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Originally Posted by clarence
For those who do not believe in binning, pls be constructive & put forward ur ideas as to how BMW decides to label which of their low compression N20's as U0's & which ones as O0's. Don't know is not an answer & "there must be sth different" is also not valid (cos already confirmed low compression U0 is part for part identical to O0).
Also, power variation between identical engines is not fantasy. On Feb 2013 issue of Automobile, they did a comparison test between an Alpina B7 and an Audi S8. They put both of those cars on the dyno. The Alpina underperformed significantly when compared to factory specs. This is after a 20% drivetrain loss allowance. Don't forget BMW made those engines specially for Alpina.
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My theory on how they decide: They allocate the engines according to demand. There is no implicit requirement that the engines be physically different. The percentage of people who chip tune their cars is so low that it doesn't register on BMW's bottom line.
Put more specifically, BMW's risk in the scenario where the engines are identical (except software) is that some customers will by a '20i car and chip tune to get the extra horsepower. That would represent a loss of top line revenue and profit because '20i vehicles have lower MSRP and thinner margins. However, BMW have differentiated the vehicles by limiting available options, which protects them in the mass market, and only exposes them to the tuner market segment. This segment is tiny in the overall sense.
Regarding the Alpina engine. That's not a matter of production variation, that's a matter of actual output versus claimed output. This is completely unrelated to the kinds of production variations we're talking about. You can't infer statistical significance from a sample size of 1.
Quote:
Originally Posted by clarence
1.) Yes cos they cannot just select engines randomly, there must be a valid & logical method used to select the engines. As each engine produced will not produce exactly the same power as the next one (i.e. some variances will exist, however low the %), it is only logical for them to detune those not so good ones as a U0 (rather than detune the best ones & give 28i customers not so good ones).
2.) Using software to differentiate power output & binning are 2 different matters. Binning is the selection of engines to be "differentiated" & software installation only comes after this selection. Of course they can just use software to detune the engines if they don't bin them, but the binning process itself is used for selection rather than the actual detuning operation. If they detune the engines randomly then it will introduce problems. Plus BMW runs every engine produced on the bench for QC purpose, so they already have all the relevant data needed for binning. So no, that's the only method I can see them using in selecting which engine is to be detuned or not.
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1) Why can't they "select engines randomly"? Although I wouldn't call it random. Why not just allocate them as they come off the line? Your hypothesis stands upon two assertions:
a) That manufacturing variances in the N20 are significant enough to justify this binning approach. What I cannot wrap my head around is why the N20 would suffer from these variances, but other BMW engines do not. If all engines do suffer from these variances, then it would be considered "acceptable", and BMW would have no reason to go through the extra effort of waiting for a "defect" engine, subjecting their production process to variances in availability based on defect rate and yields.
b) That "it is only logical for them to detune those not so good ones as a U0". Why is that any more logical than simply applying software as allocation is required?
2) I think I have a pretty good understanding of your hypothesis. I disagree that "If they detune the engines randomly then it will introduce problems." What problems will be introduced?
The binning approach flies in the face of everything I know about manufacturing and supply chain management. I build software to manage the procurement process for Fortune 500 companies. I spend a lot of time with executives in charge of supply chain management, because they're often the ones doing the purchasing. Auto makers rely on just-in-time manufacturing. Cars are built as they are ordered. All the parts arrive in the order they are needed. Literally, every sub-contractor has to load the parts in the containers in the order that they will be needed for assembly. The idea is that a part should be manufactured as late in the process as possible in order to reduce the capital required to maintain parts stock.
An engine is one of the most expensive and complex components in an automobile. If BMW uses binning, it means that the availability of '20i engines is subject to defect rates and yields. That means we're dealing with statistical probabilities. When you flip a coin, there is a 50/50 chance that you'll get heads, but anyone who has flipped a coin knows that you can end up with 6 tails in a row. Or 10. Or 20. It's possible!
The question is not why, but *how* could BMW run an efficient production process if they subject their supply to this type of statistical allocation? If the next engine needed is a '20i, and they end up with six '28i capable engines in a row, what do they do with those engines? Surplus is synonymous with waste when it comes to supply chain management. Engines are too expensive to have them simply sitting around.
This is a matter of applying Occam's Razor. There must be some advantage to the binning approach versus straight forward allocation. I can't see it. I understand the idea. I'm open to considering it, but before I can agree, I need to know the reason why.