|  | Topic : A Less Involved (and Obnoxious) Option for a Cat Bypass mod |  |
| | | DustyHarry | | Set |  |  | | Reg. Date | : | 26/01/2013 | | Posts | : | 9 | | Location | : | Round Rock, Texas, United States |
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| | Posted : 02 Feb 2013 - 04:36 Post title : A Less Involved (and Obnoxious) Option for a Cat Bypass mod | | | Like many of you, I was interested in waking up the sound of my 2011 Storm. Even with short TORS, the exhaust note was still just a little too sedate, especially when a H-D pulled up next to me. Even though I knew the T-Bird was a superior ride, I still couldn't shake vague feelings of inadequacy as the sound of my bike was drowned out. So, just to temporarily check out bypassing the cat on the cheap, I went the $6 Home Depot thin wall conduit route.
Besides verifying the well-documented need to remap the ECU (lots of backfiring with any amount of throttle reduction, and a little flat on the low end), I found the no cat decibel level to be well beyond the tolerance of my neighbors, and quite frankly, myself. Now, I like a nice raspy bike as much as the next guy, but 1700 cc's with no cat and short TORS is freakin' LOUD – to the point that I figured it was only a short time before I caught the unwanted attention of our normally tolerant police.
So, in addition to ordering proper tubing to replace the conduit...
(1.5" Stainless Steel Mandrel Bend 45 degree Elbow (2.25" radius), from Accelerated Tube Production via Amazon.com; Merchant SKU E6-VB70-VV2L, $16.00 ea. + shipping.) (These work perfectly; they have good bend radius and plenty of leg length to span the distance between the header and muffler connection. Cut 1" off one end and 3.5" the other end to get the length and profile right)
I also ordered a pair of 4" 'can opener' style inserts (Biker's Choice 1.5" Exhaust Pipe Baffles; P/N 492611 sourced from Stroker's Dallas - $4.50 ea + shipping). You don't see them so much anymore, but these little buggers used to be as common as dirt back in the 70's as an easy way to legalizing straight pipes.
The OD of the baffle inserts are a nice tight press fit (aka, whack 'em in with a hammer) into the ID of the 304 tubing; tight enough to not rattle around without the need to use the mounting bolt or a pop rivet.
The net result is the baffle inserts restore enough backpressure to still run well with the Triumph short TORS tune, while adding a little more exhaust bark without the bite. Backfires on deceleration are greatly reduced and less obvious (to about the same level that I had with the cat on), and I don't notice any real performance change throughout the rev range. Sound quality is more consistent as well – I wasn't too crazy about the bi-polar nature of the original no cat sound while cruising, going from mellow to blaring every time I nudged the throttle.
Now, I know some of you who are intent on wringing out every last horsepower and foot-pound of torque may scoff at this approach, or ask, "what's the point?" but I found this to be a cheap ($50 total), easy and effective alternative to waking up the exhaust note without incurring all of the cascading changes (remap ECU, plugging oxygen sensors, etc.) that seem to be needed to run well without the added backpressure.
Maybe some rainy day I'll pull the pipes and use a screwdriver to 'mechanically adjust' the openings in the baffles just a bit to do some sonic fine-tuning. I suspect I could have probably gotten away with cutting off half of the baffle section while still running OK.
And yeah, in retrospect I should have just gotten BC Hogslayers instead of short TORS to begin with...
| Better to have a bottle in front of me than a frontal lobotomy...
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| | | daz | | Zeus | |  | | Reg. Date | : | 12/05/2009 | | Posts | : | 7,686 | | Location | : | United States |
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| | Posted : 02 Feb 2013 - 04:54 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: DustyHarry) | | | The one thing you didn't experience tho is cat bypass WITH a proper tune. That will change the tone so it's not obnoxious. With ear plugs it's not loud at all. Yes, it's loud without them, but the proper tune helps a lot. Loudness is far worse when it's a bad kinda loud....the wrong frequencies. I was someone who felt even tors WITH cat were a bit loud. Now i'm running decat with the elbows and loving it. I mainly did it for the power tho, and with the right tune it has worlds better power when you decat. You lost power which shows how badly it is in need of a tune when you pull the cat. Look at it this way....right now mine is far more powerful than cat and tors with any tune. Yet you LOST power so you were running weaker than the normal tors and cat setup.....the one thats weak as hell compared to mine now. Point is, you are losing a lot of power. If thats not important to you then ignore this. If it is, you have to experience it. really is a different bike.
| 2010 Blue/White Thunderbird, "Brutus". 1700 kit, short tors, gutted cat, UNI filter, filter seal off, custom tune. Brutus in his native habitat: Link
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| | | DustyHarry | | Set | | | | Reg. Date | : | 26/01/2013 | | Posts | : | 9 | | Location | : | Round Rock, Texas, United States |
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| | Posted : 04 Feb 2013 - 21:12 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: daz) | | | Daz - you are absolutely right in that a different tune in conjunction with not adding in additional backpressure to compensate for the cat removal would no doubt improve performance. But, that wasn't my objective. I spent a good deal of my misbegotten youth (and treasure) trying to be the fastest kid on the block. There's always someone else with more time, money and ideas. Now I'm an old fart and am lucky to hang on to it as it is when its full potential is unleashed). So, I am satisfied with the bike in terms of performance What I am trying to do is improve the exhaust note, while keeping the bike running well and decibel level in an acceptable range. The cat represented a substantial gas volume affecting the quality of the sound. An added benefit is removing an ugly regulatory tumor from its undercarriage. Net/net, I haven't lost any power, I just haven't gained any.
BTW, my .357 isn't loud at all with earplugs either!
| Better to have a bottle in front of me than a frontal lobotomy...
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| | | Rev | | Set | |  | | Reg. Date | : | 02/02/2011 | | Posts | : | 266 | | Location | : | United States |
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| | Posted : 05 Feb 2013 - 16:56 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: DustyHarry) | | |
DustyHarry wrote:
Daz - you are absolutely right in that a different tune in conjunction with not adding in additional backpressure to compensate for the cat removal would no doubt improve performance. But, that wasn't my objective. I spent a good deal of my misbegotten youth (and treasure) trying to be the fastest kid on the block. There's always someone else with more time, money and ideas. Now I'm an old fart and am lucky to hang on to it as it is when its full potential is unleashed). So, I am satisfied with the bike in terms of performance What I am trying to do is improve the exhaust note, while keeping the bike running well and decibel level in an acceptable range. The cat represented a substantial gas volume affecting the quality of the sound. An added benefit is removing an ugly regulatory tumor from its undercarriage. Net/net, I haven't lost any power, I just haven't gained any.
BTW, my .357 isn't loud at all with earplugs either! |
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Awesome, another Austin area T-Bird owner. If you feel so inclined, sign up on the facebook Austin RAT group. Rides and meetings are posted there all the time, wouldn't mind seeing at least one other T-Bird rider at the rides/meetings. I'd love to hear what the bike sounds like with your setup some time.
Rev
| "I know just what I'm gonna do..... I'm gonna ride on" ~ Bon Scott
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| | | Cody | | Set | |  | | Reg. Date | : | 01/04/2010 | | Posts | : | 208 | | Location | : | Siloam Springs, Arkansas, United States |
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| | Posted : 06 Feb 2013 - 11:36 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: DustyHarry) | | | Removing the CAT changes the air flow characteristics and introduces more air to the fuel mixture. Properly tuning the ECU, to my thinking, would bring the air/fuel mixture back into a proper balance. I am more familiar with carburated systems, but in my experience a sharp hollow pop in the exhaust note, and popping on decel indicates a lean mixture. A lean mixture makes the bike run hotter than necessary, which is not a good thing, especially in the heat of mid-summer. So, IMHO, it would be worth tuning the ECU, or having someone do it for you.
| This country was founded on the premise that I would have freedom from your religion.
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| | | edbob | | Chaac | |  | | Reg. Date | : | 04/04/2012 | | Posts | : | 931 | | Location | : | United States |
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| | Posted : 07 Feb 2013 - 04:23 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: DustyHarry) | | | Good post - something I've long considered - how did you secure the baffles into the cans, by the way? I know you said they were a nice press fit, but with some heat and some time, and a large amount of throttle, you may find yourself with a projectile launcher
| "You will ride eternal shiny and chrome"
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| | | DustyHarry | | Set | | | | Reg. Date | : | 26/01/2013 | | Posts | : | 9 | | Location | : | Round Rock, Texas, United States |
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| | Posted : 18 Feb 2013 - 12:26 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: Rev) | | | Thanks Rev - normally I avoid Facebook like the plague, but I'll check out the Austin Rat info.
| Better to have a bottle in front of me than a frontal lobotomy...
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| | | DustyHarry | | Set | | | | Reg. Date | : | 26/01/2013 | | Posts | : | 9 | | Location | : | Round Rock, Texas, United States |
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| | Posted : 18 Feb 2013 - 12:32 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: edbob) | | |
edbob wrote:
Good post - something I've long considered - how did you secure the baffles into the cans, by the way? I know you said they were a nice press fit, but with some heat and some time, and a large amount of throttle, you may find yourself with a projectile launcher |
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I've actually launched them out of Harley straight pipes before, but no worries here. 'Press fit' might have been a bit generous... There was a couple of thousanth's interference fit, so I had to hammer the baffles into the bypass tube. I doubt they're going anywhere; the thermal expansion differences between the 304 and the carbon steel baffles is probably negligable. Besides, even in the unlikely event that they do get loose, they aren't going far - the baffles are on the inlet end of the bypass tube, and that 45 degree turn isn't far behind it.
| Better to have a bottle in front of me than a frontal lobotomy...
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| | | DustyHarry | | Set | | | | Reg. Date | : | 26/01/2013 | | Posts | : | 9 | | Location | : | Round Rock, Texas, United States |
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| | Posted : 18 Feb 2013 - 12:37 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: Cody) | | |
Cody wrote:
Removing the CAT changes the air flow characteristics and introduces more air to the fuel mixture. Properly tuning the ECU, to my thinking, would bring the air/fuel mixture back into a proper balance. I am more familiar with carburated systems, but in my experience a sharp hollow pop in the exhaust note, and popping on decel indicates a lean mixture. A lean mixture makes the bike run hotter than necessary, which is not a good thing, especially in the heat of mid-summer. So, IMHO, it would be worth tuning the ECU, or having someone do it for you. |
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So, the Triumph factory TOR tune is crap. When I bought the bike, I had the short TORs and associated tune loaded up before I ever left the dealership. It has always had some backfire on decel. No real difference before/after with the mod described. At some point I'll get to working on the tune. Right now, I'm in the middle of replacing the fence in my yard....
| Better to have a bottle in front of me than a frontal lobotomy...
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| | | zolti | | Thor | |  | | Reg. Date | : | 23/03/2010 | | Posts | : | 3,127 | | Location | : | newcastle , United Kingdom |
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| | Posted : 18 Feb 2013 - 16:22 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: DustyHarry) | | |
DustyHarry wrote:
I also ordered a pair of 4" 'can opener' style inserts (Biker's Choice 1.5" Exhaust Pipe Baffles; P/N 492611 sourced from Stroker's Dallas - $4.50 ea + shipping).
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nice and simple, something you could dyno in too 
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| | | Don_58 | | Set | |  | | Reg. Date | : | 02/11/2012 | | Posts | : | 10 | | Location | : | Auckland, New Zealand |
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| | Posted : 03 Mar 2013 - 07:27 Post title : Re: A Less Involved (and Obnoxious) Option for a Cat Bypass mod (Re: zolti) | | | Hi Guys,
Im just weighing up the same options for my 2010 1700 TB W/Short Tors, Ive been following these threads for weeks and have decided to use a couple of 45degree Stainless steel pre-fab elbows. Theyre a bit expensive down here $70 NZD each, but still cheaper than a specifically made bypass pipe with balancing tube.
I was quoted $300 NZD for a set made out of mild steel tubing, $400 for the Stainless option. I will probable go for the Stainless 45 deg elbow option.
Unfortunately my dealer is less than helpful with recommending a suitable tune, and going on from what has previously been said on this topic, the OEM tors tune is crap.
For me, sound is most important, and this is the main reason I want to remove the cat. I hate the raspy sound that some by-pass pipes create, preferring for the loud deep rumble with an impressive bark.
I only know what Ive read on this forum about tunes and by-pass pipe options and there is some very useful information. Thank God for those of you who are passionate to share what you know and have done.
You guys really are my source of knowledge.
Anyway, I heard from a tuning specialist that the most ideal way to get the best tune possible is to re-map the ECU, apparentely this it much better than using a power commander or something similar. The tuning guy said that this is the best way to get the ideal tune for your machine and set up.
As I have no idea, I would appreciate anyones opinion on this.
futher to this, will i need to purchase the "unlock key" for the ECU from Triumph to enable the ECU to be re-mapped.
I just want to un-tame the beast!
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