07:51 The faint rumble of an engine, and a circuit waking up to the sound of Formula 1 2014 - it's the second day of pre-season testing at Jerez. Welcome back.

07:53 What can we expect today, after a stunted opening day that produced just 93 collective laps.

Will we, for example, see more of the Red Bull RB10, or anything of McLaren's MP4-29?

07:57 Well, for starters, we've got a new ingredient to throw into the mix: today has been nominated as a wet weather tyre test day.

This year's regulations stated that one day of pre-season had to be used for wet weather testing. That was originally pencilled in for Friday, the final day here at Jerez.

But with overcast skies, and rain on the horizon (the track is already wet), Pirelli has declared today will be our day of wet running.

08:00 That is unlikely to affect many schedules - teams after all are focusing mainly on the basics - it's another unknown element to add to an already overwhelming mixing pot.

08:04 Tractors and F1 don't often go hand in hand, but there's one out on track right now dousing an already wet surface.

It's early, but the media centre is still awake enough to have started taking bets on whether it will complete more laps than some of the teams today.

08:05 We're past the official start, but the track hasn't opened yet as the tractor creeps round.

08:16 A new twist? The tractor is headed down the main straight in the wrong direction (and at impressive speed). Does it need more water? Some in the media centre are saying the track is not wet enough to justify a wet tyre day...

08:18 While we wait for the latest on tractor-watch (we just invented that), we've also been doing a sweepstake on how many laps will be completed today.

If you missed our lap counts, F1's 2014 designs managed 93 collective laps on day one.

Last year's count? 657.

08:18 Aha. We're green, and we have an engine fired up.

Not only that, we have a new car - the McLaren MP4-29 takes to the track and opens proceedings for day two.

08:21 Sebastian Vettel wasn't too downbeat about turning in just three laps yesterday:

"We did really just a total of three laps, just carried the car round.

"We didn't run the whole day for a reason, we weren't ready so it took longer than we thought.

"Considering the amount of total running we saw today, everybody has quite a bit on so it's just to make sure, to run the car to get everything up to temperature but no feeling yet."

08:22 Williams joins the fray, followed quickly by Sauber. Button heads back into the McLaren garage, which is directly underneath us.

08:25 Gutierrez and Bottas head straight back in, and we have quiet.

08:30 That is as good a time as any to bring you today's line-up.

We've been chasing information as it could well change given day two has been declared a wet tyre test day.

So, with the disclaimer that this could change, here's who should be driving today:

Sebastian Vettel, Red Bull
Nico Rosberg, Mercedes
Kimi Raikkonen, Ferrari
Jenson Button, McLaren
Sergio Perez, Force India
Esteban Gutierrez, Sauber
Daniil Kvyat, Toro Rosso
Valtteri Bottas, Williams
Marcus Ericsson, Caterham

08:30 It would be understandable if you found yesterday's start to F1 2014 a bit disappointing, with only six teams managing flying laps.

But there is plenty of confidence in the paddock that this situation will be shortlived, as JONATHAN NOBLE found out last night:

Why 'Formula Farce' won't last long

08:33 Given that F1 2014 could be an engine formula, we reckon this counts as fighting talk:

@MercedesAMGF1: "That's the first laps now completed for all four Mercedes-engined teams in 2014. 'From little acorns' and all that... :)"

08:36 Gutierrez heads back out for Sauber, and therefore becomes the first man to start a second lap on day two.

08:38 Which was a weak segue into our AUTOSPORT sweepstake (feel free to play along at home, we haven't decided prizes).

KEVIN TURNER: 200
JONATHAN NOBLE: 250
GARY ANDERSON: 180
SAM TREMAYNE: 201
EDD STRAW: 186

08:39 Gutierrez stays out and enters the first potential flyer of the day.

We also have two cars on track, as Perez joins the fray for Force India.

08:40 We have our first time on the board - Gutierrez comes round in a 1m49.424s.

08:43 Good start for Sauber this, as Gutierrez clocks his second flyer and drops four seconds from his time. The benchmark stands at 1m45.089s now.

The Mexican has put in four laps already today. McLaren, Williams and Force India all have one installation lap under their belts.

08:44 We have a fifth name to add to the list, as Raikkonen heads out for Ferrari.

08:45 Gutierrez improves again, working his way down to a 1m44.610s.

08:48 Perez completes a second installation lap and returns to his garage:

@clubforce: "Sergio completed an installation lap - all good on the VJM07, the car now back in the safe (and dry) haven of the garage #FeelTheForce"

08:49 His four-lap run complete, Gutierrez also returns to the pits, and we have relative quiet.

08:55 Gary Anderson, the man behind the race-winning Jordan and Stewart F1 cars of the 1990s, is part of AUTOSPORT's technical expert team this year and will be writing regular analysis pieces and features for us all season.

Yesterday he answered some of the big questions raised by the first day of running:

Gary Anderson's verdict on day one

08:58 Ferrari is keeping Michael Schumacher in its thoughts during testing this week, with this pitboard remaining outside its garage throughout.

09:03 An hour into the day, the main talking point has been the declaration that Wednesday will be devoted to wet weather running.

After one hour though we've seen a decent amount of running, even if Gutierrez remains the only man to have set a time. Here's how it currently stands:

1 Gutierrez, Sauber: 1m44.610s, 7 laps
2 Perez, Force India: no time, 3 laps
3 Button, McLaren: no time, 1 lap
4 Bottas, Williams: no time, 1 lap
5 Raikkonen, Ferrari: no time, 1 lap

09:04 And just as we write that, we have a new best.

Perez heads out for Force India, stays out for his first flyer, and duly comes round in a 1m41.444s.

09:06 Lap complete, Perez heads back in.

09:12 Bottas goes out for Williams, and is joined moments later by compatriot Raikkonen, who eventually gets his Ferrari moving after a jerky garage exit.

We're into the second hour, but we're still yet to see four teams: Red Bull, Mercedes, Toro Rosso and Caterham are all absent. Marussia of course is not expected to run before Thursday.

09:12 Commentator's curse, clearly. Sebastian Vettel heads out in the RB10.

The reigning champion was sporting some...unusual headwear earlier today while talking to FIA race director Charlie Whiting.

09:15 Another first in the 2014 pre-season: we have three cars out on circuit, as Gutierrez joins Vettel and Raikkonen.

09:16 Vettel heads straight back in, but Raikkonen stays out for his first flyer and duly lowers the day two benchmark at the first attempt.

The Finn comes round in a 1m39.148s, some two seconds faster than Perez.

09:20 Raikkonen and Gutierrez are clocking up a few laps now. The pair are on 15 collectively - already one sixth of the entirety of day one's total.

Raikkonen's three laps have all been within one second - all around the 1m39/40s mark - while Gutierrez sets consecutive personal bests as he works down to a 1m42.902s.

09:23 While Ferrari and Sauber are able to get straight down to business, other teams have still spent most of the week so far in their garages.

When should an F1 team start to panic about falling behind on mileage? AUTOSPORT asked Toro Rosso's technical chief James Key. His answer... today.

Day two will set panic levels - Toro Rosso

09:24 Our first overtake of the year, as Raikkonen - who got beautifully sideways earlier - nails Gutierrez on the inside of Turn 3.

09:27 And our first practice start too. Raikkonen again turns provider, as he pulls to the exit of the pitlane, waits and then launches from the line.

It's not the cleanest of getaways however, as he seems to have to change up early to avoid wheelspin - not entirely unexpected given the slick surface.

09:27 Button gives us our second glimpse of the McLaren in action, as he heads out.

He stays out too, and is onto the team's first potential flyer of 2014.

09:28 He'll be joined by Bottas, who exits just after Raikkonen pulls back into the Ferrari box (having completed another practice start on the previous lap).

09:31 Button doesn't complete that lap, but he's onto three for the day.

The track is drying quickly though, which means tractor-watch might kick back into gear. Everyone is currently using inters - when the day started wets were the obvious choice.

09:32 Bottas's first flyer sends him straight to the top of the timesheets, as his 1m38.944s edges Raikkonen by just over two tenths of a second.

09:34 Here's Raikkonen hunting down Gutierrez from earlier (see 0924).

09:34 Bottas improves next time round, dropping down to a 1m38.374s.

09:36 If you're just joining us, here's what's happened so far:

* Overnight rain means today becomes official wet tyre test day
* McLaren's MP4-29 makes track debut after Tuesday troubles
* Gutierrez, Raikkonen and then Bottas set the pace over the first 90 minutes.

09:40 Vettel is back out in the RB10, adding to the four laps (one today, three yesterday) the team has managed thus far.

09:40 He stays out too, although he's very much on half throttle as he comes past the media centre and heads down into Turn 1.

09:42 Williams is back in the garage and making set-up changes:

@WilliamsF1Team: "#BO77AS continues his morning programme requesting a number of set-up changes"

09:43 Latest updates in the AUTOSPORT testing gallery include the McLaren MP4-29 on track for the first time and the Jerez tractor flat-out.

09:44 Gutierrez and Perez head out just as Vettel comes back into the pitlane. Still no time on the board for the reigning champion.

09:45 Meanwhile, updates from Marussia and Caterham:

@Marussia_F1Team: "Great to see our Race Team & new @InsideFerrari colleagues arriving at the track this morning. The truck and car are making great progress - should be here mid to late afternoon. So a busy night ahead to prepare ourselves for its debut."

@Ericsson_Marcus: "Wet track today. We haven't been able to do any running yet, but the guys @CaterhamF1 are working hard! Hopefully we will start soon #ME9."

09:49 Perez and Gutierrez both post improvements, but stay third and fourth respectively.

09:51 Marussia and Caterham's slow progress in recent years has underlined how tough it is to break into F1 these days.

Their fortunes would put off most prospective new entrants, but not Gene Haas - co-owner of the Stewart-Haas NASCAR Sprint Cup squad.

He's been reiterating his commitment to launching an F1 team for 2015 during the NASCAR build-up in America this week:

Haas not underestimating F1 challenge

09:56 Here's Williams wheeling the current pacesetter Valtteri Bottas back into the pits.

Perez and Gutierrez have also returned to their respective bays, which means we have quiet.

We also have an increasingly blue sky - the morning clouds are lifting, and there are clear dry patches on the track and even in the pitlane. Time for the tractor to return?

10:00 There's rumbling beneath us - McLaren or Ferrari?

Turns out the answer is both, sort of. The MP4-29 fires up, but stays in the garage, while Raikkonen pulls out and onto the track in the F14 T.

10:03 Raikkonen hits the front once more, shaving one tenth from Bottas's mark to drop down to a 1m38.272s.

10:05 Gutierrez is out too, as Raikkonen completes three flyers covered by 1.2s.

10:07 Bottas and Raikkonen trade blows - as the latter pits, the former emerged and, on his first flyer, hits the front once more.

The Williams driver sets a 1m38.102s to demote Raikkonen.

10:08 Button heads out in the McLaren MP4-29, which has completed just three laps so far in pre-season.

10:10 So, after the first two hours, here's our order:

1 Bottas, Williams: 1m38.102, 10 laps
2 Raikkonen, Ferrari: 1m38.272s, 15 laps
3 Perez, Force India: 1m39.526s, 9 laps
4 Gutierrez, Sauber: 1m42.661s, 23 laps
5 Button, McLaren: no time, 3 laps
6 Vettel, Red Bull: no time, 3 laps

10:12 McLaren's track debut has given AUTOSPORT technical expert and race-winning F1 designer GARY ANDERSON the chance to get a proper look at the design. Here are his thoughts:

Gary Anderson's verdict on the McLaren MP4-29

10:13 We're yet to see Mercedes - which hasn't run since Hamilton's front wing failed and sent him into the Turn 1 barriers at midday on day one - Caterham or Toro Rosso.

10:14 Button is on the board. A very cautious first flyer gives McLaren its first official laptime of 2014, a 1m47.767s.

10:15 The Briton pits straight after setting that time, and just as Perez heads out for his 10th lap of the day for Force India.

It's a short stint though - just the single lap, and the Mexican is back in.

10:19 More sideways action, this time from Gutierrez in the Sauber C33.

Anyone fancy some wet races this year?

10:23 Wondering what the latest is with Mercedes?

Executive director Paddy Lowe told reporters yesterday the team would be working through the night to find out why its front wing had broken.

"We know where it failed and we are trying to understand exactly why the margin was not sufficient in that area," he said.

Read the full story

10:24 Gutierrez, the day's busiest man on 23 laps, heads back out for Sauber. He's joined by compatriot, and former Sauber man, Perez.

10:27 Three men on circuit again, as Bottas joins the fray for Williams.

10:29 Big pitlane news this morning is McLaren confirming it has signed ex-Lotus chief Eric Boullier, but it's not a straightforward 'new team boss' deal...

Boullier gets McLaren Racing role

10:31 Up to 77 laps for the day - not bad given just 93 were completed over the whole of the opening day.

JONATHAN NOBLE is looking good in our sweepstake (see 0838).

10:32 Good news for Mercedes - Nico Rosberg (pictured at Jerez yesterday) heads out for his first run in the W05, and the team's first run since yesterday's crash.

10:34 Bottas improves again, breaking below the 1m38s mark with a 1m37.762s.

Times should be falling though - the skies are blue, and track temperature has crept up two degrees in the last 15 minutes (it's now 16). So much for the forecast rain...

10:40 Mercedes clearly happy to be back out after a lengthy hiatus (nice picture by the way):

@MercedesAMGF1: "Did somebody order some @nico_rosberg / #F1 W05 action? Coming right up!"

10:41 Rosberg heads straight back in after that one exploratory lap.

10:41 Our first red flag of the day. Gutierrez is the only man out on track...

10:43 It does appear to be the Sauber man who has caused the stoppage, as his crew pack into a course car and head off. We can't see where he's parked as of yet though.

10:43 Gutierrez had just set his fastest time, a 1m41.798s, before that halt.

10:46 Gutierrez is off in the gravel.

10:46 He's had a spin at Turn 5, but there was no impact - which is rather lucky as he's only a few feet off the barriers.

10:49 As good a response as ever by the marshals and team - the car is under covers, and the crane is dropping it onto a waiting low loader as we type. Some of the attending crew have also returned in the course car that headed out.

10:51 Incidentally, that shot should show just how 'wet' this wet day is so far. Track temperature has risen to 17 degrees now, and a dry line has formed at virtually every corner (at least those we can see).

10:53 As the low loader heads back, here's a quick round-up of where we stand after the first three hours of day two:

1 Bottas, Williams: 1m37.762, 17 laps
2 Raikkonen, Ferrari: 1m38.272s, 15 laps
3 Perez, Force India: 1m39.008s, 13 laps
4 Gutierrez, Sauber: 1m41.798s, 33 laps
5 Button, McLaren: 1m47.767s, 6 laps
6 Vettel, Red Bull: no time, 4 laps
7 Rosberg, Mercedes: no time, 1 lap

10:55 Car offloaded, garage screens up, and we're back to green. Rosberg and Mercedes wastes no time and are out as soon as the pitlane opens.

10:56 Another flash of silver, as Button heads out for McLaren moments after Rosberg's departure.

10:57 Rosberg pits, but Button stays out.

10:59 That didn't take long. McLaren's second flying lap of 2014 sends is good enough to top the timesheets on a 'wet' second day, as Button comes round in 1m36.232s.

11:01 That lap has led one person in the media centre to tip Button for the world championship this year. Nothing like kneejerk reactions...

11:04 Even quicker from Button. Was the tipster right? He clocks a 1m36.094s on his third flyer (he's followed the old quick-slow-quick pattern so far).

11:05 Ferrari clearly concurs that it is no longer wet:

@InsideFerrari: "#wetTyreTesting done by #Ferrari. Now we use this time available to work on the car to prepare this afternoon's programme."

11:07 Our expert spotter (we won't name and shame) reports that Rosberg has a rear-end wobble exiting Turn 1.

He means Button, of course - unless Rosberg is twerking down at Turn 1. Easy mistake given how similar the two teams' colour schemes are.

11:09 Button (most definitely this time) heads back to the McLaren bay directly beneath us, a five-lap run completed.

11:11 A spin that escaped our attention when it happened - we've just been informed that Bottas lost the rear of the Williams earlier when exiting the pitlane. Whoops.

11:13 More weather talk. We don't mean to bang on about it, but it is very odd to have a 'wet' day which is in fact totally dry. In fairness, the forecast was for downpours - no doubt they'll come this evening when AUTOSPORT has a track run planned.

@McLarenF1: "Jenson: "The circuit's almost dry. There are still a few wet patches, but it'll be dry after lunch." #Jerez #F1"

11:19 Quiet on the track now. If you're just joining us (where have you been?), here are the main themes of day two at Jerez:

* Overnight rain means Wednesday declared the official wet tyre test day
* Button goes fastest in the McLaren MP4-29
* Mercedes returns after Hamilton's day one front wing failure
* Gutierrez causes red after spinning at Turn 5
* 98 laps completed after the first three hours

11:26 There's no official lunch break at Jerez, but everyone needs to eat. We therefore seem to have entered a natural pause in proceedings.

11:30 A reminder that we are still yet to see Caterham or Toro Rosso emerge today - Marcus Ericsson and F1 rookie Daniil Kvyat are scheduled for driving duties for the respective squads.

As Marussia confirmed earlier (see 0945), we're not expecting any running from the team before tomorrow.

11:31 Aha. The silence is broken, as reigning champion Vettel - yet to set a timed lap in the 2014 pre-season - heads out in Red Bull's latest creation, the RB10.

11:33 A brief excursion, as Vettel heads straight back to his waiting pitlane crew.

11:41 That leaves the track empty again. We're still yet to see a timed flying lap from Vettel and Red Bull this year.

11:43 Should rivals get excited about the prospect of Red Bull being reeled in this year?

AUTOSPORT's technical experts aren't so sure. In his Tuesday analysis GARY ANDERSON said Red Bull is the team he'd be most relaxed about being in charge of right now, and CRAIG SCARBOROUGH reckons there's as much clever thinking and hidden complexity as ever in the 2014 car.

Red Bull RB10 technical analysis

11:48 Still waiting to see if the tractor will make another tour or if the wet element of 'wet day' is over.

Toro Rosso boss Franz Tost didn't think a huge amount of running would be required to tick the wet tyre testing box.

"Jerez's surface is different to many other tracks, but we'll get a picture of the tyre wear and tyre degradation," he said. "It's enough."

11:54 And while we're on the subject of Toro Rosso, which has probably one of the more aesthetically challenged 2014 cars, Daniil Kvyat had this to say yesterday when asked if he thought the STR9 was beautiful:

"From the inside it is!

"We've seen many different solutions, but in the end what matters to the drivers and the teams is that it's a fast solution. For some I understand it doesn't look nice."

Very diplomatic Daniil...

11:56 And finally we have some track action again as Rosberg takes the Mercedes out.

11:58 Rosberg has stayed out so let's hope he'll set a time on this outing.

11:59 Team-mate Lewis Hamilton was quickest early on yesterday until his crash.

11:59 Button takes the McLaren out as Rosberg sets a 1m42.630.

Vettel has also just left the pits.

12:01 Rosberg does a 1m41.278, but is still far from pushing hard.

12:03 Button sets a new best time of the day, with 1m32.443s. The times should continue to come down as the track is really getting quite dry now.

12:04 Button set his new best time on slick tyres. Vettel has now also recorded a time to go fourth for Red Bull.

12:06 The McLaren and Red Bull return to the pits, leaving just Rosberg on track. He has now got down to a 1m39.276s.

12:06 And Rosberg now pits, so the track is quiet once again.

12:09 Caterham is reporting the CT05 could be out soon.

@CaterhamF1: "The bodywork's on, the garage doors are open and we're nearly ready for @Ericsson_Marcus to head out for our first day two laps"

12:10 But it is Force India that goes out first, Perez driving down the pitlane for the first time in a while.

12:13 And now Perez, also on slicks, moves to the top of the times. He's just gone round in 1m31.885s, but we're still some way off the best laps from yesterday's running.

12:14 But he is getting closer, Perez now managing a 1m29.641s effort.

12:19 With Perez returning to the pits, we have no cars on track. But we have already seen a lot more action than we did on day one.

We're still waiting to see Caterham and Toro Rosso today.

12:19 Button goes back out. Can he beat Perez's time?

12:23 We'll soon be seeing the Williams out.

@WilliamsF1Team: "Lunch done and Valtteri is ready to go. Dry tyres now fitted #Jerez"

12:24 Button has improved to 1m29.114s to go back on top, plus Rosberg's Mercedes has now returned to the fray.

12:26 The next lap is a 1m29s too. Rosberg now improves to 1m39.116s in the W05.

12:28 Another 1m29s lap from Button. This is about the closest thing to a consistent run we have seen.

Marcus Ericsson has gone out to give the Caterham its first run of the day.

12:30 Button back in, but he is now topping today's times again. He is two seconds off Kimi Raikkonen's best time for Ferrari yesterday.

12:31 Ericsson's lap was just an installation lap, so just Rosberg on track.

12:33 Perez goes back out for Force India.

12:39 And Perez moves back to the top with 1m28.624.

12:40 And follows that up with a 1m28.376.

12:42 Rosberg has now pitted the Mercedes. Perhaps a good time to remind ourselves why he selected to race with number six:

"My Dad wrote me an email in the winter saying it had been a lucky number for him when he became world champion, but that didn't convince me.

"Then my fiancee said it was her lucky number, too, so that got me thinking a bit more! And then I remembered that I won a championship with this number back in 2002. Hopefully that will be the key to an easy season!"

12:45 Button now goes out in the McLaren, just after Perez brings the Force India in. They seem to be taking it in turns to go quickest!

12:46 Our quoting of Nico's reasons for picking the number six is well-timed, as father Keke, the 1982 world champion, has also been spotted in the pits.

12:53 Button has, indeed, gone quicker, with 1m27.556. That's getting close to Kimi's best of 1m27.1 from yesterday.

12:54 Rosberg has gone back out too, and sets a new PB of 1m32.932 to put the Mercedes into third.

12:56 Rosberg continues to improve and now gets down to 1m31.227.

12:59 A bit more insight from our technical expert GARY ANDERSON on some potential issues for the Renault teams:

"It seems that Renault is having a few problems. Sebastian Vettel's Red Bull was the only Renault-engined car we saw on track for much of today, with both Caterham and Scuderia Toro Rosso being sat in the garage for a long time.

"Red Bull is the works Renault team, so it's conceivable it is doing some troubleshooting work. Yesterday, the Caterham only managed one lap before stopping with an electrical problem while the Toro Rosso had serious trouble with the engine mapping, which Jean-Eric Vergne said led to the car "oscillating". You could see what he meant as it juddered up the pitlane and out onto the track.

"Today, the Mercedes cars are averaging 14 laps per car and the Ferrari-powered machines 24 laps. Vettel has done eight laps, which means the three Renault-engined machines are averaging less than three laps each for over four hours of running."

13:00 Rosberg continues to improve and the Mercedes has just lapped in 1m29.231. He is, however, still third.

13:02 Perez's Force India squirms out of the last corner as he sets a 1m29.2.

To put these times into perspective, the best lap in Jerez testing last year was 1m17.879s, set by Felipe Massa's Ferrari.

13:07 So, with just under three hours to go, a quick summary of the positions and laps completed so far:

1 Button, (McLaren) 1m27.556s, 32 laps
2 Perez, (Force India) 1m28.376s, 27 laps
3 Rosberg, (Mercedes) 1m29.231s, 24 laps
4 Bottas, (Williams) 1m37.762s, 17 laps
5 Raikkonen, (Ferrari) 1m38.272s, 16 laps
6 Vettel, (Red Bull) 1m38.320s, 8 laps
7 Gutierrez, (Sauber) 1m41.798s, 33 laps
8 Ericsson, (Caterham) no time, 1 lap

13:08 Perez completes another decent run, but he couldn't quite beat his own previous best of 1m28.376s, let alone jump back ahead of Button.

13:16 Jerez has been quiet for a while so it is good to see Gutierrez heading out in the Sauber.

13:19 Caterham reckons it will be able to send Ericsson back out soon, which is good news for Renault.

Gutierrez has come straight back in, but Raikkonen heads out in the Ferrari. He has not been on-track for a long time, but his best time from yesterday remains the best Jerez lap so far in 2014.

13:20 Caterham is true to its word and sends Ericsson down the pitlane in the CT05 as Kimi comes straight back in.

13:24 And Ericsson comes in. Still no flying laptime for him.

13:27 Yesterday, Ericsson was pretty pleased to be conducting his first day on track as an official Caterham F1 racer:

"Even though we only did one lap it was still a very exciting day. It was great to be able to do one lap because the team has been working so hard for the last month or so and have been working day and night for the last couple of days. So at least to show the car and do one lap was a great achievement.

"It was impossible to get a feeling for the car because it was only an installation lap. We had to go around so the guys could get the data from it."

13:29 Rosberg and Gutierrez are now out on track.

13:31 Gutierrez sets a new best time for him today at 1m36.467s, while another Ferrari-engined car, the F14 T, heads out in the hands of Raikkonen.

13:33 But both come in, leaving just Rosberg on track.

13:35 The rear suspension 'blockers' on the McLaren MP4-29 are prompting a lot of intrigue at Jerez today.

Here's AUTOSPORT technical expert GARY ANDERSON's explanation of the concept, and why it could be a secret weapon that will be hard to copy:

Gary Anderson analysis: McLaren rear suspension 'blockers'

13:40 If you're just joining us, a quick reminder of what's happened so far on day two in Jerez:

* Button and Perez have been exchanging fastest times in the dry, after Button set the pace in the wet this morning.
* The Renault-engined teams appear to be struggling, with Red Bull and Caterham having completed a handful of laps and Toro Rosso not appearing at all.
* After the circuit was doused for official wet-weather tyre testing in the morning, the track has dried and times are edging down towards yesterday's best.

13:41 And now we are hearing Red Bull's running may be curtailed for the rest of the day thanks to an energy store issue. More details will follow as we get them.

13:42 Back on track, we currently have two Mercedes-engined machines, Rosberg and Perez.

13:46 Ericsson has joined in once again for Caterham. Is there a chance the team will get more laps in today then any other Renault-engined squad? Caterham is on three, Red Bull on eight and unlikely to go out again...

13:46 The Force India comes by the pits not sounding quite as healthy as it was.

13:47 Perez has stopped at Turn 1, so we've got a red flag. Small bit of smoke coming out the back too.

13:52 While we have silence, time for some reflections on the sound of the new 1.6-litre V6s.

They are not as loud as the old V8s, but do still sound like proper racing cars.

Here's what Toro Rosso's Franz Tost thinks: "It's a different music – I still have in mind the Matra V12 of the 1970s – but times are changing.

"The turbo sound is simply a different one and once all the cars are on the track we will enjoy it."

You can't hear the Matra V12 in Chris Amon's car at the 1972 French GP in our picture, but with a bit of imagination we're sure you can follow what Tost is getting at.

13:54 They seem to be having some trouble cooling the Force India down. It's still smoking.

14:01 There is now a cover over the Force India and they are about to try lifting it onto a truck. The marshals seem to be taking some care around the rollhoop area, so they could be worried about the regenerative energy systems.

14:02 Here's the full story of Sebastian Vettel, Red Bull and Renault's problems as the world champion curtails his running and flies home:

Red Bull forced to stop running on Wednesday

14:04 To give you an idea of the extent of the problem, Red Bull has completed 11 laps across two days here so far, compared to 174 laps across the first two days in 2013.

14:07 And we're green again.

14:08 The first car down the pitlane is Rosberg, with Ericsson's Caterham not far behind.

14:09 EDD STRAW reports that, unlike Red Bull, Toro Rosso is going to try to get its Renault-engined contender out on track again before the end of the day.

14:10 Rosberg improves to 1m28.149s and finally moves ahead of Perez.

14:12 And now he goes quickest, with 1m27.453s, just 0.3s from Raikkonen's best lap on day one.

Ericsson has also recorded a time, 1m38.438s.

14:14 Ericsson comes in, but Raikkonen takes the Ferrari out to join Rosberg. Gutierrez is also back on track.

14:15 Bottas takes the Williams FW36 out after a long time in the pits.

14:15 Rosberg goes quickest again, 1m27.073s. That is a fraction quicker than Raikkonen managed yesterday.

14:17 Gutierrez improves to 1m35.824s, but Kimi goes fastest of all for Ferrari with 1m26.585s.

14:18 Bottas improves too, 1m27.734s.

14:18 That lap from Rosberg has clearly gone down well:

@MercedesAMGF1: "Well would you look at that; top spot for @nico_rosberg with just under 2hrs left here at #Jerez today. He's ramping it up... #F1"

14:20 Kimi bangs in a slightly slower 1m26s, then finds a bit more with 1m26.421s.

14:21 Bottas goes second with 1m26.577s, putting him ahead of both Rosberg and Button.

14:22 Then even quicker to topple Raikkonen with 1m26.322s.

14:26 Nice message from Williams too!

@WilliamsF1Team: "It's all system & reliability checks before we focus more on performance in Bahrain. Before we can have a quick car we need a reliable one!"

14:28 After the flurry, most have pitted, leaving just Rosberg on track.

14:32 The mood seems to be pretty good in the Williams camp at the moment. Yesterday, Bottas had this to say about working with new team-mate Felipe Massa:

"It's quite early to say, but so far it's been all good with Felipe. We get along very well and he seems like a nice neutral guy, ready to work.

"We will see how the season develops, but I don't see any problems between us. I'm looking forward to working with him."

14:34 Rosberg continues to circulate in the Mercedes. He has completed far more laps than anyone else, 55. The next best is Gutierrez on 42.

14:35 Ericsson heads back out in the Caterham.

14:36 Massa makes his Williams debut tomorrow.

He's been here all week with his new team, which means we can show you what he looks like in a blue fleece.

Our photographers also captured Massa taking phone camera pics of the pitlane, and chatting to his new tech chief Pat Symonds.

From the looks on their faces, they weren't reminiscing about Singapore 2008. Massa's still a bit sore about that.

14:37 Ericsson comes past the pits, but the Caterham is still a long way away from flat-chat, despite a lock-up at the last corner.

Rosberg's Mercedes, on the other hand, sounds strong and continues to pound round. He is currently lapping in the 1m27s.

14:39 Ericsson sets a PB of 1m37.975s, putting Caterham above Red Bull!

Gutierrez is back out for Sauber too.

14:40 We spoke too soon. The Caterham has stopped and we have our third red flag of the day.

14:41 Out the back the Caterham has ground to a halt. Another Renault engine problem?

It's a shame for Rosberg too, as he looked like he was putting in something akin to a normal testing run. And we've not seen many of those so far at Jerez this year...

14:48 So we'll take this opportunity for a reminder of who has done what so far today:

1 Bottas (Williams) 1m26.322s, 26 laps
2 Raikkonen (Ferrari) 1m26.421s, 26 laps
3 Rosberg (Mercedes) 1m27.073s, 60 laps
4 Button (McLaren) 1m27.566, 36 laps
5 Perez (Force India) 1m28.376s, 37 laps
6 Gutierrez (Sauber) 1m33.363s, 44 laps
7 Ericsson (Caterham) 1m37.975s, 11 laps
8 Vettel (Red Bull) 1m38.320s, 8 laps

14:49 Rosberg's Mercedes has done 60 laps, which is more than all the Renault-engined cars have managed across two days combined (38 laps).

14:53 We're green again, but no-one yet on track.

14:55 Button takes the McLaren out, so that's another Mercedes engine putting in some more mileage.

14:57 And he is joined by Bottas and Rosberg. Button goes miles faster than anyone has so far, 1m24.165s.

15:00 Bottas improves to 1m25.462s to go second.

15:04 Bottas improves again and Rosberg also goes quicker.

Raikkonen enters the fray. The Ferrari and Button are on the mediums, Rosberg is on the normal Pirelli hard, and Bottas is on the special Jerez winter hard.

15:05 Raikkonen goes back to third with 1m25.348s.

15:08 Button is in, but Bottas, Raikkonen and Rosberg are still circulating.

15:09 Rosberg is running quite close to Bottas now and the two are lapping in the 1m26s.

15:10 Bottas now pits too, leaving Rosberg heading towards the 70-lap mark today.

15:12 Kimi comes in, stops at the pitlane exit, then blasts the Ferrari back out again after Rosberg's Mercedes has shot by.

15:15 Button goes back out. So we have McLaren and Mercedes out on the circuit, with Kimi having brought the Ferrari back in.

15:18 Touching tribute on Jenson Button's helmet:

@McLarenF1: "RIP Papa - a touching memento on the helmet of @JensonButton."

15:18 And the McLaren man manages a 1m24.591s, the second quickest lap of the test so far.

15:22 Button pits again and Gutierrez takes the Sauber out. Rosberg continues to go round. He has been lapping in the 1m27s and 1m28s for some time now, easily the longest run so far.

15:23 Scratch that, Rosberg has already made it into a double-figure run earlier today and seems to be doing so again. That is a much further range than anyone else has been willing (or able?) to try.

15:24 Gutierrez improves slightly to 1m33.270s.

15:28 Raikkonen heads out once more, Gutierrez pits. And Rosberg comes by to complete his 81st lap of the day, still in the 1m27s.

15:30 Marussia's 2014 challenger has arrived.

With luck, the team will have the car ready to run at some point tomorrow.

15:30 Kimi comes straight in, so it is just Rosberg out on track with half an hour to run.

15:31 Rosberg's time has slipped back into the 1m28s on the last couple of laps, Mercedes the only team running long enough to run the risk of proper tyre wear on the Pirelli hards.

15:33 And he finally pits, bringing to an end a 24-lap run. Rosberg's lap tally currently stands at 84, just nine short of the total of all the cars on day one.

15:35 And with that, quiet falls upon Jerez. Just 24 minutes of the day to run.

15:38 Which is a good time to recount some lap counts for the day.

Nico Rosberg leads the way with 84, followed by:

Gutierrez (51)
Button (43)
Perez (37)
Bottas (35)
Raikkonen (34)
Ericsson (11)
Vettel (8)

15:39 Raikkonen heads out for Ferrari, and is joined shortly by (who else?) Rosberg.

15:40 Incidentally, the average laps per engine manufacturer for today (so far) stand at:

Mercedes - 50 (199 total)
Ferrari - 43 (86 total)
Renault - 6 (11 total)

15:42 Williams has wrapped up its second day:

@WilliamsF1Team: "That's it for us for today folks as Valtteri adds 35 laps to his tally #Jerez"

15:44 Rosberg pits, leaving Raikkonen alone on track.

15:46 That doesn't last long however, as Rosberg heads back out.

Raikkonen meanwhile ducks into the pitlane, but he doesn't stop, instead heading down to the end for another practice start.

15:49 Mercedes using flow visualisation paint on the back of Rosberg's car for these final laps. With 10 minutes remaining, he's onto 88 laps for the day.

15:51 Gutierrez isn't done yet either, as he heads out for Sauber.

15:54 Unsurprisingly, this will be Gutierrez's final stint of the day:

@OfficialSF1Team: "Last run of the day for the #C33 #pushpush."

15:55 He heads in after a two-lap burst, and just before Raikkonen goes back out.

Rosberg is just one away from the 93-lap mark...

15:56 Sure enough, he comes round and starts his 93rd tour of Jerez, equalling the same number of laps set by the entire field during yesterday's running.

15:57 @CaterhamF1: "8 minutes left of day two and we're aiming to send out @Ericsson_Marcus for one last run. Busy garage right now!"

15:59 As Caterham counts the time down, Rosberg racks the laps up. He's almost into triple figures - 95 and counting now.

16:00 The chequered flag flies, and day two comes to a close. Rosberg and Raikkonen were still out as it fell.

16:01 So Button tops the timesheets for McLaren, while Rosberg - fourth overall - comes close to breaking into triple figures.

Not such great news for the Renault-powered cars, which managed a collective 11 laps on this second day.

16:08 Day 2 results:

1 Jenson Button (McLaren) 1m24.165s, 43 laps
2 Kimi Raikkonen (Ferrari) 1m24.812s, 47 laps
3 Valtteri Bottas (Williams) 1m25.344s, 35 laps
4 Nico Rosberg (Mercedes) 1m25.588s, 97 laps
5 Sergio Perez (Force India) 1m28.376s, 37 laps
6 Esteban Gutierrez (Sauber) 1m33.270s, 53 laps
7 Marcus Ericsson (Caterham) 1m37.975s, 11 laps
8 Sebastian Vettel (Red Bull) 1m38.320s, 8 laps

16:11 That's it for AUTOSPORT's live coverage for today. Our team of journalists have headed out to the paddock to get reaction from a day that was far busier - for some teams at least.

Keep up with all the reaction from the teams and drivers on autosport.com, and look out for the thoughts of Gary Anderson and Edd Straw in features for subscribers to AUTOSPORT PLUS as well over the next few hours.

Our live service will resume first thing tomorrow.