Harrison raced in the opening rounds for the reigning champion outfit JamSport Racing.
But the Oxford racer explained: “It’s a decision my sponsors have taken. I really like the people at JamSport, but I’m now looking forward to building a nice relationship with Pyro.
“I feel this is a move that will benefit me in the long run – this is only my third season of car racing, Pyro have won the UK Clio Cup in six of the last eight seasons and I’m sure I can come on leaps and bounds with them.”
Heading to Donington Pyro’s Mike Bushell – its 2014 Champion – jointly leads the championship and its new 16-year-old signing Jack McCarthy is fourth in the standings. Former championship runner Ash Hand is also among its high-profile line-up.
A misted windscreen and then a tangle with WDE’s Dan Zelos blighted Harrison’s performances in his first UK Clio Cup races at Brands Hatch.
However he added: “I felt we could have come away with much better results but I’ve always gone well before at Donington – I won my first ever car race there in 2015 (MINI Coopers) and got another won last year in the F56s so I’m hoping to get things going there this weekend.”