GR Yaris Balance of tuning and durability limits

Another piece of the puzzle. Piston from a GR Corolla engine that failed in the US.

Piston.webp
 
Even at this point, after 3 plus years since it was released, it still seems that even EcuTek hasn’t discovered how all tables work and for repeated track abuse is better to stay on stock map, to be on the safe side of things…
 
somewhere from the interwebz, do not know any details
4ef377cc-f453-4682-ab6e-8b54d45f7bca.webp
 
That’s Captain Gaskrank who does lots of Nürburgring vids. His insta is private rn though.
 
Seems the piston has disintegrated, hardly that's an oil starvation problem.

Edit: change of mind 😀 If the oil squirters weren't doing their job or if piston was dragind along insuficiently lubricated cylinder wall and heating up, it definitely could have helped to start LSPI/detonation.
 
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When the GR pistons fail the above mentioned picture is often the outcome (shattered). Need to check if i find the source why (material composition if im not wrong).
 
Duke said:
A year ago anyway, he was running a piggyback.

View attachment 30326

I imagine the repeated running at sustained lateral g may have had more to do with this than a little bit more boost.
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Thanks. But I thought he had 2 GR Yaris, and the one with the engine issue hasn’t been on the Ring as per his claims (so AFAIK is not the one he used for track work)…
 
watched again the great Driving for Answers video of GR Yaris. there it was stated that engine oil squirters would be run with check valve, i.e working only with sufficient oil pressure. Given the car will often start lacking oil pressure if hot enough, would this lack of oil squirter spray play a part if engine is already driven on its limit (just speculating).
 
Michael Knight said:
watched again the great Driving for Answers video of GR Yaris. there it was stated that engine oil squirters would be run with check valve, i.e working only with sufficient oil pressure. Given the car will often start lacking oil pressure if hot enough, would this lack of oil squirter spray play a part if engine is already driven on its limit (just speculating).
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I appreciate your analytical thinking, but I highly doubt that’s the actual cause of the engine failure. Here’s why: insufficient cylinder wall lubrication and inadequate piston cooling can lead to cylinder wall scoring, which is exacerbated by the fact that an undercooled piston expands, decreasing the cylinder-piston gap. If you examine the photos of the failed cylinder 3 and the 'healthy' cylinder 1 from the same engine, despite deep scratches from the piston pin, there’s no scoring on the cylinder walls from the piston. Additionally, the piston is heavy enough, with sufficient thermal capacity, to not be affected by short periods of insufficient cooling. Moreover, oil starvation usually occurs during heavy braking, which is almost always done off-throttle (unless left-foot braking), so no combustion is happening at that time.

Some random scored cylinder:
scoring.webp


Cylinder 3 of the failed GR Yaris engine:
cyl3.webp


'Healthy" cylinder 1 from the same engine:
cyl1.webp


Image source:

In my opinion, all these dramatic GRY engine failures are nothing more than LSPI leading to super-knock, caused by improper fuel/ignition mapping or incorrect oil usage. I’m not sure I’ve seen a single failed engine with stock mapping.
 
Until someone does a Failure Analysist to find the Root cause then really its just speculation why the pistons basically disintegrating.
 
There’s a new video attempting to analyze possible causes of engine failures, but its competence is questionable (no offense to the author of the video).



However, a few comments from the ACME representative are quite informative:

@stratodasser​

Hi, The Yaris from our company (ACME) is the one featured in the video with the "don't panic" sticker on the rear spoiler. After analyzing about 250 Yaris GRs (both street and rally versions), we've established that the engine failures are linked to megaknock events caused by oil ignition in the combustion chamber. This has been confirmed in both stock and modified cars. However, no issues have been found with aftermarket pistons, suggesting that tolerance in stock piston rings might be a factor.
Phil's issue is different, as he used IRP “platinum” pistons, which require a modification to the original oil squirters to avoid his failure. Ciao!
Ps: To clarify… out of approximately 250 modified GR Yaris cars, we diagnosed 3 cases of this specific type of failure.
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@stratodasser​

@throttlebuddies6356 The oil injection is not through crankcase ventilation. The issue we observed was oil being burnt in the combustion chamber, likely due to blow-by or other factors, contributing to the megaknock. A catch can may help with ventilation oil, but it would not necessarily prevent this specific failure. Regarding "megaknock," it is a single knock event that generates extremely high pressure in the combustion chamber, often breaking just one piston. In fact, we found the other two pistons completely intact, showing no signs of detonation.
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would be interesting to know from destroyed engines what has been the condition of oil, oil temperature during incident, etc.
tempting to swap to heavier oil after hearing this but its only for summer season - for winter it does not make much sense here in colder climates.

is compression or leak down test irrelevant to this issue - just thinking of is there any way to test the ring condition without opening the engine.
www.quora.com

How do you check piston rings without removing them?

Answer (1 of 16): Start with a compression test. Pull all of the spark plugs, tie back, or otherwise hold the throttle open and turn the engine over on the starter motor. In a perfect world you're hoping to get an even reading across all cylinders. 120–150psi with all cylinders within 10% of the ...
www.quora.com www.quora.com
 
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Michael Knight said:


would be interesting to know from destroyed engines what has been the condition of oil, oil temperature during incident, etc.
tempting to swap to heavier oil after hearing this but its only for summer season - for winter it does not make much sense here in colder climates.

is compression or leak down test irrelevant to this issue - just thinking of is there any way to test the ring condition without opening the engine.
www.quora.com

How do you check piston rings without removing them?

Answer (1 of 16): Start with a compression test. Pull all of the spark plugs, tie back, or otherwise hold the throttle open and turn the engine over on the starter motor. In a perfect world you're hoping to get an even reading across all cylinders. 120–150psi with all cylinders within 10% of the ...
www.quora.com www.quora.com
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This guy is a disaster for the GR owners community. How the heck can he recommend a 5w30 oil to these engines…? He creates a lot of distress for owners, just for a few views.

Use 0w20 ilsac gf-6, do not remap your car if you want it to last, change oil when the manual says, or after a track day or two…and stop worrying people.

I’m still yet to see a destroyed GR Yaris engine running on stock form. He says there are, with no more data but it is difficult to trust his claims.
 
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