By alley - Sep 18, 2014, 7:47 PM ET

IMSA: Westbrook leads first practice, Porsche impresses in GTLM

The Briton's Spirit of Daytona Corvette DP was less than one-tenth of a second ahead of Michael Shank Racing's Riley Ford Ecoboost, in the hands of Ozz Negri, but over half a second clear of third placed runner, Joao Barbosa's Action Express Racing Riley. The LMP cars, headed by Johannes van Overbeek's ESM Racing No. 2 car, were a full second slower.

Porsche's decision to run three cars in order to maximize its chances in the GT Le Mans class Manufacturers' standings looked to be paying off when the 911s locked out the top of the table. And it was the new entry, the No. 910, which will be shared by Patrick Pilet and Frederic Makwoiecki, which emerged on top in the hands of Pilet.

Best of the rest was Jonathan Bomarito in the Dodge Viper SRT, the combination of which came a very close runner-up in last year's American Le Mans Series race here in Austin. Bill Auberlen was fifth quick for BMW.

Gunnar Jeannette put the PR1/Mathiasen Motorsports entry top of the PC rankings, eclipsing the RSR Racing pair of Jack Hawksworth and Bruno Junqueira. Jeannette was also, impressively, only 2sec off Westbrook's overall lead.

James Davison was top of the GTD class in the No. 007 TRG North America Aston Martin Vantage, with Andrew Davis second in the Porsche he shares with Patrick Dempsey, and Dane Cameron third in the Turner Motorsports BMW Z4.

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