Multi Point Spark Plugs
 

I know that many cars have been using multi point spark plugs for a while now but that the SV does not.

Now i cant see any harm, but are gains noticable?

http://www.oppracing.com/products.php?id=265
http://cgi.ebay.co.uk/RACING-SPARK-P...em110043176580

The ones in my 'Blade are multi points, but at £22 each they should be gold as well !!

.

You are being ripped off there me thinks. NGK Iridium for your bike are £12 ea (www.sparkplugs.co.uk)

Never tried them on my bike but fitted them to a couple of other peoples'. No significant difference, save your money. Dunno about cars but bikes have small cylinders so no real need for double plugs or anything fancy I reckon.

My old polo used to run tri-spark plugs (luckily never had to replace them).

I think the idea is that a bunch of smaller sparks as opposed to a single larger spark are supposed to produce a more effective and efficient burn. I'm not sure whether it's correct and proven though.

I do remember a while back there was a craze for "power balls" which were like balls of plastic with something inside them to "break up" the spark on standard plugs to lots of little sparks. you had to cut your plug lead and put them in I think. A lot of hype, but my dad had some bother when he put them on his old VFR750.

I'm not really convinced that it's going to be much better than properly spaced new spark plugs, or a set of iridium ones with a good healthy spark.

One reason for the multi-ground-electrode plugs is that some engines have high levels of bulk charge motion (swirl etc) in order to generate rapid (and thus thermally efficient) combustion. It also usually allows high dilution tolerance, which used to be applied with very lean burn calibrations, or more commonly now with high EGR rates to suppress the formation of NOx.

They also have an extended life compared to a single electrode version, which is important for service intervals. Often the gaps are radial rather than axial.

One problem with high bulk motion is that unless the spark plug is "indexed" (i.e. the ground electrode is positioned relative to the start of the thread, similarly the thread in the head has to be indexed), you don't know where the earth electrode will end up and it can shroud the spark if positioned upstream. This uncertainty can lead to undesirable increases in combustion variability cycle to cycle (COV of IMEP technically).

2 approaches can help get round this, one is to have multiple ground electrodes so the variation is minimised, or (the one I prefer) is to make the single electrodes smaller (iridium etc) so that the spark is always in the same place more or less, is more concentrated, and is more exposed to the mixture.

Even on "conventional" traditional spark plugs the spark will wander round the tip of the centre electrode, so sometimes it's on the upstream side and sometimes downstream.

In my experience, an iridium type small electrode (and ideally with a similar small precious metal earth electrode - "double platinum" or double-iridium) will give similar improvement in combustion stability to a multi electrode, usually better due to reduced "delay" angle (not really a delay as in a diesel, but used to describe the start of combustion).

4-valves will usually use a "barrel-swirl" motion to generate the energy which will break down into small scale turbulence (mm scale) just before the spark as the piston approaches TDC and the geometry changes radically. Small scale turbulence systems will suit single electrode iridium plugs well.

Simple answer -----For an engine that isn't designed to run on them it is a waste of money.The only advantage you will gain is longer plug life

07 SV 650 has two plugs per cylinder
 

Suzuki claim moving to two spark plugs per cylinder improves combustion and reduces emissions.

Two plugs per cylinder can be very useful, the Honda Jazz engine is one of the best in the industry at the moment, the combination of fuel efficiency and low emissions with refinement and stability. It uses an "intelligent" ignition system though, not simply both plugs firing together all the time.

There have been twin plug engines around for years, originally for reliability (light aero etc), then for better combustion. Like most things the true benefits have only been realised with more powerful electronics to control the system.

Twin plugs not the same as multiple electrodes on a spark plug.