Brian, sorry but that's not how it works! IF the flame is initiated
successfully (ie, sufficient spark) THEN the flame will propagate all the
way until it consumes all the mixture (except for the amounts trapped in
the crevices where would never get burnt anyway). The flame cannot get
distinguished once it is initiated. In fact, after the spark event, there
is a short period of delay when the flame front is "building up" around the
spark plug. After this delay period, the turbulence inside the engine will
rapidly (but not instantaneously!) propagate the flame and consume all the
mixture. If another spark occurs during the delay period, it will do
absolutely nothing because in the area in proximity to the plug, fuel
oxidation is already taking place. If another spark occurs during the fast
flame propagation period, it will also do absolutely nothing because the
mixture around the plug has already been consumed by the flame.
Now, here is a case where the MSD will help. If for some reason the spark
is marginal (during, say a cold start), and a flame front is NOT initiated,
then the second spark could save the cycle. In normal operating conditions
though with properly functioning ignition system, this will not happen, and
the MSD at that time is virtually useless!
Now, if you had two spark plugs per cylinder, you could really make a
difference. In this case, two separate flame fronts would be initiated
simultaneously. In this case, the flame would be capable of reaching the
extremes of the combustion chamber faster (because the flame would have to
travel a shorter distance), reducing the chances of engine
knock. Therefore, you would be able to run your engine a higher
compression ratio, or lower octane, or higher boost. This is one of the
reasons aircraft engines (often with very high boost pressures) use 2 plugs
per cylinder (the other is reliability). This is not recommended for a
normal engine!
I hope the Imperial content is obvious...
D^2
At 10:04 AM 7/4/2002 -0700, you wrote:
>What happens is the cylinders get overfilled with fuel/air charge
>and the single spark cannot ignite all of it fast enough while under extreme
>pressure(11to1 compression and over) The multi spark ignitions spark first
>and then a FEW degrees later it sparks again, just far enough down the power
>stroke to make a bigger fire. This type of ignition would not benifit power
>output on a stock engine enough to feel it. But on an emmisions vehicle, the
>multispark does well with burning up all of the fuel and in turn reducing
>emmisions.
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