The so-called "world engine" has taken another step forward following what was described as a positive meeting at the FIA in Paris on Monday.
Manufacturers met to discuss the merits of the common-build 1600cc and two-litre engines as a future platform for motorsport.
One of the key discussions in the morning meeting had been the possibility of a turbocharged 1500cc, three-cylinder engine replacing the 1600cc plan. Such a move was, according to sources, scotched.
The source told AUTOSPORT: "There were some loose ends to be tied up with the world engine - and that's what the meeting was all about. The 1.5 engine had been proposed by a group of manufacturers, but following a healthy debate, even they could see the flaws in such a plan."
The problem with a 1500cc unit would be achieving more than 250bhp in economical fashion. There's also the technical problem of running 1600cc and two-litre platforms allows the use of common engine architecture and components.
The source continued: "The FIA is looking at two engines (1.6 and two-litre) so that formulas needing more than 450bhp can take the two-litre regulations rather than having to spend millions of pounds developing the 1.6 motor to get that power output. It's that simple. The meeting was all about common sense."
While the meeting had no regulatory power, it is planned that the FIA will present the world engine to its individual championships and left to the various commissions to decide whether they want to take the engine up.
The source added: "The plan is that the engine is recommended to commissions, such as the World Rally Championship Commission, and they can then take that rule and propose it to World Motor Sport Council as a regulation. The more championships which do this, the more engines are going to be built and the lower the costs can be."
Both the WRC and World Touring Car Championships will be utilising the 1.6 turbo engine from 2011 onwards.
The meeting did tackle the problem of manufacturers wanting a stronger identity with the engine under the bonnet of their own cars - and waivers will be permitted for marques wishing to build their own 1.6 or two-litre engines to strict FIA regulations.
"One of the really strong points coming from the meeting was we're looking to bring manufacturers to motorsport," the source said. "So, if Subaru did want to return with the flat-four configuration, waivers would be created to make sure that happened and Subaru or any manufacturer running a different configuration of 1.6 or two-litre engine would be welcome."