Broken Rings

[Jase007]

Ted:

Saw this post on Pelican and wonder if your ring "issue" was chip related...? Steve @Rennsport mentions this in a "to chip or not" discussion:

"If you rely on your ears to detect detonation (sub-audible or the audible kind), your bank account is at serious risk.

I cannot tell you how many SC, Carrera, and Turbo engines I have opened up to find broken rings and trashed pistons from detonation. The owners' all told me they NEVER heard a thing.

Air-cooled engines require a margin against detonation as that threshold is dynamic, not static."

The Pelican Performance improvements thread (http://forums.pelicanparts.com/showthread.php?s=&threadid=143974&perpage=20&pagen umber=1) is well written and informative about chips and the risk / trade-off one takes when running one. As I don't own a motronic (or other EFI) equipped P-car I can't comment on P-car chips. I have had a chip in my motronic equipped BMW for 8+ years, run 91 octane plus and don't hear any detonation (while adding 100,xxx miles).

Wouldn't explain the head sealing issue but, maybe the ring one (PO run a different chip?).

FFT = Food for thought

Jase

[William Miller]

OK, going deeper. how did the broken ring compaire to the others.
Were they all worn and ready to break and this one went first or was #4
substantially worse than the rest.

On my engine #4 was broken and the rest looked almost new. Indicating a problem with that specific piston. I'll let you know later if you haven't read it before.

[targa911man]

My understanding from Steve Wong is that the stock advance mapping is not extremely conservative but that there is room for adding zip without creating an unreasonable risk of detonation damage, particularly if you can use high octane. I run 93 exclusively in my car and haven't had any problems since putting the chip in, about 10k mi. ago. I need to emphasize though, that I really haven't pushed the engine to its limit, i.e. no DE, no racing, hit rev limiter twice since chipping, rarely shifting over 5500. But there are a lot of guys who have had Steve's chips a lot longer who have not had problems either.

[APKhaos]

The advance parameters can be significantly more agressive in some aftermarket chips. Seach Pelican - the actual maps were posted in 2002.

With the Autothority chip in my car, oil temperatures under hard track conditions were considerably higher than with the stock chip. So much so that I went back to the stock chip after a few test sessions. I do not like elevated oil temps no matter what the performance gain.

Steve Wong is fairly gentle with the advance maps. Too much advance kills these engines - too much heat, too much risk of detonation. Remember, there are no knock sensors on the earlier 911.

[targa911man]

Tony's post reminded me--I have seen no increase in oil temp with Steve's chip.