Quote:
Originally Posted by lindy 911
If anything over 9.5:1 CR and 95mm+ cylinder bores in a Porsche 911 engine
requires twin plugs to prevent / control detonation,
You are mistaken. Twin plugs, initiating 2 flame fronts simultaneously, simply results in reaching PEAK cylinder pressure sooner. That's why the timing advance is retarded vs a single plug engine. In one respect you are correct, without retarding the timing the engine would likely be more subject to knock/ping. Obviously there is also the potential for a more complete "burn". Which is why my '93 Ford Ranger's 2.3L I4 uses 2 plugs/coils/drivers. Clearly not for HP.
how would one live without detonation with only one box if your statement is true about only one plug firing? Mine leads a very happy, detonation free life with very hard driving for a street engine. It's 10.5:1 CR with twin plugs driven by one MSD 6AL.
IF BOTH PLUGS WERE NOT FIRING THE ENGINE WOULD DESTROY ITSELF. PERIOD.
NOT..!
I have pulled the upper and lower plug leads on #1, attached two plugs and grounded them to the engine case. I started the engine, and although it ran a little rough on five cylinders, and clearly observed both plugs firing. Not only were they firing, they were firing bright blue. When I revved the engine the spark becomes constant to my eye, but both plugs fire all the way up to 6500 rpm. How does one account for that if they are both not firing?
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Your eye could not possibly detect a few misfires.
Plus, the hardest time to initiate a spark is under full load, with a FULL cylinder fill of A/F mixture. Those are the times, obviously (WORSE of times, insofar as increased probability of detonation is concerned), when it is most likely that the "trailing" plug will not fire. Unless the 2 coils are somehow mismatched then which plug would be the trailing one would be totally random IMMHO.
Post # 231 should help alleviate your concern....doubts.