mufflers
FWIW, the advertised air flow numbers of a muffler are the last thing you should consider when choosing a muffler. It's the easiest parameter the manufacturers can jockey with to meet their marketing goals. Air Flow is only valid and meaningful if it's given with the pressure drop the number was obtained with. Since there is no mandated test process for muffler air flow that defines a standard pressure drop air flow numbers between manufacturers are useless and even within a manufacturers line of mufflers I wouldn't be surprised if they change the test to get numbers to match the marketing goals.
An example would be manufacturer A tests their mufflers at 1 psi pressure drop and manufacture B tests at 3 psi. A advertises 400 cfm of air flow and B advertises 500 cfm of air flow so you would think B is better but if you were to test A at 3 psi pressure drop it would flow 600 cfm or more a than B. These aren't real numbers just to show how not having all the info you can't compare.
Any perfromance muffler properly sized for the application has the capability of flowing more than enough air to support the engines need without creating a restriction.
Just pick your muffler based on sound, material, gaurentee, workmanship, fit, etc.
Excellent post.
The part I highlighted is exactly what the owner of the muffler shop I go to told me. This old time father & son shop in Huntington Beach, Ca, routinely installs Muscle Car and Hot Rod exhaust systems.
I've been taking my cars there for 15 years. I trust them.
I have Flowmasters on my Dart. Nothing wrong with them, but I was toying with the idea of installing Dynamax, based on the info read here..
So I went to the shop and asked a few questions..about freer flow as advertised and stuff like that..
They told me the flow numbers are BS. That they can be manipulated as was mentioned by Dave Clement in the post above.
They also told me that they won't carry Dynamax products anymore because they got tired of covering Warranty repairs on those. Busted welds mostly.
They said that in their experience, the best built muffler is Flowmaster.
They carry all sorts of mufflers. Borla, Magnaflow, etc..
So the Flowmasters are still there under my Dart, some 3 years later.
Your Mileage May Vary, and all that...
--
