Bore scoring and the base model 987.1 and 987.2
01-27-2023, 10:17 AM
#16
Rennlist Member
@Mike Murphy I look forward to reading all 74 pages. @Raudona just reading the first paragraph of the linked article, it sums up that there are a combination of factors, as you might expect. You might also want to read the technical paper written by Charles Navarro on the subject over at LN Engineering. And I would add, related to my own career, failure analysis (sometimes we called it root cause analysis) is often quite complicated. We were sometimes taken by surprise at what the final determination was versus our initial gut instincts. And IC engines in general, with a wide range of operating conditions, usage, abuse, etc. are really difficult to pin down root causes for.
The following users liked this post:
Mike Murphy (01-27-2023)
01-29-2023, 09:33 AM
#17
Rennlist Member
@Raudona I did read the Hartek report that Mike linked. It is well worth reading. The very short answer to your above question is that the very thin oil film that must exist on the cylinder bore wall breaks down momentarily at certain uncommon extreme conditions, allowing metal to metal contact of the piston skirt and thus scoring of the bore.
01-29-2023, 01:43 PM
#18
Rennlist Member
Originally Posted by harveyf;[url=tel:18595911
18595911[/url]]@Mike Murphy I look forward to reading all 74 pages.
09-28-2023, 10:04 AM
#19
Rennlist Member
Similar reason Hartec explained in the 996 world when comparing the 3.4 versus 3.6. The smaller engines produce less horsepower, less heat, and have different rod ratios. The smaller engines also need more revs to get similar torque output, so less lugging and better oil circulation at higher revs. But scoring can still happen on the smaller engines, just less prevalent.
The 987.1 S 3.4 engine has the same rod/stroke ratio as a base 2.7, so I don't think that is as much as a contributing factor with scoring since we have never seen a base 2.7 score and we see tons of 3.4 engines with scoring.
The biggest difference is that base models got cast KS pistons that have larger piston skirts and the pistons are iron plated rather than the Mahle forged pistons that have the Ferroprint printed iron wear pad.
3.6 and 3.8 engines have worse rod/stroke ratios and the piston comes out the bore about 7mm at BDC, leaving it unsupported, where the shorter stroke engines only have the piston come out about 2mm.
We lengthen the sleeves and only use full round forgings to support the piston as much as possible at BDC changeover to address these issues.
The following 5 users liked this post by Charles Navarro:
365jon (09-28-2023),
Burny (02-08-2024),
Mike Murphy (09-28-2023),
tenaciousD (09-29-2023),
The Duke (09-28-2023)
09-28-2023, 10:08 AM
#20
Rennlist Member
I constantly read posts on this forum, other forums, and YT videos saying that bore scoring is a non-issue issue on the base model 987.1 and 987.2 motors. The reason most note for this claim is because of the smaller displacement of these motors (2.7 to 2.9 liters) with little to no scientific explanation to back up the claim. I find this rather hard to understand/believe as both motors have the same problematic cylinder liner coatings as their S car 3.2 and 3.4 motors counterparts. I have a hard time buying the smaller displacement rationale, especially given that the 987.2 base and S model motors are closed deck (i.e., thermal expansion should be better managed).
We all know the 987.1 S motors can and do get bore scoring and we're also seeing it in the DFI 3.4 motors. I do have wonder if the reason why don't see much, if any bore scoring in the base motors is because:
1) Fewer of them were sold thus less reported issues with bore scoring
2) Fewer are presumably competitively driven.
3) Perhaps owners of the base model cars tend to drive less aggressively.
Am I off my rocker
We all know the 987.1 S motors can and do get bore scoring and we're also seeing it in the DFI 3.4 motors. I do have wonder if the reason why don't see much, if any bore scoring in the base motors is because:
1) Fewer of them were sold thus less reported issues with bore scoring
2) Fewer are presumably competitively driven.
3) Perhaps owners of the base model cars tend to drive less aggressively.
Am I off my rocker
For the record, we've never seen or heard of a base model Boxster or Cayman with 987.1 or 987.2 bore scoring.
Last edited by Charles Navarro; 10-22-2023 at 10:17 AM.
The following 2 users liked this post by Charles Navarro:
SeanPatrick31 (09-28-2023),
tenaciousD (09-29-2023)
09-28-2023, 10:11 AM
#21
Rennlist Member
https://lnengineering.com/free-downl...s-navarro.html
The following 2 users liked this post by Charles Navarro:
SeanPatrick31 (09-28-2023),
tenaciousD (09-29-2023)
09-28-2023, 11:45 AM
#22
Rennlist Member
I spent the better part of 9 months researching bore scoring before I wrote and published this white paper on the subject a few years back. It's probably too technical for most, but it's also worth reading:
https://lnengineering.com/free-downl...s-navarro.html
https://lnengineering.com/free-downl...s-navarro.html
09-29-2023, 03:19 PM
#23
There is no real data ever quoted because the guys pushing the idea don't want to say how infrequent it is.
09-30-2023, 12:29 PM
#25
Racer
09-30-2023, 01:27 PM
#26
Nordschleife Master
He said, "the guys pushing the idea". How is bore scoring an "idea"?
That's the million $$ question.
But... How in the world would you obtain it objectively? Random sample?
LN Engineering does keep track of the Porsche cases that come in the door to be repaired and resleeved. The above list that I provided was based on data they've provided over the years.
But people that think it's an "idea" being pushed by the aftermarket/engine rebuilding industry probably wouldn't trust it anyway. About like what was going on 20 years ago with intermediate shaft bearing failure. Everyone thought it was hype until the class action lawsuit.
That's the million $$ question.
But... How in the world would you obtain it objectively? Random sample?
LN Engineering does keep track of the Porsche cases that come in the door to be repaired and resleeved. The above list that I provided was based on data they've provided over the years.
But people that think it's an "idea" being pushed by the aftermarket/engine rebuilding industry probably wouldn't trust it anyway. About like what was going on 20 years ago with intermediate shaft bearing failure. Everyone thought it was hype until the class action lawsuit.
The following users liked this post:
The Duke (10-01-2023)
10-01-2023, 09:23 PM
#27
Rennlist Member
There's enough anecdotal data within the 987 forum alone to compile a case. This is not "fake news"!
11-12-2023, 07:48 PM
#29
Rennlist Member
Call me skeptical but if the solution is just to add one ingredient to the oil, that seems too good to be true.
Just how do you demonstrate that it is the best preventative? You'd really need to take two fairly identical cars, put the additive in only one, and drive them both identically for tens of thousands of miles. And then hope that the one that didn't have the additive developed bore scoring, just to prove your point. Not going to happen. So you are just left with very anecdotal information, concluding nothing. This basically sums up the futility of all "best oil" threads.
Just how do you demonstrate that it is the best preventative? You'd really need to take two fairly identical cars, put the additive in only one, and drive them both identically for tens of thousands of miles. And then hope that the one that didn't have the additive developed bore scoring, just to prove your point. Not going to happen. So you are just left with very anecdotal information, concluding nothing. This basically sums up the futility of all "best oil" threads.
11-14-2023, 09:45 AM
#30
Rennlist Member
Driven DI40 and DT40 have high levels of MoDTC moly friction modifiers, so no additives are needed. It would probably be detrimental to add an additive to these oils.
However an additive alone won't make a bad oil better. We all know through lots of shared used oil analysis reports that M1 is barely in grade for a 40 wt and quickly shears down to a 30 wt - you want an oil with a higher HTHS viscosity that can retain it's viscosity. That's the cushion that's needed to protect the bores and pistons in areas of hydrodynamic and mixed-lubrication regimes, where the ZDDP and moly are critical for boundary lubrication.
The following 5 users liked this post by Charles Navarro:
cavediver32043 (11-16-2023),
harveyf (11-14-2023),
lightguy (11-14-2023),
SeanPatrick31 (11-14-2023),
The Duke (11-14-2023)