After some previous indifferent kicking form, reserve back Western Hemi came on to land some great goals in the conditions, while Pirates 71st-minute try by reserve Timoci Ului in their only decent raid inside Ratana's half in the second stanza was not enough to bring them back into contention.
Inspired by their captain Vaan Rauhina, unlike in previous matches Ratana did not tire and were able to impose their will right to the finish.
"We worked on that on Thursday night in terms of our tactics," said coach Johno Kaa.
"Just drill the ball and it seemed to work out for us.
"The D [defence] has been tight all season, but today it seemed to gel better than the last three games."
Taihape lifting the Grand Hotel Challenge Shield from Border means despite another giant-killing win, Ratana still remain well adrift of the top. Pirates find themselves in a tight three-way dog fight to hang on to second spot and a home semifinal.
Coach Phillip Morris had to acknowledge they had been outdone. "We probably just didn't appreciate the elements in the first half. [Second half], that was probably the worst 40 minutes we've played this year.
"They hammered us at the breakdown. They played more rugby than us."
Starting with the cross breeze and slight downhill run, Pirates could not get the early advantage as Ririnui pinged them up for a series of free kicks, leading to Ratana first-five Te Tua Kemp's opening penalty.
Pirates also struggled with their lineout throws in the breeze, while having to contend with the runs of Rauhina and lock Marius Joseph, plus some hard hits out wide by second-five Te Rokera Matthews.
Not lacking for big men themselves, Pirates regained enough territory around halfway to turn their fortunes through goalkicking No8 Manulua Lafi landing long 40m and 35m penalty attempts.
Ratana missed touch on a couple of key clearances and Pirates pounced with hooker Junior Tume going over but being called back, then prop Brett Turner, breaking through two tacklers on the 22m and wrong footing the last defender to score on halftime.
Pirates roared into the second stanza with Tume, prop Willie Kabakata, and lock Simon Hillis combining to send winger Clive Stowers streaking away.
But Ratana immediately regained the ball and counterattacked through a Tamou chip kick, and from then on the visitors were trapped.
An attempt to drive flanker Charlie Mete over was barely stopped but committed every available Pirate, leaving Tamou to simply switch to Hughes to force his way over in the corner.
A series of scrums saw Ratana move their winger and when Pirates marked up, Hughes dashed to the now empty blind and fed Tamou, with Hemi nailing the sideline attempt for 15-11.
Hemi nailed a low 43m kick and with 10 minutes left added another from a scrum penalty to seemingly put the game out of reach at 21-11.
However, Pirates responded out of nowhere with a powerful run by Chookoon seeing him pop the pass through three tacklers for Ului to sprint away.
Yet the Pirates front rower would go from hero to villain after coming up punching at the breakdown inside his own half, being sent off while Hemi added three more points to deny the favourites even a consolation bonus point with time up.
Harvey Round Motors Ratana 24 (Jamie Hughes, Kane Tamou tries, Te Tua Kemp pen, Western Hemi 3 pen, con) bt Integrity Motors Pirates 16 (Timoci Ului, Brett Turner tries, Manulua Lafi 2 pen). HT: 3-11
