When I use a turbo, my warm up is ten minutes, where I raise my HR from resting up to around 135 and then up to 150 ish.
After ten minutes warming, I start the training session.
Depending on the type of session, which can last from 30 to 60 minutes, I can see (and hold) heart rates of 168 to 170 depending on the session I am doing, and on the road I have recorded a max of 181.
78/81 is only a touch above resting rate and you could generate that walking around the house or doing the washing up.
To get the best from your turbo and HRM you need to have a look around the net and find some (scientifically proven) training that works for you. There are also some excellent books about.
I quite enjoy turbo training, I get a sense of purpose out of it and enjoy the sheer exertion.