How To Gut a Cat - Triumph Bobber Forum
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post #1 of 13 (permalink) Old 07-08-2017, 04:22 PM Thread Starter
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How To Gut a Cat

I decided to remove the catalytic converter and clean it out. Yes, I know it is used to reduce emissions. Talk to China first. While it was out I did several measurements of it. Making a few x-pipes for some friends that want them.

Pretty simple process. Simply remove it, cur it open at the cross welds. Remove the element and weld it back together. Ensuring you have the same distance as you measured before cutting. This distance can be varied by a mm or so and you're still good because the header and muffler outlet can move slightly.

The weight removed here is significant as most of the weight is from the element inside and not the outer stainless steel shell.

The sound? Identical to an x-pipe as compared to my friend who has one installed. Yes, it does have a more "mechanical" sound out the exhaust and a very slight increase midrange 2000-3500 rpm. Not bad for a few hours. And not $300.
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post #2 of 13 (permalink) Old 07-08-2017, 06:12 PM
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Nicely done.
Thanks for sharing !
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post #3 of 13 (permalink) Old 07-08-2017, 09:27 PM
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Cut the second baffle out 1 inch in diameter in the exhaust makes a big difference also have to reset computer disconnect battery for 30 minutes
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post #4 of 13 (permalink) Old 07-12-2017, 06:31 AM
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Did you notice if was a little cooler in traffic? on the legs!
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post #5 of 13 (permalink) Old 11-26-2017, 11:28 PM
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What do you mean by second baffle? I did a mod on my old 955ST by cutting a hole in the baffle approaching through the exhaust opening and liked the sound a lot. Is this close to what you did? If so, any sound recordings? Thanks!
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post #6 of 13 (permalink) Old 02-07-2018, 09:17 AM
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Moodyblues, I once tried a x-pipe on my Bobber cause I didn't want to gut the cat knowing anything about the effects. When I compared the run times on my private quarter mile track (), I didn't recognize any improvement. The bike just got a bit louder, that's all. Maybe a x-pipe can improve peak power for 2 or 3 HP, but I don't rev my Bobber much over 3000 revs normally, so I don't care about eventual gains in peak power.

Now you have gutted your cat. Cause the gutted cat has a considerable volume (the x-pipes don't have!) I guess, that the exhaust must sound a bit deeper!? So what would you say?

Werner Wernersen
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post #7 of 13 (permalink) Old 02-07-2018, 10:22 AM
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The gasses are going into a voluminous chamber instead of being swept through curving pipes which has to be better Shirley?

Discuss.
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post #8 of 13 (permalink) Old 02-07-2018, 11:22 AM
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The more I've read and researched it seems installing an X pipe in place of the cat on the Triumph 1200 engines show's very little improvement in power gains.
A bit of volume, probably cooler engine temps, but it's a water cooled engine anyway.

Now it's a different story for the Triumph 900 engines as Triumph engineered the 900's not to complete too closely with the 1200 power over concerns of lost sales for the 1200's.
The X pipe installed on the 900's shows some nice gains.

My current plans for the New 1200 Speedmaster.
Probably add a Booster Plug to smooth out low end throttle response. Maybe modify the air filters by removing the metal cover to allow more air to flow through the paper filter. Exhaust mods or replacements, we'll see.
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post #9 of 13 (permalink) Old 02-07-2018, 12:16 PM
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Chezqui, in my opinion and after having tested the x-pipe, there is no measurable change in torque at lower revs. I did not test the x-pipe at high revs, cause I'm not focussed on peak power.

Dyno runs (I cannot remember where I found the article) have showed, that the complete removal of the cat and passing the exhaust gases straight to the stock mufflers decreases power of our twins considerably. The cat as well as the x-pipe divide the gases to the both mufflers, which obviously reduces counter pressure caused by the noise reducing baffles.

We must take into concern, that the x-pipe highly directs the exhausted gases to the opposing muffler! So eventually (and curiously) a gutted cat could work even better than the x-pipe, I guess!? Who knows.....?

Cause I'm happy with the low rev performance of the cat, I'm mainly interested in a deeper sound, and I guess the gained volume of a gutted cat could make the goal!

Cheers girls,

Werner Wernersen
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post #10 of 13 (permalink) Old 09-07-2019, 06:40 PM
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Sorry to bring up an old thread but has anyone else done this "cat gutting" vs x-pipe and have sound recordings?

2019 Bonneville Bobber - Morello Red, 1979 Bonneville T140E, 1954 BSA B31
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