A number of drivers struggled with soaring cabin temperatures in the new Gen3 cars during Saturday's opening leg of the Newcastle 500.
Reynolds appeared to be one of the worst hit by the conditions, the Grove Racing driver emerging from his Mustang worse for wear after 95 laps.
It's the second time in recent history that Reynolds has been badly hit by heat exhaustion, his run to second on the Gold Coast last November also taking its toll on his body – to the point where he was monitored by medics during the post-race press conference.
According to Reynolds, this latest episode in Newcastle was even worse than the Gold Coast.
"It's really hard to describe," Reynolds told Motorsport.com. "It's like running as fast as you can and your body is convulsing – but you still have to push on.
"You've got 50 laps to go and you're so hot that your body is giving in. You're trying to throw up, you're trying to drink water and throw that back up.
"It was the hottest, most brutal feeling I've had in a race car, in that middle stint [on Saturday]. I was in a world of hurt.
"I just tried to breathe. I was anaerobically breathing as hard as I could.
"You just keep cruising around even though you're not very conscious. You're conscious, but you're not on top of your game. I was probably half a second, a second slower than my real pace. I bled a lot of time.
"Your stress goes up, your heart rate goes up, the heat of your body goes up, and there's nothing to cool you down. You can't get rid of the heat quick enough and it implodes your brain.
"You start thinking all this weird stuff, like, 'what am I doing out here? What am I thinking?'. You're not concentrating directly on your job."
Reynolds managed to get through Sunday's Newcastle race unscathed, taking a fine third, place, which he attributed to a combination of lower ambient temperatures and the redirection of some air from the pedal box to his body.
Like Triple Eight and Erebus Motorsport, Grove Racing uses the electric ChillOut cooling system to feed the driver's cool suit, rather than a more traditional dry ice system.
While the ChillOut system is lighter and avoids dry ice freeze ups, it isn't as cold and doesn't include an integrated helmet fan.
"We can either persist wth the ChillOut system, which is lighter and in the colder races it's perfect, but in the hotter races you have to have another system to chill your helmet air," said Reynolds.
"So we need to think about if we run the dry ice system, which is proven and everyone else knows about. There's a slight weight penalty with that, engineers don't really like that. But we know it works.
"We need to sit down and have these conversations. The Gold Coast last year, that was their ChillOut system on the Saturday that destroyed me. Now it's back in the car."
