Owners have detected massive drops in oil pressure during right-hand corners on the track.
The Toyota GR86 and Subaru BRZ have had their fair share of the limelight as affordable sports cars for the masses, but as much as there has been praise, there has also been negative press after engine failures on track and drawn-out warranty claim conflicts. Now, there's another bit of bad news: a group of owners has discovered a significant drop in oil pressure on these cars during right-hand cornering at track days, which may result in spun bearings and catastrophic engine failure.
It is believed that this issue is unrelated to the RTV sealant issueCarBuzz discovered last year, but it is equally concerning as these sports cars are used frequently at track days.
In a video published this week by YouTube channel 900BRZ, the owner of a stock-ish 2022 Subaru BRZ documented findings that show a consistent, and importantly, repeatable, oil pressure drop under certain circumstances.
Claiming to know three people with blown engines from track use personally, 900BRZ states that they were all meticulous owners who use the correct oil and do not mistreat their cars. Instead of just taking their word for the supposed issues, the YouTuber sought concrete data-driven evidence to see if these cars have an inherent flaw.
With the help of oil pressure sensors in two locations and an Aim Solo2 data logger, the group of enthusiasts was able to track oil pressures in realtime on track. Instead of relying on a single car, they benchmarked a 2022 BRZ against a 2022 GR86 and a 2017 BRZ with the Performance Package, using multiple drivers in back-to-back testing around Thunderhill Raceway Park. Notably, the 2022 GR86 has had RTV sealant cleared from the oil pan.
Traditionally, oil pressure has a strong correlation with engine revs, as high engine speeds mean a greater need for proper lubrication. However, the group discovered a significant dip in oil pressure at high RPM and under wide-open throttle (WOT).
This issue occurred during fast right-handers and was repeatable by all drivers in both the new-generation cars powered by the FA24 2.4-liter motor. The sudden pressure drops were more than 60% in some cases, dropping to as low as 20 PSI from an average of about 60 PSI, despite engine speeds as high as 7,400 rpm.
In comparison, the first-gen BRZ (powered by a 2.0-liter FA20 motor) only exhibited a slight drop in pressure for a much shorter duration. Based on this evidence, 900BRZ and his cohorts are convinced that first-gen cars and their engines are more robust and resistant to this particular issue.
Their conclusion is that the size and duration of these pressure drops significantly increase the risk of oil starvation to the bearings, which may ultimately result in engine failure.
But what could the cause be?
They hypothesize two potential causes:
But instead of just identifying a problem and leaving it, 900BRZ is trying to find solutions. He has partnered with KillerB Motorsport to develop a prototype baffle he believes may help prevent oil starvation. The baffles are designed specifically to prevent oil surging into the timing cover, as mentioned in point one above, as side-to-side baffles appear to have no significant impact in reducing pressure losses.
We can expect follow-up tests with the prototype baffle in due course.
This is unlikely to be an issue on the road, as it only occurs under duress on track with 1+ G of lateral acceleration through right-hand corners. However, second-gen GR86 and BRZ owners may want to pay careful attention to their car's oil needs. All cars in this test had their oil up to the full marker on the dipstick and were running the correct oil as recommended by the OEMs, and with multiple drivers at the wheel, the results are pretty accurate.
Whether this is something Toyota and Subaru may address or not remains to be seen.
While last year's story of a GR86 owner's warranty being denied was traced back to RTV sealant as the issue, the cause of the most recent incident was not confirmed by Toyota when providing CarBuzz with a comment on the matter.
We have contacted Toyota for comment on this and will update our story accordingly.