* - General Motors Ignition Cassette System (Cadillac and Olds 2000-up 4, 6 and 8 cyl.) - (In the years GM has been building engines with distributorless ignition systems, several different configurations have been used, largely dictated by geography. In one common approach, the spark plugs for two cylinders share one ignition coil between them. Learn to test these systems in detail.)
* - GM Compression Sense Ignition (SAAB and GM Systems) (CSI enables the Powertrain Control Module to determine proper engine phasing (cam position) without the use of a separate camshaft position sensor. Learn this advanced ignition system from GM.)
NOTE: HOW IT WORKS: Stock H-D ignition systems fire both cylinders at the same time. The rear cylinder receives the wasted spark on its intake stroke, which can result in harder starting, increased engine vibration, backfire and raw fuel being spit back into the carb, all creating a power loss. Dyno and top speed testing show use of an independent firing system gives dramatic improvements in power in all areas.