Surge Protection?

Surge Protection?

BMW fixes what wasn't (wink, wink) broken

Dare we utter the word "surge?" And what if we whisper "combustion-chamber carbon deposits?" Both of these difficulties were sporadically encountered in recent Oilhead Beemers, causing rideability (part-throttle surging) and reliability issues (burned exhaust valves), but neither was ever wholly acknowledged by BMW, and recent "fixes" haven't been connected with these "non-problems." You follow?

Engineering to the res cue: Each cylinder on the 2004 R1200GS Boxer Twin is now treated by the engine-control comput er as a separate powerplant, and has its own exhaust-oxygen sensor to report its true

mixture, not an engine average as before. An extra sparkplug is added to each cylinder head, as on the previous "2-Spark" Rockster, but the GS also has a separate map for these secondary plugs that shifts timing with condi tions. At peak revs, inlet velocity generates turbu lence for efficient combustion, so the second plug has its spark retarded until it has no effect. But such roomy cylinders need help at lower speeds; the - extra plugs provide it, firing at various off set times to ensure quick, clean, consis tent combustion. So, officially, BMWs didn't ever surge-it's just that now they'll never do it again...

Kevin Cameron