Valtteri Bottas topped the timesheets for Williams on both days of the Formula 1 young driver test at Silverstone.
The Finn posted a 48.963s lap on the International circuit on Friday afternoon in overcast but dry conditions.
Bottas completed 170 laps on Friday to add to the 120 GP circuit laps he drove on Thursday when he did a 1m31.436s laptime.
Williams worked on aerodynamics and data gathering during Friday afternoon, running with a number of small holes in the nose cone linked to tubing which flowed out over the front wing.
Both Marussia drivers concentrated on getting enough mileage to gain a superlicence, with both drivers achieving the required 300km.
Chilton completed 52 laps and dipped below the 50-second barrier in the afternoon with a 49.932s lap, only 0.969s behind Bottas, while Haryanto's 50.405s time from Friday morning stood as his quickest time of the day after not going out in the afternoon session.
Pos Driver Team Time 1. Valtteri Bottas Williams-Renault 48.963s 2. Max Chilton Marussia-Cosworth 49.932s + 0.969s 3. Rio Haryanto Marussia-Cosworth 50.405s + 1.442s