Originally Posted by pommie john
I'm asking if you have direct comparison dyno charts for single and dual plugs.
I doubt you'd see much difference in HP just between single and dual plugged. The addition of another plug in and of itself doesn't really bump power up much if any. It allows a faster and more complete burn with less advance. This will result in an engine producing less waste heat and which will run cooler. Because it runs cooler it allows you to bump up compression with less likelihood of pinging. Bumping up compression WILL increase your power. So in short it's not the plug that gives the power, but the higher compression the additional plug allows that'll give you power. Also, as BMWeuro stated, twin plugging is more useful in 1000cc engines as the flame front has farther to travel in the wider bore of these engines and thus a second ignition point and two flame fronts will show a greater improvement there than in smaller 750 and 800cc bores.