Catalytic Converter delete

[jodog]

I posted a while back that I had removed the cats from a set of mufflers I have for the st1300. I finally got around to putting them on and taking a ride. One ride, so consider this preliminary data.

There were no adverse consequences from the absence of cats. No popping on deceleration, and no sound increase that I could tell.

There MAY have been a small heat decrease. It wasn't that hot of a day so it's hard to gauge, but my feet felt a little cooler.

I think the gas mileage increased. Careful measurement over a 340 mile ride indicated a 40.4 mpg. Roads included interstate (75 mph), good two lane (60-65 mph), and rougher two lane (55mph). Route was a big square so it was equally tail, head, and side wind.

As I don't have a really solid number for what my "normal" gas mileage was I can't say what the increase was precisely, but I don't normally go 340 miles (I have an aux tank) and if I did I wouldn't expect to have this much gas left. My estimation would be about a 8%+ increase. YMMV.

Bob

 

[OkieRider]

Link to post on the process?

 

[jodog]

Link to post on the process?

Are you referring to the process of removing the cats? Simple, cut the pipe either just before or just after the catalytic section of the muffler. I cut mine on the engine side. Step two, rip out the cats. This is actually harder than it sounds, somehow I expected them to just fall out but they don't. More like a dental extraction. Step three, weld the pipe back together with a very pretty weld and grind it smooth so snoopy people will be none the wiser.

If you live in one of those awful states with emissions testing you may have some worries?? If you try this and go to an emissions test post up and let us know how it went.

 

[MSgt-R]

Any new insights to this thread?

 

[Obo]

Any new insights to this thread?

Well, the guts of the cats are toxic, but worth money - so don't breathe in the dusts if gutting them or toss them in the trash as you can get some money from them.

You might be better off to purchase some aftermarket cat free mufflers and just sell the OEM ones for the valuable scrap in them. Scrap converter prices can range from a hundred dollars to over a grand.

 

[Slammer]

Ok. I´ll bite. Why on earth would you want to remove a Catalytic Converter?

 

[Andrew Shadow]

In the belief/hope that heat emanating from the exhaust will be reduced.

 

[Gerhard]

Apparently most catalytic converters get between $100 and $200 at a scrapyard, we had ours stolen from our delivery van and it was a $2000 repair covered mostly by insurance. The scrapyards should be required to ask for photo id and the source of the catalytic converter before paying for it that should make it a less attractive crime. Apparently thieves like vans and pickup trucks because they can often remove the converter without jacking up the vehicle lowering the risk of being caught.

 

[Andrew Shadow]

Saw a news story a while ago where the crooks jacked up a car to steal the catalytic. They don't use jack stands of course because they are in a hurry. The car fell off the jack and pinned one guy under the car. His two friends took off and left him there. Made it easy for the police to arrest him after the fireman extracted him. I hope that they took their time, he gets no sympathy from me.

 

[Obo]

In the belief/hope that heat emanating from the exhaust will be reduced.

And that allowing the engine to "breathe freely" will make it run better.

 

[Slammer]

And that allowing the engine to "breathe freely" will make it run better.

But isn´t that regulated by the Lambda sensor?

 

[thekaz]

Ok. I´ll bite. Why on earth would you want to remove a Catalytic Converter?

assuming your PAIR system is working correctly there will be a reduction in heat.
there will be a reduction in weight assuming PAIR removal & after market pipes
better fuel milage maybe possible if the existing cats were partically clogged
guaranteed enjoyment of watching climate cultists crying because now your an evil polluter

 

[Al st1100]

lot's of if, if, but I'm sure when designed the calculations took into consideration some back pressure caused by the converter.

 

[Al st1100]

But isn´t that regulated by the Lambda sensor?

Lambda sensor or O2 sensor can't change exhaust pressure. It is used to calculate air/fuel ratio.

 

[Obo]

But isn´t that regulated by the Lambda sensor?

I should have clarified my post in reply to Andrew's :

In the belief/hope that heat emanating from the exhaust will be reduced.

And the belief/hope that allowing the engine to "breathe freely" will make it run better.

 

[Gerhard]

guaranteed enjoyment of watching climate cultists crying because now your an evil polluter

If you believe in climate change or not there is no denying that the air quality in major North American cities is hugely improved from the ‘70s to 2000, catalytic converters have large role to play in that progress. I am sure you will just dismiss it as more fake news but you’d be wrong.

 

[Al st1100]

I should have clarified my post in reply to Andrew's :



And the belief/hope that allowing the engine to "breathe freely" will make it run better.

It will breathe easier getting near the redline and this from google "
Do all engines need back pressure?


Most road vehicle engines require a degree of back pressure in the exhaust system, including the manifold and exhaust pipe components, in order to run efficiently.

 

[Willsmotorcycle]

Having tried a pair of aftermarket, there is definitely a heat reduction. I didn't notice when I took the OEM off, definitely when I put them back on.

 

[Obo]

Having tried a pair of aftermarket, there is definitely a heat reduction. I didn't notice when I took the OEM off, definitely when I put them back on.

Well that makes sense. Catalytic converters require a temperature of 400 °C (752 °F) to operate effectively. They effectively burn any unburned hydrocarbons that make it through the engine (as well as other chemical processes to lower other emissions.) You want them to be hot, and produce some heat without exceeding a temperature that will damage the cat. That heat will radiate out from the metal shell. If there's no reaction there should obviously be less heat to disperse.

Modern cats don't really restrict the exhaust flow, unless the cat is damaged/plugged, so the extra HP gained is negligible from that.

I do agree though that there is an excess of pollutants that will make their way out that a cat would normally mitigate.

The only plus side I can really see is perhaps a small gain by shaving off the extra weight on the bike, and only from the point of view you increase the HP to weight ratio 2 ways... make more HP, or cut weight. Cutting weight is always the cheapest and easiest way to increase that ratio on any vehicle. Will it really go any faster? Not likely. Will it work better? I think that's' completely subjective to the rider as are many "upgrades" to a bike and not really based on measured reliably on before and after conditions.

 

[MSgt-R]

I like your response, Obo (are you a musician?).

I have worked with cars most most of my life, gotten all the certificates on the wall, and taught a little college. Bikes and cars are not much different in the principles of their operating systems, and are still continuing to evolve. Anything 20 years old sucks compared to the latest computer systems.
Bottom line: Emissions are a "bandaid" to a dirty engine. If you take off the cat, the noise increases, the heat decreases, and the HC / CO / NOX increases. Older type cats will also restrict exhaust flow, the new ones too, but to a much lesser degree. Gas mileage and horsepower are a bonus if the exhaust was restrictive. If the O2 sensor is doing it's job, A/F ratio will continue to be in-the-zone. Got two (one downstream)? You're screwed unless you get an ECM re-flash to eliminate the reporting of a missing converter.
Cut weight? A good exercise program will do more for your performance than to eliminate a couple of very small catalytic converters.