After a day led by Corvette DPs, a Ford EcoBoost-powered Riley led the way Saturday at Daytona in the second day of official pre-season TUDOR United SportsCar Championship testing.

RESULTS: Testing 3
RESULTS: Testing 4
RESULTS: Testing 5

NASCAR star Jamie McMurray topped the time sheets following the completion of the three daytime sessions on the 3.56-mile oval/road course.

McMurray’s 1:38.980 lap time in the No. 01 Chip Ganassi Racing DP entry, set in the 90-minute early afternoon session, was quickest of the day, although more than two-tenths slower than Friday’s pace-setting No. 5 Action Express Racing Corvette DP of Christian Fittipaldi.

“The car’s been pretty good,” McMurray said. “We’ve had a couple of small issues with headers, which they’re repairing now. The new engine seems to have good power and the balance of the car has been decent. It’s been fun to get in the car and just run some laps.”

However, persistent engine and electronic-related issues for both of the Ganassi entries has sent the five-time and defending Rolex 24 winner packing up one day early. Neither car will take part in any of the remaining testing sessions this weekend.

The No. 90 Action Express Racing Corvette DP of Michael Valiante, Richard Westbrook and Mike Rockenfeller was second quickest of the day, thanks to a 1:39.196 lap time recorded in the morning session.

Action Express Racing’s pair of similarly prepared Corvettes DPs were third and fourth on the time charts, while the No. 10 Wayne Taylor Racing entry of Wayne, Jordan and Ricky Taylor and Max Angelelli completed the top-five overall.

The No. 1 Extreme Speed Motorsports HPD ARX-03b continued to be the quickest P2 car, with Ryan Dalziel getting down to a 1:39.750 lap time, a two-tenth improvement over Friday’s time.

Corvette Racing led the way in the GT Le Mans class, thanks to a 1:46.010 lap time recorded by defending class champion Jan Magnussen in the morning session.

The Dane edged out the sister No. 4 Corvette C7.R entry of Tommy Milner, Oliver Gavin and Robin Liddell by just 0.020 seconds, giving the all-new car.

“I think it’s been a productive couple of days so far,” said Magnussen, who shares the wheel with Antonio Garcia and new recruit Ryan Briscoe. “We’ve gone through a lot of stuff with the new car.

“We also had Ryan Briscoe to try and get him up to speed and get him familiar with the team and the car. All that’s gone really well so far. We’ll see how the night session goes.”

Just as in the Prototype class, overall times in the GTLM class were slower today, as ambient temperatures rose by nearly 20 degrees.

Prototype Challenge was led by GP2 ace Sam Bird, who reeled off a 1:42.010 lap time in the No. 8 Starworks Motorsport Oreca FLM09.

Snow Racing was quickest in the GT Daytona category, thanks to a 1:48.228 lap time by the No. 58 Porsche 911 GT America of Madison Snow, Jan Heylen and Marco Siefried.

The only noteworthy incident during the day came from the No. 25 8Star Motorsports Oreca FLM09 of Gaston Kearby, who had a spin and slight contact with the wall at the bus stop.

A 90-minute night practice session is on tap for 6:30 p.m. ET.