I blew it. Da mufflers oh my.

Its no secret that some quiet mufflers kill power by ultimately restricting flow. Well here are some rough numbers.

High percission leaf blower with cardboard tube attached. Scale space 9 inches away 200g of pressure created.

Pypes Pro Street mufflers reduce overall output to ~56g of pressure.

Walker Quiet Flow SS mufflers reduce overall output to ~26g of pressure.

I wasn't expecting a 46% decrease between mufflers.

Next I'll measure the Dyno Max once removed from the Riviera.

Pictures of set up attached.

My associated thread: https://www.v8buick.com/index.php?threads/quieting-the-exhuast.361700/

UPDATE:

With inlet pressure @ 200g

Outputs are:

Pypes Pro Street - 56g
DynoMax - 53g
Walker Quiet Flow SS - 26g

 

I'm not sure you can draw parallels one to one.. The engine in your car will push the hot exhaust fumes like a plunger, instead of the cold air with a fan.. You have to take density ( how dense ) the pushes gas is, how the temperature effects it, what it do at different flows etc..

The correct way to test muffler vs muffler, would be to have your engine in a dyno, do the baseline without muffler, and then move on like you did with the leafblower..

I'm no engineer, just spilling my brain farts..

 

Either way, an interesting test

 

I just put a set of Dynomax long case mufflers on the Riv with TA full mandrel bent system. So far I like it!

 

You are correct. Wave propagation of hot gasses cooling through a channel must be considered. After all, the wave physics are universal, this is why AC is used for electricity propagation. I guess I could measure the car at idle and see what happens. But my curiosity itch has been scratched with this.

 

I'm running the short case mufflers which is one likely reason for my drone problem. The wavelength of the drone is larger that the muffler.

 

In general you have to consider exhaust as a series of pulses, not a steady-state flow situation (and in reality it's somewhere in between). Testing through a leaf blower does show one point on the scale about steady-state pressure drop, but there's more to the story when developing an entire exhaust system. Still, it's an interesting data point and thanks for posting.

-Bob C.

 

Good info:

 

Seems like if you could measure PSI at the inlet it would tell more. Might need more cfm. Testing is good though.

 

I stick with the magnaflow straight through round case mufflers. They sound great and there is virtually no performance loss vs no muffler. A turbocharger also helps get rid of a lot of the noise, it smooths out the pulses. My Skylark it not loud for what it is. Under 4000 rpm it’s not making a bunch of racket.

 

Very cool test

 

The basic rule of thumb is that for a dual system you take your HP and times it by 1.1. That will be the CFM required for each muffler before it starts to restrict power. There is some info here- https://www.classicmusclecarexhaust.com/exhaust-101 with CFM ratings from both Pypes and Dynomax. I would imagine a Quiet Flow SS would be pretty restrictive but suitable for unmodified stock small blocks. I have spoken at length with Flowmaster and MagnaFlow about their CFM ratings but they won't commit to giving them out. MagnaFlow's will be similar to Pypes Race Pro's though- pretty high. I am a dealer for all four companies mentioned here, but I will be honest and tell you that a chambered muffler will start to restrict above the 350ish HP range. If you are below 400HP and strictly street, don't worry about CFM, just go for the sound you like. If you are racing however, it's time to do some math..

 

Disagree with the article regarding Street Pro. They are not mellow and I suppose this is where physical placement and installation matter.

"
Street Pro's offer an aggressive sound under throttle, but quiet down under cruise.
"

 

Getting slightly off topic here but you're correct- Street Pro's are not exactly quiet. My customers do tell me they don't drone too much in the typical 'drone zone' of 1800-2400 rpm range, but drone and dB are not the same thing. Pypes Race Pro's flow way more than the Street Pro's, but they suffer from drone just like most straight-through mufflers. Pypes has come out with their 'Turbo Pro' muffler, which is a copy of the Dynomax Super Turbo only with a welded stainless case. Only 14" available for now but an 18" due out in August sometime. They flow similar to the Dynomax with the same sound level, only they do have a slightly more pronounced 'glasspack' sound to them. They sounded good when we tested them.

 

Ok. Measured the DynoMax. See first post.

 

The GS Club did an article on this a couple of years back, and it was published in the GSXtra. I believe the Walker Ultra Flow mufflers came out on top. Might be worth checking out.