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Re: Dual plugging. Was "Surge Free" spark plugs

On 2005 Jul  23 , at 4:47 AM,Steve M wrote:

> Yes. That is the easy answer. John Parker (Budds BMW and John Parker 
> Racing)
> confirmed this. In fact, years ago when Oilheads surging threads were
> extremely common, I asserted this on my web site and I took a lot of 
> heat from
> Big List Experts for not knowing what I was talking about. Enriching 
> the
> fuel-air mixture will amlost certainly eliminate the surging (assuming 
> the
> bike is in an otherwise good state of tune and repair), but at the 
> obvious
> cost of increased fuel consumption.

I've just returned home from a wonderful scoot around Lake Superior 
with Steve and Kandy and a wonderful group. 2500 miles is an excellent 
length for tuning the Techlusion... finally. The tuning (4 parameters) 
yielded better results than I expected in terms of surging supressio, 
control of flatspots, etc. Removing the rubber booty and twisting the 
pots is rather different than the hrs I have spent changing jets, 
needles, slides, weights, atomizers, floats........

My initial impression is that I get about 43 mpg  with no Techlusion 
boost and about 40 mpg with (just first impressions for the moment. 
That translates into lost cruising range of about 15 miles and a 
corresponding ding to the cost of gas. Not giant but not trivial. For 
me, the benefits vastly outweigh the losses because I have no tolerance 
AT ALL for the surging I was getting.

> In theory, one spark plug in the center of the head in a 4-valve 
> cylinder is
> the optimum placement for an ignition source. That's the theory, until 
> you
> think in three dimensional space + flame propagation. If you envision a
> cylinder in three dimensions with the piston at top-dead-center (TDC) 
> and a
> somewhat domed cylinder head, having the single ignition source in the 
> center
> of that three dimensional space makes the most theoretical sense 
> because the
> flame front will theoretically travel as an expanding sphere 
> throughout the
> cylinder. By having the ignition source located on the upper wall, 
> that being
> the cylinder head, the flame front theoretically travels as a 
> semi-sphere
> starting at the top of the cylinder head and taking longer to travel
> throughout the cylinder. That's the highly-simplified theory, because 
> we know
> that other factors are in play such as the "swirling" of the mix in the
> cylinder, and so on.

> The virtues of dual plugging, including in 4 valve engines, are well
> documents, so this is not news. Rapid adpotion of dual plugging in the 
> car and
> motorcycle industry tells us it's a Good Thing. More significantly, 
> you see
> dual plugging being adopted by motorcycle makers who sport large-bore 
> engines,
> especially twins (Harley-Davidson and Ducati, just to name two aside 
> from
> BMW).

I dual-plugged my Airhead and the improvement (albeit to low end only) 
was dramatic. There are lots of 550 cc cylinders with a single plug 
that work fine, esp. with four valves.