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

["Steve Makohin" <wateredg@xxxxxxxxxxxx>]

Hello Ben,

Ben Barkow <dr.ben@xxxxxxxxx>:


> Ooops, sent it before I was done.
>
> If I may critique Steve's sense of geometry, the real full benefit  occurs 
> with THREE plugs, not two.

While I agree with the spirit of your statement, the words you have selected 
may leave a reader misunderstanding it to mean that there is no real benefit 
to dual-plugging, and that a "real full benefit" is only realized with 
triple-plugging. All engineering exercises, when tainted with commercial 
production concerns, are compromises between competing factors, such as 
manufacturing costs, maintainability, aesthetics, etc. If you wanted to get 
maximum theoretical benefit from multi-plugging an internal combustion 
engine, you would have an infinite number of ignition sources, all 
individually timed for optimum performance. A little common sense tells it 
would be impossible to physically manufacture this theoretical model.

The addition of a second spark plug (i.e., dual-plugging) is not the 
ultimate and perfect solution by any means. But even so, it provides 
considerable tangible benefits while still being economically feasible, and 
physically practical. While the addition of a third spark plug, or possibly 
more, may provide additional benefits, that does not negate the fact that 
just going to dual-plugging does the job very nicely, and gets rid of the 
primary ridability problem (surging). I'd prefer not to start a thread on 
speculating why BMW didn't go to triple-plugging.




> Ordinarily, adding plugs means you need to change the timing to benefit 
> from the modified flame front. But this can nooot be done with Bosch! 
> (Well, you can move the sensor plate a bit, I understand.)

The San Jose BMW dual-plug mod replaces a number of electronic components to 
account for dual plugging. I do not know if the ignition of the two plugs 
per cylinder is staggered or synchronized. Ditto with BMW's factor 
dual-plugging scheme. I don't believe this distinction matters to the buyer. 
Every one of the over dozen people I have contacted who have upgraded their 
uni-plug Oilheads to a dual-plug configuration all say similar things, which 
include the absolute lack of surging, new-found smooth running, and a "night 
and day" difference before and after the mod.



> It is wrong to say that multi-electrode plugs have multi-source sparks. 
> There is one and only one spark and having more electrodes does not 
> result in more or better sparks. The electrodes shroud the spark  (that's 
> bad). The only advantage is that you have more metal and so the  spark gap 
> lasts through three owners instead of two. These are said to
> be helpful but I don't know much about them.


My understanding is consistent with yours. I am not sure if list members 
have made the case that the multiple electrodes are the differentiating 
factor. I think they just say a specific spark plug, like a certain model 
Autolite, works for them. It's sort of a "black magic"solution (I am not 
sure *why* it works, but it works.)

According to John Parker from Budds BMW (a professional engine tuner, NOT 
just a mechanic), he says that it is possible that a certain model Autolite 
spark plug may be effective at eliminating surging, but that the reason why 
it works would not likely be the brand name of the plug or dual electrodes. 
He says that the plug in question likely has a projected tip, and that 
projection is what makes the difference, as it has in the solution he 
devised for my bike.

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

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