Don't get me wrong! Bosch platinums, +2s, and +4s are great sparkplugs, but like fire they have to be used under the correct circumstanses to prevent complications! As a automotive tech I've come across a large number of driveability cases that stemmed from the use of these plugs in vehicles with ignition systems that were incompatible with them so I'de like to ask your pardon for a moment while I dust off the soapbox and bore you with some of my observations on this issue.
First I'de like to mention the ignition systems that perform well with these plugs... COP (Coil On Plug), and HEI distributer type systems in which each plug has it own independent secondary ckt can benefit from these plugs, but you do need to consider they're higher temp rateing. Now the problem. Alot of late model vehicles use a loop style ignition system in which one coil fires 2 plugs with each secondary discharge event. One plug fires dureing the exhaust stroke (waste spark), while the other initiates combustion dureing the power stroke. This results in a pattern like this... Induced power leaves the coil through tower A, Jumps gap in plug A (center-side electrode),passes through the engine block, Jumps gap in plug B (side-center electrode), any remaining power returns to coil tower B. This is where the issue comes up, the Bosch platinum's center electrode design produces a bias or bottle-neck that conflicts with the flow of power through the gap in plug B like a diode plug blocking reversed polarity. In exsteme cases the result is misfire, weak, or dead cylinders. In others they cause a lack of power, hiccups, poor mileage, rough idle, hesitation on takeoff, and mild miss under load because of the weakened spark in the "B" plugs! These headaches can be avoided if you know what systems use this design! Systems with coil packs that pair cylinders, coils with 2 secondary output terminals, and Hybrid COP will not benifit from the installation of these plugs! So if you come across these systems, or you aren't sure about the system in the vehicle in question its best to use a good quality standard double platinum style or OEM reccommended spark plug versus a Bosch platinum series plug. Thanks for your patiece. Hope this thread will be useful
(falls off soapbox)
