HPD technical director Roger Griffiths says that Honda would have been forced to go down the twin-turbo route with its next-generation IndyCar engine even if that configuration had not been mandated by the series.
IndyCar confirmed last week that manufacturers would be compelled to use BorgWarner twin-turbo systems from 2014.
This ruling does not affect Chevrolet, which already uses twin-turbos, however Griffiths told AUTOSPORT that it had been clear to his firm for some time that the single-turbo layout had left it at a disadvantage.
"If there was going to be no adjustments to the parity I think we'd still have had to have gone with the twin-turbo," he said.
"We cannot continue to fight with one hand behind our back, which is where we are today. IndyCar has admitted that there is not parity between them at any of the boost levels, so we're racing at a deficit at every event.
"In terms of outright performance, you're probably looking at a two or three per cent [difference]. It varies with the boost levels - at lower boost levels it's not so bad, but at higher boost levels it's pretty significant."
INSTALLATION ONLY CONCERN
With Honda having committed to the twin-turbo switch some time ago, Griffiths says that development of its 2014 engine plans are already well advanced.
While he does not anticipate any problems matching Chevrolet on performance terms, he admits that the installation side of the new package will be a challenge.
"We've got a bit of catching up to do compared with our opposition," he said. "In terms of performance development, I don't think it puts us at a disadvantage.
"The area that we need to focus on more is the car installation, because GM has had two years to figure out the installation of the twin-turbo into the chassis.
"We need to get onto that so that we don't have issues in the first couple of races just through niggly little things that GM would have put behind them back in 2012. But that's my main concern. I'm not so worried about our ability to make a twin-turbo engine work."
According to Griffiths, preparations for the 2014 engine will not impact ongoing work on the current unit, with parallel development programmes having been put in place.
Honda has won three races in succession since introducing its most recent specification engine at Pocono.