The IZOD IndyCar Series push-to-pass power boost system is to be modified for this weekend's Honda Indy 200 at Mid-Ohio Sports Car Course, to introduce a five second delay between the press and the power kicking in.

"After that five seconds, when the driver gets to full throttle or already is at full throttle, the overtake will come on. That's to stop from using it as a push to defend," said Trevor Knowles, IndyCar's director of engine development. "You can push the button before you get to the braking zone and when you get on the throttle it will be on overtake."

The overtake button - which adds 1.5 pounds of turboboost and 200RPM to the engine for up to 20 seconds or as long as the car is going full throttle - was first used in the series in 2009 and reintroduced to the series this year at Toronto after being on hiatus since the end of 2011 while the new specification engines and new DW12 Dallara chassis were bedding in.

Drivers will have up to 100 seconds of push-to-pass for the entire 85-lap race at the 2.258-mile, 13-turn permanent road course. Other than the five second delay, there is no recharge time between activations.

While the return of push-to-pass for road and street courses has been generally welcomed as adding overtaking action to street races, IndyCar officials are keen to ensure that it can't be used as a defensive measure - as Helio Castroneves did to good effect over the final 16 laps of the previous race at Edmonton on his way to a win over Takuma Sato.

The use of push-to-pass use was included on the live timing and scoring feed and even featured in the TV coverage of the Edmonton race, allowing pit crews to radio the information direct to their drivers in real time and virtually 'remote control' the deployment of the power boost.

"I just told them to tell me when he uses push-to-pass, and I'll defend it," admitted Castroneves after the race. "It worked out very good."

The five second delay is intended to stop that from happening.

"If you're the car in front trying to defend, the TV won't show when the competitor [behind] has pushed it," explained Knowles. "It will only show when the overtake is active. If [the driver in front] responds, he has five seconds before his overtake cuts in."

Knowles said that the series was looking at further modifications to the system for the future to improve racing action: "We didn't want to introduce too many things at one time," he said.

One suggestion is that the series may try the same approach used by the DRS system in F1, which only allows the rear wing flap to be activated if the car is within a certain distance of the one in front, meaning that for most of the race the system can only be used for attacking and not for defending.

"We built into the [push-to-pass] system the means to do just that," suggested IndyCar's vice president of technology, Will Phillips.

The main overtaking opportunity at Mid-Ohio is the Keyhole, a long straight after the exit of turn 2 into a looping right-hander turn 3. But the length of that straight - almost half a mile - could see drivers accidentally eat up their push-to-pass allocation faster than they were expecting.

"These straights are pretty long so 100 seconds goes by quickly," said championship leader Ryan Hunter-Reay. "You just have to use it when you need it, and it's tough to say when that is. Only in hindsight can you determine if you used it correctly.

"It's always a trade-off at the end," he added. "You're trying to make up time either catching a car or trying to get by somebody. You need it at the end to fight it out when the tires are going off so it's tricky."

Practice for the Honda Indy 200 gets underway on Friday afternoon at 2pm local time (7pm BST) at Mid-Ohio Sports Car Course with a 90 minute session divided in two, with 45 minutes for rookies and those outside the top ten in the championship standings, and the second half for all cars.

Another 60 minute practice session on Saturday morning at 8am (1pm BST) is followed by qualifying starting at 11am (4pm BST), with the track aken ver by the American Le Mans Series for the afternoon. A half hour Sunday warm-up session at 8am sets the stage for the race itself, starting at 1pm (6pm BST) and shown live in the UK on Sky Sports.