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As it happened: Test day four
By Matt Beer, Glenn Freeman, Ben Anderson and Dan Cross
The live commentary has ended. No further updates will be posted.
05:46 Good morning and welcome to the final day of 2014 pre-season Formula 1 testing from the Sakhir circuit in Bahrain.

The past month-and-a-bit has flown by, and now the teams just have today's eight hours of running to tick off everything they want to do before Melbourne.

05:47 And you can guarantee that Lotus isn't the only one feeling like this:

"Good morning from the last day of pre-season testing. It's fair to say we've got a long 'to do' list..."

05:48 Such are the vagaries of the 2014 rules and cars that even those starting to make progress still feel on edge.

Caterham completed 117 laps yesterday:

"Another day like yesterday would be good.... so whoever was crossing whatever they were crossing, please do it again. Thank you."

05:52 Yesterday's star turns were Felipe Massa and Williams, who set the fastest time of the Bahrain fortnight so far with a 1m33.258s while in what was basically a simulated pole fight against Nico Rosberg's Mercedes.

Elsewhere, just getting on track at all was a problem. Sauber and, most notably, Red Bull didn't manage a lap.

Here's the full recap of Saturday's events:

Bahrain test day three full report

05:56 It's a sunny start here in Bahrain, with air temperature at 21C and track at 37C.

06:01 The final day of 2014 Formula 1 pre-season testing has kicked off. This is the last chance for the teams to get into some proper on-track work before they leave the pitlane for free practice in Melbourne.

06:04 Here's today's line-up. Remember, Sauber made the decision last night to give Adrian Sutil half a day after he managed just one lap in the C33 yesterday. For more on that click here.

Red Bull – Sebastian Vettel
Mercedes – Lewis Hamilton
Ferrari – Fernando Alonso
Lotus – Romain Grosjean
McLaren – Jenson Button
Force India – Nico Hulkenberg
Sauber – Adrian Sutil/Esteban Gutierrez
Toro Rosso – Jean-Eric Vergne
Williams – Valtteri Bottas
Caterham – Kamui Kobayashi
Marussia – Max Chilton

06:05 Seven teams sent cars out as soon as the pits open, so we've seen Hulkenberg, Vergne, Button, Kobayashi, Sutil, Bottas and Chilton.

06:09 Alonso heads out, having taken the car over from team-mate Kimi Raikkonen for today.

Here's the Finn's assessment of his final day in the car, where he was stuck in the garage for most of the morning but managed to get a bit of race simulation work in late-on:

"I'd hoped to do more laps, but this wasn't an easy day. We lost some time this morning when we had to fix something on the car, but then we managed to make up for some of it in the afternoon.

"Running a race distance, we continued to get more data relating to fuel consumption strategies and tyre degradation, even though the strong wind upset the driving a lot. I'd like to be able to say we did better, but there's still one more day with Fernando to continue our preparation for Melbourne."

06:10 @Marussia_F1Team: "The plan for today is some longer runs, a brake evaluation, qualifying simulation and live pitstop practice #busy (hope so!)"

Sebastian Vettel06:12 We have our first sighting of Sebastian Vettel and the Red Bull.

The world champion team and driver endured a disastrous penultimate day of testing, failing to complete a lap with the RB10.

Vettel tried to put as positive a spin as he could on the situation, but he did admit that he expected the team to have recovered more ground by now. Read about that by clicking here.

06:13 Vettel has made it back to the pits, so that beats yesterday's installation lap that only lasted a handful of corners.

06:14 The only cars we haven't seen in the first quarter of an hour today are the Mercedes of Hamilton and the Lotus of Grosjean.

06:16 Hulkenberg crosses the line to set the first time of the day - a 1m38.5s.

06:17 No surprise to see Sutil and Sauber getting down to work after yesterday's running was lost. The German completes his first flying lap of the day to join Hulkenberg on the timesheets.

06:20 Button's first lap lowers the benchmark by another two tenths of a second. Hulkenberg is across the line moments later, but he can only match his previous 1m38.5s so stays second.

06:22 The next lap around for the McLaren is a cool-off lap, 12s down on Button's pace-setting time. Sutil is still going, and he's making minor improvements on every lap at the moment.

06:24 Button pushes again and goes even faster, down to a 1m38.1s now.

His time at the top is short-lived though as Bottas is the first man to break into the 1m37s today.

We've also had a first timed lap from Kobayashi in the Caterham.

06:25 Bottas goes even faster on the next lap with a 1m36.5s in the FW36. That puts him 1.5s clear of Button now.

06:27 After those two quick laps, Bottas backs off to a 1m51s. That's pretty close to the 'standard' cool-off laptime we've been seeing across these two tests here in Bahrain.

06:29 The next hot lap from the Finn is a 1m38.2s.

06:34 Chilton posts the Marussia's first time of the day.

06:35 Vettel has re-appeared, and this time he stays out at the end of the lap, so perhaps we will see a time from the RB10 - which looked reasonable pace-wise in the hands of Daniel Ricciardo earlier this week when it was able to run reliably.

06:36 The world champion's first flying lap of this test is a 1m40.0s.

Sebastian Vettel06:40 Vettel is slightly slower on his next lap. Speaking last night, Renault head of track operations Remi Taffin predicted big mileage for Red Bull today after Saturday's disaster.

"Saturday should have been a 100-lap day [for Red Bull]. It's simple for me to say that but definitely we woke up with this in mind. This day was sort of a nightmare but this happens and I prefer it happens here than in Melbourne.

"I'm not saying [Red Bull will] do 100 laps, because if the programme is 80 we will do this. But there is no reason why we could not."

As Chilton pits, the RB10 is the only car on track at the moment, with five laps in the books.

06:44 Alonso's first flying lap puts him second, while Sutil finds 1.5 seconds in the Sauber.

06:46 Vergne sets a first laptime in the Toro Rosso for today to go sixth.

06:47 Having backed off, Alonso goes for it again and his second flying lap of this run is just 0.1s shy of his current best.

06:51 Grosjean takes the Lotus out of the pits for the first time today.

06:53 The E22 doesn't come in at the end of that opening lap, but Grosjean pits after his second tour so we won't be seeing a laptime from the Lotus just yet.

06:55 Bottas opens his latest run with a fastest time through the first sector, but he backs off over the rest of the lap to end up seven seconds shy of his current benchmark.

06:56 Two more best sectors from Bottas next time around are enough for him to shave another 0.3s from his best.

Sutil also improves in the Sauber, but stays fifth.

07:00 Bottas pops in a 1m36.9s, which is still faster than anyone else has managed so far today.

07:01 Grosjean only has two laps to his name, but Lotus reports that he feels "better already" with the E22.

07:02 Here's why we haven't seen the Mercedes so far this morning:

@MercedesAMGF1: "Sunday morning lie-in for the #F1 W05 as it nurses a gearbox headache. We've all been there... #QuietPlease #CloseTheBlinds #W05sup"

07:03 The vibes from the E22 are good news for Lotus given that Grosjean was - not for the first time this winter - pretty gloomy last night:

Grosjean: Lotus won't be fully ready for Melbourne

07:03 Bottas's next lap is a respectable 1m38.7s, and then he pits to leave the track empty.

Sebastian Vettel, flo-vis07:06 Signs from our photographers that Red Bull was straight into aero work when Vettel got going, with plenty of flo-vis paint on the RB10 this morning.

The feeling in the pitlane, both inside Red Bull and among its rivals, is that the champion team's car has plenty of potential once it can run reliably enough to make up for all the time lost.

07:08 Right on cue, Vettel heads back out to end the silence on track.

07:12 Sutil moves up to third, while ahead of him Alonso finds another seven tenths in the Ferrari.

07:13 Vettel improves on that lap, putting him into the 1m39s for the first time. Progress for the four-time world champion.

07:14 Kobayashi puts in his quickest lap of the Sakhir circuit so far. A 1m38 lifts him from eighth to sixth in the Caterham.

07:17 Vettel does a personal best in the first sector, but crosses the line in 1m40.001s so doesn't improve.

07:21 Vergne heads back out in the Toro Rosso after just over 20 minutes in the pits. He joins Bottas, Kobayashi and Vettel on circuit.

07:22 The Frenchman improves straight away, knocking two tenths off his best time so far.

07:26 Grosjean's had a half-hour break in the pits but the Lotus is back out now and gets on the board for the first time today.

07:28 Sutil will be determined to make the most of his extra morning in the C33, following yesterday's disaster for Sauber. He's into the 1m36s now after that last lap.

07:30 The team reports Sutil is on a qualifying simulation at the moment.

@OfficialSF1Team: "#SuperSutil finishing a quali simulation, box box, pit stop practice and mini launch. 26 laps in the bag so far. #pushpush"

07:31 Alonso takes to the track in the Ferrari and pumps in the fastest time of the day so far.

07:33 The Spaniard is the only man on-track at the moment as he follows that timesheet-topping effort with a cool-down lap.

Bahrain GP 200607:36 A bit of news from Bahrain this morning: the first corner here at the Sakhir circuit has been renamed in honour of Michael Schumacher, with the blessing of the seven-time world champion's family as he continues his recovery from a skiing accident at the end of last year.

For the full story click here.

07:38 Alonso is back in the pits now as Bottas starts going quickly, The timing screens confusingly show the Finn going fastest of all in all three sectors, but his final lap time keeps him second, now just half a tenth behind the Ferrari.

07:42 A good number of upgrades have appeared on the Ferrari F14 T for this test, including some ideas that our tech expert CRAIG SCARBOROUGH reckons haven't been seen since 2009.

Here's his round-up of the teams' developments this week:

Final test tech round-up

07:43 Williams reports that Bottas will work through a "pretty similar" programme to Massa's yesterday. The Brazilian set the fastest lap around the Sakhir circuit so far in pre-season with a low-fuel run, so expect some similar late-session antics from Bottas today.

07:45 Sutil shaves another four tenths off his best time as the Sauber's qualifying simulation continues.

07:46 @Marussia_F1Team: "14 days until the Australian GP & we're in a racing state of mind as we work through various race weekend procedures during our programme."

07:50 Nearly two hours down in the final day of 2014 pre-season testing, and here's a recap of what we've seen so far:

*Mercedes yet to run due to gearbox problem
*Alonso and Bottas set the pace early on
*Red Bull and Vettel log 18 laps while doing aero work
*No red flags so far

07:53 And let's follow that up with our first lap count rundown of the day too:

Sutil (Sauber) 36
Bottas (Williams) 29
Kobayashi (Caterham) 25
Alonso (Ferrari) 19
Vettel (Red Bull) 18
Vergne (Toro Rosso) 14
Chilton (Marussia) 10
Hulkenberg (Force India) 9
Button (McLaren) 8
Grosjean (Lotus) 6
Hamilton (Mercedes) 0

07:55 Perhaps we shouldn't be surprised to see Alonso and Ferrari at the top of the times today. After completing a race simulation on day two of this test, the Spaniard urged Ferrari to focus on finding more performance from the F14 T over the rest of the test.

Ferrari didn't get a chance to do much work in that direction yesterday, as Kimi Raikkonen's morning running was disrupted by a problem and the focus of the afternoon had to be his first attempt at a race run.

07:56 Hulkenberg is back out in the Force India, and he moves ahead of Button to go fourth. Third-placed Sutil improves as well.

07:59 Vergne moves to third in the Toro Rosso.

08:05 Alonso, Button and Vettel are on track, and the McLaren is on course for an improvement at the moment.

08:08 Button finishes the lap 0.6s shy of his best, while Alonso's first flying lap of this run is within a tenth of the fastest lap of the day.

Jenson Button08:09 McLaren started the winter strongly but of late other teams seem to be overhauling it. That's certainly Button's suspicion, as BEN ANDERSON found out last night:

Cause for concern at McLaren

08:09 We've just had three cars cross the start finish line very close together, something you don't see much during testing when the teams only have one car each. Bottas, Button and Vettel were all sharing the same piece of track.

08:10 They haven't spread out much by the next time they come around, and Bottas - the leading car of the trio - goes back ahead of Alonso at the top of the times.

08:12 Bottas's next lap is 0.3s slower than his best, but still fractionally faster than his nearest challenger has managed today. The Finn ended the lap strongly, setting a new overall best time through the final sector.

08:15 We have clear skies here and a slightly lower air temperature than we've seen for most of the week - 22C.

Track temperature is 41C.

08:17 Bottas is still going, now lapping 2s adrift of his session-topping time set earlier in this run.

08:19 Fans of oversteer - the @InsideFerrari Twitter page is worth a quick look. It has just posted pictures of Gilles Villeneuve and Fernando Alonso fighting oversteer in their respective Prancing Horses.

08:24 Alonso explained earlier this week that the power of the new turbo engines is capable of catching drivers out.

"The driveability of these cars is different," he said, "because the turbo is coming a little bit in a hit so you need to anticipate when the power will come."

08:26 The two-time world champion also shares the view of a lot of fans regarding the best F1 engine formula in the last decade:

"The nicest cars were the V10s when I arrived in Formula 1. Then the V8, now the V6, hopefully we will not see the V4. Maybe we will, but I will not be in Formula 1 then."

08:27 Third-placed Vergne finds six tenths, pushing the Toro Rosso closer to Alonso's best time.

Gilles Villeneuve08:27 We reckon the 2014 engine is still going to be more manageable than Ferrari's first turbocharged F1 racer, the 1981 126CK.

It's seen here in Gilles Villeneuve's hands in practice for that year's Canadian GP.

In case you missed it earlier this year, Villeneuve featured unsurprisingly high up AUTOSPORT's list of F1's greatest non-champions:

The best 25 drivers who never won the F1 title

08:31 Bottas is picking up where team-mate Felipe Massa left off yesterday as he continues to raise the bar at the top of the timesheets.

The Williams is the first car into the 1m34s today.

08:32 The Williams loses 1.3s on its next flying lap.

08:35 Sutil is the first man to get past 50 laps today. Not only is he playing catch-up after his Sauber expired at the end of its installation lap yesterday, but after lunch he is handing over to team-mate Esteban Gutierrez so he has less than 90 minutes of pre-season testing remaining.

08:36 Bottas backs off for a lap, and then puts in a second low 1m36s on this run.

08:39 That run finishes with a 1m36.9s, and Bottas comes back to the pits.

08:40 Grosjean gets the Lotus a bit closer to the pace with a 1m41.3s, and returns to the pits straight after.

08:42 Lotus reports that, prior to that run, the car had been undergoing some software updates.

08:45 Vettel heads back out after a stay of nearly 30 minutes in the pits. He and fellow-German Sutil are the only cars on track.

08:47 Bottas and Kobayashi join the action as well. Will this be another 'pace' run for the session-topping Williams that has been so strong this morning?

08:51 No heroics from Bottas just yet. He opens with a 1m37.5s, and next time round logs a 1m40.8s.

Grosjean improves in the Lotus to move up to P8.

08:59 As this is the last day of testing, it also represents your last chance to put some questions to our F1 Editor EDD STRAW ahead of the 2014 season. He'll be answering a selection this afternoon, so submit yours to or using #autosport on Twitter.

09:03 We have our first red flag of the day. There appears to be a car off at Turn 1.

09:04 It's the Red Bull of Vettel. The car has a hint of smoke, but the most bizarre thing is that the Red Bull - which appears to have gone straight on - is at 180 degrees to the direction of the track.

09:05 Fire extinguishers are in action, tending to the rear of the RB10.

09:07 Red Bull mechanics are covering the car up, as the mobile crane gets into position to recover it.

09:08 When the circuit CCTV cameras cut to Vettel he was already out of the car, standing at the rear taking a closer look while taking his helmet off.

Sebastian Vettel09:09 Vettel emphasised yesterday that he didn't see any point getting "emotional" about Red Bull's problems.

But despite doing his utmost to keep positive, he did admit that "we thought we would be in a much better place this week compared to last week. That hasn't really been the case."

More from Vettel on Red Bull's state

09:11 The flatbed truck is on its way back to the pits with the Red Bull.

09:15 @Marussia_F1Team: "Progress this morning has been frustrated by an electrical problem, which is confining us to the garage while we work to resolve it."

09:16 The Red Bull is back in the garage and the track is open again. Vergne, Sutil and Hulkenberg head straight out, and Bottas follows.

Red Bull09:20 EDD STRAW is in the pits and was watching the Red Bull crew recovering the RB10 just now:

"There's no obvious damage - the car is all broadly intact.

"But the team struggled to roll the car into the garage. Something seemed to be inhibiting rolling when they were trying to back it in.

"Work is now going on underneath to work out why."

09:21 On track, Hulkenberg moves up to third, 0.7s slower than Bottas.

09:25 The Force India is now in the pits, where EDD STRAW has spotted the team taking a wheel off and putting it back on (front left), and now some work going on underneath the VJM07.

09:27 Bottas stops short of the Williams pit to give himself room to perform a mini practice start. The team then rolls the FW36 back into the garage.

09:27 Sauber has just carried out a live pitstop (replacing softs with super-softs). Sutil has 75 laps on the board already today, so race work has clearly been the order of the day.

09:31 Force India team boss Vijay Mallya arrived at the Sakhir circuit this morning. He's currently on the pitwall, chatting to deputy team principal Bob Fernley and technical director Andrew Green.

09:32 With less than half an hour to go before he hands the car over to Gutierrez, Sutil's pitboard reads 'L21' and is counting down.

Red Bull09:34 Something that's becoming a familiar picture for Red Bull fans during F1's winter - this was the scene a few minutes ago as Vettel's car was retrieved from Turn 1.

09:34 The Toro Rosso is back in the pits and being backed into the garage as Bottas does a practice start and takes the Williams back out.

09:38 Grosjean has gone back out on soft tyres in the Lotus. His first flier is a 1m39.5s so not quite an improvement.

09:40 Pacesetter Bottas is lapping two tenths quicker at the moment with Sutil, Kobayashi and Hulkenberg also circulating.

09:43 Lewis Hamilton finally ventures out in the Mercedes following the lengthy delay caused by that gearbox problem. There's less than 20 minutes to go until the lunchbreak.

09:44 The Red Bull is in the garage with the engine cover off. No one is working on the car at present.

09:46 Hamilton gets off the mark with a 1m38.6s lap, which puts him straight into seventh on the leader board.

09:52 Hamilton back into the pits now after a short five-lap run. Vergne has gone back out in the Toro Rosso as Hulkenberg takes the honour of being the fastest man on the track at present. Only in the 1m43s though.

09:55 Grosjean stops the Lotus on the inside of the back straight, bringing out the second red flag of the day.

09:56 The Frenchman will be getting used to getting picked up by recovery crew there. That's same place the E22 gave up on him for the final time yesterday afternoon.

09:57 That stoppage brings an early halt to the morning session. That's lunch!

Valtteri Bottas10:07 Story of Sunday so far is Williams versus Ferrari up front, but problems for Red Bull, Mercedes and Lotus.

Here's our full summary of the opening hours today, including results so far and the current lap count:

Sunday morning report

10:12 Our F1 editor EDD STRAW is going to answer some of your questions this afternoon, so if you've got any puzzles you're eager to put to him, email or ask using #autosport on Twitter.

10:16 When the green light comes back on in a quarter of an hour, there will be just four hours' running left for teams before practice in Melbourne - and many of them will have massive jobs lists for those 240 minutes.

On Friday, GLENN FREEMAN investigated how ready various teams are with their race preparations, and assessed what a 'race sim' actually means at this stage:

Who is most ready for Melbourne?

10:22 Beyond F1, the rest of the motorsport season is ramping up.

We've had three spectacular V8 Supercars races from Adelaide this weekend, the last of which featured a brilliant last-lap lead battle and a terrifying aerial accident.

Read about it - and watch video highlights - here:

Adelaide V8 Supercars race three report

Coming up later today is round two of the 2014 NASCAR Sprint Cup from Phoenix. AUTOSPORT Race Centre Live will be covering it as it happens from 8pm UK time.

10:28 The reason this winter has been so fascinating for F1 is of course the enormous technical rule changes.

We've already explored their specifics in detail in CRAIG SCARBOROUGH's series of features, and this week we've been taking a look at the ethos behind them and the political journey that brought us here.

ADAM COOPER tracked the gestation of the 2014 rules from the first murmurs of an eco push for F1 10 years ago, including details of some even further-reaching plans that didn't come to fruition:

F1's road to 2014

We've also had an exclusive sit down with FIA president JEAN TODT, who chatted to DIETER RENCKEN about his views on F1 and motorsport's current status, and what needs to be done next:

Exclusive Todt Q&A

10:32 Lunchtime is over here in Bahrain. The track is live again. But it looks as though the teams are still digesting their food. No cars on-track yet...

10:35 Keen to make up for his massively delayed start, Hamilton is the first to break the silence in the Mercedes.

Sebastian Vettel10:37 'Vettel-clothing-watch' has become a feature of the winter tests, not because AUTOSPORT thinks the world champion's threads are especially suave, but because Vettel is pretty quick to wander around the paddock in his civvies if he thinks the car will be out of action for a long while.

This shot from recent minutes does not bode well for Red Bull track time...

10:39 Barely eight minutes have passed and already we have a red flag. Hamilton and Jenson Button's McLaren were the two cars on-track.

10:40 Hamilton brings the Mercedes safely back to the pits. The McLaren has stopped at the end of the back straight.

10:41 The recovery crews have headed to the inside of the left-hander, where Button has parked the MP4-29.

10:46 The McLaren has been hoisted onto the back of the flatbed by the crane and the course car has driven off.

10:48 Force India has enjoyed a strong final test so far. Hulkenberg will be doing long runs this afternoon, similar to yesterday.

@clubforce: "No action yet for us in the afternoon session, which is currently red flagged. Plan for the rest of the day includes long runs #FeelTheForce"

10:51 The recovery truck has headed for the pits with its cargo so we should be back underway shortly.

10:54 Green again here in Bahrain, now the stricken McLaren is safely back in the pits.

10:55 Hamilton and Kobayashi aren't hanging around. They head straight back out following the resumption.

10:56 We should have 12 drivers on the timesheet today, as Esteban Gutierrez takes over the Sauber from Adrian Sutil. The Mexican has just headed out for his first lap.

11:00 Gutierrez gets off the mark with a 1m40.8s lap. That puts him 11th ahead of Chilton's Marussia, which has only done 10 laps so far because of electrical problems.

Nico Hulkenberg11:06 Time for a reader question now, courtesy of Bhupendra Rawat, who asks: Where do you see Force India in the current pecking order? Are they a top-three team? And who is better between Nico Hulkenberg and Sergio Perez?
EDD STRAW: "Force India will certainly be thereabouts. It has the engine of choice in the Mercedes and has shown decent, if not stellar, pace during testing. So you'd expect it to be well-placed for a big haul of points in Australia.
"As for Hulkenberg v Perez, I'd have to say Nico. He is a top-team calibre driver in a midfield team and has shown time and again how good he is. Perez had a troubled time at McLaren last year, but has ability and I suspect he will have learned a hell of a lot from his chastening experiences last season."

11:09 Hamilton moves the Mercedes up into the top six with that last effort. He's clocked 12 laps now and is into the 1m37s.

11:14 Gutierrez works his way down into the 1m39s, but he's still a quarter of a second shy of displacing Vettel's motionless Red Bull from the top 10.

11:19 We'll probably see some long runs from most of the teams early this afternoon. That's certainly the plan for Force India.

@clubforce: "The long runs have indeed started in earnest - the Hulk is out on what is currently a 9-lap run, #FeelTheForce"

11:22 EDD STRAW reports that Gutierrez is warming a set of soft Pirellis on his Sauber. "Maybe a qualifying sim coming?"

11:24 Looks as though STRAW is on the money there, as Gutierrez posts his fastest lap of the afternoon and moves up to eighth on the leader board.

11:26 STRAW has stationed himself trackside at the end of the back straight. He reports that the Caterham looks "really unstable at the rear on turn-in".

11:35 Grosjean's Lotus has stopped again, bringing out another red flag.

11:37 Another reader question now, while we wait for the E22 to be recovered.

Mitch Connor asks: When the technical rules are so new to the teams, can they afford to sandbag in testing like we've seen in the past? Or do they need to show their hand to learn what the car is capable of?

EDD STRAW: "Given the scale of change caused by the introduction of the the new 1.6-litre turbocharged V6 engines with energy recovery systems, there is very little any teams can take for granted. With a smooth pre-season testing programme, you would want to do as serious a race simulation as possible and a full-blown qualifying sim (not to mention everything in between). In these circumstances, it is difficult not to show your hand in some way. 

"The difficulty is that teams don't know exactly what they are shooting for. While single-lap pace is more straightforward to get a steer on, the 100kg-per-race fuel limit will be hugely influential on Sundays and there are all sorts of ways teams can approach the grand prix distance itself. What compromises each team's race strategy might lead to in qualifying is difficult to predict. 

"While each team has a decent idea of where it stands, the uncertainty over exactly how races will pan out means that some of the frames of reference that could be taken for granted previously are far less narrow than they would ideally be. 

"The bottom line is that there is too much to do, too many unknowns to understand, to sandbag." 

11:49 Green again in Bahrain. Bottas, Hulkenberg and Gutierrez head straight back out.

Max Chilton11:50 An update from Marussia, which is battling to overcome electrical problems.

@Marussia_F1Team: "We're hoping that we're on the home straight in terms of resolving this issue. Looking to get back out on track in a little while."

11:51 Bottas has gone out on super-softs, according to EDD STRAW, so we might be about to get another quick lap from the Williams.

11:52 Gutierrez continues his incremental progress in the Sauber. He's up to seventh on the board having worked down into the 1m37s.

12:00 It seems super-softs are the tyres of choice at the moment. EDD STRAW reports that Hulkenberg and Gutierrez are both on them, as well as Bottas.

12:01 And with that, Gutierrez improves again, now down to a 1m37.3s lap in the Sauber C33.

12:01 Hamilton's been in the pits for 45 minutes, but comes out charging and climbs to fifth with his quickest lap of the day so far.

12:03 It hasn't been a smooth day for Mercedes so far, with the W05 emerging nearly four hours late due to a gearbox issue.

That followed early engine problems yesterday, prompting Nico Rosberg to underline that things definitely aren't 100 per cent serene for the current title favourite team.

Rosberg still worried about Mercedes reliability

12:05 Hamilton's into the 1m35s now after another quick lap in the Mercedes.

12:09 There's two and a half hours left of pre-season testing. Here's the lap count for you as it stands:

Sutil (Sauber) 91
Bottas (Williams) 87
Kobayashi (Caterham) 80
Hulkenberg (Force India) 55
Vergne (Toro Rosso) 51
Vettel (Red Bull) 45
Alonso (Ferrari) 38
Grosjean (Lotus) 32
Gutierrez (Sauber) 24
Hamilton (Mercedes) 21
Button (McLaren) 21
Chilton (Marussia) 11

12:10 It's been a dismal final test for Lotus. The team confirms a fire has curtailed Grosjean's running in the E22.

@Lotus_F1Team: "Big flames from the E22 on track, but not much external damage. Investigations into cause ongoing."

Valtteri Bottas and Felipe Massa12:12 Willem Das asks: I can't help but wonder what Nico Hulkenberg could do in a Williams this season.

But what can we expect from Bottas? We know what to expect from Felipe, he's been a brilliant driver at times, but there's surely not a long-term future for him at Williams?
EDD STRAW: "In any car Hulkenberg would excel. As for Bottas, he's an outstanding driver who had a far better debut season in a dire Williams in 2013 than many gave him credit for.

"I suspect he might emerge as the long-term team leader even though Massa has settled in superbly at Williams."

12:19 Marussia might have overcome its technical issues. Chilton has done an instal lap and has now ventured back out after some quick checks.

12:23 Fairly busy on-track at the moment. Hulkenberg, Vergne, Hamilton, Gutierrez, Kobayashi, Chilton and... wait! Vettel! The Red Bull has been fixed and the world champion has just completed a couple of flying laps in the 1m44s.

12:25 Hamilton goes second fastest for Mercedes now, less than seven tenths adrift of Bottas' benchmark time.

12:29 For those of you just joining us, here are today's headlines so far with just over two hours of testing to go:

*Williams leads the way for the second consecutive day
*Vettel suffers long delay after Red Bull breaks again
*Hamilton starts late with gearbox woes but goes second fastest
*The Lotus catches fire again
*Button's McLaren breaks down just after lunch

12:29 Vettel still circulating at a reduced pace. The Red Bull has racked up 58 laps now but is only lapping in the 1m45s...

12:31 Red Bull says the RB10's problem this morning was with the front end of the car.

@redbullracing: "Seb's back out this afternoon. The front end mechanical problem has been resolved."

12:36 Amit Mandalia asks: "With all the changes to the cars for this year, and what appears to be quite a difference in performance between a number of teams so far, how much do you think DRS will influence the racing during 2014?
EDD STRAW: "It will probably be quite similar to last year. Certainly, the DRS could help a little in terms of fuel-saving but there will probably not be such a dramatic difference.
"That said, the side of the DRS slot gap when opened has been extended from 50mm to 65mm (the idea being that cars have less downforce, therefore need a bigger mechanical influence to create an equivalent drag reduction), so there could be times when it is more powerful depending on how downforce levels evolve."

12:39 Vettel back into the pits now in the Red Bull. He's got 64 laps on the board now but none of them have been quick.

12:46 Kamal Nayan Ganguly asks: If rumours are to be believed, the Mercedes engine has a mammoth power advantage over its rivals. Since the power units have been homologated, can rivals re-homologate theirs to make-up the deficit? If not, what kind of tweaks can they make (staying within the rules)?
EDD STRAW: "While much of the homologation is opened up again for 2015 (barring certain aspects), for this season it is locked.

"Engine manufacturers can attempt to make changes under what is termed the 'fair and equitable' rule, whereby approved alterations can be made based on reliability, safety or cost saving.

"Expect plenty of that."

12:55 Hulkenberg, Gutierrez, Kobayashi and Chilton on-track at present as Bottas brings the Williams back into the pits. 'Hulk' is the fastest man on the circuit right now, lapping in the 1m41s.

Pits12:55 You don't have to dodge around other pitcrews too much in testing, with simultaneous next door pitstops pretty rare, but you might have to watch out for rivals' 'privacy screens'...

Here's Lewis Hamilton preparing to dodge more display boards than the average small-town council office when he leaves the Mercedes pit and passes Ferrari.

12:57 Red flag here in Bahrain with around 90 minutes of testing to run. Looks like Hulkenberg's Force India is to blame.

13:00 Hulkenberg has stopped just after Turn 3.

13:00 While we wait for the Force India to be retrieved and running to resume, here's a chance to catch up on the current state of play with EDD STRAW's review of yesterday's action for The Racer's Edge:

13:08 Green again and Gutierrez, Hamilton and Alonso head straight back out following successful recovery of the Force India.

13:10 Another red flag. This time it's Alonso who has pulled off in the Ferrari.

13:11 The Spaniard is out of the car, which is parked up on the inside at the approach to the sweeps after the back straight.

13:19 While the recovery crews are doing their work let's give you a lap-count for the day so far:

Kobayashi (Caterham) 101
Bottas (Williams) 94
Sutil (Sauber) 91
Hulkenberg (Force India) 74
Vettel (Red Bull) 64
Vergne (Toro Rosso) 56
Gutierrez (Sauber) 46
Alonso (Ferrari) 45
Hamilton (Mercedes) 36
Chilton (Marussia) 33
Grosjean (Lotus) 32
Button (McLaren) 21

13:23 Green again in Bahrain with just over an hour to go.

13:23 A bit of healthy competition between F1's two biggest mileage merchants in pre-season.

@MercedesAMGF1: "By our calculations there's just 34km between total #F1 pre-season mileage for @MercedesAMGF1 & @WilliamsF1Team! 1hr to go... let's do this!"

13:25 Track temperatures are cooling off in the closing stages, so get ready for some quicker lap times from the cars still running.

Romain Grosjean13:29 GLENN FREEMAN has just returned from a Lotus press briefing, following the engine failure that curtailed the E22's running early again. When asked whether Romain Grosjean felt he had any chance of finishing the first race in Australia, the Frenchman cryptically replied: "optimism?!"

13:30 Hamilton is the first driver to improve in quite some time. He edges towards Bottas on the leaderboard as Mercedes and Williams continue their mileage battle.

13:34 Ferrari has got the F14 T back up and running in little more than half an hour, so Alonso heads back out to get some more laps in.

13:36 Bottas switches on to the soft tyre now as Alonso moves up to second in the Ferrari, now within six tenths of the Finn.

13:38 Kobayashi has done more laps than anyone else today, but his work is not done yet...

@CaterhamF1: "We're into the final hour and have just sent out @kamui_kobayashi for run 13 - 101 laps and counting (all usual reliability caveats apply..)"

13:39 And the Japanese pumps in his fastest lap of the test so far: 1m38.391s, but stays ninth on the timesheet.

13:42 The timing screens are saying the session will be extended by 25 minutes, presumably because of the litany of red flag delays.

Jules Bianchi and Kimi Raikkonen13:44 Mike from Cheshire asks: Have any of the teams run at race speed in the turbulent air of another car, and what is the likelihood of this causing additional cooling problems?
EDD STRAW: "Cars have run together on track at times, but not for lengthy periods of time. So teams will have had some idea of what the effect is.

"The influence aerodynamically is pretty well-known, but what is interesting is what you can gain fuel-wise from sitting in the tow of another car."

13:45 Alonso shaves another couple of hundredths from his best time, but still can't break through the 1m35s barrier. Meanwhile, Bottas has just gone fastest of all in the first sector...

13:46 ... Make that fastest of all in all three sectors! Bottas into the 1m33s now as the pace heats up.

13:50 Teams have got the message that the session is going to be extended too, so it looks like we have 65 more minutes of pre-season running (red flags permitting).

13:53 Hamilton gets himself back up to second on the timesheet with that last effort, almost into the 1m34s now and quickest of all in the final sector.

13:59 That's our sixth red flag of the day, just after Alonso returned the Ferrari to second spot on the leaderboard. Looks like Bottas' Williams has stopped on the startline!

14:00 The Finn has tucked the Williams up against the pitwall. At least it shouldn't take too long to recover it.

14:05 A clutch problem has curtailed Caterham's pre-season early with an hour left to run.

@CaterhamF1: "A clutch problem unfortunately ends our day a little earlier than planned, stopping us before our final planned performance runs..."

14:09 That's the first time the Williams has stopped on-track this season, but the team is proud of the fact it still hasn't needed the recovery crews.

@WilliamsF1Team: "Car is wheeled back through from the pit straight - we've still not needed it to be brought back for us!"

14:10 Chilton improves in the Marussia just after the session resumes, while Hamilton sets the fastest lap of the day so far, just two hundredths of a second slower than Massa's benchmark from yesterday.

Boxes14:12 It's been a long stint in Bahrain, but F1 is preparing to get on the move again.

Freight is being packed up in the paddock - next stop Australia (via the factories).

14:13 An engine problem has curtailed Force India's day early. The last 40 minutes of this test will run under floodlight as the circuit has just switched on its beams.

14:21 Button's day is also done early. McLaren suffered an engine failure on a high-mileage unit.

14:22 Hamilton is about to head out on super-softs in the Mercedes...

14:26 Alonso's done Ferrari's best lap of the test so far, but is still third overall, behind Bottas and Hamilton.

14:28 Hamilton goes fastest of all in the first sector but loses three tenths in the middle of the lap. Backs off into the 1m41s across the line.

14:33 Hamilton manages a 1m33.8s lap last time around, but hasn't been able to get close to his previous best.

Esteban Gutierrez14:35 First shots are coming in of F1 under lights at Sakhir.

There will be plenty more of this on race weekend next month as the Bahrain GP becomes a night race for the first time, with practice two, qualifying and the race all set to be twilight/after dark.

14:36 ...although the World Endurance Championship field would point out that racing after dark at Sakhir is nothing new... This was the venue for Allan McNish, Tom Kristensen and Loic Duval's coronation last November.

14:38 That's our eighth red flag of the day. Gutierrez's Sauber to blame this time. The C33 has stopped at Turn 8.

14:44 The Sauber is on the recovery truck and heading back to the pits, and with 10 minutes remaining we are 'green' again.

14:46 Hamilton, Vettel and Chilton are the first to make the most of the remaining track time.

14:46 The darkness is setting in quick here now, giving everyone a sneak peak at what the Bahrain GP will look like under lights for the first time in April.

14:48 Sauber reveals that there was no problem with the car - the team ran a "fuel system test". Translation: it ran it out of fuel on purpose.

That's usually a regular feature of pre-season testing, but we've hardly seen it at all this year because the teams have had so much else to focus on.

14:49 Chilton vaults from bottom of the times to seventh, finding four seconds to get the Marussia into the 1m36s.

14:49 Five minutes to go here and Hamilton has just posted a 1m37.1s.

14:50 We're seeing a few out- and in-laps from Alonso and Vettel at the moment. One sits third in the times, the other is at the bottom...

14:52 Vettel moves himself off of the bottom with a 1m37.7s. He's now P9.

14:54 Into the final 60 seconds here and we have Hamilton, Alonso, Chilton and Vettel on track. The first three of those don't appear to be going for improvements, while Vettel has just completed a cool-off lap following his new PB.

14:55 The flag is out, and we have two PB sectors from Vettel...

14:55 Nothing too exciting from the Red Bull in the end, as he finds another 0.3s.

14:57 And that's it. Pre-season F1 testing is over for 2014.

As ever we'll have all the reaction to today's events in testing through the evening on AUTOSPORT, and there's more Live coverage later too with commentary on round two of the NASCAR Sprint Cup at Phoenix beginning from 7.45pm UK time.

And that's just the start...

14:58 Between now and the Australian Grand Prix there will be a host of 2014 pre-season features on, including our predictions of the championship outcome and more technical insight from CRAIG SCARBOROUGH, GARY ANDERSON and the SECRET MECHANIC.

14:59 AUTOSPORT's comprehensive 2014 F1 season preview magazine is published this coming Thursday (March 6) and is available both in shops and in digital formats online.

Melbourne15:00 Then our new expanded AUTOSPORT Live grand prix weekend service commences from 1.00am UK time on Friday, March 14, offering commentary and insight throughout the Melbourne weekend as the most eagerly-anticipated F1 season in years begins.

15:02 Thank you for your company (and there have been record numbers of you) through winter on AUTOSPORT Live's testing coverage, we hope you all enjoy the coming season with us too.

15:11 Here's the full story of the final day of pre-season testing in Bahrain:

Lewis Hamilton and Mercedes end winter on top

P Driver Team Time
1  HamiltonMercedes 1m33.278s
2  BottasWilliams 1m33.987s  +0.709
3  AlonsoFerrari 1m34.280s  +1.002
4  HulkenbergForce India 1m35.577s  +2.299
5  VergneToro Rosso 1m35.701s  +2.423
6  SutilSauber 1m36.467s  +3.189
7  ChiltonMarussia 1m36.835s  +3.557
8  GutierrezSauber 1m37.303s  +4.025
9  VettelRed Bull 1m37.468s  +4.190
10  ButtonMcLaren 1m38.111s  +4.833
11  KobayashiCaterham 1m38.391s  +5.113
12  GrosjeanLotus 1m39.302s  +6.024
All timing unofficial. Updated: 14:55 GMT
Clear skies High Temp: 22°C / 72°F
Track: Dry
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