Thought about this while in chair (and if you respond real time Martin your social life is even more pitiful than mine): Is major sweeping generalization to merely say "advancing ignition time increases HP". *PART* of lower HP on Volvo F series is earlier spark (yes, I know compression is lower too -- turn off the burners). Horsepower maximized when power stroke is driven by maximum explosive force (if flame propogation was instantaneous, this would be ignition at TDC). Laws of physics require flame to start travel sometime before. But if flame travel starts too soon, mixture is not only combusting unnecessarily against compression stroke, but is combusting mixture before maximum compression. Have seen in print (book -- Robert Sikorsky's I believe. Will look it up at home) that there's something like 5 degrees between optimum ignition and point at which valves start to clatter. Advancing spark towards bottom of that window actually LOWERS HP. If Jim Strickland is reading same post: maximum PRV compression was 10.5:1 on Volvo's B280 redesign. Yields 170 HP. Us 9.5:1 boys are either 145 or 155 HP depending on B27 or B28 (E series). Since Martin's still running original F series heads, I'd argue he's only marginally above 135 (whatever benefit is obtained from richer "jetting" -- old carburetor term). Wouldn't it be something if Martin's performance gain on what remains just a B28F -- sans Lamda screwing around with otherwise richer mixture -- was actually achieved by moving ignition *BACK* to optimum point in compression stroke... Bill Robertson #5939 To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx _____ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/DMCForum/ * To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx <mailto:DMCForum-unsubscribe@xxxxxxxxxxxxxxx?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
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