Bahrain third 2014 test Test day four

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

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.

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.

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

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

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

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

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:

Hulkenberg has stopped just after Turn 3.

Pits

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.

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.

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."

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.

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."

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

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

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.

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

Valtteri Bottas and Felipe Massa

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."

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

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

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.

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

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.

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

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

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." 

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".