CHEAP NGK SPARK PLUGS OF THE WRONG HEAT RANGE CAUSE PROBLEMS
We see and hear of people who have put BCR8ES or very similar spark plugs in there Cooper S R53 and had problems with misfire/spluttering/holding back etc or other running problems . These may have been included with a pulley upgrade . The facts are these are a very cheap Copper Core Large electrode plug of too Colder heat range.
1) NGK are a great brand, but these are £1.50 each copper core plugs that have soft (… fast wearing) electrodes. The wear rate is reduced by using wide electrodes, the downside is the quality/voltage of the spark is much inferior.
2) The number (‘8’ in this case) is the heat range .The higher the number the colder the plug . Note you need the correct heat range whereby the plug loses( or keeps) just the right amount of heat to maintain optimum plug tip temperature . A higher number is not a better plug ! Most heat ranges are the same or similar price within a certain model of plug anyway . Too low a heat range and yes the plug tip could get too hot and in extreme circumstances could melt and drop off (Not good), but equally too cold a plug doesn’t get enough tip temperature to burn off the fuel . This results in plug fouling/misfire. Normally this will occur on a colder ie not fully warmed up engine. Maybe worse on a cold morning or when sitting in traffic . ie when internal engine temps are lower than average…
The answer is to use only the correct heat range , std is 6 but 7 is correct for almost all modified R53s ( inc our GTT 400bhp car). Also you need smaller electrodes for higher voltage spark and more ‘space’ for flame spread . And finally those tips need to be hardest material AND on both electrodes ( Double Iridium) . IX is the only range that give this . Laser Iridium are lower spec, and Laser Plarinum one lower again . The cheap copper core plugs we see are inferior even to the std 4 electrode types! We have offered only one plug since 2003 …The right one and best one! When we fit these plugs we ALWAYS apply a little copperslip to the threads and a little di-electric grease to the nipples…..We also tighten the plugs up to correct tightness so they don’t come loose a few thousand miles later then rip the remaining threads out of the head !…You have been warned