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Discussion Starter · #1 · (Edited)
There are models that are industry standard for reliability. In general it is called six sigma and the failure rate is measured in PPM (parts per million). PPM is a measurement of failures per million.

Generally failure rates vary but for the purpose of this exercise I'm using the following manufacturing values as guidance.

0-25 PPM Green or acceptable
26-500 PPM Yellow or warning
501-2500 PPM Red or high defect
2501+ PPM unacceptable failure rate

I am not using ancedotal information as a measurement. I only use failures where the cylinder has been replaced. I am also excluding any data for pentastars built in vehicles other than Wrangler. There are obvious flaws to my calculations because I don't know the actual number of units built or the actual number of cylinder heads replaced. Anecdotal would be " I hear tapping of my valves". It cannot be used for this exercise.

The formula for calculating PPM is:
Failures/number of units produced X 1,000,000

If we have a specific date range the data can be refined and made more accurate. So far I know mine was built on 7/19 and I have verified another was built in July but without a specific date.

Using the max production rate of 700 units per day here are 12 days production for July from the 19th to month end. So the formula in this case is:

2 (confirmed failures in July)/(12*700)*1,000,000 for a 238 PPM

There are 3 more that have had the cylinder heads replaced that I can find but I don't have build dates so I'm excluding that unless I can get something more specific. I also suspect the rates will rise over time. The rate we are referring to here is the early failure rate versus a long term (normal, anticipated) failure rate.

So, for today and this moment only the PPM for this failure is 238 or 238 failures out of every million builds.
 

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So far everything is fine, I'm going to sit back and wait mine was built on...
Scheduled for Build (D1) 06/24/2011 07:35 AM EDT Toledo Supplier Park, OH
Built - Pending Inspection (I) 07/21/2011 08:57 AM EDT Toledo Supplier Park, OH

:popcorn:
 

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Discussion Starter · #5 ·
Six Sigma in the forums......Really?
Wow...

Would you rather draw conclusion by what you feel or what you know, based in fact. I have knowledge in the area..sorry if your underroos got in a bunch over my contribution my friend.
 

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Six Sigma in the forums......Really?
Why not? The calculations seem close enough.

Mainly I am interested since my father is a champion/master black belt in Six Sigma.

My general rule of vehicle mechanical failures is that if there are a few handfuls of confirmed failures getting into public forums there is a cause for warning to look into the affected parts.
 

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Wow how many threads can we start on the same subject? Maybe it's time for its own section.
 

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sandbaja said:
Wow...

Would you rather draw conclusion by what you feel or what you know, based in fact. I have knowledge in the area..sorry if your underroos got in a bunch over my contribution my friend.
Work paid for a coarse in statistical process control :thumb:

Have a certificate but don't remember squat :)
 

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Discussion Starter · #9 ·
Work paid for a coarse in statistical process control :thumb:

Have a certificate but don't remember squat :)
I know a lot of folks that were trained and never used it. A total waste of money for most people and companies. Few get a chance to apply it to a practical situation and fewer understand how it works to improve a product. I look for occasions to use it so it doesn't go rusty.

Alexia...Some of the smartest people I know are black belts. It's a different world when you live in it.
 

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I know a lot of folks that were trained and never used it. A total waste of money for most people and companies. Few get a chance to apply it to a practical situation and fewer understand how it works to improve a product. I look for occasions to use it so it doesn't go rusty.

Alexia...Some of the smartest people I know are black belts. It's a different world when you live in it.
My father teaches statistics and probability to engineers to calculate failure rates.(Was a college professor long before that.) I learned a ridiculous amount of information from him. Some of it I actually use to calculate how many users might experience a software programming failure on any given web site.

I am really curious is this engine issue was isolated to a batch last year or will be a continual problem throughout production.
 

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Work paid for a coarse in statistical process control :thumb:

Have a certificate but don't remember squat :)

X2 well i have multiple certificates in it but same.


I'm curious to the validity of this test with only input on this forum.
 

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Discussion Starter · #12 ·
I am really curious is this engine issue was isolated to a batch last year or will be a continual problem throughout production.
Curiosity is what started me on this path (plus mine failed and I work in a technical field). I'm still trying to determine the date range.

I'm curious to the validity of this test with only input on this forum.
The source data is not truly valid. It's more an educated WAG. There are factors you can use to normalize..but not here, not now.
 

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If you ask me only the manufacture can truly do a six sigma. They use the data to improve the part being manufactured. In essence you’re developing a statistical model not a true six sigma. Also I would be curious if all the failures are the same. There could be multiple failure types that could also skew the data. Also just because the jeep was built in July dose not mean the engine was built then. I understand its kinda fun to track data, but unless you’re working for or getting your data from someone in Chrysler this test is not valid. Just my 2cents but good luck.
 

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The letters and numbers are eating my brain.....
 

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Ya, Ya, Ya. Is there problem with the 2012 engine above normal failure rate. Is there a specific build date we should be looking for?
 

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Discussion Starter · #18 ·
Ya, Ya, Ya. Is there problem with the 2012 engine above normal failure rate. Is there a specific build date we should be looking for?
Other than July 2011 no, until folks offer dates up that have confirmed failures.
 

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I guess the new mini van engine has a few quirks of her own. My old 11 3.8 mini van engine doesn't have enough compression to damage the head!
 

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sandbaja said:
Curiosity is what started me on this path (plus mine failed and I work in a technical field). I'm still trying to determine the date range.

The source data is not truly valid. It's more an educated WAG. There are factors you can use to normalize..but not here, not now.
You just said your data is useless.
 
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