More Horses removing Cat?

[chrisstroh]

Do you gey any more horsepower removing the CAT and maybe some hypo mufflers- maybe a pair of them? just curious.

[No_Twilight]

Opinions will vary and it might depend on what else you do but I've decided to believe the prevailing opinion that you don't get any more HP from a catless system. However, you lose weight and get rid of that huge heat source. --Jerry

[Ken H.]

Nope.

[Jim VonBaden]

Nope, you just create more emissions.

 

The loss of 7 pounds equals 1hp, so you sort of gain HP though. I lost 120 pounds, and gained 17HP!

 

Jim

[chrisstroh]

What about going to dual exhaust? Does someone make a pipe kit that will BOLT on to a 2002 RT? Is it worth the cost and trouble?

[RFW]

If it's plugged, yes. Otherwise, NO. A cat is a straight-through device. The exhaust goes in one end and straight out the other, via a lot of small "tubes", whose combined cross sectional area is ample for the exhaust flow in question.

 

Bob.

[RFW]

Nope, you just create more emissions.

 

The loss of 7 pounds equals 1hp, so you sort of gain HP though. I lost 120 pounds, and gained 17HP!

 

Jim

Does this work for your bike, too?

 

Bob.

[FlyingJoe]

I don't want to come across as a eco-nazi but it is really much more environmentally friendly to keep it on. In a January study by the American Chemical Society it pointed out the average motorcycle "produced more harmful exhaust emissions per mile than cars or even large sports utility vehicles".

 

I'm no model citizen but I enjoy hiking/outdoors so much I am trying to 'be green' these days.

1) http://www.sciencedaily.com/releases/2006/01/060101155000.htm

 

(1)

[bugsquawsher]

You think possibly they were comparing Carberated Bikes to Fuel Injected Cars?

 

I don't want to come across as a eco-nazi but it is really much more environmentally friendly to keep it on. In a January study by the American Chemical Society it pointed out the average motorcycle "produced more harmful exhaust emissions per mile than cars or even large sports utility vehicles".

 

I'm no model citizen but I enjoy hiking/outdoors so much I am trying to 'be green' these days.

1) http://www.sciencedaily.com/releases/2006/01/060101155000.htm

 

(1)

[Larsen]

Today there are so many generalized studies regarding everything. You have to do what you can but at the same time use common sense! I've found many Studies that are Self Serving the Industry that made the Study. Next someone is going to come up with a Study showing that Life Leads to Death! Then what?

 

I’m surprised that nobody made a comment on the Study that “Chemists Detect Toxic Emissions Linked To Catalytic Converters In U.S.”

http://www.sciencedaily.com/releases/2005/12/051206084209.htm

[FlyingJoe]

You think possibly they were comparing Carberated Bikes to Fuel Injected Cars?

 

Most likely they just took a slice of registered vehicles out there, a greater % of motorcycles are probably carb'ed vs cars these days. They made the generic statement "Particularly worrisome are the high levels of hydrocarbons emitted by Japanese, German and Italian two-wheelers, according to the study." (which is like 95% of the market, and Harley's can't be good)

 

I have pendelum swung to being more granola, eat organic, race Ironman's, etc.. but earlier in my motorcycle days I did things like replace my FZX with kerker pipes, causing birds to scatter whenever I started it, polluting who knows how much.. Like I said, trying to be more eco-friendly now.

[No_Twilight]

I'm no expert and I've never studied it in detail but it is my belief that cat's do almost nothing. They are designed to clean up a poor running engine. On a good engine they help a little bit on startup but then don't make a difference. I observed the emissions test on a catless 500 hp 300zxtt and the results were almost identical to the stock car with cats. If your vehicle is tuned up and running well, there is little for the cat to remove. I wouldn't feel guilty at all removing them but I wouldn't do it because of the fine. I've considered gutting the cat on my R1100RS just to eliminate all that heat but it's too much work to bother with.

 

Now if someone wants to point out where I'm wrong I won't be offended or suprised since I haven't studied this but eco-nazi propoganda won't get anywhere in trying to convince me. I'm a scientist, not a politician.

 

--Jerry

[ShovelStrokeEd]

The cat does nothing on startup. It needs to get up to temperature before it will start removing oxides of Nitrogen from the exhaust which is its primary function. Lean running engines, which are necessary to keep hydrocarbon emissions down tend to have high NOX output. Thus the cat.

[RFW]

Today there are so many generalized studies regarding everything. You have to do what you can but at the same time use common sense! I've found many Studies that are Self Serving the Industry that made the Study. Next someone is going to come up with a Study showing that Life Leads to Death! Then what?

 

I’m surprised that nobody made a comment on the Study that “Chemists Detect Toxic Emissions Linked To Catalytic Converters In U.S.”

 

And don't forget the dangers of the Dihydrogen Monoxide that is produced when the cat oxidizes unburnt hydrocarbons.

http://www.dhmo.org/

 

Bob.

[smiller]

If your vehicle is tuned up and running well, there is little for the cat to remove.

 

I don't believe that is correct and I would expect that removing a properly functioning cat from a vehicle will definitely increase emissions. But... the operative phrase there is 'properly functioning' and it wouldn't surprise me if the cat on a high-mileage vehicle would have enough of its function impaired by age that it may indeed may not make much of a difference in that particular case.

[FlyingJoe]

And don't forget the dangers of the Dihydrogen Monoxide that is produced when the cat oxidizes unburnt hydrocarbons.

http://www.dhmo.org/

 

The danger of producing water?

[chrisstroh]

Right on Jim. If their study says that, I beleive it's to prime us up for mandatory bi-yearly smog inspections for motorcycles...God help us.

[Joe Frickin' Friday]

I'm no expert and I've never studied it in detail but it is my belief that cat's do almost nothing. They are designed to clean up a poor running engine. On a good engine they help a little bit on startup but then don't make a difference.

 

OK, I'll bite. I do this stuff for a living, so I feel qualified. Emissions regulations do not mandate particular technologies. The ubiquity of cats on automotive exhaust systems suggests that it is virtually impossible to meet existing regs without them - which implies that they do in fact serve a purpose, even on a healthy engine.

 

And in fact, they do work very well on a warmed-up engine with closed-loop fuel injection (e.g. Oilhead BMW's). They actually do more for emissions reduction on your bike than they do on a car. Bikes lack a key emissions control strategy employed on cars: EGR. Without that, the engine-out NOx emissions from the boxer is far higher than your car, and the cat has a big job to do.

 

I observed the emissions test on a catless 500 hp 300zxtt and the results were almost identical to the stock car with cats.

 

Were you watching CO, HC's, *and* NOx? Were the readings in PPM, or g/hp*hr? Same speed/load for both engines?

 

...eco-nazi propoganda won't get anywhere in trying to convince me. I'm a scientist, not a politician.

 

No eco-nazi propaganda here. Some recommended reading:

 

Internal Combustion Engine Fundamentals by John Heywood (older, but still useful)

 

Internal Combustion Engine Handbook - Basics, Components, Systems, and Perspectives by Richard Van Basshuysen and Fred Schaefer

 

Bosch Gasoline-engine Management by Robert Bosch

 

Ed sez:

Lean running engines, which are necessary to keep hydrocarbon emissions down tend to have high NOX output. Thus the cat.

 

FWIW, I'm still waiting for evidence that these engines run lean of stoich. 3-way cats do their best work when you dither the mixture slightly back and forth across stoich, so it doesn't make sense to run in an honest-to-God lean condition. If, however, by "lean" you mean "leaner than the bikes of yore, which ran well rich of stoich," then I guess we're in agreement.

[RFW]

And don't forget the dangers of the Dihydrogen Monoxide that is produced when the cat oxidizes unburnt hydrocarbons.

http://www.dhmo.org/

 

The danger of producing water?

 

Ooops. I've been discovered! Still, check out the wensite for the terrors of this stuff!

 

Bob.

[No_Twilight]

Ok. I'm a little more convinced. I thought EGR was a thing of the past. They still use it?

 

As for the 300ZXTT, that was years ago back in Atlanta and I don't remember what pollutants Georgia was testing for then. I also did quite a few upgrades to my 300zxtt, chip, boost upgrade, etc but I never took the cats off. I remember comparing the before and after smog tests (in CA) and concluding that if you want to make lots of hp, you need to burn all the gas, apparently cleanly. Thanks for the reply.

 

Jerry

[smiller]

I thought EGR was a thing of the past. They still use it?

 

You betcha. However current EGR systems are much more advanced than they were in the old days when flow was controlled by ported vacuum and a single orifice in the EGR valve, nowadays the recirculated exhaust gas flow is precisely measured and controlled by the ECU (resulting in both better control of combustion temps and less negative side-effects than the older systems)... but they are definitely still around and are quite common.

[TracyPrier]

For my answer to your question check out my web site:

 

http://www.myr1100rtp.netfirms.com/catelement.htm

 

Short answer: it made a BIG difference to how the bike ran AND got better fuel economy.

 

Do you gey any more horsepower removing the CAT and maybe some hypo mufflers- maybe a pair of them? just curious.

[steve.foote]

Hi Tracy,

 

Nice write up on your website. Not discounting your perceptions of performance gains after the cat-erectomy, but do you have some before and after dyno results? Something recorded in a controlled environment with static benchmarks to guage by?

[LJR]

Tracy, I don't see any reference to the post-cat sound level. Did it make much of a difference? I always thought the cat did a lot of muffling.

[TracyPrier]

Only marginal difference in sound.

 

 

Tracy, I don't see any reference to the post-cat sound level. Did it make much of a difference? I always thought the cat did a lot of muffling.

[TracyPrier]

Thanks

 

No dyno results as they are expensive to get time on down here in New Zealand.

 

Hi Tracy,

 

Nice write up on your website. Not discounting your perceptions of performance gains after the cat-erectomy, but do you have some before and after dyno results? Something recorded in a controlled environment with static benchmarks to guage by?

[smiller]

I'm not discounting your perceptions of performance gains after the cat-erectomy either... but since such a claim goes against logic it kind of needs some sort of objective backup.

[big-t]

I thought EGR was a thing of the past. They still use it?

 

You betcha. However current EGR systems are much more advanced than they were in the old days when flow was controlled by ported vacuum and a single orifice in the EGR valve, nowadays the recirculated exhaust gas flow is precisely measured and controlled by the ECU (resulting in both better control of combustion temps and less negative side-effects than the older systems)... but they are definitely still around and are quite common.

 

 

 

...And they still carbon up and stick just like the old ones.

 

 

The good news is...they are getting replaced by varible cam timing which allows the valves to close quicker at higher RPMs and minimize the unburnt fuel that gets mixed in with the outgoing exhaust.

 

 

 

Already out there on a number of vehicles

[chrisstroh]

Thanks alot Tracey! O ne question, did gutting the CAT make it ANY louder. I could go for just a bit louder.

Chris

[TracyPrier]

Hi Chris

 

No not really any louder.

 

Thanks alot Tracey! O ne question, did gutting the CAT make it ANY louder. I could go for just a bit louder.

Chris

[TracyPrier]

Hi Smiller

 

Well the increase in fuel economy certainly isn't a perception thing. I took the trouble of recording pre and post economy on a tank full doing the same commute using the same type of fuel.

 

Also, the engine is comfotable now to run in 5th gear at 3000rpm without any feeling of it labouring or "lugging".

 

Plus the significant surging the bike used to suffer from almost comletely disappeared with the CAT removal (and that was with the yellow CCP still in) and with the CCP removal is now gone.

 

Also, I never claimed that there was any increase in horsepower, only the effects mentioned on the web site.

 

Plus you say this goes against logic, which logic would this be then?

 

I don't see how removing a restriction in the exhaust is NOT meant to have some positive effect. I liken it to trying to run a marathon with a rolled up sock in your mouth (ok that's the intake but you get the idea).

 

This experience is not just limited to this bike. All of my recent cars have been used Japanese imports (something that is popular here in New Zealand) and they all come with a CAT.

 

Down here you aren't required to use a CAT and so I have replaced the CAT units in these cars with a straight-through glass-pak muffler. The results have been the same as noted on the bike; better performance and WAY better fuel economy.

 

Lastly, both the Australian and New Zealand-market BMW's come without any CAT element in the exhaust, they also do not use a CCP but use a CP pot for idle mixture adjustment. The first thing that was suggested to me by other BMW owners here was to bin the CAT as it reduces performance... among those advocating this was the GM of a local BMW dealership.

 

Cheers

Tracy

 

I'm not discounting your perceptions of performance gains after the cat-erectomy either... but since such a claim goes against logic it kind of needs some sort of objective backup.

[JamesW]

Hi Tracy, I wonder how a Dremil with 1" aluminum oxide cut off wheels (disks) would work for cutting open the cat chamber? I am about ready to eliminate this heat source, I think.

[TracyPrier]

Should work fine. Actually I used a cut off wheel on my angle grinder to do the bulk of the cut but had to resort to the little air grinder to get right into the corners anyway. The easiest way to actually remove the cat element was to cut it out with a gas torch (which the muffler shop guy did before MIG welding the outer cover back in place.

 

Cheers

Tracy

 

 

Hi Tracy, I wonder how a Dremil with 1" aluminum oxide cut off wheels (disks) would work for cutting open the cat chamber? I am about ready to eliminate this heat source, I think.

[JamesW]

I chickened out and took the muffler/cat to a local machine shop and told them to do the whole job. They said OK and it will cost about two hours at $52/hour. I printed a picture of the the procedure from your WEB site so thanks Tracy.

[TracyPrier]

Glad to be of help. Don't forget to remove the fuse to reset the motronic unit once it's back on.

 

I chickened out and took the muffler/cat to a local machine shop and told them to do the whole job. They said OK and it will cost about two hours at $52/hour. I printed a picture of the the procedure from your WEB site so thanks Tracy.

[chrisstroh]

James, I'd like to hear feedback on how your bike runs when you're done.

Thx!

Chris

[smiller]

I don't see how removing a restriction in the exhaust is NOT meant to have some positive effect.

 

If there is a true restriction (meaning something unusual and not intended by the designers) then removing it would indeed have a positive effect. But a normal cat should not present any kind of significant restriction nor cause any reduction in the output in an unmodified engine.

 

Perhaps your cat was plugged or somehow faulty? In that case I could certainly see how you would experience an improvement after removing it. If it was in good condition then the improvement you describe would not be, well... logical. That's all I meant, and no disrespect intended.

[steve.foote]

Seth, that's why I was asking about dyno results. These kinds of things are measureable and it would be interesting to see if there is any documentable advantage to removing the cat.

 

Without some kind of measurement against a fixed baseline, it remains a matter of perception.

[chrisstroh]

Tracey,

Did you mention what is actually inside the CAT to cause back pressure? Was yours free from any debris?

 

Chris

[JamesW]

My reason for removing the cat is to eliminate the high heat produced by the cat in very close proximity to the underside of the transmission. The air flow on an RT in the small space between the cat and the transmission is where I have an issue. I noticed that the transmission noise increased greatly from when the bike was cold to what it was after several hours of operation. I noted a huge improvement when I changed to Castrol synthetic 75/140 gear lube for the transmission. Synthetic gear lubricants are known to perform better in high heat environments. I don't look for or expect any performance improvement. My machine does not surge and gets great fuel economy and it has all the performance I could ask for or need. I just don't like the extreme heat thing. I can ride my R100RT for several hours and the trans lubricant is pretty warm but not scolding like the lubricant in my oilhead. I will post my findings after cat removal which should be accomplished between now and early next week.

[ShovelStrokeEd]

James,

I think you might be exaggerating the heat thing. A couple of things are at play here.

 

First off, if the bike is running properly, the cat won't get all that hot. Internal temperatures will be hot but the case, which is made of stainless is a poor conductor of heat.

Second, the air gap makes a quite effective heat barrier as well, in particular when the bike is kept moving. It takes very little air flow to conduct the heat away from the transmission, leaving only radiant heating.

Third, most of the heat you are feeling in the transmission is generated within the transmission itself by friction of gear faces and shear of the oil.

 

In short, I doubt you will see even a 10 degree C drop in transmission oil temperature for your efforts. Why not pick up a spare transmission drain plug and have a machine shop install a small thermometer well within. You can then monitor the transmission oil temperature and compare it with the oil manufacturer's recommendations. Scalding to you is barely warm to gear oil which doesn't break down until temperatures are much, much higher. Given that most folks can barely tolerate 140 deg F and the oil won't start breaking down until well above 280 deg F. That is sizzle temperature, where water will flash into steam within a second or so. Doubtful you are coming close there.

[JamesW]

Ed, you could be right. I thought it would be kind of interesting to somehow measure the actual temperature but then I thought what the hey, I'll just get rid of the cat. I also thought about what I would do if my bike started running poorly because of a plugged up cat. Might be hard to troubleshoot and besides, I just don't like the idea of a cat on a motorcycle. Cat converters are not restrictive so the only performance increase should be between my ears. Now watch the splines go "T" up and the dealer says oops, no warranty for you because you gutted your cat. As if the beast should have anything to do with it.

[RFW]

James,

I think you might be exaggerating the heat thing. A couple of things are at play here.

 

First off, if the bike is running properly, the cat won't get all that hot. Internal temperatures will be hot but the case, which is made of stainless is a poor conductor of heat.

Just a niggling little point.

 

It is definitely true that the cat will not get excessively hot if the bike is runing properly. The job of the oxygen sensor is to feedback O2 conetent in the exhaust so the engine management system adjusts the mixture so there is very little HC or CO in the exhaust. If this is done correctly (and it MUST in order for system to work properly) then there is almost nothing in the exhaust for the cat to "burn" and generate heat with.

 

That means that the cat simply gets only a bit hotter than the exhaust going into it.

 

Now the niggling part. The semi-stainless 400-series "stainless" steel used to make cats indeed is a poor heat conductor. But given that the heat only has to go through a millimeter of metal thickness, and that the surface area available for heat transfer is very large (compared to the cat's shell's thickness), the outside of the cat's shell will not be at a significantly lower temperature than the inside surface.

 

But I completely agree that the cat will not significantly heat the transmission in normal operation of the bike. Air is a lousy heat conductor!

 

Bob.

[Pilgrim]

And don't forget the dangers of the Dihydrogen Monoxide that is produced when the cat oxidizes unburnt hydrocarbons.

http://www.dhmo.org/

 

The danger of producing water?

 

Ooops. I've been discovered! Still, check out the wensite for the terrors of this stuff!

 

Bob.

 

The danger comes in that, if enough vehicles with cats drive enough miles generating moisture, and exceed the atmosphere's capacity for absorption of water vapor, it will bring about increased precipitation. Since that water will no longer be stored as ice in glaciers(global warming, y'know), it will eventually run off to the ocean. Sea levels will rise, inundating places like L.A. San Francisco, Miami, and New York. To say nothing of Tokyo, etc.

 

Hmmmm . . . where's the downside? I think I'll go for a drive.

 

Pilgrim

[smiller]

Sea levels will rise, inundating places like L.A. San Francisco, Miami, and New York. To say nothing of Tokyo, etc.

 

And I guess that would also include Seattle?

[TracyPrier]

Hi Smiller

 

No the CAT wasn't plugged up. Have to disagree about CAT's not being restrictive too. (chk out the attached pic of the element after removal)

 

The very design of a CAT places material in the path of the exhaust gases. BMW only puts CAT's in the exhausts of bikes whose government requires them by law. It was not the engineers at BMW who decided CAT's should be there but some U.S. government bureaucrat.

 

Same thing with running a CCP. These just activate alternate fuel maps that comply with various countries emission restrictions. I have read from some on this and other boards (who mostly have people from the USA on them) that removing the CCP puts the motronic unit into some kind of "limp home" mode which is utter rubbish.

 

What it does is take the bike back to the original fuel map that the clever chaps at BMW designed to make the bike run at it's best... as I've mentioned previously the New Zealand and Australian (and I think the UK also, someone correct me if I'm wrong) market bikes have neither a CAT in the exhaust OR a CCP plug.

 

I would also point to the instant 25 mile increase in tank range after removing the CAT (and doing nothing else to the bike) which proves that the CAT element was causing the engine to work harder, using more fuel to push the exhaust gases past the CAT, remove the CAT and it needs less effort to do the same amount of work, hence the lower fuel consumption.

 

Which to be honest is one of the main reasons I think the whole CAT converter thing is a nonsense anyway. How can it possibly be better to use more fuel to travel a given distance?? surely with the world about to run out of fossil fuel (after which we'll be renaming this board bmwhorseandcarttouring.com and debating the big issues like which feed produces less gas and more mileage) using less of the stuff has got to be better...surely???

 

BTW, no offense taken at all, I was just keen to explain that I did take measures to gauge what difference removing the CAT made.... must make friends with someone who owns a dyno!

 

If the US gummint wants to lower car emissions it should worry less about CAT converters and worry more about the number of people driving 'round in Hummers, Escalades and those other assorted road-going battleships. 7 litre engines!!!! bloody ridiculous when you consider most of the time there's only one person in the darn thing.

 

Cheers

Tracy

 

 

 

Also point out that racing bikes (including Beemers) don't run a CAT for one simple reason, they restrict performance.

 

 

 

 

I don't see how removing a restriction in the exhaust is NOT meant to have some positive effect.

 

If there is a true restriction (meaning something unusual and not intended by the designers) then removing it would indeed have a positive effect. But a normal cat should not present any kind of significant restriction nor cause any reduction in the output in an unmodified engine.

 

Perhaps your cat was plugged or somehow faulty? In that case I could certainly see how you would experience an improvement after removing it. If it was in good condition then the improvement you describe would not be, well... logical. That's all I meant, and no disrespect intended.

[Boffin]

I know that cats are not a legal requirement for motorcycles in the UK but BMW have been fitting them here for years.

 

Race bikes don't have then because they are heavy.

 

total cross-sectional area of the gaps is what determines restriction, though turbulence will also be a factor. If the cross sectional area is sufficiently greater than the pipes diameter it will not restrict flow.

 

The weight though will make a difference.

 

Cya, Andy

[JamesW]

One more dumb question. How does a motor that consumes oil as in long break in periods affect a catalytic converter? My RT consumed oil at a pretty good rate until about 8K miles and then stopped almost completely. Oh, and funny thing about stainless and heat transfer, I can't help but notice how many pots and pans in our kitchen have stainless steel bottoms. On the other hand BMW engineering saw fit to install stainless steel exhaust valve seats in the airheads from '80 until '84 which resulted in many machines experiencing severe valve recession problems because of the poor heat transfer properties of stainless steel. Now, I am positive that the heat transfer properties of stainless were well documented before 1980. So much for sound engineering. I am most curious to take a look at the cat after the beast has been properly removed. I am even more curious to take big blue out for a run after catectomy and really find out if there is any noticable performance improvement. I really think there won't be but then again

 

[ShovelStrokeEd]

James,

This is not aimed specifically at you but more a general observation.

 

Removal of the cat and the cat code plug without installing a CO pot to properly trim the idle mixture might just result in a decrease in fuel consumption as the base map is a bit on the lean side in part throttle operation. The feedback loop of the O2 sensor/Motronic reaction actually serves to richen the mixture about every other pulse to keep the cat "lit" and the mixture very near stochiometry. Removal of same can result in slightly lean mixture which, within limits, will consume less fuel at a slight penalty in performance even though throttle response might even feel a bit crisper. Sounds contradictory but I spend hundreds of hours of dyno time tuning open loop EFI systems and found this to be the case at small throttle openings.

 

Now, specific to your post, the valve recession was not caused by the heat transfer properties of the stainless but the lack of lubricating and insulating lead deposits on the seats and valve faces. It is the valves that are made of what we typically call stainless steel, the orginal seats were plain stainless as well and later were changed to an Martensitic stainless to better handle the wear. It has much more to do with the hardness of the seats and their ability to retain that hardness at elevated temperatures. The exhaust vavles remain Austenitic stainless.

[RFW]

One more dumb question. How does a motor that consumes oil as in long break in periods affect a catalytic converter? My RT consumed oil at a pretty good rate until about 8K miles and then stopped almost completely. Oh, and funny thing about stainless and heat transfer, I can't help but notice how many pots and pans in our kitchen have stainless steel bottoms. On the other hand BMW engineering saw fit to install stainless steel exhaust valve seats in the airheads from '80 until '84 which resulted in many machines experiencing severe valve recession problems because of the poor heat transfer properties of stainless steel. Now, I am positive that the heat transfer properties of stainless were well documented before 1980. So much for sound engineering. I am most curious to take a look at the cat after the beast has been properly removed. I am even more curious to take big blue out for a run after catectomy and really find out if there is any noticable performance improvement. I really think there won't be but then again

 

In no particular order....

 

The stainless exhaust seats had a problem of erosion, as a result of the emergence of leadfree gas here in North America at that time. German "Bleifrei" (Lead free) gas came a few years later. The problem was hardness, not thermal conductivity. In fact, many of the hardened alloys now used have similarly lousy thermal conductivity.

 

Pots and pans. Thermal conductivity THROUGH the thin bottom of a pot is not an important issue. Because the area of the bottom of the pot is very large, the thermal density (so to speak), that is the number of watts per square centimeter of pot area, is relatively low. Thermal resistance does not stop heat flow. It simply forces the bottom of the pot to get to a higher temperature, to drive the heat through to the other side.

 

Compare an aluminum and a stainless pot, both of which hold boiling water. The inside temperature of the bottom is the same for both, namely 100°C. Because the thermal resistance of the stainless pot is higher, the temperature on the bottom of the stainless pot will automatically rise to a correspondingly higher value than the Alu pot in order to drive the much the same total amount of heat into the water.

 

Oil and cats. It is the ZDDP (zinc dialkyl dithioposphate) extreme pressure additive in the oil (in particular, the phosphorous in the ZDDP) that can poison the cat over time. An engine that is an oil burner, can therefore cause cat damage onver an extended period. This is why car oils have, seen a constant reduction in their ZDDP content over the past 10 to 15 years. Many "bike" and most "diesel" oils still have a somewhat higher ZDDP content. Still, I suspect that the amount of oil passed through the cat during the breakin process is not enough to cause problems.

 

Bob.