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Another potential dead horse to beat: right turn oil starvation

2K views 19 replies 12 participants last post by  fdps  
#1 ·
Assuming this is a potential issue on 2nd-gen cars, has anyone realized this with a stock vehicle (tires, suspension, drivetrain) outside of track use?

I get this includes a bunch of "ifs" but if for sh1ts & grins, one wanted to drive a highway cloverleaf repeatedly until they ran out of gas, will the oil pickup ever starve?
 
#6 ·
I just overfill half a quart to avoid this. I realize it's a hot topic and people either insist it can not happen or are so nervous they don't buy the car but for me a over fill of that level will not hurt the car and I hear the Japanese manual recommends 5.8 anyway which would be in line with what I do. Better safe than sorry.
 
#8 ·
Based on the data that 900BRZ shared: If you’re over 6,000 rpm, then yes it’s likely you’ll be aerating. Especially if you aren’t a quart overfill. 5w-30 or 0w-40 doesn’t matter because empty is empty. Keep it at 6k and it should be fine.

Doesn’t mean that doing a clockwise cloverleaf at 7,000 rpm all day will ruin your engine, but you would have oil pressure drops. Not to zero, just below design. These are documented on track with NOT sticky tires.
 
#12 ·
RPM is just part of the equation. It increases the oil demand, but 6,000 RPM in 1st gear is still pretty damn slow, and isn't demanding enough lateral load/G force to contribute to oil starvation.

You could be at 4,000 RPMs and moving much quicker, which would more likely generate oil starvation issues.

1st gear @20mph/6k might generate 0.7G, while 3rd gear @50MPH/4k might generate 0.9G. (These are just hypothetical numbers to give an example).

Can it happen on the street with a stock car? Yes, but you'll have to carry quite a bit of momentum and/or be at or near the limit of the tires to do so. Is it enough of an issue to worry about? Doubtful.

If it is, you may want to consider how you're driving on public roads during your daily commute lol
 
#17 ·
Don't forget that high oil temps at the track play a significant factor as well. It's not just about lateral grip.

If you're concerned, just run 0.5q overfill on 5w30 and you'll be fine. If you're somehow exceeding 250F oil temps at the same time as pulling ~1.00g sustained on on-ramps (and you haven't lost your license yet), then add an oil cooler.
 
#20 · (Edited)
We've come across four "types" of oil starvation / pressure loss events with this car: sloshing, capacity, aeration, and "transients". Sloshing and capacity type losses are most discussed, most clearly observable (if you have a oil pressure sensor), and the most severe. In the limited number of data samples we've seen on road courses, we've so far only observed these events when approaching 1.0G lat. On centre handling is considered to be under 0.2G lat.

The cloverleaf test would essentially be a constant radius, variable speed skidpad test. This is a static/quasi-static test that would isolate for capacity type losses, so the idea is definitely valid. However, I would preferably perform this test on a skidpad or on a vehicle dynamics test area, but who has the connections to arrange that (unfortunately, not us, sadly)!

Which bring us to the slosh type loss. Throwing more oil at the problem (ie. overfill) helps as well, but when Subaru only gives you so much space around the oil pan, you have to do something else to manage these types of losses. Most of our testing has focused on road courses, but it would be neat to see oil pressure data for a BRZ/GR86 around an autocross, preferrably for an extremely technical layout.