NASCAR Boom Tubes: A Deep Dive Behind the Iconic V8 Rumble

The sound of a V8 engine is music to the ears of a racing fanatic. The popular video of seven-time Formula 1 champion Lewis Hamilton falling in awe of the V8 engine’s rumble is probably still afresh in racing fans’ minds. However, the roar of NASCAR engines is only feasible in some places. Street races like Chicago can cause problems for people around the racecourse. But what is the reason behind drivers calling for the addition of mufflers to their cars?

Earlier this year, Kyle Larson called for NASCAR to introduce mufflers in the cars to reduce the loudness by a fair amount. NASCAR reciprocated with a short track testing session at the Phoenix Raceway shortly after the season’s conclusion. Moreover, as they tested the changes in the car’s noise output with mufflers, Larson denied any significant changes. In this case, the boom tubes are a major aspect of the vehicle that could need a revision. Let us dive deeper into the mechanical side of things and understand more about boom tubes in NASCAR.

NASCAR Boom Tubes explained

NASCAR Cup Series cars use V8 engines irrespective of the manufacturer. There is a restriction on the capacity of engines, which prevents them from being larger than 5.9 liters. The engines generate power by igniting a mixture of fuel and air in the cylinders. Every combustion cycle generates a high-pressure gas output that pushes the piston up and creates a loud pop sound as it exits the cylinder and moves to the exhaust pipes.

The more an engine exerts itself, the faster the car goes, and the frequency of the tailpipe noise increases simultaneously. This has been a problem for NASCAR. The V8 engines in Next Gen cars have generated noise close to 112 decibels.

Boom tubes in NASCAR are wider than a normal street car. The reason for its design is very specific. When a NASCAR racecar decelerates, it produces a very loud pop due to the explosion of the excessive fuel. A normal 3-inch exit pipe would start to split under that pressure. However, a wide flat exit, which is used by NASCAR, spreads this boom to protect the exhaust pipe. A wider area also improves the exit flow of the gases.

As modifications and advancements in motorsports continue to arrive, boom tubes have also experienced changes in the past. Boom tube exhaust pipes start with a thin profile, with parallel flat upper and lower pieces, which are usually flattened metal sheets. It also comprises U-shaped cross-section sheet metal pieces connected to resemble a flattened tubular body.

Its first evolution arrived with a large diameter, thin-walled steel tube flattened to form a slim tubular body. The next type of boom tube would resemble a rectangular steel tube welded with U-shaped cross-section metal side pieces.

NASCAR’s idea to reduce the sound in its cars has been progressing steadily. However, from the looks of it, muffling NASCAR race cars isn’t the way to go forward.

Amid calls for an increase in horsepower, it is possible that muffling won’t be of much help

NASCAR drivers have been demanding an increase in horsepower in their cars. However, an increase in horsepower would mean more speed and, as a result, probably more noise. With the mufflers’ introduction, NASCAR expects to reduce the sound by 6-10 decibels. However, a different result could also be expected.

Street cars are equipped with mufflers as well. The mufflers on those cars undergo destructive interference as sound waves bounce from the engine. This results in a reduction of the volume output from the engine. While mufflers can help reduce sound slightly in the case of NASCAR cars, the crowd would require earplugs to be barely able to converse with someone beside them.

One of the possible additions could be directing the exhaust output through a sound-absorbing material. Currently, fiberglass is the most used sound-absorbing material despite better options in the market.

As things stand, the horsepower debate has tilted towards a delay in an increase of power in cars. Looking at how the loud noise can affect children and older people around the race track, NASCAR will need to inspect many more facets of the situation.

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