Second(ary?) spark plug?

[PhilBolton]

I saw somewhere a comment about the second(ary?) spark plug, and how it only works at low RPM.
Is that right? So, can someone explain to me how it works?

Phil

 

[terayon]

Basically, engine sensors tell ecu what rpms it's doing and if below a set threshold the ecu tells coils to fire up secondary spark plugs.

Designed to make the burn/ignition more economical/less emissions

 

[terayon]

They also help on over runs, basically when you shut off after having the throttle open you will get some unburnt fuel the secondaries fire a split second after the primaries, causeing any unburnt fuel to ignite and help with pushing the piston.

Suzuki on the other hand get rid of their unburn fuel in the exhaust by using a "PAir" system, Pulsed secondary Air injection. They take air directly from the air box and inject it into the exhaust to burn the fuel. But it requires a lot of sensors and air pipes to do.
But the new Vstrom 650 uses secondary spark plugs to get rid of pair and help in emission control. Try changing 4 plugs every 7500 miles