Under the skin of the Lotus E21

At a simple launch ceremony at Enstone last night we were able to see the first 2013 F1 car.

Although the Lotus E21 looks very similar to the 2012 car, this is a reflection of the lack of rule changes in the formula this year. Thus we can see the E21 is clearly evolved from the race-winning E20, with the main changes being in the sidepods and in the details.

As this is the first 2013 car, most fans expected to see a different nose. The rules do allow for an infill panel to be fitted over the stepped nose, but Lotus has chosen not to devote time and resources to this, citing weight saving as more important than any small aero gain it might give.

We know other teams will take up the option of the so called 'vanity panel', but for James Allison and the Renault design team this isn't a path they will follow until the panel provides some real aero benefit for its weight.

Lotus has chosen not to use a vanity panel, but the front end will likely be updated before testing begins

Although the nose still wears a step, the front end of the car is likely to feature updates before testing begins.

Lotus released two sets of images: one of the car on stage and the other three-dimensional renderings of a car with more representative bodywork.

We can see in the renders that the car will wear turning vanes under the nose, while the wing that will be used for testing is very much based on the design used late last year.

Another interesting detail in the renders is the lower front wishbones, which wear an unusual profile. They are much thicker in their outer halves than the relatively thin sections nearer the chassis. These wider profiles will no doubt provide some aero benefit downstream on the car.

While the nose and front-end aero is not particularly new, the sidepods on the launch car do show a step change in Lotus's thinking around blowing the diffuser with the exhaust.

Lotus was the most successful team not to blow the diffuser last year, instead opting for the engine-power benefit that a simpler exhaust system brings. Indeed, it was only from the Korean Grand Prix onwards that the team raced a blown diffuser.

Its 2012 exhaust followed the Coanda style used by McLaren, with bulges in the flanks of the sidepods housing the exhaust and a channel to divert the exhaust gasses towards the diffuser edge.

Blowing the exhaust between the rear tyre and diffuser helps seal the diffuser, thus creating more downforce. This allows the car to run higher rear ride height, which in turn makes better use of the available diffuser height.

Rather than continuing the McLaren format of exhaust/sidepods, Lotus made an extra step and followed Red Bull's tunnelled sidepod idea for its E21.

In this set-up, which is similar to the end-of-season Red Bull specification, the exhaust exits up and over a ramped section of bodywork that leads down towards the diffuser edge. To prevent this ramped section blocking the airflow around the sides of the car, there is a tunnel to allow airflow to pass beneath the exhaust ramp.

Lotus has followed Red Bull's tunnelled sidepod idea on the E21

Red Bull struggled with this design, attempting to make the 50mm-tall tunnel direct airflow to the starter-motor hole and out along the sides of the gearbox.

Lotus has a simpler solution in which the tunnel ducts to large outlets at the tail of the sidepods. This should allow better airflow around the back of the car, while accurately aiming the exhaust at the diffuser.

The exhaust exit and bodywork varied between the different images coming out of Enstone. The renders show a large metal exhaust outlet, similar to the titanium exhaust shield used on 2012 Coanda set-up. This is likely to be the Jerez testing spec, as the metal exhaust surround deals better with the heat than carbon fibre bodywork.

One detail that helps to divert the exhaust plume towards the diffuser is the pair of horizontal vanes over the front of the sidepods. These are similar to those used by Sauber last year and also adopted by McLaren mid-season.

Two versions of the vanes were shown, the car on stage having wider vanes joined to the sidepod fin. The 3D renders featured shorter vanes mounted to the side of the chassis. Both designs deflect the air coming up over the sidepods and create a stronger airflow to bend the exhaust plume downwards.

On both versions of the car, the tail end of the sidepod does not appear to completely seal against the floor, allowing some airflow to pass under the tail of the sidepod behind the tunnel. This will require closer inspection when the car starts testing.

The other Lotus innovation seen in 2012 was its Drag Reduction Device (DRD), which was the team's take on a passive version of the Mercedes double DRS. While double DRS is now banned, the Lotus system of a duct that blows under the rear wing to stall the wing at speed for a higher top speed is still legal.

Lotus's Drag Reduction Device is still legal in 2013

Again, the rendered images show the tell-tale twin inlets around the roll structure that feed the passive ductwork. The tall engine cover and the removable sections at the end of the sidepod further suggest Lotus will continue to develop this problematic drag-reduction system.

Last year the team found the switch from normal airflow to stalling the rear wing was unpredictable and cost the cars downforce when at lower speed. Even with this DRD working it is not expected to offer a massive gain in performance, but merely a useful step in top speed.

Elsewhere on the car the evolution is clear. The monocoque is barely distinguishable from the E20. The top surface of the chassis is slightly concave and sports small asymmetrical blisters to clear the front suspension rockers. Lotus has chosen not to follow Ferrari's lead and has stayed with pushrod front suspension.

At the rear the car retains a titanium gearcase with inboard mounted pullrod suspension. As with other aero parts on the car the rear wing and diffuser appear to be in 2012 specification and are likely to change for testing in Jerez.

Lotus of course uses the Renault engine and KERS. As no mention has been made of any changes in the layout of the KERS components, Lotus looks set to again mount the KERS battery under the fuel tank rather around the gearbox in the way Red Bull does.

Last year Kimi Raikkonen won a race and was in contention for the championship until the last few rounds. With regulations being so static this year, the evolution of the E20 into the E21 should be enough for Lotus to continue this momentum and challenge for greater prizes.