Almost a quarter of the field at Saturday's Milwaukee IndyFest will be starting ten places further back than they manage in qualifying, after a number of engine change penalties came to light.

The two top drivers in the championship, Will Power and Scott Dixon, will both take penalties after their Chevrolet and Honda engines respectively both failed during testing at Iowa Speedway earlier this week following the weekend's race at Texas.

Dixon's engine - fresh in after the previous engine was deemed to have been damaged in his race-ending crash at Texas - failed toward the end of the morning's track time at Iowa, and Power's followed suit later in the day.

"It's going to be hard to win from back there," was Power's view.

Justin Wilson and Mike Conway will also be hit by starting grid penalties after failures of their Honda units at Iowa, and Takuma Sato and Josef Newgarden will also have to serve penalties after apparently not reverting to the race engine they used for the Indianapolis 500 when they should have done in time for the race at Texas.

Meanwhile there have been growing complaints about the penalties levied against Justin Wilson's car at Texas Motor Speedway for failing post-race technical inspection, with other drivers unhappy by how lightly the Dale Coyne Racing team got away with using a prohibited bodywork parts on Wilson's race-winning car.

"I asked my engineers how much downforce would that have given him," Dario Franchitti told the Associated Press. "They gave me the number and I said I would cut a body part off for that amount of downforce during the race. I'm not going to say which body part."

Team Penske's Helio Castroneves agreed, saying that while he wouldn't want to see Wilson's win overturned, the penalties "should be in my opinion a little more severe."

"I would have given up five [championship] points and $7,500 to run it," agreed Penske Racing president Tim Cindric, referring to the specific details of the penalty finally handed out to the Dale Coyne team on Tuesday.

IndyCar appear to have taken a lenient stand because the standard part was originally approved for use at Texas but was prohibited late in the day as the series made a string of late changes to the rules in order to reduce downforce on safety grounds at the 1.5-mile high-banked oval.

Also factoring into the decision on penalties was that the IndyCar technical inspectors themselves missed the now-banned sidepod attachment when scrutineering the cars before qualifying and for the race itself. The officials had noticed another prohibited piece of bodywork on the car (rear wheel backing plates) and once informed the team had immediately changed them to comply with the revised rules.

IndyCar's vice president of technology Will Phillips said that the bodywork did not give Wilson any significant advantage in the race, pointing out: "He ran the same parts in qualifying - if it was such a big deal, would that not have put him higher up than 17th [on the grid]?"