03-07-2018, 10:25 PM | #1 |
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BMW Parts Up Close
My local CCA chapter had a Tech Day event hosted by a local dealer, Motorwerks BMW. This has become an annual event, where the dealers top mechanics present new BMW technology bits to the club.
This year they covered the tools they use to troubleshoot the cars. Surprisingly, they didn't like the official BMW tools very much. They spent a lot of time on unusual tools, like the FLIR camera they use for several things. They showed how they use the FLIR for finding bad comfort access connectors in door handles (they get hot), and diagnosing heated seat and steering wheel issues. The highlight for me are the part displays. They have several large tables loaded with parts from different cars, many of them disassembled, with the relevant ISTA docs explaining various things. They use these parts to train mechanics, and talk with customers to explain repairs. There is a long informal question and answer period with the mechanics hanging around the tables to answer questions. Last year, the thing I found most fascinating is how the DME computer on some engines is mounted to the intake manifold, with the metal base of the housing exposed to the intake air flow to cool the DME down. These were some of the cool things they had this year. I've put the picture inline to better comment on them, so apologize for having at the end as attachments also. This is the automatic shift assembly. On an intellectual level, you know it's all electronic. But actually seeing it out of the car like this, you realize it's really nothing more than a computer joystick. No mechanical attachment at all. Just a box with a plug on the side. This is an M Active Differential. You can see the electric motor on the bottom right that actually does the lockup. It drives the matching gear on the axle that controls the actual lockup clutch. Neat to see how it's controlled by the electric motor, and not traditional clutch packs. Also amazing that it can actuate and spin fast enough to lock/unlock sub-second. This is a cutaway of a 6 cylinder head (I think they said from an N55). You can see where the spark plug comes in, and the direct fuel injection. Not obvious in this picture, but you could also pick it up and see how the valves and intake/exhaust paths all fit together. It was fun to see how complex the head casting is, and how all the parts go together. They had some other more fully assembled heads they were using to explain VANOS. They also had some parts in various levels of destruction. This is what happens when you lose a brake pad, then ignore the squealing as the backing plate grinds away along with most of the disc, until the brake cylinder ejects, gets stuck in the disc, locks the wheel up completely, and then get the car towed in. Just wow. |
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03-07-2018, 11:14 PM | #2 |
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Drives: '17 F22,15 E84 M Sport,02 R53
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Good info thanks for sharing!
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03-10-2018, 11:17 AM | #5 |
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CAN Bus troubleshooting
This is a picture from the event. The BMW mechanic is showing how they use an oscilloscope to troubleshoot CAN BUS issues. It's hooked up to the older 328 in the back. Here you can see that there are two CAN signals, CAN+ and CAN-. They car will actually run mostly fine if one of these is shorted, but may act wonky. Super easy to see with the o-scope. Typical process is to start unplugging a few things, usually the wonky thing first, and see if the signal stabilizes. They actually shorted one side to demonstrate.
Photo credit: North Star BMW CCA and Motorwerks BMW A bit later they had the engine CAN on the lower half of the screen. It graphically showed how much faster the engine CAN BUS operates than the body CAN. The engine CAN will also fail if either side is shorted. Apparently on purpose, as it is safety critical. To demonstrate, they shorted the engine CAN, both signals went bad, and the window wipers started working. He said that the wipers are often a symptom of a failing engine CAN. Apparently partially tied in for speed compensation. So, if your car starts running bad, and the wipers turn on, your engine CAN is broke. He didn't show it, but said the brake CAN runs even faster. And again, thanks to Motorwerks BMW for sponsoring such a great event, and my local CCA chapter for organizing. This is a shameless plug for the BMW CCA. If you aren't a member, you should really consider joining. |
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Tpeterson156.50 |
03-10-2018, 11:34 AM | #6 |
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You mean, there's an actual engine under the hood?
Seriously, very nice post.
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03-11-2018, 07:52 PM | #7 |
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I've attended three of these sessions and this was by far the best.
I just wish I would have won one of the two trips to the BMW performance center that were raffled off. Last edited by Tpeterson; 03-11-2018 at 08:06 PM.. |
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