Exhaust rasp... now a whistle.

[Charlie207]

Exhaust setup: Speed Engineering 1.75" long-tube headers with 3.5" collector, to 3" reducer to 3" dia. 28" long AP Racing muffler (magnaflow clone), to 3" tailpipe. There was no rasp prior to the headers, just a deep truck tone... nothing fance. After headers there was noticeable rasp along with a louder/deeper engine tone (headers, ftw). There was also a subtle chirp/whistle... but, I didn't know why.

https://imgur.com/a/TnPD6RR

I added a 3" dia, Dynomax bullet muffler about 18" upstream of the tailpipe to try and cut down on the raspy secondary tone. It does seem to reduce those soundwaves; much less rasp, and I can hear mostly just the deeper engine noise, but now there's a freaking whistle when I stab the throttle, lol!

Decided to try swapping in the smaller muffler with the Heimholz resonator built-in, to see what would happen, and it made the whistling louder.

The brocolli-heads will be so jealous.

https://imgur.com/UuQyGXt

I guess I'll cut out the Dynomax bullet, and relocate it in front of the muffler, and see if that does the job.

 

[Charlie207]

Fixed the whistle by welding the bullet muffler about 18" in front of the regular muffler. Less rasp too, but unfortunately it's a little late to be revving the engine like Frank the Tank.

https://imgur.com/a/WBKtMcn

 

[Joseph Garcia]

I'm not header knowledgeable, but I believe that I've heard that the long tube headers add that raspyness tone to the exhaust sound. Folks knowledgeable in this area will chime in.

 

[Charlie207]

I'm not header knowledgeable, but I believe that I've heard that the long tube headers add that raspyness tone to the exhaust sound. Folks knowledgeable in this area will chime in.

Yeah, in reading a lot & watching a ton of videos, it seems like its the deletion of the cats that allows the rasp to propagate, along with the thickness of the header tubing.... and if they are coated or not. Basically a lot of variables, but there are ways to mitigate it. I'd like to eventually weld in some cats, just to cut down on the fuel smell. I assume that an accurate tune can help cut down on that, but we'll see once the revised BBP tune arrives.

 

[Charlie207]

I'm not header knowledgeable, but I believe that I've heard that the long tube headers add that raspyness tone to the exhaust sound. Folks knowledgeable in this area will chime in.

For some reason my other reply didn't copy/paste.

If you don't have headers on your SC'd engine, then you might consider them. There's probably another 50hp or so waiting to be uncorked.

 

[Joseph Garcia]

For some reason my other reply didn't copy/paste.

If you don't have headers on your SC'd engine, then you might consider them. There's probably another 50hp or so waiting to be uncorked.

There could very be. But, I want to keep my cats, just because.