Indy Racing League officials say five engine manufacturers are still in competition to provide new engines for the IRL.
The companies still in discussions with the league are Honda, Audi, Fiat, Porsche and Volkswagen. Honda has been the sole supplier of Indy V8 engines since 2006.
New specifications are not expected to be finalized for several months and would not be used in IndyCars until at least 2011.
The most significant change could be the addition of turbochargers to normally aspirated engines, which has become the IRL's norm over the past decade.
Series officials have held three round-table meetings over the past six months with chassis, tire and other manufacturers. Read more here.
-- The Associated Press