Anybody gut their catalytic converter?

Anyone do it yet? Any Negatives, like Popping? Backfiring? Running lean?

thanks,

Don

On the BMW R1100 and R1150 models it makes no difference to the performance of the bike. No extra HP, no more torque, no dip in the power curve, no back firing or popping. No diiference at all except a weight savings and less heat in the area of the cat. May or may not apply to other FI cat equipped bikes.

X1Glider said:

On the BMW R1100 and R1150 models it makes no difference to the performance of the bike. No extra HP, no more torque, no dip in the power curve, no back firing or popping.

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That's simply not true. It does remove a flat spot (dip in the torque curve) and makes the engine run smoother. It also allows the engine to rev more freely and improves the fuel consumption. The exhaust note becomes slightly deeper because you've lost the silencing effect of the cat. The difference is even more marked if (as you should) you use a jumper to change to the appropriate map in the ECU so that the fueling is correct (as far as any of the standard maps allow). I've had two 1150GSs and an 1100S and it's generally acknowledged on this side of the Atlantic that fitting a Y-piece in place of the cat on an oilhead BMW is the most cost effective engine-related improvement that can be made. Maybe US-spec BMWs are restricted in other ways that make cat removal less effective?

On the Bandit, which revs considerably higher than a BMW twin, removing the cat will have even more effect - the higher the engine revs the more exhaust gas you're trying to pump through the exhaust and a restriction will have correspondingly more effect. This, I think it's fair to assume, is what allows Holeshot's 1250 to make 130bhp - most of that will come from using cat-free headers.

Well I found it hard to believe that it didn't help performance and mileage, but apparently, from the responses I've received so far, not many are doing it. I've posted this question on 3 boards to get as much input as possible.

I was a mechanic many years ago on VW's, when the Rabbits first came out. Had terrible probs with cats plugging,and/or coming loose, and rattling...... so gutting them was a recall item back then, believe it or not (late 70's)

With the angle of the outlet, it would be tough to get it all, but I'm sure I can work something out. I have no problem with converters on cars/trucks, but NOT on a bike for cryin' out loud. It just ain't right!

I'm gonna' hold off a few more days till I see if anyone has actually done it, but, early next week, barring any unfavorable reports, that ***** is mine!

Any opinions on the O2 sensor? Should sense O2 the same, with or without the Cat, no?

Any opinions on the O2 sensor? Should sense O2 the same, with or without the Cat, no?

I would lean towards an 02 bypass , pair plug and a fuel management device like a TFI if I were going to do something that major to the stock system.
A couple of people around the forums have gutted there cats and claim some increased performance , but I would like to see some dyno charts my self.A detrimental increase in turbulence could be a real possibility

modifying ones bike, and claiming a performance increase, seems to be the easiest thing to do. verifying an actual increase with dyno comparisons before and after, seems lacking in everyones outrageous improvement claims.

i'm afraid, so many homebrew modifications of intake and exhaust, simply increase noise. and this is the measure that is used for HP increase.

sadly, few have scientific data, dyno numbers, to prove any of their wild claims.


this has been the best performance increase i have done to my bike so far.

gunzip said:

Any opinions on the O2 sensor? Should sense O2 the same, with or without the Cat, no?

I would lean towards an 02 bypass , pair plug and a fuel management device like a TFI if I were going to do something that major to the stock system.
A couple of people around the forums have gutted there cats and claim some increased performance , but I would like to see some dyno charts my self.A detrimental increase in turbulence could be a real possibility

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The 02 sensor has no real effect on performance as its only real function is to control engine emissions typically at or below 2,500 RPM, as they are a narrow band sensor, meaning that only work within a certain RPM range of the engine.

I don't go nuts on mods, aftermarket stuff is overpriced. I can afford it, but, I have principles. The Cat, is also one of those principles.

If it makes no difference at all, it'll still make ME feel better, just knowing it's gone.

And, a few more MPG's wouldn't hurt.

doing something because YOU like it, makes sense to me.

everything i have done, was because I liked it.
some things i changed, i didnt like afterwards, and changed it back.

gutting the header, seems to be a one way street. no going back.
i think worm gutted his cat, maybe he can confirm.

suzukijo said:

gutting the header, seems to be a one way street. no going back.

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Which is why I wanna' make sure it doesn't do anything nutso!

I'm not against Cats on bikes IF/WHEN the alternative is WORSE!

I think rworm's on a trip, as I recall.

Not trying to hijack the thread but after reading it a bit,.... How many of them are "true" catalytic converters?

Reason I ask is that it is labeled as such on my 05 nomad but all it appears to do is provide back pressure. Standard mod on the kaws is to remove/gut the "goat belly" (converter).

Are any of these truly converting anything?

Grumpy

(afraid to have bike rejected by the gubmint watchdogs)

Grumpy said:

Not trying to hijack the thread but after reading it a bit,.... How many of them are "true" catalytic converters?

Reason I ask is that it is labeled as such on my 05 nomad but all it appears to do is provide back pressure. Standard mod on the kaws is to remove/gut the "goat belly" (converter).

Are any of these truly converting anything?

Grumpy

(afraid to have bike rejected by the gubmint watchdogs)

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Mine looks like your avg. cat. Honeycomb ceramic. So I assume it works as such, up to and including getting incredibly hot !

Oh CRAP!! I wish it was honeycomb ceramic! It's some kind of metal. I've got thru' to each of the header pipes, and am quitting for the day....got other stuff to do, but DANG, I don't think there is any way to get it all....I figured get a big hole down the center, and it would start busting up pretty easy. Uh, not so much!

Took a couple hours so far.....if ceramic, my test ride woulda' been done by NOW!

A somewhat popular mod among '02 and newer VFR riders is to swap out the header system with one from a '98-'99 model. They bolt right up, but have slightly larger diameter header tubes and no cat. One guy on VFRD did this, and his before-and-after dyno tests showed a HP increase of about 10% (98-->108 or something similar if I recall correctly). Of course, this was with a properly mapped PCIII. I found a set for sale last year and swapped them out, and while I did not do any dyno runs, there is a definite seat-of-the-pants difference (ie, the front end didn't used to come up under power in 2nd gear). It also made a definite difference in the exhaust note--only slightly louder, but much lower and more 'burbley'. No problems with backfires or hesitations; however, after spending time in slow-moving traffic, you may smell slightly of unburnt hydrocarbons.

I think it's one of the best mods I've done; the $/HP ratio is pretty impressive compared to other modifications, and I enjoy the aesthetic difference in the exhaust tone. The best part of mine is that it's completely reversible; I can just pull of the catless headers at any time, sell them to the next guy in line, and put the original back on. You won't have this option if you gut yours, but I really don't think you'll regret it. If you do, I'm nearly certain you'll be able to find someone who just bought the same model bike as you who wants a bit of a power boost and will be willing to trade his stock system for your gutted one. Just remember that you have to add in a PCIII to the cost of the mod. Also, be sure to check your environmental awareness guilt level to be sure it can accomodate the thought of boosting your global warming contribution.

connick said:

Also, be sure to check your environmental awareness guilt level to be sure it can accomodate the thought of boosting your global warming contribution.

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hmmmmm, Let me check real quick.......
........................................
........................................
........................................ YEP, I'm good!!

connick said:

Also, be sure to check your environmental awareness guilt level to be sure it can accomodate the thought of boosting your global warming contribution.

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I think I'm right in saying that by removing the cat you actually reduce your global warming contribution? Doesn't a cat convert (amongst other functions) most of the CO from the exhaust to CO2? Well CO2 is the 'greenhouse gas', CO isn't. Cats are the answer to one percieved problem and a contributing factor to another one.

I'd guess that the only way to remove the cat properly (well, more 'properly' that sticking sharp things up the pipe!) would be to cut off the top or bottom of the cat (to the seam that runs around the side), remove all the contents and then weld the bit you removed back on. That just means you need a means of welding stainless.

I finished it up today, not sparking clean inside, as I'd prefer, but nevertheless, it's open. There's an outer sleeve to the cat that is not removeable anyhow, unless you cut the chamber open.

I really haven't ridden mine much yet, but the only sign of running lean, is 1st and 2nd gear, if you run it up a bit, then hold it at a steady speed, it surges.

But, I'm pretty sure it did that before too. Other than that, runs great, and sounds basically the same.

I'm gonna' hold off on a PC-III for now.
I had one on my VStrom, they're very nice if really needed.....the Strom had a nasty stumble that was dangerous if pulling away and turning.

EDIT: I checked it after riding a few days, and with a small mirror, found a hunk I missed. It's now squeaky clean inside, just the thin liner remains. All told, I probly had 4+ hours doing it. Woulda' been much easier/quicker, if I had a lift table to get it up to a comfy working position.

...tried to gut my cat once. Took weeks for the claw marks to heal up, at least it quit trying to 'mark' it's territory.


sorry folx, coulnd't resist.

ulric said:

...tried to gut my cat once. Took weeks for the claw marks to heal up, at least it quit trying to 'mark' it's territory.


sorry folx, coulnd't resist.

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I have no love for those kind of Cats either! Keep up the good work, but wear long sleeves, ya' big dummy!!

dmerc said:

I really haven't ridden mine much yet, but the only sign of running lean, is 1st and 2nd gear, if you run it up a bit, then hold it at a steady speed, it surges.

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Apparently all injected Suzukis run retarded ignition timing (and possibly different fuel maps) in 1st and 2nd than they do in higher gears. This is to pass emissions tests and is probably the cause of the surging which mine does too. Fitting a TRE should reduce this by allowing a high-gear map to be used in all gears - the HealTech gear indicator incorporates a TRE and I'm planning to fit one of these (along with a speedohealer from the same place) as the next mod that I do to my bike. Once I've assessed the effect that this has I'll know whether I need (OK, want....) a PC111 now or whether that can wait until I fit replacement headers.

Today was the warmest day I've ridden the bike so far (around 18 centigrade) and I could feel my right foot being toasted by heat from the cat in slow traffic. It's gotta go......

sproggy said:

A
Today was the warmest day I've ridden the bike so far (around 18 centigrade) and I could feel my right foot being toasted by heat from the cat in slow traffic. It's gotta go......

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We're finally getting nice weather here in Ohio too. Time to quit screwin' with my bike, and actually RIDE it!! I still don't have 200 miles on it yet!!

dmerc said:

I finished it up today, not sparking clean inside, as I'd prefer, but nevertheless, it's open. There's an outer sleeve to the cat that is not removeable anyhow, unless you cut the chamber open.

I really haven't ridden mine much yet, but the only sign of running lean, is 1st and 2nd gear, if you run it up a bit, then hold it at a steady speed, it surges.

But, I'm pretty sure it did that before too. Other than that, runs great, and sounds basically the same.

I'm gonna' hold off on a PC-III for now.
I had one on my VStrom, they're very nice if really needed.....the Strom had a nasty stumble that was dangerous if pulling away and turning.

EDIT: I checked it after riding a few days, and with a small mirror, found a hunk I missed. It's now squeaky clean inside, just the thin liner remains. All told, I probly had 4+ hours doing it. Woulda' been much easier/quicker, if I had a lift table to get it up to a comfy working position.

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Hi dmerc.
I no it was 2years ago, but i'm about to remove my catalytic converter.

Did u leave the headers on the bike or removed them?
what tools did u use to get it out (hammer, long bar/chisel/screwdriver) magic?
can u see the cat or do I work blind & hope for the best?

Your help well be most appreciated
Reardo

Ozbandit1250s said:

Hi dmerc.
I no it was 2years ago, but i'm about to remove my catalytic converter.

Did u leave the headers on the bike or removed them?
what tools did u use to get it out (hammer, long bar/chisel/screwdriver) magic?
can u see the cat or do I work blind & hope for the best?

Your help well be most appreciated
Reardo

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I left the headers on. I used a pry bar from Harbor freight, and my trusty hammer. It had the perfect curve for getting at it. You can see it. Just keep driving it in, then twisting it, to break it up as you go. I occasionally sucked the crap out with a shop vac. Resist the urge to start it up, it'll blow that stuff all over the place!! And, make sure you take the o2 sensor out before you start. Good luck, it's not bad, I'm just not as flexable as I used to be.

I just sold my Bandit, dang that was a fun bike!! Wheelieing animal! ;o)

I got a Concours 14. It has 4 seperate cats, but they aren't as thick, so they were pretty easy.

Had a R1100GS and I eliminated the cat and could not tell a difference in performance. If there was a difference, it was so little, that I didn't even go to the trouble of removing the one off my present R1150GS. I did take the muffler off though.

Fred

Fort Bend Rider said:

Had a R1100GS and I eliminated the cat and could not tell a difference in performance. If there was a difference, it was so little, that I didn't even go to the trouble of removing the one off my present R1150GS. I did take the muffler off though.

Fred

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I could definitely tell the difference in the power wheelies, AND, the heat at my right foot. Bikes with cats? It's just wrong!