Spent the last 4 days at Sebring Road races as a spectator. I missed last year so this observation may be dated. Seemed like a lot but not all of the turbo cars, under braking had a rather different sound from years past. I'd describe it as a fast staccato, and not downshifting related, almost like cross between a rev limiter and a SemiJake exhaust brake. No way were engines at high revs. My suspicion it was some trick to keep turbos spooled for corner exit, However if those were power pulses, it would seem in a 12hr endurance races, that bwould eventually reek havoc on the powertrain, as I doubt cars were coasting in neutral under braking. There was the occasion a back fire under full throttye during corner exit, that is a completely different sound then I am mentioning.

So what was going on?

I am assuming this is an efi related question, as everything is high dollar BMW, Porsche, Aston Martin, Caddy, etc factory supported, without a carb on the track.