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      08-24-2012, 01:17 PM   #89
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Real question: how many of you actually read these massive wall of text replies?
Answer: Maybe it'll go a little easier for you if you use ChapStick.
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      08-24-2012, 01:23 PM   #90
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I wouldn't call the s65 "wheezing" at 8k RPM, that's rather demeaning and argumentative at best. My tiny S65 has no problem passing just about anything on the track (including the mighty AMG) and I've never heard it gasp for air... Now let's get back to the classroom :
Heh, heh, heh... [bite].

Let's see if I can catch another one.
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      08-24-2012, 01:28 PM   #91
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I have to agree with Bruce on some of his statements. As someone who works with engines for a living I can tell you that during a rebuild or after a block or crankshaft comes back from machining you measure, measure, measure and then measure again.
You do work with pretty small volumes of engines and from a repair perspective, not a high volume manufacturing perspective, correct?

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By simply taking parts off of the shelf and putting them together without measuring, many times can result in failure since the tolerances are not within stated dimensions. I don't know if you guys remember the infamous "GM Piston Slap" fiasco a few years back. That issue started when they stopped the hand fitting of pistons in their blocks and relied on the tolerances of the pistons and bores being within stated dimensions.
Of course this is contradictory to the ENTIRE concept of mass production, assembly line manufacturing. As you know the idea here is that each and every part is identical enough that it is fully interchangeable. I find it hard to believe that the accuracy and tolerance control of modern CNC equipment, statistical process control and 100% inspection that the bore-piston clearance is so absolutely sensitive to its value that this it simply must have hand/human involvement.

We should dive a bit deeper for this specific case as to what "hand" means and what advantages it brings.
  • Are the parts themselves made by hand - no.
  • Are the parts measured by hand, perhaps but very unlikley. Again, robots can measure much more consistently and precisely than human hands.
  • Are the rings fitted by hand - highly likely not
  • Are the pistons chosen to match each cylinder bore - this seems to be what you and Bruce claim
  • Are the pistons installed by hand - again this appears to be an affirmative. Clearly though machinery exists that can do this job perfectly well.

What is the human part of this process exactly? Matching a piston to a bore? Wow that is really the peak of human ingenuity. The requirement for the human in the loop here is deep and compelling... What is the human doing that is superior to what existing equipment can do?

Again, it appears that there is some ongoing glorification of the human aspect of this based on hot-rodding, blue printing, race engines or repair/rebuild. The necessity of hand building in all of those cases is clear.

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I do agree that modern automated machining can make extremely tight tolerances and is very good, but, if you get out your feeler gauges, vernier, micrometer, or bore gauges you can actually show the areas where the measurements are barely within tolerance. A good engine has all of its measurements evenly within tolerance and not all over the place with some on the high side and some on the low side of spec.
Such hand instruments are not capable to quickly and accurately measure to support some of the tolerances we know already exist in modern production engines. Other non contact techniques such as laser, optical etc. Are ones that are fast accurate and integrated into the 100% inspection requirement for precision machined components. Such inspection techniques are also accurate at the micron level. Just no where close to what is possible with a caliper, vernier, micrometer, etc. and a good experienced set of hands

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I can guarantee you that there is some human involvement when building any good high performance engine. Even if each and every engine is not hand assembled, some of the parts or even a complete engine will be pulled from the assembly line every so often and measured to verify that all of the dimensions are indeed within spec and as a form of QC.
I don't disagree, it is simply driven by cost and volume not necessarily by some magic skill that a human has over a machine.

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One final thing, even the S65 which BMW does not claim is hand assembled has three sizes for main bearings. If you look at parts list the bearings have colours assigned to them. This is due to the main bearing bore variance and the need to keep the oil clearance proper. Now I don't know if they hand measure and then select the bearings or if they have a machine measure but either way this shows that even high tech machining equipment can have some variance that has to be made up for with correctly sized bearing shells.
Your conclusion does not follow from the facts. This could be because the tolerances were actually adjusted during manufacturing stages. It could be because a large volume of a certain component - block, bed or crank were produced out of spec. In any case I agree that this fit/clearance is one of the most critical dimensions of the engine.

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As for pistons, the S65 only shows one piston size. Since Mahle makes the S65's pistons and they are known as one of the best piston manufacturers in the world, they probably verify dimensions before shipping them, and BMW may very well check all of the bores of the blocks after machining and only build engines out of the ones that meet their specs.
Agreed, we are right back to precision manufacturing, mass manufacturing and 100% inspection. Here the parts are interchangeable as it is must be the case for the manufacturing to be successful. Both the pistons, by Mahle and the bores absolutely positively receive 100% inspection/measurement and I'd even pretty well guarantee this is done (for critical dimensions) by machine.

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Originally Posted by BMRLVR View Post
The moral of this post is that having a skilled craftsman measuring and building you an engine is definitely worth it, as good as machines are, many times we have had to send back brand new parts that were supposed to be within spec but were indeed not even close. If you work with this stuff all the time you realize that machines, while as amazing as they are, do not always build the perfect parts. Finally, Even with automated assembly there is always a programmer or machine operator that has to be added into the equation too!
I simply disagree with your first claim.

I enthusiastically agree with the last statement. The machines are all just as clever, useful an accurate as their brilliant designers, engineers, programmers and maintenance folks.

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P.S.: Swamp, their is indeed evidence that hand fitting of pistons does offer benefit and it is not merely anecdotal, it is a fact and has been proven. While it may not always be measurable in terms of power, it will definitely be measurable in longevity. Excessive piston to bore clearance will result in piston slap and piston to bore clearance that is too tight will result in scuffing and excessive wear. Over time piston clearance that is too tight or too loose will make the bores wear out of round which can eventually lead to oil burning and/or loss of power. Basically if you want an engine to run quiet, make power and last, you need to ensure all of your measurements are nicely within spec. ( I know you know this but I thought I would add my $0.02)
I don't disagree with the basic sentiment or causality here. You would know way better than me on this. Everything must have a context and scale though. If pistons and bores are being produced with relatively low tolerances AND an engine is being manufactured in a relatively low volume then it would necessitate more human/hand involvement. This, however, is not really the case for any BMW or MB engines we are discussing here.

Ultimately, as many similar discussions go, I think the only way to settle this would be to have candid access to BOTH a design engineer responsible for setting the piston-cylinder clearance specification as well as the corresponding manufacturing engineer responsible for engine assembly and meeting that requirement. Of course we would need to know from these guys working at a large company working on a typical large volume engine.
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      08-24-2012, 02:05 PM   #92
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Quote:
Originally Posted by BMRLVR View Post

The moral of this post is that having a skilled craftsman measuring and building you an engine is definitely worth it, as good as machines are, many times we have had to send back brand new parts that were supposed to be within spec but were indeed not even close. If you work with this stuff all the time you realize that machines, while as amazing as they are, do not always build the perfect parts. Finally, Even with automated assembly there is always a programmer or machine operator that has to be added into the equation too!

P.S.: Swamp, their is indeed evidence that hand fitting of pistons does offer benefit and it is not merely anecdotal, it is a fact and has been proven. While it may not always be measurable in terms of power, it will definitely be measurable in longevity. Excessive piston to bore clearance will result in piston slap and piston to bore clearance that is too tight will result in scuffing and excessive wear. Over time piston clearance that is too tight or too loose will make the bores wear out of round which can eventually lead to oil burning and/or loss of power. Basically if you want an engine to run quiet, make power and last, you need to ensure all of your measurements are nicely within spec. ( I know you know this but I thought I would add my $0.02)
Definitely agree with you on all of this! Took the words out of my mouth.
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      08-24-2012, 02:11 PM   #93
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Seems pretty obvious you are speaking to me so I'll reply.

I have built motors by hand, myself but only very simple single cylinder ones contrasted with any modern multiple cylinder automobile engine.

Human error is a huge factor in any process and that is why industrial, manufacturing and reliability engineers prefer to remove them from the process. Your point only helps mine, it does not provide an argument against it.

I understand German manufacturing pride just as well as American manufacturing pride, thank you very much. I know dozens of engineers from both countries and I am a (recovering) Mechanical Engineer myself. I've done design, manufacturing engineering, tolerance studies, test engineering, test and assembly tooling design, assembly automation, fatigue/static/dynamic testing, thermal testing, physics based product simulation, product data management and on and on. Perhaps ask others involved in the discussion their relevant professional experience... Although I don't do any of that professionally any longer I continue to build a great deal of things with my hands. I don't sign my name on them but you can be assured there is an enormous degree of pride and perfection in the things I build, it's simply my nature.

Any other questions?
I Agree with you as well. We also have to consider it is a high performance engine and machines make mistakes. They can not auto correct themselves if their programming is for one function and they machine too much material etc. Now you add in auto laser measurements and inspections, the setup gets pretty complicated. In the mean time its still being over seen by a human operator looking at a screen. Not to forget the retooling costs of a factory to assemble these engines would cost 100's of millions of dollars. Automation is not always the cheapest way. They might calculate that the robotic automation costs would need to assemble 25,000+ engines before they break even on retooling. Sometimes labor is cheaper vs setting up the space and additional programming or machining. Nissan has their GT-R engines hand assembled as well. Its a level of double checks and inspections when you are making something this high performance. Its much easier to have an engine builder with 40 years experience double check the work and give him some blueprint specs. From a business standpoint, it is easier that way since the car is low production compared to a regular C Class. You would really have to ask Mercedes and BMW why they made the choices to do this.

Of course yes the signature thing is probably a joke and I remember my Ford GT had one on the valve covers and I always envisioned some big guy with a huge beard wrenching my engine together and sipping down a cold Budweiser. I say this because one day, I had the dashboard out to do a mod and a beer bottle cap fell out of the car. I dont drink Bud, and no idea how it got there as I was the first owner lol.
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      08-24-2012, 02:28 PM   #94
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Now imagine the uproar in this forum if the M3 motor were hand built and the AMG motor was machine built, and the OP called out the M3 motor like he did the AMG motor. There would be a fanbois going nuts saying stuff like, "The M guys have passion", "They give the M its soul", "hand built because BMW cares", "real race engines are hand built" Unbelievable.
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      08-24-2012, 02:45 PM   #95
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This is a ridiculous thread...I love it!
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      08-24-2012, 02:56 PM   #96
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Now imagine the uproar in this forum if the M3 motor were hand built and the AMG motor was machine built, and the OP called out the M3 motor like he did the AMG motor. There would be a fanbois going nuts saying stuff like, "The M guys have passion", "They give the M its soul", "hand built because BMW cares", "real race engines are hand built" Unbelievable.
A very good observation and surely some of those replies would have been made.
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      08-24-2012, 04:07 PM   #97
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Now imagine the uproar in this forum if the M3 motor were hand built and the AMG motor was machine built, and the OP called out the M3 motor like he did the AMG motor. There would be a fanbois going nuts saying stuff like, "The M guys have passion", "They give the M its soul", "hand built because BMW cares", "real race engines are hand built" Unbelievable.
Spot on.
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      08-24-2012, 06:47 PM   #98
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I am no engineer and don't have the faintest idea when it comes to engines and its intricacies. But looking at the video, the S65 engine, the pistons are hand assembled and then the rest of the assembly is hand torqued and individually measured and entered into the computer so in the future when something drastic happens with the particular engine they can refer the assembly process.
I don't see an automated process to build the S65 engine accept for may be casting the blocks and machining the cylinder heads and pistons amongst other things. Putting the engine together is done by human just by watching that video.

Now how is this different to AMG's claim? But BMW doesn't claim it is hand building the engine. It's a pure marketing gimmick as far as I am concerned. Just noting my point here.
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      08-24-2012, 06:57 PM   #99
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I love reading these, all of these.

Me too. BTW, I brought some to go with the
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      08-24-2012, 07:55 PM   #100
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I have no clue what you guys are saying, but I did stay at a Holiday Inn Express last night.
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      08-24-2012, 09:08 PM   #101
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Can someone enlighten me as to the "glorious sound" of the c63? Granted my opinion is only reached through YouTube videos but it doesnt sound all that great to me. Just sounds like any other v8. Am I way off base?
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      08-24-2012, 09:34 PM   #102
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You have to hear it in person to appreciate it. Before I got my M3, I thought it didnt sound that good according to the videos, until I bought one and heard it live. I loved the way it sound.
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      08-24-2012, 09:37 PM   #103
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Can someone enlighten me as to the "glorious sound" of the c63? Granted my opinion is only reached through YouTube videos but it doesnt sound all that great to me. Just sounds like any other v8. Am I way off base?
You need to hear one... both inside and outside... to appreciate it. It is an amazing sound and, IMO, one of the best available. It sounds deep, smooth, angry and raw all at the same time if that's even possible.

But, like everything else in life, everyone will have a different preference to sound. Sound is one thing that sets AMG apart IMO.
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      08-24-2012, 10:03 PM   #104
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You need to hear one... both inside and outside... to appreciate it. It is an amazing sound and, IMO, one of the best available. It sounds deep, smooth, angry and raw all at the same time if that's even possible.

But, like everything else in life, everyone will have a different preference to sound. Sound is one thing that sets AMG apart IMO.


I loved the exhaust note on my C63. Startup was fantastic every morning.
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      08-24-2012, 11:35 PM   #105
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I am no engineer and don't have the faintest idea when it comes to engines and its intricacies. But looking at the video, the S65 engine, the pistons are hand assembled and then the rest of the assembly is hand torqued and individually measured and entered into the computer so in the future when something drastic happens with the particular engine they can refer the assembly process.
I don't see an automated process to build the S65 engine accept for may be casting the blocks and machining the cylinder heads and pistons amongst other things. Putting the engine together is done by human just by watching that video.

Now how is this different to AMG's claim? But BMW doesn't claim it is hand building the engine. It's a pure marketing gimmick as far as I am concerned. Just noting my point here.

The Video in Question was of pre-production S65 Engines (some of the first ever built). Production S65's are indeed assembly line built since the hand building that the video shows could not come close to keeping up with the volume required.

@ Swamp: I can't disagree with anything you have said above in reply to my post, as usual you have your facts in order.

Like you mentioned, cost is key in this equation and it costs a lot to hand assemble engines. As for machines making perfect parts time after time, you are almost correct, but many times the first parts from a batch will be better than the last parts out of a batch simply because cutter heads and other parts wear and that is where your variance comes from. At some point a machine needs to be re-calibrated to make up for this wear. A machine is only as good as the preventative maintenance program of the company that owns it, and since cash is king, preventative maintenance is getting cut back everywhere. When a machine has to go down for maintenance, production is affected and so is profit. However, with proper maintenance and adequate QC machines are definitely able to make virtually exact parts one after the other, the maintenance and QC is the variable and like I said above that is up to the company. (This reminds me of a story of a friend of mine who worked at the GM assembly line in Oshawa, Ontario........ He told me that by the end of the production run of the Eighth generation Chevrolet Impala, the dies used to stamp the body panels were so worn that the rear windows barely even fitted the body any more and GM refused to spend the money to replace them since the car was going out of production soon. The solution was to use extra urethane to take up the added gap between the window and body and stick the molding over top of it. I know we are not talking about GM here, but where ever cash is king sometimes corners are cut, no manufacturer shy of Bugatti or Rolls Royce are free of this type of thing)

Anyhow I can ramble on and on, but in the end I think we are both right, machines are simply amazing at mass production of identical parts, so much so that no human could ever hope to even come close to matching the volume yet keeping tolerances so close. At the same time a hand built engine is almost always going to have tolerances that that are tighter than the one produced by machines simply because there is more time and hands on involvement to allow this.

One thing that should be noted though, no automobile assembly line that I have ever seen has been able to totally eliminate people from the equation, there are always some humans in there!

Finally, I don't know of a machine made that can feel a grinding or drag, or hear a particular noise like a trained craftsman can. There are some things that machines just don't have and that is the human touch. If AMG engines are hand assembled like they claim, I think there is at least some value in that. They may not necessarily be better because of it, but as an engine builder myself I feel a connection to the fact that another person from my craft put it together with his hands even if it was from parts largely made by an automated machine with many high tech tools.
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      08-25-2012, 04:40 AM   #106
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Good post. Let's continue.

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The Video in Question was of pre-production S65 Engines (some of the first ever built). Production S65's are indeed assembly line built since the hand building that the video shows could not come close to keeping up with the volume required.
Correcto. And this MB engine in question here is running a substantially higher volume than the S65.

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Like you mentioned, cost is key in this equation and it costs a lot to hand assemble engines. As for machines making perfect parts time after time, you are almost correct, but many times the first parts from a batch will be better than the last parts out of a batch simply because cutter heads and other parts wear and that is where your variance comes from. At some point a machine needs to be re-calibrated to make up for this wear. A machine is only as good as the preventative maintenance program of the company that owns it, and since cash is king, preventative maintenance is getting cut back everywhere. When a machine has to go down for maintenance, production is affected and so is profit. However, with proper maintenance and adequate QC machines are definitely able to make virtually exact parts one after the other, the maintenance and QC is the variable and like I said above that is up to the company. (This reminds me of a story of a friend of mine who worked at the GM assembly line in Oshawa, Ontario........ He told me that by the end of the production run of the Eighth generation Chevrolet Impala, the dies used to stamp the body panels were so worn that the rear windows barely even fitted the body any more and GM refused to spend the money to replace them since the car was going out of production soon. The solution was to use extra urethane to take up the added gap between the window and body and stick the molding over top of it. I know we are not talking about GM here, but where ever cash is king sometimes corners are cut, no manufacturer shy of Bugatti or Rolls Royce are free of this type of thing)
Almost completely agree with you here. There is however a key difference. Machining vs. stamping. One has very low consumable tooling costs (replaceable cutting blades) and they other has really high ones (replace an entire stamping tool). Also in the case of machining, in cases where tolerances are critical (pretty well all internal engine dimensions) statistical process control and 100% part inspection are used. Those things together can pretty much eliminate the effects of slow and steady wear on cutting tools. There is much less luxury for stamping dies. I suspect they can be tuned up a bit along the way at a relatively low cost, perhaps welded, ground and or polished. Either way there is a fundamental difference.

[quote=BMRLVR;12565885]Anyhow I can ramble on and on, but in the end I think we are both right, machines are simply amazing at mass production of identical parts, so much so that no human could ever hope to even come close to matching the volume yet keeping tolerances so close. At the same time a hand built engine is almost always going to have tolerances that that are tighter than the one produced by machines simply because there is more time and hands on involvement to allow this. [quote]

Still don't fully agree with this. It is a but subtle. There are certainly combinations of team, process and equipment which are better than others combination of team process and equipment. One might compare a really well funded OEM engine production team (company) like BMW Porsche or even Ferrari (the latter is probably not the best example because of low volume they will necessarily have a higher percentage of human involvement) with a somewhat crude back yard team of buddies building big block Chevy drag engines for their team. They latter may fully blueprint and may do everything by hand but their limitations in terms of their sourcing, machining and inspection accuracy will not allow them to match the OEM who is perhaps 99% automated. Just because one complete team takes one small step (or even an entire process) by hand does not immediately let you conclude they have actually improved something over another teams outcome. The devil is in the details.

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Originally Posted by BMRLVR View Post
One thing that should be noted though, no automobile assembly line that I have ever seen has been able to totally eliminate people from the equation, there are always some humans in there!
Absolutely. Humans are physically present in some places, always but their ingenuity is omnipresent. This video does not cover engine assembly but does show a large part of the assembly of a modern BMW 3er. A truly amazing video.

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Originally Posted by BMRLVR View Post
Finally, I don't know of a machine made that can feel a grinding or drag, or hear a particular noise like a trained craftsman can. There are some things that machines just don't have and that is the human touch.
Acoustic and ultrasonic inspection techniques have been widely used since the 1970's for the inspection of the wear and functional state of machinery! A very commonplace application for this is for the non-contact inspection of ball bearings. Again, it is mostly about volume and cost.

Perhaps an interesting and loosely related topic would be a short list of the the very common things that humans are much better at than machines...

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Originally Posted by BMRLVR View Post
If AMG engines are hand assembled like they claim, I think there is at least some value in that. They may not necessarily be better because of it, but as an engine builder myself I feel a connection to the fact that another person from my craft put it together with his hands even if it was from parts largely made by an automated machine with many high tech tools.
The personal allure or romance of the craftsmanship has been discussed earlier. It is something with a strong emotional content for some. However, it should not be allowed to interfere with the facts! Personally I get the same type and level of allure and amazement for the omnipresent nature of the feats of manufacturing engineering that go into the making of some pretty mundane objects, not to mention something with the complexity of a modern automobile...
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      08-25-2012, 05:17 AM   #107
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A quick check into the annual sales volume of Mercedes AMG indicates a mere 20,000 vehicles in all of 2011. AMG is gunning for about 30k this year. That means the engines are being cranked out at only (very roughly) 100 engines/day. This volume is significantly lower than my initial gut feeling which was driven by the understanding that there is a great deal of engine commonality among many different AMG vehicles. Heck the E46 M3 sold at about 15,000 vehicles per year. This volume is certainly quite small compared to the 380,000 or so 3ers BMW sold in 2011. There certainly are cars that sell in much higher volumes than the BMW 3er, that was just another reference point.

Based on this relatively low volume I do expect a significant amount of engine (and other) hand assembly. That being said I'll stick firmly to my primary point that any such hand operations are done purely from a cost perspective. That is of course assuming I understand the AMG engine situation correctly in that they are entirely specific to the AMG cars and are not used in the non AMG Mercedes line.
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      08-25-2012, 07:28 AM   #108
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Just so you guys know, there was or still is a woman who assembles engines in the AMG plant so technically, the "One Man, One Engine" slogan isn't politcally correct.
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      08-25-2012, 09:43 AM   #109
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Quote:
Originally Posted by swamp2 View Post
A quick check into the annual sales volume of Mercedes AMG indicates a mere 20,000 vehicles in all of 2011. AMG is gunning for about 30k this year. That means the engines are being cranked out at only (very roughly) 100 engines/day. This volume is significantly lower than my initial gut feeling which was driven by the understanding that there is a great deal of engine commonality among many different AMG vehicles. Heck the E46 M3 sold at about 15,000 vehicles per year. This volume is certainly quite small compared to the 380,000 or so 3ers BMW sold in 2011. There certainly are cars that sell in much higher volumes than the BMW 3er, that was just another reference point.

Based on this relatively low volume I do expect a significant amount of engine (and other) hand assembly. That being said I'll stick firmly to my primary point that any such hand operations are done purely from a cost perspective. That is of course assuming I understand the AMG engine situation correctly in that they are entirely specific to the AMG cars and are not used in the non AMG Mercedes line.
I have no doubt that cost is always a factor, however, at a production rate of about 100 engines per day, there is time to have extra QC and be tighter on tolerances.

Your knowledge of mechanized/automated assembly is obviously much greater than mine and I can't intelligently rebut against many of the points you make since I simply don't have the knowledge.

One thing I do have knowledge of is engine assembly, and I can safely tell you that I have seen many mass produced engines from automated assembly lines that have issues from either improper clearances, defective parts or incorrect assembly (gaskets or o-rings left out). I have no doubt that machines are able to make perfect engines provided that every bore, part, fastener, etc. are of perfect dimension and free of defects, however at extremely high volumes I don't think manufacturers are inspecting every part for quality or dimension, they are probably only inspecting every 100th or 1000th part. This less than 100% QC is the main reason for recalls, and manufacturers warranties, to deal with the inevitable problems that get past the machines.

I am still confident that an engine that is hand assembled by a craftsman who is verifying every measurement with a hands on nature is going to be built tighter compared to an engine that is built by a machine where maybe every 100th engine is pulled from the production and inspected. I may be wrong on this but this is my feeling. I also think that if BMW were hand assembling the S54 and S65 blocks that they wouldn't have had the main bearing issues that seem to be cropping up because they would have had the oil clearance adjusted to the proper specs instead of trusting in mass produced parts that may be off 0.0005" here and 0.00025" there causing issues down the road!
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      08-25-2012, 01:35 PM   #110
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Quote:
Originally Posted by BMRLVR View Post
I have no doubt that cost is always a factor, however, at a production rate of about 100 engines per day, there is time to have extra QC and be tighter on tolerances.

...

One thing I do have knowledge of is engine assembly, and I can safely tell you that I have seen many mass produced engines from automated assembly lines that have issues from either improper clearances, defective parts or incorrect assembly (gaskets or o-rings left out). I have no doubt that machines are able to make perfect engines provided that every bore, part, fastener, etc. are of perfect dimension and free of defects, however at extremely high volumes I don't think manufacturers are inspecting every part for quality or dimension, they are probably only inspecting every 100th or 1000th part. This less than 100% QC is the main reason for recalls, and manufacturers warranties, to deal with the inevitable problems that get past the machines.

I am still confident that an engine that is hand assembled by a craftsman who is verifying every measurement with a hands on nature is going to be built tighter compared to an engine that is built by a machine where maybe every 100th engine is pulled from the production and inspected. I may be wrong on this but this is my feeling. I also think that if BMW were hand assembling the S54 and S65 blocks that they wouldn't have had the main bearing issues that seem to be cropping up because they would have had the oil clearance adjusted to the proper specs instead of trusting in mass produced parts that may be off 0.0005" here and 0.00025" there causing issues down the road!
Mostly agree here. There can be both good and bad hand assembly and machine assembly. It actually comes down to both quality assurance and engineering - the actual design. Engineers are responsible for setting tolerances on each part. The balance is on cost vs. engineering function. Obviously some dimensions are way more critical than other, again here main bearing clearances and piston-bore clearance being tight whereas something like a bearing width or total camshaft length is not nearly as critical. Problems arising from these values not being proper to insure good and long engine function can be design, manufacturing or inspection. Certainly more critical dimensions receive more scrutiny in each domain. I'm not up on the details of the SPC (statistical process control) of engine block and internals machining. I am pretty confident though that on critical parts such as these, contributing to these kinds of high precision fit requirements, 100% in line inspection is occurring. Again machines can do this extremely fast and extremely inexpensively.

I've never argued that all machine built engines are superior. Only that given the choice for a high production volume engine, I would place my bets (and personal buying choice if I actually had one...) on the machines for the vast majority of the process. Even in the case of hand assembly, the vast majority of the part production and inspection is still likely done by machine (I guess that is obvious to many but still worth stating again). As discussed prior, we can eliminate the human from the line but for any reasonably high volume we can not eliminate the machines. Bringing it full circle faults due to machines are ultimately problems with the human team behind the machines themselves (again could be design, QC, inspection, maintenance, etc.).

It would indeed be fascinating to see a video like the one above of the 3er main assembly for engines, comparing something like the Honda Accord (very high volume) to something the the M156 (AMG Engine - mass produced but much smaller volumes).
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