Monday's official Mugello MotoGP test may have only lasted one-day, but Ducati has remained at the circuit for further private testing.

Although factory riders Valentino Rossi and Nicky Hayden are not present, Ducati is giving track time to 2012 Came IodaRacing CRT rider Danilo Petrucci.

The 21-year-old has done a solid job on the most underpowered of the CRT machines, scoring nine points, including an eleventh place at Assen.

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In 2011 Petrucci won the Italian Superstock title for Ducati and finished runner-up in the FIM Superstock Cup. He has previously worked with Ducati as a Superbike test rider.

Petrucci and official test rider Franco Battaini are putting further mileage on various engine, electronic and chassis updates.

It is not yet known which of the updates Rossi and Hayden will use at next weekend's US GP round.

Rossi's test was cut short after an ECU fault while testing a new engine management system, a development the Italian described as an intermediate step towards future 'substantial changes' planned to improve the Desmosedici's power delivery.

A new engine will be 'sealed' for use by the factory riders from Laguna Seca, but has been designed to accept future upgrades without breaking the seals. This rules out any major changes to the engine internals.

Ducati Corse director Filippo Preziosi told MotoGP.com: "In Laguna we will seal engine number four [out of six for the season] as planned. Engine number four is ready to use some additional parts we are developing. Some parts could be delivered directly to Laguna, and some other parts will be delivered in the following races."

Ducati's Mugello test is expected to conclude today (Thursday).