The +4s are great for most automotive applications, however they are not well suited to the Duratec & here is why:
Despite having "4 times more platinum than the Bosch Platinum plugs", the outer electrodes of the Bosch +4 plugs are not platinum or platinum capped.
Bosch +4 desc Most ignition systems operate in one direction only. As I understand it, the waste fire ignition system on the Contiques fires twice for each burn cycle. Once from one electorde on the "fire" stroke and once on the "exhaust" stroke in the reverse direction. It is a VERY good ignition system & I am not aware of any upgrades that are able to outperform it in any meaningful way.
The outer electrode of the single plat OEM plugs had a tendency to "scallop" because of the reverse direction of the waste fire cycle. This causes misfire contidions as wear widens the plug gap. This happened to me & many other CEGers. My spark plug outer electrodes looked little spoons.
The Bosch +4 outer electrodes will gradually wear away in a similar manner. This will cause mis-fire conditions in short order, & require replacement of the plugs in much shorter intervals compared to double platinum Autolite plugs.
Additionally, I would suspect that the configuration of 4 outer electrodes surrounding the center electrode to have a tendency to cause considerable quenching in the combustion chamber of a high compression engine like the Duratec, which would result in a less efficient ignition of the air/fuel mixture. Again, more prone to mis-firing under less than ideal conditions. As soon as a plug wire even begins to degrade, your +4s will let you know about it. That is my own theory.
Jim R
