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-   -   Ignition Question (http://www.bimmerfest.com/forums/showthread.php?t=386916)

gahawkins 07-29-2009 11:23 AM

Ignition Question
 
I suspect this question below pertains to many BMW engines, although the sensors and the leads from the sensors differ slightly Model to model. Any philosophical advice appreciated; or suggestions on other forums to post such questions!

My 1991 E34 M5 has a broken "cylinder identification" sensor. This device appears to be a toroidal coil on the #6 ignition wire, which apparently provides an inductively sensed pulse to tell the DME (engine management computer) the cam position - ie are we firing on the exhaust or the compression stroke. The car runs fine, despite this disfunctional part. So my question is: what is the ignition spark doing? Same for the fuel injectors, which are usually timed to the cam shaft position?

For example, is the ignition firing on both the exhaust and compression? Or after starting, does the computer gues a cam position and check whether the engine keeps running of begins to slow? Why would one need the part if the engine seemingly runs so well?

-Gil

Prairieman 10-07-2010 07:29 PM

The induction coil on the spark plug wire is used for DME feedback/control of ignition timing. Camshaft position is fixed on the S38 engine, no VANOS for E34 M5's. Spark occurs only on the compression stroke and is determined by the distributor cap and rotor which is driven by the camshaft. For the S38 engine, the distributor is driven by the exhaust cam. During initial start up and warm up, and all RPM's the DME is adjusting ignition timing for best performance and driveability. If the referenced device is malfunctioning, am guessing the DME defaults to a particular ignition setting which is likely rather conservative. Hope this helps.

paris 74 03-20-2011 06:22 AM

which cylinder???
 
hi guys,

i replaced my leads , the new set didn't come with the ignition timing wire and i want to fit the the original one back on

But cant remember which cylinder it went on as it was some time ago.

Its an 89 e34 m20

Thanks


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