Piston slap/bore scoring in Cayennes
04-20-2021, 03:31 PM
#46
Rennlist Member
with me happens cyl. Number 3 . Already 2 times in the last 10 years. The cylinder exactly under the engine mount. I was even thinking, people are to lazy taking away the engine mount when changing the spark plugs. Worn plugs?! Don’t know if this can be a reason. No proper ignition- to much fuel in this area- washing out the oil film.
04-20-2021, 03:32 PM
#47
Rennlist Member
I have several observations I have made over all these years.
We don't see scored bores very often in Boxster 2.5, 2.7, or 3.2 engines. These all received cast KS pistons, not forged mahle. The iron coating is much more durable on the skirts. I also believe the piston to cylinder clearance was too tight on the forged mahle pistons.
Porsche did not have bank specific offsets until somewhere around 2012 or 2013 (I can't remember exactly), which means on one bank you end up with increased side loading of the skirts. This is my opinion why they score worse on one bank than the other, however we have seen scoring in all cylinders.
On the M96/M97 engines with the 82mm stroke, the pistons come out of the bore 7mm at BDC which I think also makes the problem worse with the 3.6 and 3.8 models. I have never looked at a Cayenne to see if this also is the case.
Injectors going bad and washing the bores down is another element we've seen and this is likely caused by ethanol enriched fuels.
Lastly, long drain intervals with oils formulated to improve fuel economy rather than reduce wear add to the issue.
It's not one thing alone that contributes to bore scoring - it's multiple things coming together to form a perfect storm.
We don't see scored bores very often in Boxster 2.5, 2.7, or 3.2 engines. These all received cast KS pistons, not forged mahle. The iron coating is much more durable on the skirts. I also believe the piston to cylinder clearance was too tight on the forged mahle pistons.
Porsche did not have bank specific offsets until somewhere around 2012 or 2013 (I can't remember exactly), which means on one bank you end up with increased side loading of the skirts. This is my opinion why they score worse on one bank than the other, however we have seen scoring in all cylinders.
On the M96/M97 engines with the 82mm stroke, the pistons come out of the bore 7mm at BDC which I think also makes the problem worse with the 3.6 and 3.8 models. I have never looked at a Cayenne to see if this also is the case.
Injectors going bad and washing the bores down is another element we've seen and this is likely caused by ethanol enriched fuels.
Lastly, long drain intervals with oils formulated to improve fuel economy rather than reduce wear add to the issue.
It's not one thing alone that contributes to bore scoring - it's multiple things coming together to form a perfect storm.
04-20-2021, 09:11 PM
#48
Rennlist Member
Rebuild
Don’t start to laugh now but the engine from my project car will be rebuilt in Poland. Cayenne Turbo engine with 450 HP. They are really experts with a lot of experience and cost will be have than in Germany. I will report when the job is done
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VoilaGT3 (07-23-2024)
07-23-2024, 05:49 PM
#49
Hi Joel,
Thanks for your thoughts on this and the updated V-list. My older version of the V-list did not include the engine codes and dates of production so this is extremely helpful. If one references the original TSB from 2013, the GTS engine codes are included in the list of structurally honed blocks. The codes are: 9PAAL1 for the tiptronic and 9PAAL7 for the 6 speed manual. My 2009 CTTS engine is listed as well.
Here is the list from the original 2013 TSB:
"Only engines with structurally honed cylinder liners are used in vehicles as of the shown engine numbers:92AAH1, 92AAI1, 92AAL1, 970110, 970111, 970120, 970121, 970410, 970411, 970420, 970421, 970430, 970431, 970440, 970441, 970450, 970451, 9PAAH1, 9PAAH7, 9PAAI1, 9PAAL1, 9PAAL7, 9PAAN1, 9PAAS1
Model year as of 2008"
Note that the new TSB from Mar 6, 2020 posted above is referencing the later 958 and Pano models. It is interesting that they do not note the actual engine numbers in this TSB.
I will dig deeper again into the data. Often as time passes, information slips through in revisions of TSBs or parts catalogues that is very helpful. I have a suspicion that there is more to be discerned from some of the recent documents.
Thanks for your thoughts on this and the updated V-list. My older version of the V-list did not include the engine codes and dates of production so this is extremely helpful. If one references the original TSB from 2013, the GTS engine codes are included in the list of structurally honed blocks. The codes are: 9PAAL1 for the tiptronic and 9PAAL7 for the 6 speed manual. My 2009 CTTS engine is listed as well.
Here is the list from the original 2013 TSB:
"Only engines with structurally honed cylinder liners are used in vehicles as of the shown engine numbers:92AAH1, 92AAI1, 92AAL1, 970110, 970111, 970120, 970121, 970410, 970411, 970420, 970421, 970430, 970431, 970440, 970441, 970450, 970451, 9PAAH1, 9PAAH7, 9PAAI1, 9PAAL1, 9PAAL7, 9PAAN1, 9PAAS1
Model year as of 2008"
Note that the new TSB from Mar 6, 2020 posted above is referencing the later 958 and Pano models. It is interesting that they do not note the actual engine numbers in this TSB.
I will dig deeper again into the data. Often as time passes, information slips through in revisions of TSBs or parts catalogues that is very helpful. I have a suspicion that there is more to be discerned from some of the recent documents.
07-23-2024, 05:58 PM
#50
From my recent digging into this to learn more(mechanical side) the best way I learned to recognize this phenonenon is from advice a buddy described as rythmic knocking, listening under many 955-957 engines it is now very clear what is a BS knock, term intentional. The top end of these motors are very click and tappy, but the sound you will hear is concise and not fall into the top end tempo. I recommend watching a few videos with good headphones, you will quickly learn how to spot it. From what I know, the lining for our gens help but did not alleviate the issue entirely.
Last edited by VoilaGT3; 07-23-2024 at 06:07 PM.
07-24-2024, 08:42 AM
#51
Race Car
tips I used avoid bore scoring:
Keep fuel injectors clean to minimize fuel spray issues and cylinder washing (Often overlooked)
Avoid low quality/low octane fuel
as detonation will lead to inventory piston loads causing skirt to impact cylinder wall.
Run quality oil with high shear characteristics (MOTUL 5w-40 8100 or equivalent).
Consider anti-friction additive like Ceratec
Drive conservatively (low load) until engine and oil warmed up. High loads when cold cause piston to expand at a faster rate than cylinder (just my theory).
I changed my oil at 5k miles….half the recommended interval.
My 05 CS saw extreme weather, never stored inside, many sub-zero starts while skiing. Sold at 120k miles and is still running awesome with new owner.
Keep fuel injectors clean to minimize fuel spray issues and cylinder washing (Often overlooked)
Avoid low quality/low octane fuel
as detonation will lead to inventory piston loads causing skirt to impact cylinder wall.
Run quality oil with high shear characteristics (MOTUL 5w-40 8100 or equivalent).
Consider anti-friction additive like Ceratec
Drive conservatively (low load) until engine and oil warmed up. High loads when cold cause piston to expand at a faster rate than cylinder (just my theory).
I changed my oil at 5k miles….half the recommended interval.
My 05 CS saw extreme weather, never stored inside, many sub-zero starts while skiing. Sold at 120k miles and is still running awesome with new owner.
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lkraav (07-25-2024)
07-24-2024, 11:00 AM
#52
This is so confusing to me. I have no reason to suspect I have scoring, no symptoms, truck runs great, but while under the car doing trans service I figured I'd look for my engine code. I couldn't find it, but there is a serial number tag sticking out from the oil pan: M48/5184808129. Also, my VIN is WP1AC29P38LA93628, which when I put into the vin decoder on this website it says MFR Model Code 9PAAI1 which is in the list I quoted. Does that mean I have a good or bad engine?
2009 or newer received the updated engine.
07-24-2024, 05:28 PM
#54
That's the way I'm reading it too. Yippee!