Saturday’s Indy 500 qualifying featured multiple instances of drivers suffering power hiccups during their runs, affecting their ability to turn in a good time in the competitive field.
The short interruptions to power delivery exclusively affected drivers with Chevrolet engines, and the manufacturer confirmed after the session was over that all the events were indeed related.
Six different drivers suffered from what Chevy calls a plenum fire, which means that pre-mixed fuel and air ignites and vaporizes before it enters the combustion chamber.
The problem is felt by the driver as a momentary loss of power similar to a misfire, and ruins any momentum the drivers had built throughout the first portion of their runs.
Chevrolet held an emergency press conference at the end of the day Saturday to explain the situation that caused six different drivers to have their runs ruined throughout the day.
Rob Buckner, IndyCar Program Manager at General Motors, responded to a question posed by Motorsportweek.com by saying that the manufacturer does suffer from plenum events from time to time, but did not note any problems during this year’s Indy 500 lead-up, including during Fast Friday.
“I don’t remember having any drastic ones throughout the week at 1.3 bar, or yesterday at 1.5 bar,” said Buckner. “Conditions evolve, engines are being operated as hard as they possibly can be today.
“This is really the day we hang everything out; us, the teams, the drivers. We always have seen some unique things pop up, every Indy 500 qualifying weekend is an adventure. We got some parts of it right, and other parts we have some work to do.
“Today was the start of [the plenum issues]. I don’t think we had any awareness of [the problem] coming into today. We’ll quickly get our arms around it and get it resolved.”
The first affected driver was Kyle Larson, who had his early run disrupted by a plenum fire that caused him to abandon his run after just three of his four laps completed.
Later in the day, no less than five other drivers including Pato O’Ward, Conor Daly, Ed Carpenter, Christian Rasmussen, and Agustin Canapino suffered the same fate.
Once so many drivers started having troubles, many of whom were quite upset at having their runs ruined through no fault of their own, Chevrolet went into disaster mitigation mode.
The company already has plans to activate their dyno centers around the world and operate them constantly until tomorrow’s qualifying sessions in an attempt to track down the issue.
“The good news is no harm to the engines,” said Jim Campbell, VP of GM Performance and Motorsports. “The engines are strong and great. We obviously put those drivers at a deficit when they were trying to make their fast four laps.
“Our team is going to work here overnight. We’re running in our dyno facilities around the world overnight. And we’re working on ways to mitigate the issue and error proof for tomorrow the controls and calibrations.
“There’s some team strategy, as the ambient conditions are clearer for tomorrow, there are some decisions they can make as well. We’ll be working with them on that.
“Everybody [will be working on this]. We do have teams in different parts of the world that will be running, dynos that we have access to around the world. So we’ll be running the dynos there.
“And then our team here. Rob and his team will be poring through all the data. Data analysis is what you have to do. We got to be ready to go tomorrow.
“We did put some pressure on drivers that were making great runs. The 78 [Agustin Canapino] had a great run going, and that was on us. We gotta make sure we’re ready to go for tomorrow.”
The representatives also related that the added boost pressure for Indy 500 qualifying, 1.5 bar instead of the typical 1.3 bar, contributed to the troubles.
There is no real-world testing done at the higher turbocharger pressures, and Chevy has to rely on dyno data to find problems before they are discovered in critical moments.
The last time a plenum fire was talked about publicly was during the opening round of the 2023 IndyCar season, when Pato O’Ward lost the lead due to a momentary loss of power on a late restart.
While the engines do apparently suffer that problem occasionally, it has not affected results as much as it did on Saturday.
Of note, Chevrolet engines seem to have impressive power delivery in the higher boost setup that is used exclusively for Indy 500 qualifying.
The fastest four drivers on the day all were powered by Chevy engines, and no Chevy driver is in danger of missing the cut during Sunday’s bump session.
That is little consolation to the half dozen drivers that were affected during Saturday’s session, and they will all expect that the manufacturer find the source of the problem so it does not continue to affect their results.
Honda, IndyCar’s other engine manufacturer that powers approximately half the field, is not believed to suffer from the same type of problem.
