommend any testing you do, be in a controlled environment, not on-track.

I thought that the biggest issue is more than they can only help so much, as in only as much as you can store in the accumulator. I would of thought that setting the min PSI for refill helps a lot with ensuring you don't bottom out the pressure.

How would one create a controlled environment? I'd hazard a guess that testing on track where you know the exact conditions to your issue exist, with careful monitoring might be the only practical was to test, but interested in your thoughts.

[zeroomega]

Originally Posted by KillerBMotorsport

Couple of questions here... How many degrees of a turn is T4, and is it banked? In short, how many seconds are you IN the turn and at what lateral load? Sustained banked corners like at Daytona and the Nurburgring's Carousel are great examples of corners that eventually (at some level of experience, mods, etc.) causes problems with the Suby H4 engines.

Laguna T4 as far as I can tell is flat. I never did track walk there so I could only say from driving perspective. From turn in (lateral g increase) to turn out (lateral g decrease) it takes about 4 secs. With 86cup spec tires we only pulling 1.0g most of the times there.

I assume "positive" banking like the oval tracks should slightly improve the oil pressure drops since the gravity will slightly make the oil in the pan more flat, so the pickup is less likely to encounter oil starvation. I could be wrong cuz my calculation uses an ideal square oil pan model and didn't consider oil return flow under high lateral g.

[KillerBMotorsport]

Originally Posted by Blighty

I thought that the biggest issue is more than they can only help so much, as in only as much as you can store in the accumulator. I would of thought that setting the min PSI for refill helps a lot with ensuring you don't bottom out the pressure.

That is one issue depending on how much time it's emptying, but also as the accumulator empties, the pressure out of it decreases, because the plunger inside uses a spring or air pressure as the force that empties the accumulator. As that plunger moves, the output pressure decreases.

Originally Posted by Blighty

How would one create a controlled environment? I'd hazard a guess that testing on track where you know the exact conditions to your issue exist, with careful monitoring might be the only practical was to test, but interested in your thoughts.

Definitely NOT on track. Again, a pressure loss while cornering is not a big deal, under WOT (full load) it is a big deal.

On the dyno is where it needs to be done. It's a controlled environment. You monitor inlet/outlet pressure and flow. You do pulls and recharge the accumulator at various RPM points and watch what happens.

You could test on track if you had the right sensors and feedback solutions in place, but without, you're just speculating on what is happening.

[KillerBMotorsport]

Originally Posted by zeroomega

Laguna T4 as far as I can tell is flat. I never did track walk there so I could only say from driving perspective. From turn in (lateral g increase) to turn out (lateral g decrease) it takes about 4 secs. With 86cup spec tires we only pulling 1.0g most of the times there.

That's lower than I would have expected. 4 seconds is not an excessive cornering time.

Originally Posted by zeroomega

sume "positive" banking like the oval tracks should slightly improve the oil pressure drops since the gravity will slightly make the oil in the pan more flat, so the pickup is less likely to encounter oil starvation. I could be wrong cuz my calculation uses an ideal square oil pan model and didn't consider oil return flow under high lateral g.

Well, this is where we get into the flaws of boxer engines... When running banks, it's like adding considerable aero to the car, so lateral loads go up. The boxer engine, specifically the head facing the outside of the turn, fills with oil that does not drain back into the pan. On a more 'normal' track the side loading typically is over before any significant pooling in the heads. On a LONG-banked turn, it can be very problematic.

I don't know (yet) at what levels the stock setup has lateral loading limitations. I can say from our EJ STi experience, the OEM setup is good for ~1.2Gs (track dependant). Our standard performance pan bumps that up to ~1.6Gs, and our Super-G is for anything beyond that.

[KillerBMotorsport]

Another member had questions on the backside. Thought it might be relevant to some folks in here too.

[Dzmitry]

Originally Posted by nissanfanatic

@Dzmitry was the data collected with the engine under full load for each of the data points you posted (obv excluding 800/2000 RPM)? Or, inverse, was each of them collected while free revving the engine?

Wondering how AVCS behaves under varying load...

I believe they were WOT, but have to go back and watch the video. I agree with KillerB that we won't have any good answers here until a tuner gives us a better understanding on AVCS behavior with respect to other variables. But after a decade of this car existing, I have always believed that these oil pressure drops have to be normal in some way with respect to higher oil temps. I'm sure we can get to the bottom of that soon enough. It seems that a greater concern would be related to the pressure drops during cornering, as that is clearly something that has been known to occur under high lateral loads as the OP describes.

[KillerBMotorsport]

Originally Posted by Dzmitry

It seems that a greater concern would be related to the pressure drops during cornering, as that is clearly something that has been known to occur under high lateral loads as the OP describes.

Has anyone killed an FA24 yet? Or the better question, has anyone killed an FA24 due to oil starvation?

[nissanfanatic]

Originally Posted by KillerBMotorsport

Has anyone killed an FA24 yet? Or the better question, has anyone killed an FA24 due to oil starvation?

Only one I've seen that developed rod knock is here:

/threads/2022-brz-rod-knock-and-positive-subaru-experience.3025/

And that obv is likely due to running factory 0w-20 for multiple track days. I'd imagine that oil had sheared down to who knows what viscosity.

But I also wondered this as there has to be quite a few people running much higher grip than SX2's. Also, is it confirmed that this issue doesn't exist on the first gen? I know it's a different pickup design...

[JDMChris]

Originally Posted by nissanfanatic

Only one I've seen that developed rod knock is here:

/threads/2022-brz-rod-knock-and-positive-subaru-experience.3025/

And that obv is likely due to running factory 0w-20 for multiple track days. I'd imagine that oil had sheared down to who knows what viscosity.

But I also wondered this as there has to be quite a few people running much higher grip than SX2's. Also, is it confirmed that this issue doesn't exist on the first gen? I know it's a different pickup design...

Haven't seen an issue ever on the first gen on race tires on the banking of Auto Club or Daytona. (Both Left handed banked turns for extended periods of time 120-140mph)

Also no issue at Auto Club on 200TW tires in the 2nd gen.

[nissanfanatic]

Originally Posted by JDMChris

Haven't seen an issue ever on the first gen on race tires on the banking of Auto Club or Daytona. (Both Left handed banked turns for extended periods of time 120-140mph)

Also no issue at Auto Club on 200TW tires in the 2nd gen.

No issue as in no failures? Or no issue as in you logged oil pressure and observed no drops in pressure similar to those shown in this thread?

You happen to have any data on what sustaned lateral accel is on those banked turns?

[zeroomega]

Originally Posted by JDMChris

Haven't seen an issue ever on the first gen on race tires on the banking of Auto Club or Daytona. (Both Left handed banked turns for extended periods of time 120-140mph)

Also no issue at Auto Club on 200TW tires in the 2nd gen.

Local 86cup fb group. Gen1 car with 2015 engine. I don't know the owner so I don't know more details. I guess now you see one example.

[smoltz]

Originally Posted by KillerBMotorsport

Has anyone killed an FA24 yet? Or the better question, has anyone killed an FA24 due to oil starvation?

I know someone that believes oil starvation was the cause of death on their FA24. Warranty was denied, they ended up finding a used motor. Running high grip tires. They had FA20 cars prior and never any issues on similar tire setup.

[KillerBMotorsport]

Always tough to trust second hand or partial info. This is where speculation gets the worst of us.

Is there any comprehensive data logging with any of these failures?

Are there any images of the main bearings?

Do the rods look over heated or warped from excessive heat, or just damaged?

When there IS oil starvation, there are heat tells in the bearings, rod, main, and sometimes even the crank will warp some. Since the mains are fed before the rods and loose oil flow first, starvation almost always leaves a tell on the main bearings. With ONLY rod bearings damaged and no data or heat signatures anywhere, you really need to tear down the entire engine and have some one that knows what they are looking for review to find the failure mode. With solely rod bearing failure, I would more likely suspect rod knock.

Mahle has a nice bearing failure guide if anyone wants to dork out on this stuff.

[JDMChris]

Originally Posted by nissanfanatic

No issue as in no failures? Or no issue as in you logged oil pressure and observed no drops in pressure similar to those shown in this thread?

You happen to have any data on what sustaned lateral accel is on those banked turns?

Both. I will check with our data engineer to see if we still have that available, as I don't know it off the top of my head.