SpeedSource will enter only a single Mazda SKYACTIV-D prototype in this weekend’s Chevrolet Sports Car Classic at Detroit’s Belle Isle, Mazda confirmed Thursday.

Tom Long and Joel Miller will pilot the No. 07 entry in the Prototype class, with the No. 70 car, driven this year by Jonathan Bomarito and Tristan Nunez, remaining at SpeedSource’s shop to undergo further development.

“A large part of this program is to learn, refine and develop SKYACTIV technologies,” said Mazda Motorsports director John Doonan.

“The development of the diesel engine has been a steep climb upward, especially with peak horsepower and fuel efficiency that has allowed the team to lead two of the four races thus far.

“But, we believe we are best served by continuing development and simulation work with one car at the SpeedSource shops rather than both cars being at the track this week.

“This does not reflect any changes to the long-term commitments and goals of the Mazda program.”

Mazda’s temporary reduced effort has resulted in a seven-car Prototype entry for Saturday’s 100-minute TUDOR United SportsCar Championship race an a total of 24 cars between the P, Prototype Challenge and GT Daytona classes.