Lucas Luhr topped official American Le Mans Series testing at Sebring this week on the maiden outing of HPD's 2012-spec LMP1 car.
The Pickett Racing squad, which is running one of the ARX-03a machines this year for GT1 world champion Luhr and Klaus Graf, set the pace on the second day of running at the Florida circuit in 1m48.192s with Luhr at the wheel.
Simon Pagenaud, who will join the pair for next month's Sebring 12 Hours - the opening round of both the ALMS and the World Endurance Championship - said that the Nick Wirth-designed car was "awesome".
"It's such a big evolution from last year's car," the Frenchman said. "The engine gives us good power, the front splitter gives the car additional downforce and the new tub gives us better efficiency as well. It's generally the same aero package as the car we ran last year."
With no other LMP1 cars present at Sebring - including the works WEC-registerd Audi R18s, second place on the timesheets went to the LMP2-spec HPD run by Level 5 Motorsports. The Christophe Bouchut/Scott Tucker/Luis Diaz was 3.330s off the pace.
The Risi Ferrari set the pace overall in GT after going quickest in three of the four sessions in the hands of Toni Vilander, Gianmaria Bruni and team newcomer Olivier Beretta.
Half a second down was the similar 458 Italia of Extreme Speed Motorsport's Scott Sharp/Johannes van Overbeek, while Krohn Racing's Nic Jonsson/Michele Rugolo/Tracy Krohn-driven version completed a 1-2-3 for the Italian manufacturer.
The two factory Corvettes completed the top five with the best of the works BMWs and the fastest Porsche - the Flying Lizard entry of Jorg Bergmeister/Wolf Henzler/Pat Long - further back.
The LMPC pace was set by Dane Cameron in the Dempsey Racing ORECA, while Green Hornet driver Damien Faulkner was fastest in GTC.