Products have promised hotter sparks for 50 years. We almost gave up waiting, until dyno tests proved that hotwires really work. The secret? Each wire houses a capacitor to accumulate the energy from the ignition until it discharges a more powerful spark. Even with a nearly perfect ignition system, we saw 2-4% more horsepower, better fuel burn and reduced emissions on our own dyno tests. If you have a dirty-running engine, hotwires will give you a better chance of meeting the new emission standards. Note: may cause radio interference.