| Author | Message | ||
     Paintballtommy |
why is it that i hear everyone saying that buell developped this engine to be water cooled because of the epa and emmisions. air cooleds dont have a problem at all passing emmisions. where does this myth come from and how can we dispell it. | ||
| Barker |
Ask where they got that idea. IMHO, Ignorance, XB's pass EPA/EURO/CARB no problem. They just assume the "old harley engine" is not efficient or since they are still using air cooled that Buell is some how stuck on the 1950's technology or something like that. I think some just dont realize all of the great technology inside of our bikes. | ||
| Spatten1 |
Making emissions with an air cooled 100hp motorcycle engine is much different than making emissions with an air cooled 150hp engine. No one is pulling that off. Sound emissions are also easier with liquid cooled engines because the water jacket absorbe much of the engine noise. | ||
| Xl1200r |
BMW's 1200cc air-cooled boxer makes 127hp and passes emissions no problem. Noise emissions are not a real problem with bikes. The limits are so high it almost doesn't matter. And as far as emissions are concerend, HD engines have typically been among the best in the industry when in stock form. | ||
| Jaimec |
BMW's boxer doesn't have the same cooling problems the Harley style V-Twin has, either. BMW sticks the heads out in the airflow which is probably the best idea for an air cooled engine. The Harley design hides one cylinder completely out of the airflow making cooling an interesting challenge. The drawback to the BMW design, of course, is engine width. In order to get adequate cornering clearance with that design you have to design a really tall motorcycle. | ||
| Fullpower |
quote:"BMW's 1200cc air-cooled boxer makes 127hp and passes emissions no problem" The BMW uses 3 way catalyst. The Buell does not require such. The Buell XB12 is easily capable of 56 MPG on the Highway. Very fuel efficient, and intrinsically low emissions. | ||
| Spatten1 |
BMW's 1200cc air-cooled boxer makes 127hp and passes emissions no problem. And what is the power of their liquid cooled "sportbikes"? It is just a fact that you can squeeze more power per size and weight of the engine, and still make emissions (and be reliable) with a liquid cooled engine. It is consistent for Buell, Ducati, and BMW. That doesn't mean you can't prefer air cooled engines. | ||
| Djkaplan |
"air cooleds dont have a problem at all passing emmisions." Air-cooled bikes supposedly emit more pollutants during warm up because piston to wall clearances have to be larger than on water-cooled bikes. It's more than just pollutants in the exhaust, though. Aircooled engines are noisier than water-cooled engines. Seems like a lot of R&D went into the air boxes and mufflers on tubers and XBs... a lot of time and money spent on something most people modify or just replace on their bikes as soon as they get them. If the mechanical noise wasn't so bad on our bikes, a lot more noise could be emitted from the tail pipes right from the factory. | ||
| Blake |
"Air-cooled bikes supposedly emit more pollutants during warm up because piston to wall clearances have to be larger than on water-cooled bikes." If that rationale is true, then why wouldn't air-cooled engines emit more pollutants all the time? The issue is much more that cold engines require a richer air-fuel mixture. Catalytic converters don't work well until they are hot, real hot. I've been told by knowledgeable people in the field, and it sure makes sense from an engineering/physics point of view, that the combustion chambers in air-cooled engines typically warm up much more quickly than in liquid cooled engines, on account of they don't have all that water to also heat up; water requires a lot of heat energy to get it warmed up, which is why it makes such a good coolant; it can carry and transfer a lot of heat. So air-cooled engines warm up more quickly than liquid cooled engines. This in turn allows the air-fuel mixture to be brought to the normal ideal ratio more quickly and thus pollute less. The noise issue is another thing. An interesting one too. Currently the noise regulations are so rigorous that tire noise is by far the most prevalent noise pollution as vehicles drive by on any street let alone highway. Even at just 25-35 mph, almost all I hear when automobiles drive past on our residential street is tire noise. It's worse for a concrete surface than for asphalt, a LOT worse. I thus have a hard time imagining that noise regulations are likely to be tightened any further on automobiles. I doubt they will be on road legal motorcycles either. Case in point, right now sitting in my office, the air-conditioner, ceiling fan, and computer running, the most prevalent noise I hear is the lawn mower that is running outside about 100 yards away. Line trimmers, edgers, blowers--yeah, even the electric ones--chain saws and all manner of powered lawn and garden equipment are by far the most heineous emitters of noise pollution in our society today. I'm not opposed to the EPA clamping down on that kind of noise. It makes sense. It can be irritating. How tough can it be to put an effective muffler on a machine that pretty much runs at a constant speed or in a very narrow speed range? But putting politics and enviro-activism issues aside, there are some relatively simple techniques for addressing the issue of excessive (according to the gubment) mechanical noise emissions from air-cooled engines, techniques that have yet to be employed. Automobile manufacturers use the same techniques to reduce the amount of road/street noise that penetrates the passenger compartment. The aircraft industry has used one technique, dating back at least to the 1970's to protect structure from severe acoustic environments, where the noise from a jet engine can actually cause metal structures to resonate and fail. What is this technique? It's a way to prevent metalic enclosures/panels/parts from resonating audible frequencies and instead actually attenuating/diminishing audible acoustic emissions. If you have a tuning fork, or triangle dinner bell, or wind chime, or any such metalic form that resonates audibly, and you wanted to prevent that resonance while maintaining its structural integrity, and you want to do so without radically altering its geometric form, then what could you do? What could you do to prevent a metalic structure from resonating and/or transmitting undesirable acoustic frequencies? What could you do to say a primary drive cover, the gearcase cover or even the cooling fins on the cylinders themselves? If you recall the old Lexus commercial--I think it was Lexus--you probably have a good idea. I dig it; this is fun stuff to talk about.  (Message edited by blake on July 12, 2007) | ||
| Nicozzzz |
BMW use sohortstroke engine .. and rev higher this permit power .. whit long stroke of xb you are close to the macanical limit of the engine .. pistons are at 24meter /second in linear speed if i'm not wrong for euro 4 i think from 2008 no new bike can be selled euro 2 ( now on buell you pay ab 15% more of annual tax more than same power other euro 3 models ) if you put 2 lambda sensor and double catalitic system to get euro 4 probably the 82 rw hp became 72 rw hp or less . every people desire it or not ? like a 600 monster ... (Message edited by nicozzzz on July 12, 2007) | ||
| Blake |
Paintball, I sure appreciate this thread you've started. The issue seems to pop up at least every couple of months or so. You are right, it is a myth. The only source I know of involves ignorance. Someone, somewhere thought it made sense and started propagating the idea, then since it sounds plausible, folks take it on faith and propagate it further. The bigger factor in an engine configuration is bore to stroke ration and operating speed. Longer stroke slower revving engines can be more efficient. How many high efficiency automobile engines do you know that have wildly oversquare bore/stroke ratios or a rev limit above 11,000 rpm? Besides being a pain to drive on the street such racing inspired engines just don't provide for optimal efficiency (thorough combustion) at lower speeds. Engines designed to operate optimally at stratospheric speeds have trouble getting a clean burn at more sedate speeds on account of they have valve actuation pofiles that allow unburned fuel to escape out of the exhaust. The reason we don't see super high HP in air-cooled motorcycles is partly due to the noise issue, but it also has very much to do with a four cylinder motorcycle engine being much more challenging to air-cool while maintaining a compact form. How did BMW get so much more power from their venerable air-cooled boxer engine? Could they get more with a more over-square configuration and a higher rev limit? I'm still hoping to see a Buell turbocharged model come out some day. A couple of small state of the art turbochargers, one on each header-pipe, feeding a pressurized airbox. Nothing radical, just an extra 20% peak HP or so. Automatic boost limiting. The folks living at high altitude would surely dig it; they could enjoy the same arm-stretching performance as us lowlanders. | ||
| Spatten1 |
I seem to remember that in the old days Wiseco specs for air cooled engines had a smaller gap than liquid cooled. The reason being that as the gap increased with heat, the air cooled engine would grow more than the liquid cooled engine. This assumes that the cylinder ID expands more than the piston OD with heat. Am I remembering this backwards? | ||
| Reepicheep |
Blake, why turbo instead of supercharging? I could never figure that out. It must be the right decision, because turbo cars and planes are a dime a dozen, and supercharged versions are very rare. I just never understood why... seems like it would be a TON easier to engineer an effective super charger then putting a turbine in an exhaust header and spinning the stupid thing at a bazillion RPM... | ||
| Spatten1 |
Common wisdom is that superchargers are parasitic and turbochargers are not. In the old days V-Twins at the Harley drags were usually supercharged and the inlines were turboed. I was told, anecdotely, that the supercharger worked better for Big V-twins because turbos did not work so well with the exhaust pulses. However, in the last decade I've seem many more turboed twins. I'm curious how that evolution came about. | ||
| Ceejay |
supercharging is parasitic, turbo is not. plus most of todays autos are already trying to figure out ways to burn unspent fuel, why not use the already heated gas which moves faster to turn a turbine to push more air to creat more fill... intercoolers are even more interesting I'm guessing as I haven't read anything. | ||
| Cheesebeast |
I have been mystified by why my Buell is so much more fuel efficient than a friend's 600cc machine. I get a good 20mpg more than he does. Does the current (and future) EPA/CARB standard take mileage into account, or are they tied strictly to emissions? If, for instance, my Buell goes 50% farther per gallon consumed and it does so with 25% higher emissions than a 600cc machine, so what? Less fuel consumed = less emissions in the end, does it not? | ||
| Spatten1 |
The 600 is optimized to run over 10,000 rpm. With that much overlap it will not be efficient at low rpms in cruise mode. Without variable valve technology it is always a compromise. | ||
| Ceejay |
spatten you and I must have posted at the same time great minds thinking alike I suppose.... how that came about... better manufacturing, closer tolerances, better bearings, etc... Cheese-I always thought that to be a problem too. When I lived in Alb., NM they would do emission testing while sitting of course, when most engines run thier worst. thus never taking into account lbs emitted/mile driven. Of course it would be pretty tough for a stand alone shop test cars while they were moving | ||
| Cheesebeast |
So are the 600cc machines tuned for emissions reasons, not fuel economy? Why isn't fuel economy (or hours per gallon) the top consideration, as opposed to emissions? If you consume a gallon of fuel, doesn't it produce X amount of C02 and X amount of C0 and X amount of NO(?), etc no matter what kind of an engine it is consumed in? I see a lot of bikes are fitted with catalytic converters. Is the catalytic converter installed to remedy inefficient combustion? Can anyone recommend a book that I can use to slap the ignorance out of my head with? It should be at least 2" thick. I got a powerful case of the "I don't understands." | ||
| Hootowl |
Stroke has a lot to do with efficiency. Boyles Law. Internal combustion engines are only something like 20% efficient. Most of the energy is lost to heat. A longer stroke extracts more heat energy from a given amount of fuel. So the short stroke 600 is simply less efficient than the long stroke 1200. I'm sure there's more too it than that, but it is a factor. | ||
| Spatten1 |
So are the 600cc machines tuned for emissions reasons, not fuel economy? Actually, they are tuned for max power, which happens at high rpms. Fuel economy is not a consideration. The problem is that with high rpm you need a lot of valve overlap. At low rpm a lot of unburned fuel (HC) and partially burned fuel (CO) is emitted due to the overlap. The Catalyst burns that unburned fuel and partially burned fuel (HC and CO) into CO2 and H2O. This is a simplification, but the general principals apply. | ||
| Spatten1 |
One more thing: you read about drivablity problems off idle and at low rpms on stock IL4s. This is entirely due to the engine being tuned for max hp at high rpm. At low rpm it will often be starved of fuel to meet emissions. The quick fix is to richen up the fuel at low rpm and drivability returns. | ||
| Djkaplan |
"Air-cooled bikes supposedly emit more pollutants during warm up because piston to wall clearances have to be larger than on water-cooled bikes." "If that rationale is true, then why wouldn't air-cooled engines emit more pollutants all the time?" I'm not clever enough to come up with a lot of the information I relay, it's just stuff I've gleaned from the publications I've read over the years. If you want me to explain the rationale, then I'll give it a shot, but in the statement I posted I made sure to say two things up front: 'supposedly' and 'during warm-up'. The only reason I can think of why air-cooled engines need more piston to wall clearance than water-cooled engines is because of the wider range of temperatures the cylinder operates at when the engine is running. It starts at ambient temperature and I'm assuming the cylinder will get to a higher temperature than a typical water-cooled cylinder might. This wider range of temperatures means a wider range of expansion that has to be accounted for during operation. Perhaps the piston also gets hotter and expands more than in a typical water-cooled engine and it's thermal expansion needs to be addressed as well. This is not my theory, it's a statement I've read time and time again through the years in more than one publication. I can't recall the exact texts, so I made no reference to them and I made sure to issue that statement as a supposition and not fact. But, as always, I will stand by what I posted on this subject. | ||
| Djkaplan |
"What could you do to say a primary drive cover, the gearcase cover or even the cooling fins on the cylinders themselves?" A lot of magazine editors lambasted Japanese cruisers because of the fake and stylized engine covers that make the cases look more 'engine like'. But by doing this, engineers were able to take advantage of the fact that the 'fake' cases transmitted less gnashing from the crankcase. This is one of the very constraints Harley-Davidson engineers placed on themselves on the new generation air-cooled engines: no exposed case would house a bearing or shaft. | ||
| Djkaplan |
"I'm still hoping to see a Buell turbocharged model come out some day. A couple of small state of the art turbochargers, one on each header-pipe, feeding a pressurized airbox." Perhaps you will... on the Helicon. | ||
| Reepicheep |
Thanks for the explanation. I assumed that the exhaust restriction of a turbo charger robbed the same relative amount of power as a supercharger would rob... but can see how that would not be the case (highest pressure part of exhaust pulse is captured in inertia of the turbine, which then helps suck out lower pressure parts, for a net breakeven or even gain). Thanks! | ||
| Swordsman |
Wait a sec... did I just read a coherent thread debating the merits of water cooled vs. air cooled that DIDN'T turn into a flamefest? I'm going to church RIGHT NOW. Armageddon has finally arrived.  ~SM | ||
| Jlnance |
If you consume a gallon of fuel, doesn't it produce X amount of C02 and X amount of C0 and X amount of NO(?), etc no matter what kind of an engine it is consumed in? No, it doesn't work like this. The amount of CO2 is almost the same per gallon of fuel. But CO2 isn't a regulated emission. What the EPA is really worried about are nitrous oxides and paritally burnt fuel being emitted. These are not directly related to how much gasoline is burnt. | ||
| Blake |
Hey DJ, I can accept why an air-cooled engine may require greater tolerances between piston diameter and cylinder bore. No problem, I'm with you there. Yet the question remains concerning the assertion by some, even in publications, claiming wrt air-cooled engines that during engine cold startup they emit more polution than liquid cooled engines. I cannot see how if that is valid why air-cooled engines would not emit more pollution after they are warmed up too. I'm skeptical of the claim. Especially in light of the other factor mentioned, that liquid cooled engines require a significantly longer warm-up interval, thus a longer interval running with an enrichened air-fuel charge while catalytic converters are cold, thus largely ineffective, thus allowing more unburned hydrocarbons to be emitted. | ||
| Stealthfighter |
i also don´t think the thunderstorm development is to ends. there is still much to modernize. what do you think about these ideas? * new cylinder head design with 4 valves and a close valve angle for more efficiency * central sparks * cylinder heads with an oil jacket ("advanced oil cooling") * higher compression ratio (11:1...) * "up to date" engine management with 2 broadband oxygen sensors * 2 throttle bodies like XBRR * modern 12-hole-injectors * 6-speed-transmission with overdrive i believe all these things are possible in our pushrod engines. erik, don´t let the thunderstorm twin die! |
