Friday morning sees the field head south towards Waiouru for the morning stages with a lunch stop in Taihape. In the afternoon two stages will be raced during a crossing of the Gentle Annie en route to Havelock North.
Saturday's route is similar to last year's with three stages northwest of Hastings in the morning and three south of Havelock North in the afternoon. Sunday will see competitors head south into Central Hawke's Bay and Tararua before a ceremonial finish in Havelock North.
All-up there are 19 closed road special stages covering 459.95km linked by 730km of touring stages.
Knauf, 58, and Corbin, 62, will race a Subaru Impreza which Knauf purchased off Troy Toomey of New Plymouth. Toomey had done seven Targas in the car.
"We've rebuilt the engine and refreshed it in the countdown to this week. I see everyone of the other crews as our main rivals ... they might have dome more practice drives and they might have hotted their car up a bit more," Knauf said.
"You're only as good as your last corner. You've got to concentrate because the car in front might have spread out a bit of gravel or some mud ... you can't take anything for granted.
"I did circuit racing for seven years before my son Rhys got me into rallying. In circuit racing you just worry about the guy next to you but in these Targas the leader could be kilometres ahead of you," Knauf explained.
Crews have to stick to the 200km/h speed limit on stages.
"Organisers use the Rally Safe System which tracks us down to the last kilometre. There are heavy penalties if you go over," Knauf said.
Corbin has been involved in motorsport for 40 years and was quick to reply when quizzed on the secret to his and Knauf's success.
"Trust in each other to do the job they are supposed to do. All he has to do is drive and I do all the other stuff. It's important to have a lot of fun too.
"We are confident about retaining our class title but at the same time it is going to be a real challenge. We just have to go out and do it."
He ranked the five Silver Fern rallies which are eight-day gravel events as the highlights of his motor racing career. Corbin completed his last one in 2014.
"Just doing them is a highlight because they are quite an event."
He is also enjoying his first year as president.
"People have got to stand up and do their bit for the club. It's good to be able to encourage youngsters to race in a controlled environment and they have the opportunity to do gravel or tarmac events."
In October Corbin and Knauf will tackle the six-day Targa New Zealand event in the South Island. It will be Knauf's first taste of racing in the South Island.
Last year they finished 16th overall in Targa Hawke's Bay and eighth overall in Targa New Zealand. Taking that gradual improvement into account they could threaten the podium on the overall standings this week even if retaining their class title is the main priority.
Other Hawke's Bay entrants are the father-and-son combo of Robert and Nick Webster in their Mini Cooper, Paul Dippie and Kevin Campbell in their Porsche Cayman, Robert and Simon Mellor in their Porsche Boxter and Mark and Ray Pearson in their Lotus Elise.
