use to be a couple of guys sprinting supercharged singles at houghton, one was a bsa c15 with a shorrocks charger and the other was a weslake 500 with a shorrocks on it. up the hill(quite steep) was only 1/8th of a mile, the c15 was tripping the lights in about 9.5 seconds and the weslake in about 8 seconds, as a guide, my 1170cc suzuki katana with a bit of tuning some whopping carbs and a race pipe running a cut slick tyre at 4psi did a fastest run of 7.97seconds, so these old thumpers werent hanging about, having said that, they had power deliveries like light switches, they were either flat out or off, they had no tickover.
incidentally, as has been said, the so called electric superchargers on ebay are snake oil. if they worked, then the manufacturers would have been using them rather than messing with complex blowers or turbos. theyre just small electric fans, and offer no boost at all.