Following last week's confirmation that two teams are to part company with their engine manufacturer, the organisers of the IZOD IndyCar Series confirmed on Wednesday that a new rule would prevent any such further changes happening during a season in future.

Under the amended rule 3.8 of the series' Supplemental Guidelines for Engine Manufacturers, which went into effect on April 30, teams can only pair up with one engine manufacturer in a season unless permission is granted due to extra-ordinary circumstances.

"The intent of the rule is to try to help build a partnership between a team and its engine manufacturer," explained Trevor Knowles, the series' director of engine development. "Having a long-term commitment helps ease concerns about confidentiality of any information the manufacturer may share with a team.

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"It also limits a manufacturer's ability to drop a team from its line-up if they are going through a bad patch, he continued. Without it, one would see a drift of all the teams with the best results to the manufacturers with the best results creating a big imbalance across the field."

Just such a situation has arisen in 2012, with Lotus' late entry into the IndyCar engine supply chain leading to shortages of reliable units that have affected their teams' ability to test, and have also led to multiple starting grid penalties for unscheduled unit placements. In general, the Lotus engine also appears to be down in power compared with the units provided by its rivals, Honda and Chevrolet.

As a result of these problems, Bryan Herta Autosport and Dreyer & Reinbold Racing both sought to be released from their engine supply deals with Lotus, and after receiving the sign-off from IndyCar both teams severed their relationship with the British company following the Sao Paulo Indy 300 in Brazil on Sunday.

Neither team have yet announced a replacement deal with one of the other manufacturers for the Indianapolis 500 in three and a half weeks time, with the situation particularly acute for BHA given that they won last year's Indy 500 with Dan Wheldon driving.

However, while wanting to ensure that engine swaps do not become a chronic problem in the future, the organisers say that they are pragmatic about understanding that exceptional occasions may occur in the future where engine deals have to be changed even mid-season, and have duly left themselves with some room to manoeuvre.

"We have to be pragmatic and realise that there have been and will be times when a team and its manufacturer have to go their separate ways to their mutual benefit," agreed Knowlees. "This change allows that to happen while still maintaining control of the process."