The IZOD IndyCar Series announced on Thursday that it had given the go-ahead to Lotus to introduce a series of upgrades to its engine design in order to allow it to catch up with rival manufacturers Honda and Chevrolet.

"Now that the IndyCar Series has giving us permission to improve the engine performance, things will be moving soon," said Olivier Picquenot, Lotus' IndyCar program manager. "The purpose is to get some outside help to assist in the new development plan for the Lotus engine. Everyone has been working well together and looking to make some quick progress in a concrete way."

The approval came under an existing provision in the series rulebook which allows the engine suppliers to petition for the chance to change their engine specification even though the units are meant to be frozen through to the end of the 2016 season.

Rule 4.7 states: "At June 18 and again at the end of the year manufacturers whose engines are statistically more than 2.5 per cent deficient in power may, at the sole discretion and evaluation of IndyCar, make improvements to be homologated immediately."

Lotus duly lodged the paperwork on the stated date, supplying data from testing, practice and race sessions proving that the engine was more than 2.5 per cent down on power. There was little problem demonstrating this, with Lotus' cars painfully down on speed on the ovals and even getting parked ten laps into the Indianapolis 500 for being unable to run within 105 per cent of the leaders' times.

Two IndyCar teams - Bryan Herta Autosport and Dreyer & Reinbold Racing - started the year with Lotus engines but negotiated their way out of their contracts when the power shortfall became apparent. A third team, Dragon Racing, split in more acrimonious circumstances in the weeks building up to the Indy 500 in May, after filing a lawsuit against Lotus.

The June 18 homologation waiver application laid out the requested series of changes to be phased in, which will start with a test on July 2 at Mid-Ohio Sports Car Course with the HVM Racing car of Simona de Silvestro, the only driver now using Lotus power full time in the series. The rules are clear that the proposed solution cannot simply be through allowing more turbocharge boost or turning up the RPM, but has to come from design-led improvements to the engine itself.

"The intention of the rules is that you can't just go and request more boost or revs," agreed John Judd Jr. of the family-run UK-based Engine Developments Limited company that is contracted to design and build the Lotus engines. "You give them a shopping list of items you'd like to change, but wouldn't be allowed to under the existing homologation regulations."

Judd pointed out that changes to the camshaft profile were just one thing not allowed under the formal rules that they wanted to be able to introduce under this mid-year dispensation.

Under Rule 4.7, the engine manufacturer can submit a request for a programme of improvements seeking to claw back up to 2 per cent of that performance shortfall to that of its rivals, as demonstrated in computer data simulations submitted for analysis to IndyCar. If the outcome in reality overshoots, then IndyCar can intervene and dial back turboboost or rev limiters to compensate; and if it under-delivers, then the manufacturer will just have to wait until the end of the year before the next opportunity to appeal for a homologation waiver.

"We'll keep an eye on how they're doing, but they can't really come back and say they want to change more," said IndyCar's director of engine development Trevor Knowles. "If so, they've missed their chance until the end of the season. We don't want to leave it so it's open engine development in order to catch up."

Now that the current upgrade request has been signed off by IndyCar, the new specification 2.2-litre twin-turbo Lotus V6 will likely make its race d?but in de Silvestro's car next weekend in Toronto, with further modifications coming on line at Sonoma in August and Baltimore in September. Any new engine can only be introduced as part of the normal process of switching out end-of-life engines that have reached their 1850 mileage target, or else starting grid penalties will be incurred.

Lotus has already carried out upgrades where they can to the non-homologated parts of the engine such as the pistons as part of the normal cycle of engine supply. In a similar way, Honda Performance Development was able to make some improvements to their engine ahead of this year's Indianpolis 500 which gave their teams an unexpected boost going into the race after a lacklustre qualifying.

However, such refinements are quite different from the major changes required to overcome the huge 2.5 per cent deficiency Lotus faces, and John Judd insisted that work would continue across the board for the remainder of 2012 to show that his company and Lotus are committed to the series long-term.

"We're certainly not limiting our development to just this process here," he said. "Our efforts will continue to improve the engine through the standard means as quickly as possible."