High Performance Mufflers Dyno Tests

Do high performance mufflers make horsepower gains or are they marketing pipe dreams? It might seem strange why I am writing about this subject on a nature related blog, but it will become abundantly clear below.

One of my hobbies is tinkering and building automotive engines, transmissions, and other drivetrain to increase performance, and more recently to increase fuel economy. Aftermarket muffler manufactures such as Dynomax, Thrush, Flowmaster, Magnaflow, Cherry Bomb, and others all make a good deal of money selling their performance mufflers. They advertise that their mufflers increase performance quite dramatically from a stock muffler, but never seem to have dyno tests to provide proof. They often only quote muffler flow rates in comparison to a “stock” muffler. The question should then become how much flow is required and how much does more than good enough make? 

Finally, Horsepower TV on Spike TV (episode HP2010-07) did a dyno comparison test of some Cherry Bomb mufflers for sound levels and horsepower. I will ignore the sound level tests they did as they have no real world relationship to being inside an enclosed dyno room. They compared Cherry Bomb’s glass pack, turbo, pro, and high priced Vortex brands to a stock muffler on a test engine running headers and dual exhaust. A common stock style muffler gave 472 horsepower, the glass pack gave 480 horsepower, the turbo style muffler gave 477 horsepower, the short pro muffler gave 476 horsepower, and the Vortex muffler gave 480 horsepower. At the very best, the gains were less than 2% and only 1% for two of the mufflers. This proves that more muffler flow is not needed to make performance gains. Performance gains of 5% are barely noticeable, and certainly not worth it for any other than competitive racing.

What these aftermarket mufflers are good for is increasing, quite dramatically, the sound from the engine. Increasing engine sound has a psychological effect of feeling like the vehicle is faster. Now you know that it isn’t from the above dyno tests. The muffler manufactures are truly selling a pipe dream.

When I was younger, I bought into the hype and used loud mufflers, but it was always irritable to drive around a loud vehicle that could be heard from a few miles away. Now that I am much more sensitive to noise pollution, I use high flow stock style mufflers. I can sneak around the back woods and my tires rolling on the gravel make more sound than my engine.

I am writing this article to emphasize that loud mufflers do not help performance and will only make those that use them a menace on the roadways. Believe me, almost nobody wants to hear loud vehicles, especially while relaxing in a country or forest setting trying to enjoy the wonderful sounds of nature. Loud mufflers are technically illegal, because of the disturbance they cause, and at anytime when an officer wants to stop you, they can on sound alone. Save your ears and everyone else’s by using stock style mufflers. Dynomax sells Walker HushFlow mufflers that run very quiet yet offer improved performance than the worst stock mufflers.