Oil pressure drops on race track in S corners

[zeroomega]

Originally Posted by mpg9999

Would you mind sharing your exact datalogging setup? I'd love to capture some oil pressure data while autocrossing.

Well the datalogger itself is AIM Solo DL2, which is the one of the go to choice for most of track rats. But how I connect it to GR86 is completely customized and complicated.

I got the AIM Solo DL2 connected to car's canbus through a DIY adapter, you can find my guide at https://docs.google.com/document/d/1...it?usp=sharing , alternatively you can get an off the shelf product from https://ansixauto.com/2022-brz-gt86-can-adapter/ , which convert the Can bus signal from ASC unit to an OBD2 port. The car's factory OBD port also works if you don't need to see oil temperature and brake pressure.

The oil pressure gauge I use is AEM 30-4407 which has a 0-5V (actual readout is 0.5V-4.5V) analog data log output. I just hack it with an ESP32 MCU (the thing on my dash in the video) and send the oil pressure data to AIM solo DL2 through the CAN bus. I am planning to open source my MCU project design when I have enough free time, but it would be a few months later. (Edited, the channel expansion hub does not seem to work with AIM Solo DL2)

Alternatively, you can just point a camera to your oil pressure gauge when you are on track. My friend did this and saw the exact same oil pressure drops at same locations.

@timurrrr probably has some ideas to log the oil pressure through RaceChronos, I am not familiar with that app but he is.

[KillerBMotorsport]

Originally Posted by zeroomega

Oil pressure sensor is installed at engine block oil galley port.

At the OEM location like here?



Just an FYI, this port is after the oil filter and the LH-Head feed. Your feedback is showing pressure after that pressure drop from those items.

[timurrrr]

Originally Posted by KillerBMotorsport

this port is after ... the LH-Head feed. Your feedback is showing pressure after that pressure drop from those items.

That would explain why a left-to-right transition affects the measured pressure?

[NoHaveMSG]

Originally Posted by KillerBMotorsport

Just an FYI, this port is after the oil filter and the LH-Head feed. Your feedback is showing pressure after that pressure drop from those items.

I didn't know that. Guess I am redrilling the timing cover too this winter.

[zeroomega]

Originally Posted by KillerBMotorsport

At the OEM location like here?



Just an FYI, this port is after the oil filter and the LH-Head feed. Your feedback is showing pressure after that pressure drop from those items.

Nope, the port near the throttle body:

It is a post filter location as well. I used to plug the pressure sensor at the oil cooler sandwich plate so I knew there the oil filter will causes some pressure drop.

[zeroomega]

The cause that right turns seeing oil pressure drops while left turns seem to be fine might due to the fact that the oil pickup tube is actually located slight to the passenger side. Oil sloshing to the driver side in right turns will be more likely to cause oil pickup not getting oil than sloshing to the passenger side in left turns. It could be a possible reason, but difficult to verify.

[BioRebel]

So...

1. It looks like some baffles in the pan should alleviate this issue
2. Do those numbers get low enough for long enough to cause issues?

[JDMChris]

Originally Posted by BioRebel

So...

2. Do those numbers get low enough for long enough to cause issues?

From the video, No. It didn't get low enough, for long enough for it to be concerning. Just make sure to run good quality oil while on track.

[nissanfanatic]

@zeroomega you ever figure anything out on this or learn anything more on causes/band aids?

[zeroomega]

Originally Posted by nissanfanatic

@zeroomega you ever figure anything out on this or learn anything more on causes/band aids?

I did continue to log the oil pressure and see similar oil drops patterns at other tracks and my friend (TrackAndBuild at Youtube) also did similar oil pressure logging.

The gen2 car will suffer oil pressure drop in hard right turns, especially at the top of a hill, not necessary in S corners. One possible explanation is that the oil pickup tube is installed slightly positioned to the passenger side. So in hard right turns, the oil pickup tube has higher chance of running out of oil in the pan due to oil sloshing than the left turn. And due to the fact that boxer engine is mounted, the oil pan is shallow, which makes the oil sloshing issue worse. The boxer engine design also makes the oil return flow back to the pan an issue. The oil delivered to the engine head took longer time to flow back to the pan than a normal inline engine (in which return oil will be pulled easily by the gravity).

Both me and TrackAndBuild tried oil pan baffles. He used the 2 layer Tomei pan baffle and he had a side by side comparison video at

.

I have the Syms Racing oil pan baffle installed. But I haven't had a chance to drive the car at Sonoma or Thunderhill West track again for a side by side comparison. I did tried it at Thunderhill East Cyclone last December (video:

).

The conclusion is, both oil pan baffles didn't eliminate the oil pressure drop in hard right corners/hill top. There seems to be a little bit improvement of minimal pressure but not by a lot. We suspect the issues is caused by the fact that the Subaru engine has relatively high oil flow rate (from TIS, FA24 oil pump is rated at 48.9qt/mins at 6000 rpm). Which means it will deplete a full oil pan (assuming the lower pan has 4qt of oil, the upper pan has oil but they won't be there in a turn) in roughly 5 sec. When car is in hard turns, the lower oil pan will have less oil due to sloshing. Due to the boxer engine design, under high lateral G load, the oil pumped to the one side of engine header will have trouble to return to the pan (the oil at left header will have trouble to return in a hard right turn and vice versa), which will make the oil level in the oil pan low, causing oil pressure drops. The situation of left turn is better than right turn is due to the oil pickup tube position, in left turns, the oil pump can still get oil even if the oil level in the pan is low. The oil pan baffle will slow down the oil sloshing (which is why we see some improvements), but it cannot help with the oil return flow (if not make it worse). We are not engine experts so this is just our guess. Please take it with a grain of salt.

I don't think there is any easy solution for this problem. A real solution will be either go for a AccuSump, which is very difficult to setup correctly and expensive. Or go for dry sump system, which Porsche uses in their boxer engines. There is no off the shelf dry sump system for FA24 engine as far as I know, and the way engine is placed in the bay will make it very difficult to build one. And it costs a lot as well. It may be cheaper to just run through engines.

My current ways to mitigate the issue is just trying to bump the minimal oil pressure a bit more. I have a oil cooler and I will monitor the temperature to avoid reaching 250F. I run 5w30 oil in winter track days and I am considering using 5w40 in hot summer days. If it still breaks, it breaks. Maybe just get a junk yard FA24 or get a K24 swap if it happens.

[KillerBMotorsport]

The Gen 1 cars have a similar issue, and I suspect we'll see it on the new FA24 WRX as well. We're a few weeks away from testing a prototype piece that I believe will address this issue.

Horizontal baffles historically don't provide good results on Suby engines. IMO, if you have oil starvation or surge, the last thing you want in the way of oil making it to the bottom of the pan, is a horizontal baffle. Subaru themselves battled this issue as they became more involved in motorsports. If you want to nerd out on this, call up a bunch of old WRX and STi oil pan part numbers and you can see, as the performance increased over the years, they ditched the horizontal baffles for straight through, or vertical guiding baffles. We also know from our own experience; the older flat bottom horizontal baffles pan has oil supply issues ~1 G lateral loading. Newer designs are good to ~1.3Gs, which is a decent upgrade for cheap.

The oil flow rates you're quoting, and what many others do (EJ guys do too), is from the Factory Service Manual. It is correct, BUT... it's bench data. It is NOT engine data. Oil flow through the engine is ~9 quarts/min at peak value/RPM, and ~7 quarts/min ~5,000 RPMs. A bigger pump does NOT increase flow through the engine either, another common misconception due to bench testing data being marketed as real life. The oil pumps Subaru uses have significant excess flow, and never need to be upgraded in my opinion. In fact, due to larger pumps flowing more oil through the bypass valve, they have a higher probability of aerating the oil at high RPMs.

As far as increasing oil pressure, we don't recommend it. Increasing pressure 10 psi will net you a 3-4% increase in flow, which is marginal at best. It does add additional wear to the pump and based on theory, adds more heat to the oil (but we've never tested for that). If you increase pressure too much, you can actually split the gerotor too (at cold start). I would set your max oil temp for 260°, with a good quality synthetic you have ample safety from being too hot.

The Porsche stuff is VERY different, and they've done many things over the years. Wet sump, dry, and hybrid, which is most common today. The GT cars do have a dry sump, but a moderately modified 911 GTS can lap a GT car and will have zero issues with oiling system performance. With the designs being so very different, I don't like to compare them, because addressing oiling system shortcomings requires very different paths vs a Suby engine. Additionally, the P-cars have a variable flow oil pump. It doesn't vary flow/pressure with RPM, but with torque load.

A 5-stage dry sump is the way to go on any Subaru engine but shelling out +$7,500 on a $30K car seems less than ideal. Plus, dry sump setups do require additional maintenance vs a wet sump. If you have a hard-core competitive race car and are pulling the engine every off-season for a refresh anyway, who cares, it's just one more item on your already long list. For a weekend warrior who wants 5-10 years of weekend track fun time without incurring racecar time commitment and costs, not so much.

[BioRebel]

Really liking this thread. Since mine is gonna double as my daily I'm far more interested in reliability mods than stuff that just gives me more power. I'll be adding whatever solutions come up in here to my list of stuff to install before track season starts in the spring here.

[zeroomega]

Originally Posted by KillerBMotorsport

The Gen 1 cars have a similar issue, and I suspect we'll see it on the new FA24 WRX as well. We're a few weeks away from testing a prototype piece that I believe will address this issue.

Horizontal baffles historically don't provide good results on Suby engines. IMO, if you have oil starvation or surge, the last thing you want in the way of oil making it to the bottom of the pan, is a horizontal baffle. Subaru themselves battled this issue as they became more involved in motorsports. If you want to nerd out on this, call up a bunch of old WRX and STi oil pan part numbers and you can see, as the performance increased over the years, they ditched the horizontal baffles for straight through, or vertical guiding baffles. We also know from our own experience; the older flat bottom horizontal baffles pan has oil supply issues ~1 G lateral loading. Newer designs are good to ~1.3Gs, which is a decent upgrade for cheap.

The oil flow rates you're quoting, and what many others do (EJ guys do too), is from the Factory Service Manual. It is correct, BUT... it's bench data. It is NOT engine data. Oil flow through the engine is ~9 quarts/min at peak value/RPM, and ~7 quarts/min ~5,000 RPMs. A bigger pump does NOT increase flow through the engine either, another common misconception due to bench testing data being marketed as real life. The oil pumps Subaru uses have significant excess flow, and never need to be upgraded in my opinion. In fact, due to larger pumps flowing more oil through the bypass valve, they have a higher probability of aerating the oil at high RPMs.

As far as increasing oil pressure, we don't recommend it. Increasing pressure 10 psi will net you a 3-4% increase in flow, which is marginal at best. It does add additional wear to the pump and based on theory, adds more heat to the oil (but we've never tested for that). If you increase pressure too much, you can actually split the gerotor too (at cold start). I would set your max oil temp for 260°, with a good quality synthetic you have ample safety from being too hot.

The Porsche stuff is VERY different, and they've done many things over the years. Wet sump, dry, and hybrid, which is most common today. The GT cars do have a dry sump, but a moderately modified 911 GTS can lap a GT car and will have zero issues with oiling system performance. With the designs being so very different, I don't like to compare them, because addressing oiling system shortcomings requires very different paths vs a Suby engine. Additionally, the P-cars have a variable flow oil pump. It doesn't vary flow/pressure with RPM, but with torque load.

A 5-stage dry sump is the way to go on any Subaru engine but shelling out +$7,500 on a $30K car seems less than ideal. Plus, dry sump setups do require additional maintenance vs a wet sump. If you have a hard-core competitive race car and are pulling the engine every off-season for a refresh anyway, who cares, it's just one more item on your already long list. For a weekend warrior who wants 5-10 years of weekend track fun time without incurring racecar time commitment and costs, not so much.

Thanks for your insight.

I have seen FA20DIT from a 2015 WRX to have similar oil pressure drop in same the pattern, but not as severe as my GR86. In our club, there will be a 2017 BRZ to have oil pressure data logging soon so we will see some comparison oil pressure data between FA20D and FA24D in the future.

For increasing oil weight. Factory TMG GT86 CS-V3 racecar is spec-ed to use RAVENOL 5w50 oil with a unmodified FA20 engine (a different ECU and intake/exhaust though and of course with an oil cooler). So likely anything below that won't harm. In our club, one guy runs 10w60 (the original spec oil weight for Japanese GT86 cup cars) for 16 trackdays without changing it. The UOA data looks pretty good. His car is mostly track only. We haven't yet to see a GR86 racecar oil weight spec but it should be similar. So 5w40 should probably be fine. The oil weight concerns also came from the oil pressure at hot days. With 250F oil temperature, the pressure logged from post oil filter position is start dropping below 45psi at 7k rpm. At daily drive 210F oil temperature, this number is more closer to 70psi.

For dry sump system. the reason I mention Porsche is that they are the only other company that uses boxer engine in production car and their sports car uses a different oil system and we rarely hear track side oiling issues from Porsche owners. Also Subaru factory backed GT300 BRZ racecar uses dry sump system as well. See: https://www.racecar-engineering.com/...aru-brz-gt300/ . This is an old article though, the Subaru's latest iteration of GT300 car now uses FA engines and gen2 body styles now. I see this as a signal that they knew the engine oiling is a weakness at circuit racing condition and beefed it up accordingly. But for normal HPDE enthusiast, go for dry sump is not cost efficient at all, unfortunately.

[Spektyr]

This is probably too simple a solution to work, but most engines aren't hurt by a little excess oil volume. Too much is obviously bad, but half a quart more than "full" won't damage an FA24 in normal driving.

Would that hold true in track driving and if so, would that maybe add a little extra time in those corners before the oil gets too low?