In 2013 cars may look more like this 1998 McLaren, with a lower nose and smaller rear wing

Formula 1 teams have revised plans to make radical changes to cars for the 2013 season but still aim to make them more efficient.

A move to bring back 'ground-effect' aerodynamics external-link has been abandoned - but cars will still have reduced drag to ensure a cut in fuel consumption.

Cars will use 35% less fuel and be more challenging to drive but will be no more than five seconds slower per lap.

This will be achieved by reducing the size of the wings and other changes.

The changes still need to be approved at a meeting of F1's technical working group on Wednesday but, although there are a few fine details to be agreed, that is expected to be a rubber-stamping exercise.

The rules are to be introduced in tandem with new engine regulations, which will see the introduction of 1.6-litre four-cylinder turbos with hybrid energy recovery technology, rather than today's 2.4-litre normally aspirated V8s.

Initially, as exclusively revealed by BBC Sport in December, the idea had been to reintroduce shaped underfloors as a more efficient way of reducing drag while retaining high levels of aerodynamic downforce.

quote The biggest concern [about a 'ground effect' underbody] was that it's a massive amount of investment for the teams; it's quite a big departure

But the teams, through their umbrella organisation Fota, felt this would require a lot of work and expense and that the aims of governing body the FIA could be achieved in a way that, as one insider put it, required "less pain".

Instead, a number of detailed aerodynamic restrictions will be introduced to reduce drag, but the current design of the underside of the car, with a stepped but flat floor, would be retained.

These changes, it is felt, will achieve the same targets as those set by the FIA, but the cars will not be as aerodynamically efficient as had initially been hoped.

The cars' drag co-efficient will reduce from existing levels of 0.9Cd to about 0.7Cd, while the FIA's initial hope had been to cut it to 0.5Cd.

The changes will include:

* a front wing of reduced width

* a much shallower rear wing, similar to those used at the high-speed Monza track

* significantly lower noses on the cars

* the retention of the moveable rear wing - or drag-reduction system (DRS) - that was introduced this season to make overtaking a little easier

* a restriction on all the extra pieces of bodywork that have sprouted in front of the sidepods of the cars

* a restriction on the design of front wing endplates, to limit the intricate designs seen today.

The initial 'ground effect' rules were arrived at after veteran F1 engineers Patrick Head of Williams and Rory Byrne, formerly of Ferrari, were asked by the FIA to come up with a set of rules that could make the cars more efficient and more challenging to drive yet no more than five seconds slower per lap.

These rules were submitted for analysis to F1's technical working group, a panel of leading engineers from the teams.

This led to the teams deciding to come up with an alternative proposal, which Byrne produced for their umbrella group Fota.

quote We think the DRS has been effective and if we decide not to continue, it's easy to go back on it

After a meeting on Sunday at the Turkish Grand Prix, this is the one that will be adopted on Wednesday.

Williams technical director Sam Michael said the teams had been reluctant to go down the route of a shaped floor because it involved a lot of work and expense and there were uncertainties over the outcome.

"The only point of contention between Fota and the FIA has been on the tunnelled floor, having a shaped undertray," Michael said.

"Everything else is pretty much the FIA proposal, or pretty close to it with just some tweaks.

"The biggest concern was that it's a massive amount of investment for the teams. It's quite a big departure.

"If you were going to go down that route and have a very different set of drag and lift coefficients that you couldn't achieve with the current rules, fine, that's different.

"But the teams saw it as a massive amount of investment and work for something we don't really understand.

"We're not scared of that but if you do spend all that money, why do that and not something you can get to very quickly and cheaply with the current floor. The FIA understood that in the end.

"There's the budget effect of doing the tunnelled floor, a shaped undertray, but there's also the fact that it's unknown.

"So you could predict the downforce you'll get from it, but you could easily achieve double. Whereas if we stay with the current floor you can be controlled where the downforce and drag are going to be."

The inclusion of the DRS in the 2013 rules reflects a feeling that the device has been successful since its introduction this season.

Michael said: "We think it's been effective. And if we decide not to continue, it's easy to go back on it.

"If all the teams decided later it wasn't useful, we could easily get rid of it. It's not a fundamental design, whereas something like the curved floor is."