GO FISHING, use SLABSAUCE Fishing Attractant
Page 1 of 5 123 ... LastLast
Results 1 to 10 of 42

Thread: MPG and charcoal canister

  1. #1
    Join Date
    Jul 2004
    Posts
    778

    Default MPG and charcoal canister

    I've looked into threads that talked about charcoal canister and found an allusion that it may be responsible for poor MPG. For some while now I've been trying to improve the performance - but no success... Everything has been changed besides charcoal canister. Wires, distributor, injectors, fuel regulator, etc... Good compression.
    Does someone have experience with the effect of charcoal canister on MPG?

    deleted air conditioning

  2. #2
    Join Date
    Dec 2004
    Location
    Sydney, Australia
    Posts
    4,374

    Default

    Quote Originally Posted by Rustam
    I've looked into threads that talked about charcoal canister and found an allusion that it may be responsible for poor MPG. For some while now I've been trying to improve the performance - but no success... Everything has been changed besides charcoal canister. Wires, distributor, injectors, fuel regulator, etc... Good compression.
    Does someone have experience with the effect of charcoal canister on MPG?
    Sounds like a gaseous illusion to me. Why would it do this, waht did this source say- and who was it? Tho you might know this already- your probs are likley to be AFM, ICV, intake leaks or worn valves/rings, in that order.

    Join the Aussie
    540i LE yahoo forum

    08/88 535i e34 M30+miller MAF, 'stiens, tints & teeth!

  3. #3
    Join Date
    Jul 2004
    Posts
    778

    Default

    Quote Originally Posted by genphreak
    Sounds like a gaseous illusion to me. Why would it do this, waht did this source say- and who was it? Tho you might know this already- your probs are likley to be AFM, ICV, intake leaks or worn valves/rings, in that order.
    Someone said in the threads that "bavauto.com" states that bad charcoal canister can affect MPG...

    What is ICV?

    deleted air conditioning

  4. #4
    Join Date
    Mar 2006
    Location
    Great Britain
    Posts
    446

    Default

    ICV is the Idle Control Valve.

  5. #5
    Join Date
    Jul 2004
    Posts
    778

    Default

    Quote Originally Posted by genphreak
    Sounds like a gaseous illusion to me. Why would it do this, waht did this source say- and who was it? Tho you might know this already- your probs are likley to be AFM, ICV, intake leaks or worn valves/rings, in that order.
    How can bad ICV affect MPG?

    deleted air conditioning

  6. #6
    Join Date
    Mar 2006
    Location
    Maryland, Virginia, D.C.
    Posts
    705

    Default

    What the hell is a charcoal canister?

  7. #7
    Join Date
    Jul 2004
    Posts
    778

    Default

    Quote Originally Posted by ThoreauHD
    What the hell is a charcoal canister?
    Charcoal canister is used to collect gas fumes from the tank - to reduce pollution.

    deleted air conditioning

  8. #8
    Join Date
    Mar 2006
    Location
    Maryland, Virginia, D.C.
    Posts
    705

    Default

    I'm not familiar with that but my mpg and efficiency increased with an 02 sensor replacement and spark plug/ignition coil replacement. And if you have a intake manifold/head gasket vacuum leak- that would be the first place to start.

    Found a write up on the charcoal canister:

    Do you know how the system works? What it does is take the gas vapor from when the gas heats up or is poured into the tank and then condenses it and inserts it into the intake. This makes for a wet manifold as well as non-metered air entering the intake. This system was a complete after-thought from BMW and all true Euro cars don't have it. The reason why is because the US EPA wanted to prevent the gas vapors from escaping to the atmosphere. What really they are doing is creating a situation where you are getting extra air and fuel vapor into the combustion. As you will know, gas vapor does not combust as easily as liquid, and in fact is very hard to combust, and is therefore put through the cat and out the tail pipe. This increase the emissions of the car and also robs power because of the wet manifold condition and the increase in un-metered air going into the motor.

    After completely understand how this system works and what it does to the operation of the motor, you will see that it has no benifit and in fact the claim you made of having your premium evaporting should happen because of the way the system works in the European cars where the expansion tank is vented to the atomsphere. What expansion tank does in European car is that it acts as a collector for the gas vapor and then once the gas vapor converts back to liquid, it flows back into the tank. This is also shown by the placement of the expansion tank in the car. The expansion tank is placed higher than the main tank and is also far away from a hot exhaust. This allows the gas vapors to cool and therefore condense back into a liquid and flow back into the tank. Thw only reason why there is a line to the outside of the car is that in cases when you are filling up the car, you are inputing more gas than air can come out. This therefore allows for the pressure in the tank to be released and so you are able to fully fill the tank. I have had this happen on a 7-series where I was filling it up and the pump stopped, but the tank was not full. This was caused by the charcoal canister system and the fact that it doesn't allow pressure to be released from the main tank quickly in situations like filling the car. Also, the possitioning of the line port on the expansion tank that runs to the charcoal canister is also at the top of the tank. If you know about chemistry, the gas vapor will settle to the bottom of the tank because of the fact that it is heavier than the normal air. Therefore, the normal air will go out of the expansion tank, and the fuel vapor will stay in. Now you are correct in saying that when you fill the car it will smell like gas for a little bit, but you are incorrect in saying that you want positive pressure in the gas tank. While positive pressure will allow for the tranfer pump to work easier, you will not be able to fill the car fully after driving. Also the charcoal canister system does not keep positive pressure in the tank. If you have ever looked at the canister and how it works, it is open to the air on the underside. This allows for the prevention of a build-up of pressure in the tank, but it doesn't work very well.

    In closing, the charcoal canister system was an after-thought by BMW to abide by the EPA laws. Personally, after reviewing how the system and the problems that it cause, such as rough idle, incorrect mixture, poor emissions and difficulty in filling, I see no reason to keep the system on the car unless it is required by the emissions laws in your state.

    So in effect if it ain't working, it don't matter.

  9. #9
    Join Date
    Jul 2004
    Posts
    778

    Default

    Quote Originally Posted by ThoreauHD
    I'm not familiar with that but my mpg and efficiency increased with an 02 sensor replacement and spark plug/ignition coil replacement. And if you have a intake manifold/head gasket vacuum leak- that would be the first place to start.

    Found a write up on the charcoal canister:
    Well, O2 is brand-new from last year, spark plugs and the coil are ok... I guess by "head gasket leak" you mean "valve cover gasket leak"? I changed the gasket last summer - everything seemed ok - I am a bit puzzle by what you mean.

    Where did you find the write up? I am planning to upgrade the charcoal canister so that the mixture is unaffected by it. I will create new page on my website.

    The write up is very right on the effect on idle by the charcoal canister. Two nights ago I disconnected the purge valve that lets the fumes from the canister into the intake. The result - rock steady idle that I had never seen in my car. Defied Bruno's statement that the idlling performance on m30 is inherently bad. The ability to suck in unmeasured air through charcoal canister is often overlooked incidentally because of no idea what this canister does to begin with.

    It's interesting to note that the air gets to be sucked in so much that it is possile to get resonance from the charcoal canister while adjusting the mixture. Apparently leaner mixture can induce relatively high pitched whine from it.
    Last edited by Rustam; 05-15-2006 at 09:48 AM.

    deleted air conditioning

  10. #10
    Join Date
    Jan 2004
    Location
    Lexington, Kentucky
    Posts
    2,561

    Default

    Charcoal canister change is recommend by Bavauto every 120,000-150,000 or so miles. I understand if it clogs it will reduce gas mileage. If clogged you might smell gas fumes. Also, if you are in the habit of topping off your gas tank, it can send raw gas and not fumes to the canister.

    I replaced mine with no change in in gas mileage. Even so, you might want to recheck all the rubber hosing associated with the canister/blow-by/PCV like operation for vacumn leaks.
    Thanks,

    1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment

Page 1 of 5 123 ... LastLast

Similar Threads

  1. Removing charcoal canister...
    By Jon K in forum 5 Series BMW
    Replies: 8
    Last Post: 10-29-2006, 01:48 AM
  2. purge valve---charcoal canister
    By krazy00kanadian in forum 5 Series BMW
    Replies: 2
    Last Post: 06-28-2006, 09:52 PM
  3. Activated charcoal cabin filter
    By Russell in forum 5 Series BMW
    Replies: 4
    Last Post: 04-20-2006, 06:37 AM
  4. replaced charcoal canister 1995 525i
    By Russell in forum 5 Series BMW
    Replies: 13
    Last Post: 07-08-2005, 06:04 PM
  5. Replies: 6
    Last Post: 05-07-2004, 03:39 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •