That gasoline-gargling backfire exhaust sound some cars make decelerating, which can really only be described as “snap crackle popping,” has become pretty popular since motorheads almost unanimously got enamored with it in cars like the Ford Focus RS and Jaguar F-Type. But what’s really happening there, and does it add any actual performance benefit?
Automotive vloggers Jason Fenske and Matt Maran went for a little ride in a Hyundai Veloster N, a car with pops for days, for this quick technical overview and analysis of appreciation for the sound.
Fenske starts explaining how these exhaust pops occur at around the three-minute mark. But basically, as you probably know, the way a normal four-stroke gas engine works is that it sucks in fuel and air, compresses it as the piston goes up, ignites it when the piston’s up high in the cylinder, and then spits the smoke out as exhaust when the piston goes back down.
In the Hyundai Veloster N, according to Feske’s conversation with Hyundai’s reps, when you let off the gas pedal the engine actually waits until the exhaust valves are open to ignite the air and fuel mixture, allowing a lot more noise to escape.
This changing of where peak pressure occurs off-throttle, apparently, is “specifically done to prevent turbo lag” in the Veloster N’s N Mode.
“So that when you’re shifting gears,” explains Fenske, “instead of having that pressure force the cylinder down and cutting all power, you create that pressure and you have it in the exhaust. By doing so, it keeps that turbocharger spooled up while you shift. And so you don’t lose that boost as you get into the next gear.”
Hyundai didn’t invent this concept, but it makes a pretty good example of how those intense “gunfire noises” you hear coming from the car aren’t exclusively for theatrics.
However, on cars that are supercharged or naturally aspirated, the snap-crackle-popping a lot of us are fond of isn’t quite as easy to justify. In fact, it hurts your fuel economy, forces your revs to hang high longer as you let off the gas, and inhibit engine braking.
But, it sounds cool.
Fenske and Maran get into some more abstract discussion in the second half of their video about “fakery” like this, and what fakery is fun and what is scornful. They seem to come to the conclusion that cars making fart sounds just to show off is fine, but synthesized stereo-based exhaust notes, not so much. Similarly, non-functional air vents also have their place, I guess.
Personally, I couldn’t care less if a feature is “functional” as long as it looks or sounds cool. But I also got over my infatuation with exhaust snap-crackle-pops as quickly as I went wide-eyed over it... I like my cars calm and quiet now, for the most part.