INDIANAPOLIS -- A seemingly minor event that occurred in Indianapolis Thursday evening could have a significant impact on Sunday's Izod IndyCar Series race in Brazil.

After an eight-hour hearing, a three-man panel denied a protest by Chevrolet and upheld INDYCAR's decision to allow Honda to introduce an alternate homologated turbocharger housing (known as the 0.74 A/R compressor cover) starting this weekend at the Itaipava Sao Paulo Indy 300.

IndyCar Series engine manufacturers Honda, Chevrolet and Lotus were permitted to submit two compressor covers for approval. The turbocharger assemblies contained within the shrouds are the same with either housing.

Following a test at Infineon Raceway paced by Target Ganassi Racing's Dario Franchitti, Honda believed the alternate housing improved the throttle response of its single-turbo V-6 engine, and the components were installed on all the Honda cars prior to the start of practice for the Grand Prix of Long Beach.

When Chevrolet protested, the Honda cars were restored to their original turbocharger configuration before a wheel turned at Long Beach. Despite a 10-place starting position penalty for an unscheduled engine change, Team Penske's Will Power then won the LBGP from 12th on the grid, giving Chevrolet a clean sweep of all three races in 2012.

Rubens Barrichello was a popular draw for fans in St. Pete. Imagine what it'll be like for the Brazilian this week in Sao Paulo. Chris Trotman/Getty Images

Chevrolet argued that INDYCAR should not allow the modified housing because engine specifications were locked in on Feb. 28. Honda reportedly claimed that the turbo housing change was a modification to the exhaust system. Honda also documented that the participating manufacturers approved changes of this nature during a new car development meeting in late 2010.

Either way, the three-man panel (featuring one representative nominated by Honda, one by Chevrolet and one by the league) was persuaded by Honda's case.

"INDYCAR committed well in advance of the 2012 IZOD IndyCar Series season to structure engine regulations focused on creating parity between competing manufacturers, and this commitment played a significant role in our decision to adopt a single turbocharger configuration for the new HI12RT Honda Indy V-6," read a Honda Performance Development statement.

"The new compressor cover helps to offset the performance disadvantage of the current IndyCar single turbo hardware as measured by INDYCAR's turbo supplier [Borg-Warner]. This correction was designed and provided by the turbo supplier under the direction of [INDYCAR] and was approved prior to the 2012 season. We look forward to deploying the new compressor cover to optimize performance of the Honda Indy V-6, as we continue to do battle with our worthy adversaries from Lotus and General Motors."

Chevrolet has until 5 p.m. Monday to appeal.

"Chevrolet believed the modification was contrary to the applicable series rules, and asked INDYCAR to thoroughly review the issue so that the rules were applied fairly," Jim Campbell, Chevrolet's U.S. vice president of performance vehicles and motorsports, said in a statement. "We respect the diligence of the panel appointed to hear the protest and examine the situation. While we are disappointed with today's decision, we are prepared to continue to compete at the highest level in the IZOD IndyCar Series."

Meanwhile, the 2.536-mile street course in the heart of Sao Paulo, Brazil, will be an interesting gauge of how successful the upgraded Hondas are, because that's the type of track Honda's single-turbo configuration was allegedly at a disadvantage to the twin-turbo layout of the Chevy and Lotus engines.

Brazil is the last of four road-racing events to open the 2012 campaign, followed by a sequence of four oval races in five weeks in which the single turbo of the Honda is expected to be marginally superior.

Drivability will be an even more critical issue in Brazil if it rains. The IndyCar Series shipped 400,000 pounds of freight to Brazil on April 22, and included in that payload were 332 Firestone rain tires -- five sets for each of the competing drivers in Sunday's 75-lap race.

The IndyCar drivers naturally hope they won't have to call on the Firestone wets. But rain has played a key role in the Brazilian weekend in the first two years of the IndyCar Series' Sao Paulo event, and the forecast calls for a 60 percent chance of showers on Saturday and 90 percent on Sunday.

It's unlikely that it will rain hard enough to have a repeat of last year's scenario -- the race was started, but postponed until Monday because the track became flooded after intense storms. Still, improved drainage was a factor in the minor modifications made to the 2.536-mile, 11-turn street course for 2012.

"The layout of the track has not changed and the curbs have not changed," track designer Tony Cotman said. "Reducing some of the bumps was among the goals that have been addressed. Also, drainage in five or six locations has been addressed.

"Now that it's all done, we hope we don't need it."

“ We want to continue carrying this good momentum with the team, especially here in my hometown of Brazil. Certainly there is a lot of hype and there is a lot of excitement for this race. ” -- Helio Castroneves

The other main storyline this weekend is the Brazilian drivers at their home track. All eyes will be on Formula One transplant Rubens Barrichello and, to a slightly lesser extent, fellow Brazilians Helio Castroneves, Tony Kanaan and Ana Beatriz.

With nearly 1.6 million Twitter followers, Barrichello is extremely popular in Brazil and around the world. Ticket sales for this weekend's race are well ahead of last year, and the event is expected to sell out.

The lure of a home race was a big reason why Barrichello committed to a second career in Indy cars at age 39. The results haven't been sparkling so far -- an eighth-place finish at Barber Motorsports Park is his best so far -- but the experience has been great.

"I am so happy that IndyCar races in Brazil and what I have been telling people is that we changed addresses," Barrichello said. "The fans that used to come to Interlagos to watch me will now come to Anhembi. There was such a great energy with me racing here in the past and I want the same thing at the Sambodromo.

"It's the best week of the year for me, and the one that time flies by so fast, so I have to make sure I enjoy every single moment."

With a victory in the season opener at St. Petersburg, Castroneves is enjoying his best start to a season in years. He sits second to Penske teammate Power in the championship standings.

Castroneves is coming off his worst season in more than a decade, finishing 11th in the 2011 title chase.

"The team has certainly been doing a phenomenal job, capturing three wins in three races at the start of the season," Castroneves remarked.

"I feel very good about the season, especially after what we had last year. We want to continue carrying this good momentum with the team, especially here in my hometown of Brazil. Certainly there is a lot of hype and there is a lot of excitement for this race. Everybody is really pumped. Hopefully Mother Nature helps this year so that we can have a dry race, and that will help the Brazilians."

With a wet race the past two years and more rain predicted for Sunday, it's difficult to get a form guide for the Brazilian event. If it does rain, the driver and team with the best tire management strategy should prevail.

Power has won both races staged at Sao Paulo.

"It's a great crowd, everyone is so passionate and enthusiastic, and there's always the threat of a big downpour," Power said. "It's kind of unpredictable, but hopefully we can put the Verizon car in victory circle again."