Hey Nyroc or anyone else with experience on this, what would be the effect if you did 3 3/8in. holes and 3 1/2in. holes and spread them out evenly? I understand the noise would be a little more than just 3/8in., but possibly not as much as just 1/2in? What kind of performance does this mod gain for your by the way? Has anyone dynoed it at all?

 

I used four 1/2" diameter holes and lined up 2 holes on top (directly in front of the top header pipe) and 2 holes on bottom (directly in front of the bottom header pipe). My thinking was that by lining up the holes with the header pipe, I would have less restriction/back pressure than if I just spaced the 4 holes evenly. However, I have no access to a dyno and no other pipe to compare it to, so I don't know if my design had any impact (good or bad) over the typical Nyroc Modded pipe.

I also tweaked the design of the end cap opening to incorporate a stainless steel screen (to function as a home-made spark arrestor) and also retained the angled 2" pipe going into the end-cap so that sound would be forced downward like the stock (un-modded) pipe. I think these changes helped keep the noise down to reasonable levels, but like I said above...I really don't have another pipe to compare it to.

I believe that Nyroc (at one time) suggested that drilling different size holes into the baffles might make a difference in the noise level...but it seems to me like its all trial and error with muffler designs.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

My twist on the NYROC muffler mod was to drill out the baffles with as many 3/8in holes I could without totally destroying them.
Next I cut out the spark arrester and welded a large washer into the hole. I was then able to fine tune my exhaust further by drilling holes into the washer until I got the best performance, kinda like adding disks to a supertrapp for more flow.

The sound kinda reminds me of the flowmaster exhaust I used to have on my mustang, with that deep crackly sound, and it looks pretty cool too.

 

Do you have to rejet after the muffler mod? Did you notice an increased performance over stock or is it just mostly to make the exhaust sound better?

 

Significant increase in power!!!!

I used to race my buddie who had a p700 against my p650 and we both had modules. He used to be able to take me by several quad lengths in a 1/4 mile. After I piped snorkled and rejetted I could take him by almost a quad length every time. I have also cut some holes in my air box lid. If you make one end more free flowing you must do the same to the other end. Keep in mind that back pressure is important as well.

See my sig for exact mods.

 

I have eight 1/2" holes drilled in my baffles and the spark arrestor removed. Mine is noticably louder than nyrocs but not overly loud. It sounds more like a Big Gun than anything else. Its not near as loud as an HMF. Monday we will try to get another sound clip of my muffler. Im very satisfied with my modified stocker and will "more than likely" never buy an aftermarket pipe.