A regular spark plug has one spark gap. The spark jumps from one electrode across the gap to the other. When you look at a spark plug, the end that goes in the engine, you see the "hook" on one end. That's the electrode. The inside space in the "hook" is where the spark happens.
For decades man was happy with that one spark that took place in the gap. (By the way, the stronger and hotter the spark, the better the gasoline explodes-thus more power. We could go into flame propigation and timing etc., but that's more reading you can do on your own.)
With the plus 4 plugs there are 4 of those "hooks" around a the central electrode. If you were looking straight on to the plug you'd see a "+" sign, but the middle would be empty.
The spark will jump accross the gap with the least resistance. So, having 4 electrodes gives the spark 4 possible paths to choose. Theoretically, since there is a "best" path for it, you get a better spark.
A plus 2 has two "hooks."
See here:
http://www.boschusa.com/AutoParts/Sp...PlatinumPlus4/
"Four ground electrodes provide multiple spark paths which allow the spark to travel the most efficient path and deliver a longer and more powerful spark than conventional single electrode spark plugs. This offers superior burn characteristics for ultimate engine performance."
The Splitfires do somthing similar. From what I've read, they use a split "hook" to make a wide, flattened out spark. Supposedly, this also achieves a hotter, longer spark than a regular plug. Thus, more power.
http://www.splitfire.com/triple.htm
"The patented SplitFire "V" design on the side electrode is instrumental in helping to improve combustion efficiency. Because the flame kernel is not blocked by the side electrode as in other spark plugs, it can travel upward through the "v" notch into the combustion chamber . . .
That's the SplitFire Performance "V" Advantage."
(While we're at it, I just read on the Splitfire website that they do not pre-gap thier plugs. That means YOU will need to adjust the gap in the plug. It's NOT hard, but do it right. It will be important to the proper running of your engine.)
Same ideas, different methods.
Not that I mind helping, or I wouldn't have found this for you...but, I'd like to mention that the web is a wonderful place to learn all this stuff. All of it was available for you to find using google. Though, I do understand that if you don't know the right questions to ask, you'll get nowhere.
Don't be afraid to google just what you want to find. I typed "bosch" and found the plus 4 info with three more left clicks.
"Splitfire" took two. It's all out there.
The huge price difference is becuase Splitfire is really proud of thier product, and charges more.
Sparkplugs, in a stock application such as yours, are NOT going to make a noticable difference (unless the engine is running really poorly and NEEDS new plugs just to run).
Best case, high performance plugs get you 1-3 hp. Yeah, spend your money wisely.
Once you start pumping in modified fuel charges, NOS, turbo or supercharging, etc. the ignition system WILL need to be up to the task. <i>There's</i> where plugs make an important difference.
This link,
http://www.howstuffworks.com/ignition-system2.htm
is pretty damn good at explaining spark plugs.
I wish more people used howstuffworks.com, it's incredibly detailed, and as far as I've read all of the info is correct. Great site, I HIGHLY recommend using it.
Luck.