Another Way to "Skin the CAT"

[Wannbe]

I did have a dyno tune. Wanted to be certain it wasn't harming the engine. The sound change was minimal the first try. Which is why I tried the 2nd time. I would have liked somewhere in the middle. But I'm still happy wit the end result.

 

[Rick Morris]

Excellent post, great pictures and great welds. I think I have a weekend project.

 

[Idaho Red Rocket 3]

The Roadster TORs do make a better throatier sound, and only raise the volume no more than a couple of notches. They don't get crazy loud like the 3 pipe TORs do.

 

[RKTNMYPKT]

Poor little cat

 

[1olbull]

Next week I will set up a way to record the bike running with the stock mufflers and then In the exact same setting with these "skinned" CAT's. I will also try to detect if there's any appreciable performance increase before changing the stock tune.

That there is SOME WELDIN'!!!

 

[Rocket3Pilot]

FOLLOW UP to Another way to skin the CAT: Sorry it took so long to do this follow up, as you know ******t happens?

So I slipped these De-CAT'd stock pipes on after the stock ones cooled off to see what, if anything changed much. Maybe? As far as sound, I thought it was a slightly better tone, a little lower note and more pleasing to me going down the road. More power? Maybe? Very hard to detect as I hadn't changed anything else. I initially thought I would record the sound changes to compare stock, to these De-CAT's, to TOR's and actually did. The problem is that at idle sitting still and with the recorder (my iphone6 ) in the exact same spot the audible difference in the recording is negligible and I didn't think it was worth wasting peoples time trying to hear that difference.
So my take on it is this: The stock sound was fine but I new performance would be restricted. TOR's of course are straight through with one big baffle and would not be restricted at all but I didn't want more volume as I like cruising fast and the drone would be fatiguing. The solution that I imagined was gutting the CAT's from the stock mufflers and for me it worked perfectly.

If anyone is interested in doing this and needs more info or help let me know and I'll do what I can. I think it's a great solution especially when you consider how hard it is to find TOR's these days.

So now my Paul Bryant headers arrived and all I can say is WOW! Is this the same bike? I just got them on and will make that a separate post with comments as he clearly deserves his own accolades.

Thanks everyone, hope this inspires all the gear heads out there.

 

[BigNorm]

Very well written. Thanks for taking the time to do this. What size pipe does Triumph use in it's TOR silencers that go all the way through? After reading your post my mind wanders to doubling the pipe size of the TOR to have it run through one muffler. What I mean is that I'd totally gut the pipe and run a single drilled muffler pipe through the center of the stock pipe maybe packing the surrounding open space in fiberglass to make a glass pack muffler. Can anyone tell me the down side in my thinking?

 

[Rocket3Pilot]

Very well written. Thanks for taking the time to do this. What size pipe does Triumph use in it's TOR silencers that go all the way through? After reading your post my mind wanders to doubling the pipe size of the TOR to have it run through one muffler. What I mean is that I'd totally gut the pipe and run a single drilled muffler pipe through the center of the stock pipe maybe packing the surrounding open space in fiberglass to make a glass pack muffler. Can anyone tell me the down side in my thinking?

The only thing I can think of is LOUD? The TOR"S are 2" diameter already and straight through. Check Wannbe out. He did a version where he gutted the can and then welded a cone inside for a megaphone effect. He posted the project and it's sort of what inspired me to try my take one it.

Keep in mind that bigger is louder, shorter is louder, and megaphones are louder still. Performance of course is a different conundrum and way more complex.

 

[BigNorm]

The only thing I can think of is LOUD? The TOR"S are 2" diameter already and straight through. Check Wannbe out. He did a version where he gutted the can and then welded a cone inside for a megaphone effect. He posted the project and it's sort of what inspired me to try my take one it.

Keep in mind that bigger is louder, shorter is louder, and megaphones are louder still. Performance of course is a different conundrum and way more complex.

Thanks to this site I've learned that the interior tube size affects the pulses coming out of the motor. The bigger it is the more efficient at high rpms. smaller helps with low end torque. A balance can be reached when increasing the pipe size and making it longer. I just don't know what that size is. I guess that's why we pay the big bucks for custom tuned exhaust.

 

[hoopla]

I wanted to thank @Rocket3Pilot for his write up and further discussions we have had. Also thank @D04011 for generously donating a set of stockers for my de-cat project. I want to also give my take on how to best remove the cat from the mufflers, believe me if you go about it the wrong way, and I did the first one, but I learned from my mistakes, you'll enjoy a tooth extraction more. The first took me 4-5 hrs of tough work, while the second took only 2-3 hrs of relatively easy disassembly.

Once you cut off the ends, easily done with a hacksaw with a good blade, you are faced with a dense pattern of very small holes in a metal film that is not brittle and will not cut, but will bend and flatten out, making it very difficult to remove. so.

for those of us that noise is a problem,

-starting with a 1/4 in drill bit, make a hole in the center of the cat material, then enlarge it with a 1/2 in hole all the way through, around 4.5 in or so. You will have removed little material at this point.
-now take a screw driver about 3/8 in wide and force it between the next two layers near your 1/2 in hole, tap it in with a hammer and -once snug in the cat material, twist it, to fill in the 1/2 in hole you created.
-go all the way around the 1/2 in hole, filling it in with the adjacient cat materials. you'll be creating a larger hole area about 1 1/4 inches wide, but not so deep yet, maybe 1/2 to 3/4 or an inch.
-now take a 1/2 in wood bit, in a power drill and work at the area you've created over the 1/2 in hole. You can try other sizes of wood bits too, larger, you want to break off the folded in area, it takes some work.
-continue all the way down to the bottom of the original 1/2 in hole, to creat a new hole about 1 1/4 in wide. this gives you an area in which to work.
-now go around the 1 1/4 in hole and seperate 2 layers of the cat material, drive the screw driver in and twist, loosening the walls, do not fold all the way into the center, just break it away. Move along and break away 1 in of the cat material.
-now take a pair on needle nose, heavy duty ones, grab the loosed material and twist and break away the cat material.
-continue around the 1 1/4 hole, all the way.
-now you have a larger hole on top, maybe down an inch or so into the 1 1/4 hole, but now it's larger near the top. Continue on down the hole, until the entire length of the hole is cleared to the new diameter. Near the bottom of the hole, a long pair of needle nose is a must, 10-12 inches. You are grabbing the loosened cat material and twisting it loose.
-start at the top again and repeat what you just did. Making the hole uniformly larger each trip
-continue until the cat material is removed.
- take your time and in 2-3 hrs it'll be done.

Hoopla