Koop Posted October 30, 2008 Share Posted October 30, 2008 Anyone have a photo of the hex head combustion chamber? Looking at the spark plug orientation I'm having a difficult time understanding the secondary plugs relationship to the combustion chamber. With the CR of this engine, there shouldn't be much room to have a plug introduced from the side. How'd they do that?? Link to comment
FLTRI Posted October 30, 2008 Share Posted October 30, 2008 I've often wondered the same thing. Interested to hear the answer, or see a photo... Link to comment
Chris K Posted October 30, 2008 Share Posted October 30, 2008 This is the best I could find. If you look at the closest cylinder you can see the tip of the secondary spark plug in the lower part of the cylinder. Link to comment
Koop Posted October 30, 2008 Author Share Posted October 30, 2008 Thanks for the illustration. I wish the service manual (CD) had system overviews and iilustrations. Now I'm wondering why there's a gear drive and chain on the front of the crank. Kind of like wearing a belt and suspenders! Link to comment
T__ Posted October 30, 2008 Share Posted October 30, 2008 Koop, gears drive the balance shaft & the chain(s) drive the cam intermediate shaft & pumps.. The balance shaft runs backwards to engine rotation.. Twisty Link to comment
Semper_Fi Posted October 30, 2008 Share Posted October 30, 2008 Seconday plug view with spark plug cover removed Link to comment
Ken H. Posted October 30, 2008 Share Posted October 30, 2008 Here's a picture of a head, taken while I had it off to repair a crashed piston. You can see both the center and lower (angled in) spark plug holes: Link to comment
FLTRI Posted October 30, 2008 Share Posted October 30, 2008 Thanks Ken May be a dumb question, but what is the purpose of having two plugs??? Link to comment
Penforhire Posted October 30, 2008 Share Posted October 30, 2008 Wasn't the 2nd plug added to reduce the infamous "surging" caused by tightened emission controls (hunting for the perfect fuel:air mix)? Link to comment
Boffin Posted October 30, 2008 Share Posted October 30, 2008 Wasn't the 2nd plug added to reduce the infamous "surging" caused by tightened emission controls (hunting for the perfect fuel:air mix)? It was not added to cure surging, though it did have that effect. It was added to allow the boxer to meet the newest European emissions regulations. Essentially, not all of the mixture was getting burnt - possibly due to the spare-squirt FI that fires on the fiting stroke as well as the induction stroke. The second plug burns all of the fuel leading to less surging, more power and lower fuel consumption as well as lower emissions. Link to comment
TomfromMD Posted October 30, 2008 Share Posted October 30, 2008 IIRC, a number of airheads were fitted with dual plug heads back in the late 1970's to alleviate the detonation caused by lower octane gas as lead was phased out in U.S. The alternative was thicker base gaskets to effectively lower compression (and power). Tom Link to comment
Koop Posted October 31, 2008 Author Share Posted October 31, 2008 Thanks for the info guys. Link to comment
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