By Peter McLaren

If Valentino Rossi's Sepang race simulation is anything to go by then the Italian looks to have made a giant leap forward in the three-and-a-half months since last October's Malaysian Grand Prix.

The Fiat Yamaha rider finished fifth in the Sepang race, riding the '07 YZR-M1 with Michelin tyres, but the Bridgestone-shod 2008 machine delivered a dramatic improvement in pace.

The fastest race lap during the 21-lap grand prix was a 2mins 2.108secs, set by Ducati's Casey Stoner, on his way to victory.

But on Thursday, Rossi put 16 of his 21 laps under that time, with a best of 2mins 1.437secs and a worst of 2mins 3.419secs (his first lap). In total, 14 laps were in the 2min 1secs bracket and all but his opening lap was under 2mins 2.312secs.

It is impossible to directly compare Rossi's full 21 laps with the 2007 race times, due to the standing start for the grand prix, but if for the sake of comparison the first lap of both the real race and Rossi's simulation are removed then the shortened 'race times' are as follows:

2007 Malaysian Grand Prix (laps 2-21):Rider: Time over 21 laps - first lap = Time over 20 laps

Casey Stoner: 43mins 4.405secs - 2min 9.233secs = 40min 55.172secsValentino Rossi: 43mins 9.178secs - 2mins 12.729secs = 40mins 56.447secs

February Sepang test race simulation (laps 2-21): Rider: Time over 21 laps - first lap = Time over 20 laps

Valentino Rossi: 42mins 41.066secs - 2mins 3.419secs = 40mins 37.646secs

That means Rossi was 17.525secs faster than Stoner's 2007 grand prix winning pace, over the 20 laps in question, and 18.8secs inside his own grand prix time.

Of course, direct comparisons with Stoner are far from fair - not only was the reigning MotoGP world champion not at Sepang this week, but he was also obviously riding last year's version of the Desmosedici during the race.

But Stoner did appear once at Sepang with his new 2008 machine - in late January - when he set the fastest race-tyre lap of the winter, a 2mins 0.964secs cracker.

It is also worth noting that, although Stoner didn't complete a full simulation at the January test, 14 of his 27 laps - during the third and final day - were in the 2mins 1secs, suggesting that he and Rossi are closely matched...

Meanwhile, Rossi was naturally delighted at having found almost one-second a lap since October 21, 2007.

"I'm really happy about today's race simulation and about the overall balance of this test," said the former five-times MotoGP world champion. "Everything has gone well and the race-simulation was an improvement on the one from last time; this is the real test of where we are."

'The one from last time' refers to the race simulation Rossi completed during January's Sepang test, however Rossi took a 'rest' (one very slow lap) three-quarters of the way through that simulation, making his 'race time' harder to calculate.

Nevertheless, during the January simulation, Rossi was only able to complete two laps in the 2mins 1secs bracket, compared with 14 laps this week. His best individual lap was also 0.415secs slower than on Thursday.

"Today's race simulation was good and an improvement on January, plus the individual lap times within it were fast and consistent," confirmed team manager Davide Brivio. "This is a very important indication of our level."

Rossi completed his 48th and final lap of the day at just after 2:00pm and was later knocked from the top of the timesheets by team-mate Jorge Lorenzo, who used a qualifying tyre to cut 0.485secs from the #46's own soft-rubber effort, set just before his race simulation.

After two tests in Malaysia, Fiat Yamaha now heads for Jerez, from February 16-18, to face a full line-up of its 2008 rivals.

"We've only done 50% of our [2008] pre-season testing, we have two more to go before the first race but we hope to continue improving like this and arrive at the first race in good shape and ready to commence our challenge," concluded Brivio.