Yup, platinums and iridiums etc we're designed long after these car were. The e30's use a standard cap and rotor with a single coil. Firing KV is around 15-20 and can only last 1-2ms as a result (and that's actually a LONG time in spark terms for this system). The copper cores they are designed with are of lower resistance which means less voltage is needed to jump the gap so you get a longer lasting spark which promotes better combustion in these engines. Plat's and ir's are of a higher resistance value which mean more voltage is required to initiate spark. This results in a more intense hotter spark initially but it goes out almost as quick as it ignites and leads to poor combustion in these engines. Plat's and Ir's are great if you have say, MSD or some factory version of it, Coil on plug ignition and the like. Those system create more voltage, multiple sparks at idle and can actually handle those types of plugs. Single stock coil running 6 cylinders........not so much. Champion makes copper cores for these cars, use those and then just put the Iridium sticker in the back window :-)
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