A friend who is an electrical engineer got tired of waiting for his toast in the morning, so he plugged his toaster into an autotransformer and boosted the voltage to 160 volts. Toasting time dropped from a leisurely seven minutes to two and a half. As far as I know, the toaster has survived the experience so far - though it's only been running in turbo mode for a few months. He told me that the nichrome wire used in heating elements generally has a pretty high tolerance.