Rossi said a new method of balancing the car through high and low speed corners proved effective, especially as he was conducting Caterham's first trial of the new system.
The team elected to test 2014 ideas in a bid to gain practical experience ahead of the massive regulation changes that accompany the advent of the 1.6-litre V6 turbo engines next year.
"We were running a new mechanical system of balancing understeer and oversteer between high speed and low speed corners," he told AUTOSPORT.
"Its something we have never run before, this was the first time. We understand what it does, and tomorrow will offer another chance to tune it.
"The rule changes are so big that any idea you can get before the actual car comes to the track is going to be a benefit, so our focus was on the mechanical side of things, working a lot on trying things out for next year.
"It means going into next year we're not bolting something on that has never had track mileage; we've done that now.
"Every day I get to drive an F1 car is good anyway, but running quite a few new things, and genuinely helping the team, was great."
While he has been restricted to just one Friday outing for Caterham so far this year, Rossi said his experience in the 2012 car was enough to convince him the new system offered immediate gains.
"To be perfectly honest the 2012 and '13 car are not massively different and I do have a lot of experience in the 2012 car, so putting this on I was very easily able to determine what the pros and cons were," he said.
"This was the first time we've put it on the car and the initial impressions were very good.
"If the development continues, I think there will be a massive buzz in the factory because of it."