DAYTONA BEACH, Fla. -- NASCAR officials monitoring the second day of Preseason Thunder at Daytona International Speedway Friday evening presented a trio of technical adjustments for the test's third and final day Saturday.

Sprint Cup Series director John Darby announced teams would return to the 29/32nd-inch restrictor plate they started the test with, a four-pound reduction in the radiator pressure-relief valve, and a slight closure of the bottom of the radiator vent, whose sides were narrowed after Thursday's opening day.

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On Friday, the best single-car speed was more than 196 mph, the fastest tandem-drafting lap was better than 206 mph, and the highest mass-draft speed a little better than 204 mph.

NASCAR tinkered with the same three areas Thursday evening and said they weren't done.

"I think we've had another good day of testing," NASCAR vice president for competition Robin Pemberton said. "As the teams worked on it, even though we gave them some more plate back, it shows that the cars can actually handle that type of speed.

"We feel like the things that we're learning here are things that we'll be able to apply toward our baseline when we come back for Speedweeks. We're not done yet. We're gonna continue to work on aero packages and plate sizes and all types of things from now until the day we sign back in here [for Speedweeks 2012 in February]."

NASCAR's unofficial time sheets didn't differentiate between single, tandem or pack laps but officials' observations and the information they were able to download from the cars' electronic control units of the electronic fuel injection system gave them what they felt was a good direction to further eliminate tandem drafting.

Immediately after Friday's lunch break, 21 cars left pit road in a group that fluctuated but might have peaked at about two dozen cars for the roughly 20-lap run. Darby and Pemberton agreed that session was valuable but they weren't sure if enough cars would be left to request a similar session Saturday.

As of 6:30 p.m. local time Friday, 30 transporters remained set up in Daytona's garage area of the 32 that started the test Thursday morning. Ryan Newman's Stewart-Haas Racing hauler was packed and moved to the back of the garage.

"Some of these things that we learned in [Friday's] draft at 1:00 have helped point us in [the] direction [of] understanding what water temperatures run and radiator pressures and cooling system pressures do in an old school or a conventional style of draft and trying to install those parameters into the race cars so that it becomes maybe a preferred way of getting around the race track," Darby said. "Knowing it's a test and there wasn't any points or money up on the board, it just looked like 24 guys having a hell of a lot of fun out there, and that's kind of what they reflected to us when they got back in the garage."

Dale Earnhardt Jr., who's been a critic of tandem drafting, was one who agreed with Darby's assessment of the pack session. But Earnhardt also said tandem drafting would never go away.

"Everybody was having a good time and trying to get everything they could out of it," said Earnhardt, who at one point slipped coming off Turn 4 and came down pit road rather than trying to force his way back into the pack. "Maybe, just maybe, you won't have to stay in a two-car tandem to stay with the lead pack.

"The two-car tandem is definitely the way to go, as far as speed. You're not going to be able to out-run that. You'll try to save the tail and nose of your car -- and save yourself -- just trying to draft normally if we find that'll keep up, just to get through the race so you'll be there at the end.

"But that tandem stuff is what's gonna win the race."

Darby had decent news for fans of pure speed. He said NASCAR's aerodynamicists' work to raise the cars' liftoff speed had erased the need to avoid the 200 mph barrier, particularly for race pace.

"We'll still end up over 200 miles an hour," Darby said. "We'd like to stay as close to that mark as we can. Probably the last four or five plate races we've been in a range of 200 to 203 miles an hour, maybe not a consistent, every lap speed, but we've seen those speeds.

"If we were to put a target mark, it would probably be right at 200 for our race speed, which the drivers like. Obviously the excitement level of 200 miles an hour is always present for the fans. But a lot of the work we've done is to try to close the [difference] between a conventional draft and a two-car push.

"And what's become very apparent very quickly is that as we get into a little bit of the higher speeds of racing that helps us greatly. Last year it was a seven-mile-an-hour difference. We've more than knocked that in half just in a couple of days. That's what we'd like to continue to work on."

Darby also eliminated any thought of 200-plus mph qualifying laps, saying any move in that direction would create more work and expense for teams. Darby reiterated his thought that Daytona 500 qualifying speeds would be between 194-195 mph.