"The thing that gets you is how much grip and how fast they are on what looks like a slippery but what can be a very sticky dirt, clay-based surface. It really is quite ridiculous the speed these things can go and the grip they get out of these cars."
While Murphy points to fun being his motivation for competing, when the flag drops the competitive side will come out in him and his fellow competitors, he says.
"Absolutely. It is one of those things - it is a lot of fun because there is nothing at stake but you can't help yourself and go as fast as you possibly can.
"It is always a laugh mixing with guys from all sorts of different walks of life. Sarah Walker is out there as well, which will be cool.
"It will be great for her having a play with something she doesn't need to use her legs to power.
"Mad Mike was hilarious last year - he was off the front of the field and he and Nick Cassidy put on a show side by side for a number of laps and I was giggling to myself behind them watching them go at it."
While Murphy and company will be having fun behind the wheel, the regular drivers and owners of the cars will be hoping the celebrities keep them in one piece so they can be raced in the competition races later in the evening.
"We just have to keep them off the walls and running so that they continue running for the rest of the evening," Murphy said.
"We are lucky we have a bunch of drivers and owners that are prepared to hand over their keys for racing cars to amateurs to go and flog and have a run around in."
The 24 Super Saloons will be the main highlight of the night and a big crowd is expected to watch the sprintcar drivers compete for the Rolling Thunder Title, which pays $15,000.
Fans will also be aware of more public discussion around the future of the venue after construction of an international cricket stadium was proposed beyond speedway's current deal, which expires in 2019.
Murphy is staunch in his support for speedway at the inner-city venue beyond 2019.
"It is such an important part of motorsport history. It has been there for such a long time. It has been the Holy Grail for so many people that have enjoyed watching or participating. It really is a historic part of New Zealand sporting heritage.
"It is great that it is confirmed through until 2019. At the end of the day, it should never be in question. It is a shame that we have to bow to minorities when it comes to things like this."
The first race is set for 6.15pm.