In a finishing position reversal to the opening round, they were second to the Christchurch father-and-son driver pairing of Angus and George McFarlane (Porsche 997 Cup R) in the series' second round at Mike Pero Motorsport Park, Christchurch, on Saturday.
''To drive with my son and win is absolutely fantastic. The car ran well, it was a good clean drive and I thoroughly enjoyed it,'' Angus McFarlane said.
It was a particularly sweet victory for the McFarlanes, who incurred a disappointing puncture on the penultimate lap while leading at the series opener at Teretonga in September, before dropping back to the runner-up spot.
Invercargill driver O'Donnell said he and Dunedin's Dippie, were ''rapt'' with their Porsche 997 Cup S's result after the three-hour race.
''On paper there are cars out here that are much quicker per lap, but the Porsche is such a reliable and consistent car and you always need to finish,'' O'Donnell said.
However, all three struck trouble.
First the McLennan-Moore SuperTourer spun off after 12 laps with a broken differential.
Then just before the halfway mark, the Carter's V8 Supercar took a long pitstop with a sway arm problem on the left front wheel.
This problem continued to plague them and saw their eventual retirement after 90 laps.
Southland-based Tulloch's Camaro GT3 then struck electrical problems which affected the paddle-shifting gear selection.
While still able to circulate, they were not able to challenge for the lead and finished fifth.
Series secretary Chris Dunn calculated that to ensure a win, the Dippie-O'Donnell Porsche needed to beat the McFarlanes in the final three-hour race, as there were 95 points on offer.
Points were tight across the classes and often the overall winner had been decided by a solitary point in previous years, Dunn said.
''Nothing is over until the proverbial fat lady sings.''
Dippie and O'Donnell have been on the overall podium (third in 2014 and second in 2013) and were keen to move up from the bridesmaid role, Dippie said.
The McFarlanes' ''slightly newer car'' meant he and O'Donnell needed to find about 0.5sec a lap of extra speed over 120 to 160 laps at Timaru.
In the one-hour race series, Dunedin's Brian Scott took his second Class 1 (3501cc+) win in a row in his Chev Corvette C5.
After several years in which mechanical issues sidelined him, Scott was thrilled his 725hp Corvette was having a ''clean run.''
He intended to continue his pragmatic approach of driving at ''92%'' in order to finish the final round as the class winner.
''As long as I don't make a mistake and no-one crashes into me, I'll be fine,'' Scott said.
Alexandra's Johnny Waldron was second again in Christchurch, as he was in the opening round in his Nissan Skyline R32.
Dunedin driver Chris Henderson had taken the race lead on the first lap before being overtaken by the faster GT cars.
He then lost a wheel after five laps.
In Class 3 and 4 (0-2000cc), honours went to Wanaka's Gary Ponting (Honda EF Civic) ahead of round one winner Grant Aitken, of Queenstown, in a Toyota GT86.
The series now moves to the final round at Levels Raceway, Timaru, on Saturday, October 17.
