CHARLOTTE, N.C. -- NASCAR officials are scrambling to solve a couple of potentially serious issues with the "Car of Tomorrow."
Denny Hamlin and several other drivers complained about an unusual amount of carbon monoxide in their system after Sunday's inaugural COT race at Bristol Motor Speedway.
Some teams had issues with the protective foam in the right side door overheating, melting and producing toxic fumes.
Some had springs that failed for no apparent reason, which may have been the reason for the No. 16 car of Greg Biffle being too low during post-race inspection.
NASCAR officials plan to talk with crew chiefs before they arrive in Martinsville on Friday to discuss solutions to these issues. They will look at adjusting the tolerances for minimum height until it is determined what makes the new car settle.
They will suggest that teams use a thicker exhaust pipe after determining those that had exhaust systems failures used a thinner pipe to conserve weight.
They already have talked to Roush Fenway Racing officials about putting a heat shield over the pipe near the right door and notching the foam higher around the pipe to keep heat from compromising it.
NASCAR vice president of competition Robin Pemberton and Nextel Cup series director John Darby have scheduled a Friday morning press conference to discuss the issues.
Biffle, whose team was exonerated from wrongdoing, on Wednesday applauded NASCAR's effort.
"The thing that we're very excited about is they've been very flexible with the teams on the compromises this new car has," said Biffle, who finished fifth. "The main message is this new car is a work in progress. There's going to be adjustments and fine tuning along the way.
"They understand that and the teams understand that."
Biffle agreed that NASCAR did the right thing in taking his car to the Research and Development Center in Concord, N.C., to investigate why it was low.
He also agreed that the governing body made the right decision in not issuing penalties, but he wasn't happy with the impression left on Sunday that his team cheated.
"They didn't confiscate it like Michael Waltrip's car at Daytona because it had some scientific formula involved," he said of Waltrip's car that had an unidentified substance in the engine. "They took it for observations, to check out what happened.
"So things kind of snowballed and got out of control fairly quickly."
Biffle said NASCAR and Roush Fenway Racing engineers still don't know for certain why his car was low.
"If we were going to race at Bristol tomorrow, we would do the exact same thing we just did," he said. "We don't know what to do different."
Biffle said the team never made wedge wrench adjustments -- which NASCAR officials verified -- that would have been necessary to lower the car. He added that lowering the car would have been "stupid" because it would not create an advantage at a half-mile track like Bristol.
Biffle said the cars of teammates Carl Edwards and Matt Kenseth also were lower than when they began the race, noting Edwards' car would have registered a quarter-inch below the limit as his did had the crew not made wedge turns in the right rear.
"His springs had distortions to it," Biffle added. "So did [Kenseth's]. Do we have springs that there may be something wrong with? Hell, we have no idea. We are investigating."
Hamlin still has concerns about the exhaust systems that go beyond the thickness of the pipes, noting the inside of the car was hotter than the traditional cars.
"I heard some cars broke tailpipes during the race," he said. "We broke ours in practice, but we went with a totally different exhaust system during the race. Ours wasn't tailpipe related."
Biffle said he smelled more exhaust than normal during the COT test last month at Bristol.
"We moved where my air intake picked up its air over to the left side of the car behind my head," he said. "That seemed to help."
Biffle was more concerned that fumes from the melting foam might be dangerous, but he was assured by NASCAR officials they weren't.
"We've got a ways to go on this thing," he said of the COT, which will be used in 16 races this season. "But for the first race, I have to say that it was pretty uneventful.
"Yeah, some guys had exhaust problems and some had problems with the foam, but to put a car on the track for the first time at a track like Bristol, that was a pretty damn good success."
David Newton covers NASCAR for ESPN.com. He can be reached at email@example.com.