Twilkes
Guru
Another bit of nostalgia, if you only had a heavy cheap bike to train on, because that was all you could afford, when you borrowed a proper lightweight racing bike for local races you were much faster.
You still used all of your energy, but you could cover the distance faster on a light weight racing bike.
All that is really saying is that if you train on a cheap bike your training speed will be lower, there's not some magical effect that means you'll be faster than you otherwise would have been on race day.