How effective is the canister at controlling pollution?

Discussion in 'GS Boxers' started by New Adventurer, May 18, 2007.

  1. New Adventurer

    New Adventurer Been here awhile

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    If it does any good at all, I'm willing to live with the extra 3 lbs. that it weighs and the slightly altered cosmetics. On the other hand, if it's useless, it would give me a weekend project. Does anybody have any idea how much good the canister does?
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  2. Pir8te

    Pir8te over forty victim of fate

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    my guess is that the carbon foot print of a motorcyle with or without a canister would make every car look like :topes even the hybrids

    that was my best effort at politically correct speach

    ansd yes when I fill the tank for less than 10 bucks the look on the SUV driver next to me is priceless
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  3. DriveShaft

    DriveShaft Long timer

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    It's actually quite effective. People don't realize how, precisely the canister works, and just assume that it catches "overflow" fuel from your tank, and lets air in while you ride, or lets air out "when the gas expands" (a total myth of misunderstood thermodynamic principles). In actuality, it's doing its job even when your bike sits in the garage for months, unused. What happens in the course of any day is that the air in the tank expands with the warming of the day. It can go through 40 degrees of temp change in a normal day, and it's the *air* that expands...carrying alot of fuel vapor with it. If the filter wasn't there, your bike would be "breathing" fuel vapor out to the atmosphere even when you aren't riding it, every time there's a warming temperature change. The air and fuel in the tank is actually quite dynamic when you ride too, and your tendency to "gas off" or breathe is even more bcs there're more factors warming and cooling the tank. With the catalytic converter, and the charcoal filter, these bikes are actually not too bad in terms of their pollution abilities.
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  4. SocalRob

    SocalRob Long timer Supporter

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    Would not be too sure about low pollution footprint of a bike v. a new car.

    A 2005 or newer car produces less pollution while running than a 1999 car does while shut off & parked. A big 2 stroke bike engine produces about the same pollution in 8 hours as a 2005 camery class car does driving 60,000 miles. Of course I've heard that a big ocean freighter making a round trip from Japan to CA will put out as much pollution as all the 2 stroke bikes ever sold in the US (ocean freighters do put out something like 10 percent of all pollution in the world).

    New cars are getting pretty clean. I think bikes are still a bit behind. I keep my canister on & keep my catalytic converter on. Quiet & clean.:D
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  5. TUCKERS

    TUCKERS the famous james

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    The charcoal canister works really well. Vapors from unburnt gasoline are more pollutive than from burnt gasoline.
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  6. 2wheelsrule

    2wheelsrule youth survivor

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    Wow, that's quite a claim. Do you have data to back up that statement? I seriously doubt the tailpipe emissions from a running 2005 car are less than whatever off-gassing a 1999 model has (given evap controls on cars have been around a long time).

    Evaporating gasoline contributes to photochemical smog.

    http://en.wikipedia.org/wiki/Photochemical_smog

    In my garage I have an old stand-up jet ski, 2003 wr250f, lawn mower, and my GS, none of which have an evap can, yet somehow I don't smell gasoline in there. It's a very small amount that evaporates. If you consider the millions of cars on the road, then the cans make a difference for smog formation. However, it's nothing compared to the exhaust. Most developed countries require cats on vehicle exhaust systems, yet we're the only ones requiring evap cans on motorcycles. I don't think they make much difference for motorcycles.

    So leave your exhaust system stock, and remove the can if it bothers you. My $.02.
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  7. 1longbender

    1longbender ?

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    Does the canister stop the VOC's from evaporating? I think it just cleans them on the way out to the atmosphere?

    Surely a better soultion would be to compress the gases back to a liquid and put them back in the tank :D I wonder how many PSI you'd need to liquify the petroleum gases?
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  8. Paul Mihalka

    Paul Mihalka Old Fart

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    Besides the charcoal can, the newer bikes have a pressure relief valve in the gas tank. Normal expansion because of temperature change just builds up pressure without blowing fumes into the athmosphere. When the gas/fumes in the tank cool down, it just reduces the pressure again without sucking air in from the outside.
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  9. DriveShaft

    DriveShaft Long timer

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    I'm not familiar with any bike that maintains pressure in the tank, Paul. Can you give a model reference? I know the BMWs that we're talking about are all vented and equalize pressure unless of course the canister is clogged. There's a purge valve that then draws air into the engine through the canister when the engine's running, but that doesn't involve the tank, really. Its purpose is specifically to scavage fuel vapors that have built up in the canister.

    Any bike equipped with a vent line equalize pressure internally and externally. I wouldn't call it a valve, per se, in the gas tank. A valve implies a way to stop flow. There is a vent trap to prevent the liquid fluid from sloshing into the line (which works exactly like the vent traps you use in your house plumbing), but again that's not a valve, per se. It doesn't "maintain" pressure in the tank.

    The evap can works identically to the one in a car's pollution control system. They've been around since the seventies. They do indeed take pollutants out of the venting air, cleaning the vented air of hydrocarbons. What else would it be "cleaning?!" It's not exactly new technology. Here's a blurb about it:

    "EVAPORATIVE CONTROLS
    Gasoline evaporates quite easily. In the past, these evaporative emissions were vented into the atmosphere. 20% of all HC emissions from the automobile are from the gas tank. In 1970 legislation was passed, prohibiting venting of gas tank fumes into the atmosphere. An evaporative control system was developed to eliminate this source of pollution. The function of the fuel evaporative control system is to trap and store evaporative emissions from the gas tank and carburetor. A charcoal canister is used to trap the fuel vapors. The fuel vapors adhere to the charcoal, until the engine is started, and engine vacuum can be used to draw the vapors into the engine, so that they can be burned along with the fuel/air mixture. This system requires the use of a sealed gas tank filler cap. This cap is so important to the operation of the system, that a test of the cap is now being integrated into many state emission inspection programs. Pre-1970 cars released fuel vapors into the atmosphere through the use of a vented gas cap. Today with the use of sealed caps, redesigned gas tanks are used. The tank has to have the space for the vapors to collect so that they can then be vented to the charcoal canister. A purge valve is used to control the vapor flow into the engine. The purge valve is operated by engine vacuum."
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  10. Paul Mihalka

    Paul Mihalka Old Fart

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    I stand corrected.
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  11. JessieS

    JessieS Adventurer

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    Thanks for the post, very informative, that will push me not to park my bike int hot places as in Europe our GS don't have canister.

    Jc
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  12. KiltBoy

    KiltBoy Mahout

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    Doesn't the canister also catch fuel when you drop the bike - not that I would ever drop it :D

    I was told that if you drop the bike a lot the canister can fill with liquid fuel and cause a problem.

    Myth or fact?
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  13. 1longbender

    1longbender ?

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    I was wondering how the charcoal wouldn't become saturated over time, but that explains it.

    Also, why is the canister on the BMWs connected to the CAN bus, what is it monitoring or controlling?
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  14. DriveShaft

    DriveShaft Long timer

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    Quick answer is yes, dropping the bike can fill the canister with liquid fuel, which isn't good. The vent trap isn't designed to work upside down.

    Here's a picture of the vent trap (thanks to johnjen for this excellent shot as part of his siphon sucker instructions)
    [​IMG]


    Most people have no idea what that hexagonal plastic thing is (and subsequently toss it). It's your vent trap. There's an upside-down cup-shaped form inside that thing, and a right-side-up cup-shaped thing in there as well, forming a labrinth of sorts. The fuel sloshing around your tank finds it difficult to work its way through the labrinth because the labrinth maintains a fairly well protected air pocket in front of the vent line (unless it is entirely submerged and under pressure...something that can happen if you happen to drill the fuel nozzle...but that's a totally separate discussion). That's what traps do. However if your bike is on its side, the labrinth is turned 90 degrees, and the airpocket that would normally block the vent line bubbles out to the side...fuel goes in.

    Fuel going through the vent line ends up dislogging particles of charcoal from the packing. Think of the bits of charcoal in your Brita water filter...same principle. The charcoal doesn't "dissolve" per se (another myth or misnomer) It's simply dislodged. The risk in clogging comes two factors. Free-floating charcoal will tend to clog the inlet and outlet ports. And secondly, moisture will promote rust. That is the risk from having fuel clog the canister.

    When you next start up the engine, though, the engine vacuum will start sucking that fluid out, and the evaporative effect of having airflow going from the atmosphere into the engine will evaporate the fluid in the canister, and draw it into the engine for combustion. The best thing you can do for an overturned bike, as far as the canister is to run the engine.
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  15. MarkV

    MarkV Been here awhile

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    my ohlins pre load is now mounted where the canister used to be... ohlin's most likely picked that spot because the cannister doesn't exist on european bikes; just the kalifornia legal ones.

    those that believe the canister design afterthought really does more than act as a temporary vapor trap have been sniffing way to many fumes. i'd argue that the amount of toxins generated in making the components equal or outway any it may prevent escaping into the atmosphere. most california emmissions are the very first thing that is pulled off, right behind worthless decals.
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  16. DriveShaft

    DriveShaft Long timer

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    That is a bold and unsubstantiated argument, but I'm not one to stop you.
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  17. MarkV

    MarkV Been here awhile

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    ok, go determine the mass of the canister, fittings, and assorted hoses... now calculate the mass of the gases it prevents exscaping into the atmosphere say over an average 75000 mile life...
    #17
  18. 1longbender

    1longbender ?

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    there's another urban myth along the same lines that says a photovoltaic panel takes more energy to produce than it will ever yield over its life span:huh
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  19. DriveShaft

    DriveShaft Long timer

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    First go determine what the correlation between the mass of steel, charcoal, and rubber tubing is versus the damage to the environment of an equal weight of hydrocarbons.
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  20. johnjen

    johnjen Now, even more NOW!…

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    I thought I recognized that pic. It was the bucket in the background that was a dead give away. :evil

    That vent trap is also a 'tip over limit valve', or some such label. It is a refinement over the 1100's 'pillow' device. It's main function is to stop fuel from flowing out of the tank when the bike is on its side. It works really well. I had one guy install that valve upside down when he installed a S4 kit. He created quite a vacuum inside his tank until he re-installed it correctly.

    Also it needs to be noted that the cannister is really only meant to deal with fuel VAPOR and not liquid fuel. When liquid fuel is 'stored' in the cannister, and after the solenoid opens, the engine tends to run like crap until the fuel is all used up. AND liquid fuel tends to break down the cannisters ability to keep the charcoal granules inside the cannister, which leads to clogging the hoses that feed into and out of the cannister. When that happens it MIGHT be possible that they (the granules) can be allowed to get sucked into the engine via the vacuum lines at the TB's. A decidely BAD thing.

    JJ


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