Wilson fastest at wet Houston

The test took place in wet conditions following continuous rain, and last year's runner-up Wilson showed his speed, beating three-time champion Sebastien Bourdais to the top of the times.

Despite the poor weather, Wilson was pleased with his day's work.

"I think it's very important for us to test in the rain, any miles you can get in the wet in these cars are a big help in the learning process," Wilson said. "We really learned a lot today, the car was reliable and ran all day with no problems and we got a lot done.

"We still have a lot of ground to cover to be ready for the opener, and hopefully it will be dry tomorrow so we can get more done."

Canadian Paul Tracy was third on the timesheets behind Bourdais and in front of Minardi Team USA driver Robert Doornbos, who continued with his acclimation to the demands of a Champ Car machine.

"After the rain we had during the first test, at Sebring, and now with what we've encountered here today, I'm beginning to think we're jinxed with the weather," said Doornbos.

"The track was damp and slippery first thing, but once we had some proper rain, it cleaned the surface up and we were able to start working on chassis set-up.

"It's fun getting to know everyone on the team, and I'm really enjoying myself in the car, although I have to keep reminding myself that I'm in a Champ car, not a Formula One car, and there aren't all the driver aids available to help out - you just have to get on and drive it."

Nelson Philippe got a last-minute call-up to test for Conquest Racing, and the one-time race winner showed good form by setting the fifth quickest time of the day, ahead of Graham Rahal.

The teams spent an hour practising standing starts following the rule changes that will come into play this year.

Monday's times:

Pos  Driver               Team                       Time     Laps
 1.  Justin Wilson        CDW-RuSPORT                1:30.162   59
 2.  Sebastien Bourdais   Newman-Haas Racing         1:30.378   56
 3.  Paul Tracy           Forsythe                   1:32.063   14
 4.  Robert Doornbos      Minardi Team USA           1:32.286   48
 5.  Nelson Philippe      Conquest Racing            1:32.847   26
 6.  Graham Rahal         Newman-Haas Racing         1:33.163   54
 7.  Neel Jani            PKV Racing                 1:33.168    8
 8.  Alex Figge           Pacific Coast Motorsports  1:33.981   25
 9.  Will Power           Team Australia             1:34.256    8
10.  Andreas Wirth        Dale Coyne Racing          1:34.314   51
11.  Oriol Servia         RuSPORT                    1:34.989   83
12.  Ryan Dalziel         Pacific Coast Motorsports  1:35.573   33
13.  Alex Tagliani        Rocketsports Racing        1:35.714   19
14.  Simon Pagenaud       Team Australia             1:35.719    9
15.  Katherine Legge      Dale Coyne Racing          1:36.215   40