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Discussion Starter #1
I know this Technology is not new and has been seen for many years in other industry's.

But how does this application benefit from the 2 plug per head design.?

Better fuel economy, Improved throttle response, Lower emissions , etc.

I might have the bases covered above but are there other reasons ?


And my first question is : if one of the plugs stopped working would you know it ?

Trigger check engine light ? Engine rpm stumble ? :confused:
 

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I think combustion efficiency is the main reason. Piston engine aircraft have run a dual magneto/ spark plug arrangement for years. Mainly for redundancy in case a magneto fails. Part of a pilots and mechanics check is a magneto drop test. During engine runup at a specified RPM each magneto is shutoff to check the other. There was usually about a 150 RPM drop with one mag switched off.
 

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Initial reasons for two spark plugs per cylinder were for reliability. Spark plugs commonly fouled decades ago.

Then they were used to lower emissions. And to increase power. Some combustion chamber designs are more efficient than others. Adding a second spark plug would help a less efficient design meet emissions requirements or produce more power.

Why does a second spark plug lower emissions or increase power? It adds a second flame front. When the fuel/air mixture ignites, how it travels from that point has a lot to due with how well the fuel/air mixture is consumed. There can be pockets of mixture that don't "burn" due to stagnant movement or other issues that combustion chamber has. The further a flame front travels, which takes time, the more likely the controlled burn can become out of control and explode ( detonation ). By using a second flame front provided by a second spark plug, the distance traveled is reduced, as is time for the mixture to completely burn, and this tends to more completely burn the fuel/air mixture. This reduces hydrocarbon emissions, lessens detonation issues. And a by product is increased power for the same amount of fuel used.

A really good combustion chamber design may not benefit from a second spark plug ( which in itself complicates combustion chamber design ).
 

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Discussion Starter #5
I would think it might be more likely to decrease emission levels due to the fact that one plug is on the side of the head
and one is located more central to the head nearer to the intake and exhaust valves.
 

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I would think that anything that creates a fuller and more complete combustion process will also create more power, lower emissions, and greater fuel economy.
 

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Discussion Starter #7 (Edited)
Do many ( or any) of the newer motorcycles other than Suzuki use this design engineering Trait ?


It is amazing that they are able to squeeze allmost 70 h.p from a 650 cc 2 cylinder engine ( in my case )

I have seen Single Cylinder Briggs and Stratton engines used in Junior dragsters Hopped up to the point
they run Alcohol /methanol and turn more than 8000 rpm. and 50 h.p And these are just run of the mill
5 h.p go kart engines that have been extensively modified. You have to give these engineers a lot of credit for
knowing how to make power in a small package. Motorcycle engineers just do it with a warranty in mind.
 

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Adding a second spark plug was a way to boost HP a few years ago on my 1974 Moto Guzzi SP 1000. I suspect it was done way before that year, too.
 

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The tenere runs a 2 plug head and they are located side by side. It also uses coil packs on the plugs to direct fire the spark plugs. For a 1200cc, the tenere is mildly tuned at 100 hp.
 

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I bet new v-strom 2020 won't use 2 sparks per cylinder anymore, cost saving will take effect
plus all good technology seams to be disappearing recently so pick up your strom while you still can :)
 

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I bet new v-strom 2020 won't use 2 sparks per cylinder anymore, cost saving will take effect
plus all good technology seams to be disappearing recently so pick up your strom while you still can :)
Not sure I agree with this, as all the motorcycle companies are fully embracing "good technology" IMHO. Suzuki saves money by using budget brakes and suspension, plus whatever else in the parts bin can be transferred to another model, this is a pretty common practice all around. The Stroms for example are being improved with every edition, they can hopefully only get better. :fineprint:
 

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Discussion Starter #12
I kind of think this is a trend. If you market a great all around motorcycle like the Vstrom series (lots to offer )
In a durable powerful package - they will come. And if sales figures remain actively brisk number crunchers will
keep it in play. Similar to what Honda has done with the tried and true entry level Rebel 250. Which has been
around for over 25 years.

To me the Vstrom has a gem of a motor. And an easy platform to season to taste. :)
 

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The Stroms for example are being improved with every edition, they can hopefully only get better. :fineprint:
wishful thinking, look what is happening with other Japanese brands...
cost saving cuts all over the place. That's the only reason I didn't buy new Africa Twin. I knew it's gonna happen first because of that horrible tsunami
and then emission BS...
 

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Discussion Starter #14
You know it could very well be a time for Suzuki to shine. In the auto industry with so many players at the table,
all it takes is one manufacturer to come out with a design thats a real hit with consumers and then everyone wants
to build something that looks like it or is very similar to it. This means they try to steal market share from the ones
getting the big sales figures. Copy catting. Think about how many bikes out today have the pointed beak style the Vstrom
has had for several years. Not that they were first , but they offer something that covers all the bases which makes it a home run.

It's what farkles are made for ....:var_17::wink2:
 

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My 2002 aprilia etv1000 has dual spark plugs. It a Rotax powered vtwin. It just boils down to more complete combustion.

It was a fairly common mod for Harley’s.
 

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Has to be for combustion efficiency. Emission Reduction.

I think it may decrease horsepower though. GSXR's don't have 2 SP heads and pass emissions testing.

I just converted my L2 to stick coil single spark plug firing.

Now you wonder if dual spark plug electrodes or E3 spark plug design increases...what? :confused:
 

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Discussion Starter #17
Back in the early 70's I rode several 2 stroke dirt bikes that had twin plug heads. One was for the sprk plug and the other
was for a spring loaded cable operated compression release. You used the lever on the bars to dump compression prior
to entering a corner. It was like brakes. it just slowed you down. Ahhh the good ole days.....
 

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Discussion Starter #18
Has to be for combustion efficiency. Emission Reduction.

I think it may decrease horsepower though. GSXR's don't have 2 SP heads and pass emissions testing.

I just converted my L2 to stick coil single spark plug firing.

Now you wonder if dual spark plug electrodes or E3 spark plug design increases...what? :confused:
So does it seem to be better, faster or quicker than before ?
 

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I owned a 1984 KDX200 to which I added a decompressor by drilling an extra spark plug hole into the head and fitting the unit there.
It was great on steep downhills and in slippery terrain. Maximum braking without any chance of locking up the rear wheel.

Unfortunately Kawasaki then introduced water cooling.
 

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To get fuel to ignite properly you need the correct mix of fuel and air at and near the ignition point and a source of heat, like a spark.

Sounds simple, but what actually happens in an engine is pretty complex and not only depends on things like air pressure, temperature, rpm and fuel but also on what happened on the last stroke. Some of the air coming in tends to bounce and the same thing happens at the exhaust. The resuit with a single plug engine in a good state of tune is the occasional misfire due to the mix being way off at the point where the spark is. Maybe 1% or so of cycles. That also tends to screw things up somewhat on the next cycle as well.

A second spark reduces the odds of that happening, the 1 in 100 odds drop to perhaps 1 in 10,000 and make for a smoother feeling engine and better emissions performance. It's mainly emissions that's the problem for a bike engine, a car can have a large enough exhaust and cat to get rid of the effects of unburned fuel before it exits the tailpipe, a bike, not so much.
 
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