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

["Steve Makohin" <wateredg@xxxxxxxxxxxx>]

Hello Ben,

Ben Barkow <dr.ben@xxxxxxxxx> wrote:

[snip]
>> 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.

Your statement above is correct, but there is potential for misunderstanding 
by the reader. Note that I do not state nor imply that just because a bike 
has two large cylinders (e.g. 500 cc +), that it will surge or run rough. I 
*am* saying the following...

When a manufacturer intends an engine to be fuel efficient, either through 
design or through "enhancements" to increase this property, and the engine 
is a two cylinder large-bore bike, the risk of some sort of rough running 
increases significantly. This is more prevalent in air and air/oil cooled 
engines than it is in liquid cooled engines because those engines also have 
to deal with additional design constraints that are in place purely because 
the engine cannot dissipate heat as well as a liquid cooled engine. 
Dual-plugging is an attractive option because is requires no additional fuel 
(thereby maintaining fuel efficiency), allows more thorough and more 
consistent combustion, and in doing so, produces a smoother running engine 
(e.g., no surging on a BMW Oilhead).

- -Steve Makohin
 '01 R1100S/ABS
 Oakville, Ontario, Canada

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