AFAIK the o2 sensors are only used in very low speed running. probably because it works better.
a similar car engine would have a MAF sensor on the inlet, but these bikes don't.
Just a thought re de-catting headers
- Thread starter The Prospector
- Start date
AFAIK the o2 sensors are only used in very low speed running. probably because it works better.
a similar car engine would have a MAF sensor on the inlet, but these bikes don't.
Bendy toy
Registered user
@ Alan R could be right so I'll do some digging. But check out the metal colour around the catalyst - its blue like the header tops. That's the heat it generates in burning off (oxidising) the excess HCs and CO.
Catalysts run at 500 degs C. An exhaust pipe should be be hotter after the cat than before it. Heat can't be used to drive the vehicle. On a spark ignition engine, the stoichiometric (Lambda) point is about 10% richer than the lean burn point. Running an engine with retarded spark timing will create a hotter exhaust gas. But the downside is less energy going to the pistons. Lean burn on the other hand can also produce hot gasses. Take it too far and the valves can fail. One reason for cars going to 16V engines was to handle the hot exhaust gasses. Many flowed gasses no better than their 8V counterparts.
Newer cats are lighter weight so need less excess fuel to keep warm. but they all use more fuel than they engine would without the cat. They need that energy to burn off the nasty stuff.
Here is the guff
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Case_Studies/Catalytic_Converters
http://www.krioma.net/articles/Catalytic Converter/Catalytic Converter.htm
This doesnt discuss alternatives to catalysed exhausts
http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt039e/qr39pdf/STTqr3902.pdf
A bit historic but more stuff on cats
http://en.wikipedia.org/wiki/Catalytic_converter
This explains (amongst other stuff how engines are calibrated to run rich to deal with Nox emissions. it is a reduction process that absorbs heat.
http://www.rsc.org/Education/EiC/issues/2011June/TheEvolutionOfCatalyticConverters.asp
If there is not enough fuel from the upstream exhaust the engine has to run rich to give enough fuel to keep the catalyst hot. A lean burn engine would have better mpg, but could be more dirty as it's catalyst might not be hot enough. Too much unburnt fuel can burn out the catalyst as it burns off the excess.
The modern ECU will run the engine lean when it can, but often it will be running rich just to keep the catalyst happy. Low power levels and tickover are typical. Also catalysts are rarely built for the engine. they will be off the shelf packages. That said the R1200 has a special system so can we assume its been optimized for the engine?
Lean or rich burn?
Has anyone seen a grey spark plug tip (lean burn) on a modern engine? They are usually dark grey at best. Compare a 1990's motorbike spark plug with a modern cat engine spark plug. The older engine's plug is light grey - less unburnt carbon in the cylinder.
Wikipedia says:
Removing a modern catalytic converter in new condition will not increase vehicle performance without retuning,[21] but their removal or "gutting" continues.
Correct of course, but they do say "without retuning". Do that and the emissions will improve considerably. Cats do a complex job and are far from perfect.
It also says that in 1999 BMW had an electrically heated catalyst ("E-CAT") to get the core up to running temperature more quickly. Presumably it only worked from cold. The dirty exhaust stream would do the job once up to temperature.
Nobody seem to discuss the option of no catalyst at all. Maybe, the industry is so big there is no head of steam to research that option.
Catalysts run at 500 degs C. An exhaust pipe should be be hotter after the cat than before it. Heat can't be used to drive the vehicle. On a spark ignition engine, the stoichiometric (Lambda) point is about 10% richer than the lean burn point. Running an engine with retarded spark timing will create a hotter exhaust gas. But the downside is less energy going to the pistons. Lean burn on the other hand can also produce hot gasses. Take it too far and the valves can fail. One reason for cars going to 16V engines was to handle the hot exhaust gasses. Many flowed gasses no better than their 8V counterparts.
Newer cats are lighter weight so need less excess fuel to keep warm. but they all use more fuel than they engine would without the cat. They need that energy to burn off the nasty stuff.
Here is the guff
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Case_Studies/Catalytic_Converters
http://www.krioma.net/articles/Catalytic Converter/Catalytic Converter.htm
This doesnt discuss alternatives to catalysed exhausts
http://www.nistep.go.jp/achiev/ftx/eng/stfc/stt039e/qr39pdf/STTqr3902.pdf
A bit historic but more stuff on cats
http://en.wikipedia.org/wiki/Catalytic_converter
This explains (amongst other stuff how engines are calibrated to run rich to deal with Nox emissions. it is a reduction process that absorbs heat.
http://www.rsc.org/Education/EiC/issues/2011June/TheEvolutionOfCatalyticConverters.asp
If there is not enough fuel from the upstream exhaust the engine has to run rich to give enough fuel to keep the catalyst hot. A lean burn engine would have better mpg, but could be more dirty as it's catalyst might not be hot enough. Too much unburnt fuel can burn out the catalyst as it burns off the excess.
The modern ECU will run the engine lean when it can, but often it will be running rich just to keep the catalyst happy. Low power levels and tickover are typical. Also catalysts are rarely built for the engine. they will be off the shelf packages. That said the R1200 has a special system so can we assume its been optimized for the engine?
Lean or rich burn?
Has anyone seen a grey spark plug tip (lean burn) on a modern engine? They are usually dark grey at best. Compare a 1990's motorbike spark plug with a modern cat engine spark plug. The older engine's plug is light grey - less unburnt carbon in the cylinder.
Wikipedia says:
Removing a modern catalytic converter in new condition will not increase vehicle performance without retuning,[21] but their removal or "gutting" continues.
Correct of course, but they do say "without retuning". Do that and the emissions will improve considerably. Cats do a complex job and are far from perfect.
It also says that in 1999 BMW had an electrically heated catalyst ("E-CAT") to get the core up to running temperature more quickly. Presumably it only worked from cold. The dirty exhaust stream would do the job once up to temperature.
Nobody seem to discuss the option of no catalyst at all. Maybe, the industry is so big there is no head of steam to research that option.
The Lambda or O2 sensor on bikes like the R12 series is only used some of the time, at low engine loads and idle, in closed-loop mode to control the mixture. Most of the time the engine runs in open-loop mode and the 02 sensor plays no part. In open-loop mode the ECU relies on a "map" that tells it how much air the engine flows at a given rpm/throttle opening. The ECU also has other maps for A/F ratio, ignition timing etc.
The Prospector
Registered user
So at the end of the day with a standard silencer and no re-map will removing the cat make it run too lean or will it improve the mid range as some post.
Here's the real world advice and it's no problem removing the CAT and your engine will run fine. Running lean will only cause a problem if you have a straight through system and K&N filter. You really need it re-mapped or have a power commander if you go the whole hog.
You will get a slight increase in mid range and your engine will rev better. It's not a huge amount but you will notice it and it's well worth doing. You will also notice more popping on overrun which is no problem.
Big Lee
Registered user
I had the remus headers and titanium can on my 12GS and after I replaced them with the oe before selling the bike I noticed no difference at all. TBH the money can be spent elsewhere for better value 
Just imo
Just imo
I felt that the combination of headers, akrapovic & accelerator module made quite a difference to my 1200
Bendy toy
Registered user
I picked up my pipes used. I personally would not pay the full price for new but then I do have a good low cost pipe specialist nearby.
Hilltop told me the headers (I have Remus) will make a difference if its being remapped and even more with a good quality can.
He said the engine is fine with original headers and free flow can or original can with free flow headers. He said changing both should be ok wioth posh petrol. But if I was to do lots of motorway (which I do) the exhaust valves would be at risk. He said dont even think about using cheap petrol.
I was surprised to hear from him that the boxer doesn't use the O2 sensor and cat like most engines. But to be fair the Remus headers I bought were seriously pale grey inside. That engine had been running far weaker than a stoichiometric mixture.
Right now I have the standard can with (used) Remus headers. My plan is to fit a used Acroprovic Ti system with stacked twin cans. I like the look, but it has to wait for remapping.
Hilltop told me the headers (I have Remus) will make a difference if its being remapped and even more with a good quality can.
He said the engine is fine with original headers and free flow can or original can with free flow headers. He said changing both should be ok wioth posh petrol. But if I was to do lots of motorway (which I do) the exhaust valves would be at risk. He said dont even think about using cheap petrol.
I was surprised to hear from him that the boxer doesn't use the O2 sensor and cat like most engines. But to be fair the Remus headers I bought were seriously pale grey inside. That engine had been running far weaker than a stoichiometric mixture.
Right now I have the standard can with (used) Remus headers. My plan is to fit a used Acroprovic Ti system with stacked twin cans. I like the look, but it has to wait for remapping.
88,000 miles with de catted headers and no issues. The engine needs a bit of back pressure to make it run well with the standard set up in my experience.
It really is no problem with de catted headers on their own but problems come when you want straight through pipes, K&N etc.
I've been running a straight through system and a PC3 for a while and it's a fantastic set up. My bike has never run so well
I took the tight mans solution, a de-catted header with a £30 accelerator module to richen it up a shade, it ran far better and the module did not affect MPG.
A common misconception is lean = fuel efficient, but often the engine runs like crap when lean so you need to throw more lean mixture in to get the same power out, so a richer motor (or more to the point optimal) will normally be better on MPG.
I have yet to remap a bike (done a few) and not end up with better MPG.
All this modern stuff with Cats and closed loop areas is to get through emmisions, the bike ends up running really crap in those areas the tests are conducted at, which means owners either modify their bikes, or ride around the problem.
On most sportsbikes owners will be way out of the closed loop Euro-test area and caning the crap out of their GSX-R throwing all sorts of shite into the atmosphere to avoid the flat spot.
Same goes for high power cars, and both cars and bikes are now having exhaust flaps fitted, unlike the grunt boosting EXUP valves of bygone days these are to keep the vehicle running silently / limit power output so it passes noise and emmissions regs, before opening up to give you your 200BHP bike / 500 BHP car.
The rules don't make sense, how can a low performance bike like the GS (Or Tenere / Stelvio etc) be affected by emmisions guff, when a 200BHP ZZR1400 passes - and how the f*** can a 500BHP+ car get a certificate FFS!
If the rules where based on real running of the engines and how far they go on x fuel and how much crap they spit out in x miles we would have fantastic 100BHP bikes and 200BHP cars that fuel beautifully through the range and are good for the environment, and probably see then end of 200BHP bikes and 500BHP+ cars, and I doubt on a Sunday blast, or foreign tour any of us would actually be any worse off.
In the meantime I need to get my f***** ECU remapped to get some bloody grunt at 40MPH in 3rd / 4th - of course I could drop into second and rev the motor senseless - which must be far better for the environment
A common misconception is lean = fuel efficient, but often the engine runs like crap when lean so you need to throw more lean mixture in to get the same power out, so a richer motor (or more to the point optimal) will normally be better on MPG.
I have yet to remap a bike (done a few) and not end up with better MPG.
All this modern stuff with Cats and closed loop areas is to get through emmisions, the bike ends up running really crap in those areas the tests are conducted at, which means owners either modify their bikes, or ride around the problem.
On most sportsbikes owners will be way out of the closed loop Euro-test area and caning the crap out of their GSX-R throwing all sorts of shite into the atmosphere to avoid the flat spot.
Same goes for high power cars, and both cars and bikes are now having exhaust flaps fitted, unlike the grunt boosting EXUP valves of bygone days these are to keep the vehicle running silently / limit power output so it passes noise and emmissions regs, before opening up to give you your 200BHP bike / 500 BHP car.
The rules don't make sense, how can a low performance bike like the GS (Or Tenere / Stelvio etc) be affected by emmisions guff, when a 200BHP ZZR1400 passes - and how the f*** can a 500BHP+ car get a certificate FFS!
If the rules where based on real running of the engines and how far they go on x fuel and how much crap they spit out in x miles we would have fantastic 100BHP bikes and 200BHP cars that fuel beautifully through the range and are good for the environment, and probably see then end of 200BHP bikes and 500BHP+ cars, and I doubt on a Sunday blast, or foreign tour any of us would actually be any worse off.
In the meantime I need to get my f***** ECU remapped to get some bloody grunt at 40MPH in 3rd / 4th - of course I could drop into second and rev the motor senseless - which must be far better for the environment
Bendy toy
Registered user
@Rasher echos my attitude exactly. What the F are the industry regulators playing at? I read somewhere (but now cannot find it) that when an O2 sensor is fitted the manufacturer must also fit a catalyst. However they can fit a cat with no sensor. There is no technical reason for this just politics.
This might have (probably has) changed over time, but I have never ever seen an engine with an O2 sensor that does not have a catalyst.
The exhaust catalyst is a cheap and nasty solution to the pollution problem. Its only "essential" (as the various commentators say), because money has not been spent optimising the engine design.
Much fuss is made about HCs and CO both of which are toxic. However both are also quickly reacted by weather and sunlight into CO2. Only in relatively unusual areas like San Fransisco, Naples, etc, is smog a serious problem. (the South Asian cities are another special case).
The real nasty is NOx its very toxic and long lived. Its also a much greater greenhouse gas than CO2.
Exhaust catalysts will remove NOx but need fuel (rich running engine) to drive the reaction. A much better way is to design a low NOx engine. The VW TDI diesel used to have a big problem with NOx especially when running biodiesel - a naturally oxygenated fuel. A diesel cant run rich (usually) so there isnt enough fuel to keep the cat hot. Careful engine design cleaned it up but it wasnt cheap. Our obsession with 95RON unleaded or lower also contributes to NOx as it causes engines to knock. 97 RON or better would have made far more sense, unless you want to make money and raise tax from fuel volume sales.
2 strokes are also naturally low NOx and modern designs don't pump oil and smoke down the tail pipe and are very fuel efficient. Back in the late 1990s, Ford ran a fleet of DI 2-stroke Fiestas. They were cheap to make, performed well, fuel efficient and needed little maintenance. Engine wear and high oil consumption common with old style 2 strokes wasn't an issue. The suits chickened out and we are still stuck with 4 strokes. At least they keep the dealers busy doing oil and cam belt changes along with warranty claims.
Bombardier have recently fitted a 150bhp 800cc Rotax DI 2-stroke into their snowmobiles. It more than meets the latest USA EPA regulations and uses much less fuel that the 4 strokes used by competitor products.
Bombardier own Rotax, SkiDoo, Evinrude and KTM. When will we see that technology in a bike?. It's in the other two.
Such stuff shouldn't be about the engine strokes or catalysts etc it should be about what is best to get the job done. Bombardier seem to be able to work outside the box. Shame the others cant or won't (Yamaha also have a DI 2 stroke in petrol and diesel options but are sitting on it).
http://www.brp-powertrain.com/en/desktopdefault.aspx/tabid-235/374_read-355/
Its not new. Check the date on this!
http://www.yamaha-motor.co.jp/global/news/1999/03/23/super-diesel.html
Yamaha also have a petrol version. Maybe others can find a link to it.
This might have (probably has) changed over time, but I have never ever seen an engine with an O2 sensor that does not have a catalyst.
The exhaust catalyst is a cheap and nasty solution to the pollution problem. Its only "essential" (as the various commentators say), because money has not been spent optimising the engine design.
Much fuss is made about HCs and CO both of which are toxic. However both are also quickly reacted by weather and sunlight into CO2. Only in relatively unusual areas like San Fransisco, Naples, etc, is smog a serious problem. (the South Asian cities are another special case).
The real nasty is NOx its very toxic and long lived. Its also a much greater greenhouse gas than CO2.
Exhaust catalysts will remove NOx but need fuel (rich running engine) to drive the reaction. A much better way is to design a low NOx engine. The VW TDI diesel used to have a big problem with NOx especially when running biodiesel - a naturally oxygenated fuel. A diesel cant run rich (usually) so there isnt enough fuel to keep the cat hot. Careful engine design cleaned it up but it wasnt cheap. Our obsession with 95RON unleaded or lower also contributes to NOx as it causes engines to knock. 97 RON or better would have made far more sense, unless you want to make money and raise tax from fuel volume sales.
2 strokes are also naturally low NOx and modern designs don't pump oil and smoke down the tail pipe and are very fuel efficient. Back in the late 1990s, Ford ran a fleet of DI 2-stroke Fiestas. They were cheap to make, performed well, fuel efficient and needed little maintenance. Engine wear and high oil consumption common with old style 2 strokes wasn't an issue. The suits chickened out and we are still stuck with 4 strokes. At least they keep the dealers busy doing oil and cam belt changes along with warranty claims.
Bombardier have recently fitted a 150bhp 800cc Rotax DI 2-stroke into their snowmobiles. It more than meets the latest USA EPA regulations and uses much less fuel that the 4 strokes used by competitor products.
Bombardier own Rotax, SkiDoo, Evinrude and KTM. When will we see that technology in a bike?. It's in the other two.
Such stuff shouldn't be about the engine strokes or catalysts etc it should be about what is best to get the job done. Bombardier seem to be able to work outside the box. Shame the others cant or won't (Yamaha also have a DI 2 stroke in petrol and diesel options but are sitting on it).
http://www.brp-powertrain.com/en/desktopdefault.aspx/tabid-235/374_read-355/
Its not new. Check the date on this!
http://www.yamaha-motor.co.jp/global/news/1999/03/23/super-diesel.html
Yamaha also have a petrol version. Maybe others can find a link to it.
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