Dr. Diandra’s FAQ on Muffling NASCAR Racecars

Don't get too bent out of shape: Its 4-6 dB and only two races.

In anticipation of the upcoming Busch Light Clash at the Coliseum, here is Dr. Diandra’s FAQ on muffling NASCAR racecars.

Why would NASCAR muffle their racecars?

Let’s remember that the only places NASCAR will utilize mufflers is at the L.A. Coliseum and the Chicago Street Race. No mufflers anywhere else, so don’t get bent out of shape about it.

Racing in a high-density population area requires some concessions. The people who brought property around the L.A. Coliseum expected football traffic, but they almost certainly never expected racecar noises.

The people who approve races are elected by the people who live there and they need to keep those folks happy.

What fun is racing if the cars are quieted down?

NASCAR says that the mufflers to be used in 2024 make the cars 4 dB to 6 dB quieter. A Cup Series racecar usually has a peak sound intensity of 110 dB to 115 dB. The muffler reduces that range to approximately 104 dB to 111 dB.

These numbers come from my measurements during last year’s test at Phoenix Raceway. I was standing on Pit Road at the time, so if you’re in grandstands, the sound will be a little less.

To put the numbers in perspective, a 100-decibel noise can cause hearing damage or hearing loss if you listen to it longer than 15 minutes. It’s not like you’re going to be able to have a conversation with the person next to you during the race.

The perceived volume reduction falls between 19% to 34%. But even two-thirds of very, very loud is still very loud. And there’s a complicating factor if you’re inside the Coliseum. The walls around the track will reflect some of the sound. The same happens when you have cars racing along streets bordered by lots of tall buildings.

So there’s a possibility that the noise could actually be a little louder inside the facility, even though it’s a little quieter outside.

Do the drivers like the mufflers?

Most don’t have strong opinions as long as the effect is the same for every car. Their main concern is getting too much heat in the cockpit.

But you know who likes mufflers from a sound perspective? Kyle Larson. Here’s what he told me during testing last December in Phoenix.

You know, I can definitely tell a sound difference, which I like and I think I definitely think our race cars are way too loud and probably are still too loud with the mufflers… I think the cars can be quieter just to help the fan experience

Kyle Larson, Phoenix testing 2023
Chris Graythen/Getty Images

How does this muffler differ from the previous mufflers?

Dr. Diandra's FAQ on muffling NASCAR racecars includes this photo of the 2024, bespoke muffler being used at the Busch Light Clash at the Coliseum

This muffler was designed specifically for these car. The previous attempts to muffle the cars used off-the-shelf components; however, the exhaust gases from a NASCAR Cup Series car are extremely hot. The materials inside many mufflers can’t survive that much heat.

The photo comes from the Stewart-Haas Racing Twitter account. See their tweet for a movie that shows more.

The old muffler was much longer and exhausted the gases toward the rear of the car. The muffler that will be used this year is shorter, and outputs toward the front of the car, which should help keep the temperatures down.

The picture below (also from SHR tweet) shows the muffler in place on the car. The NextGen car has exhausts on both sides, so there are mufflers on both sides as well.

Dr. Diandra's FAQ on muffling NASCAR racecars includes this photo showing how the new muffler is mounted, with it's output at the rear edge of the numbers.

Won’t the new positioning make the driver hotter?

It seems that way, but the shortness of the muffler and directing the heat away from the car should actually make the cockpit cooler.

That’s Dr. Diandra’s FAQ on muffling racecars

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