What is this?!? under the battery tray 1g AWD

[ECLIPSE95]

I am pulling my motor out of my TSI AWD and I am getting really close to getting it pulled out..to make some more room I removed my ABS hydralic and took out the battery tray and I notice some lines comming out of a can shape thing that has a line running to where the intake used to be and a couple of other smaller lines running around the engine..what is this for?..is this somthing that can be removed? because I have seen pics of engine bays without those lines that run up to the throttle body and they have them blocked off and i was just wondering if I can do the same thing, and what else I can remove that isnt needed..Thanks ~Dustin

 

[VelocitàPaola]

Im not trying to argue with you

and yet...

What you say looks good on paper but has no real world effect.

Actually, the EVAP system on 1g DSMs works in the opposite way; the fuel tank is constantly pressurized and the EVAP system is a vent of sorts. It works by relieving the gas tank's vapor pressure by storing it in the charcoal canister and releasing it into the throttle body when needed.

The check valve you're referring to let's air into the tank to prevent vacuum from forming after the gasoline vapors are siphoned off.

 

[DROOPY209]

Now this is how DSM'ers should argue....

Both stating great points, but who is right?

Either way, I'm keeping my EVAP canister.

 

[92awddsm]

and yet...




Actually, the EVAP system on 1g DSMs works in the opposite way; the fuel tank is constantly pressurized and the EVAP system is a vent of sorts. It works by relieving the gas tank's vapor pressure by storing it in the charcoal canister and releasing it into the throttle body when needed.

The check valve you're referring to let's air into the tank to prevent vacuum from forming after the gasoline vapors are siphoned off.

If that is the case, why has my car always had a vacuum in the tank everytime I remove the gas cap? It has been the same since the day it was new, with and without the evap system?

 

[MyBeatGSX]

This is another topic we beat to death on the Saturn/J-Body boards back in the day.

The Evap Canister is all part of the evaportive emissions system (ironic huh?) its there to pressure test the gas tank for microscopic leaks that may leak air or gas vapor but aren't actually leaking gas. It occationally diverts manifold vacuum to create vacuum in the gas tank (by first creating vacuum in the canister and then opening the valve leading to the tank). After a certain period of time the ECU reads the remaining vacuum in the gas tank and makes sure its within specs... if not it throws a CEL. This process of creating vacuum for the leak test also has the benefitial side effect of sucking all the evaporated gas out of the tank, which is then vented to the engine to be burned. This is why, if you remove it, when you take the gas cap off you get a rush of gas vapor coming out. Which means you need to be especially careful about smoking, sparks, static, etc.

Under normal conditions, the tank DOES NOT leak vapors. It is designed to hold pressure (within reason). There is no open air vent, so your gas cannot evaporate.

Why we don't get a CEL light when disconnecting it on these cars is beyond me, we must have some pretty dumb computers.

Its not there to increase gas mileage. Removing it won't make your car blow up (if you properly cap that line). And your full tank of gas is not going to vaporize in a week, the same way my 2 gallon jug of lawnmower gas hasn't lost a drop all winter, and doesn't lose a drop all summer even with the vent open (ok maybe a drop, but not a noticable or measurable amount).

For the record, mine is removed. Its just one more emissions device to cause problems. And I passed without it.

 

[VelocitàPaola]

I disagree with you about the effects on gas mileage - as I said before, I have experienced these effects first hand on more cars than one.

Another reason for the reduced gas mileage is because even if the the gas tank is a perfectly closed system (which is unlikely), the vapors still remain largely unused. Fuel pumps are great at moving liquid fluids, but pretty bad at moving gaseous ones. So what happens to them? They either find their way out of the tank through small leaks toward the top of the tank, or rush out as the tank is being filled again.

As I've said before, gasoline is nearly 100% volatiles, so most of it evaporates quite rapidly; meaning a surprisingly high fraction of the total 12-14 gallons you just put in your tank is evaporated at any given point. The pressurization that occurs naturally as the gasoline heats and vaporizes does counter the total evaporation to a point, but the effects are negligible.

The gasoline will continue to vaporize until it reaches a saturation point within the tank itself. If a 14 gallon tank has a maximum capacity of roughly 15 gallons, and the maximum saturation point of gasoline is about 6% the total volume, then that means there could be almost 1 gallon (0.96 gal.) left in vapor by the time the fuel pump has sucked out all of the liquid gas.

From this we can construct a maximum ratio of 1:14 gallons of gasoline lost per filled tank. If you estimate an average driver uses about 581 gallons of gasoline in a year (EPA figure), then 41.5 gallons are lost solely to evaporation, which is a loss of more than $100.00 considering an average fuel price of $2.50 per gallon (and even more for race gas!).

Obviously the situation above is influenced by a variety of factors, but this still shows you the potential for loss without the EVAP system.

 

[VelocitàPaola]

If that is the case, why has my car always had a vacuum in the tank everytime I remove the gas cap? It has been the same since the day it was new, with and without the evap system?

How do you know it's vacuum? Have you set up a gauge to measure positive/negative pressure or are you just going by sound? Positive pressure sounds just the same as negative pressure when a valve or otherwise is opening; it's all air rushing by, just in different directions.

 

[MyBeatGSX]

As I've said before, gasoline is nearly 100% volatiles, so most of it evaporates quite rapidly; meaning a surprisingly high fraction of the total 12-14 gallons you just put in your tank is evaporated at any given point. The pressurization that occurs naturally as the gasoline heats and vaporizes does counter the total evaporation to a point, but the effects are negligible.

The gasoline isn't going to vaporize that much in a closed container (it IS a closed container, I just explained how the Evap systems makes SURE its a closed container), the same way that soup you had for lunch will stay almost indefinately in the tupperware your wife put it in so you can eat it later in the week. If you left it in the bowl it would be dried and nasty by dinner time.

Have you looked a bottle of rubbing alcohol recently? Its at least as volitale as gas (I'm not a chemist like you, just trying to use common sence and experience). If you put a hole in that bottle it would be gone in a day. But yet I've had a bottle on my shelf for over a year... why? Because its a closed container, and without exposer (sp?) to open air, it isn't going anywhere.

Now the fact that you believe the gas mileage will decrease doesn't even make sence. You're trying to tell me that a once daily (depending on how and where you drive) vapor test is actually gathering enough vapor to power your engine in any capacity? Look up information on Evap operation and you'll see the extremely limited conditions that have to be met before it actually operates.

I can't talk against your personal experience or your situation, but I know functionally and factually it won't decrease gas mileage, and it didn't decrease gas mileage on my car.

ALL cars gas mileages take into account the small amount of vaporization that you just calcuated (and I'm not going to argue against that, because you seem to know what your talking about). The thing you're missing is that burning those vapors isn't powering the car, and isn't accounted for in the ECUs fuel tables. Its an insignificant amount of fuel, and is burned purely so it doesn't pollute the atmosphere, not because its actually useful to make power.

So techincally, if you are really that anal retentive about your money, you will get more gas run through your engine for your money with the EVAP in. In reality, that gas vapor is being wasted either way. Whether its vented to the air when you open the filler cap, or its burned as waste (like PCV gases) in the engine. That ECU will NOT miss that gas vapor, and therefore will NOT have to inject more fuel to compensate, therefore NOT decreasing your mileage. That vapor probably makes up <0.001% of the total fuel being injected at any given time. We're talking miniscule amounts of vapor, not atomized liquid fuel.

 

[VelocitàPaola]

Have you looked a bottle of rubbing alcohol recently? Its at least as volitale as gas (I'm not a chemist like you, just trying to use common sence and experience). If you put a hole in that bottle it would be gone in a day. But yet I've had a bottle on my shelf for over a year... why? Because its a closed container, and without exposer (sp?) to open air, it isn't going anywhere.

It's all about saturation points. The small amount of air in alcohol bottles gets saturated quickly, thus no more alcohol can evaporate. The hole in the bottle exposes it to the atmosphere, which is not going to be saturated by a 20 oz. bottle.

It takes a significant portion of gasoline, however, to saturate the ~14 gallons of air in a near empty tank, though.

Whether or not it's closed really doesn't have anything to do with it. Take a capful of rubbing alcohol and pour it into an empty 2L soda bottle, then put the cap back on. If you come back in half an hour or so, it will have all evaporated.

The thing you're missing is that burning those vapors isn't powering the car, and isn't accounted for in the ECUs fuel tables.

Sure it is. The ECU would almost prefer to burn vapor; it's gasoline in the optimal state for combustion. Injector atomization is, in fact, a synthetic attempt for quick vaporization. Perhaps the ECU doesn't account for purged vapors in pre-OBDII vehicles, but it is taken into account in '96 and later models.

I still think it makes up a fairly significant portion of burned gasoline (~50 miles worth when ~350 miles is the average for a full tank). Either way, we're not getting anywhere. I want to thank you for the respect you show to other members whil arguing, but we'll just have to agree to disagree.

 

[MyBeatGSX]

You're probably right, but I'm just talking from the practical experience of myself and everyone on turbosaturns.net.

So we agree to disagree. I hope you weren't being sarcastic about the respect thing.

Take a capful of rubbing alcohol and pour it into an empty 2L soda bottle, then put the cap back on. If you come back in half an hour or so, it will have all evaporated.

Where are my matches?!!! I got a bomb to make.

 

[VelocitàPaola]

I hope you weren't being sarcastic about the respect thing.

Oh no, I was quite sincere. Not very many people can keep an argument technical and solely about the facts.

 

[Fortium2012]

This has been an interesting thread to read. You both do have valid points and I feel more educated from this reading. I know everyone has noted the incredible sportsmanship from both sides. Gotta love it!

I removed my EVAP canister soley for the purpose of less boost leaks to look for, less vacuum lines to decipher through, as well as just that little, little more weight I can shave off my car . Whether my car kills gas or not, typically doesn't bother me as long as my DSM runs... for the sake of keeping it simple .

 

[xveganxcowboyx]

As mentioned above, I've left 1 gallon gas cans open for weeks on end and seen no noticeable difference in gasoline level. I have a hard time believing there is any signiffigant loss by evaporation through that hose.

Whatever though, I see no reason to take it out.

 

[92awddsm]

How do you know it's vacuum? Have you set up a gauge to measure positive/negative pressure or are you just going by sound? Positive pressure sounds just the same as negative pressure when a valve or otherwise is opening; it's all air rushing by, just in different directions.

Pressurization will create a rush of air by my hand that I would feel. I feel no rush when opening the cap. Pressurization will try to blow the cap off when fully unscrewed. A vacuum tries to pull the cap closed when loosened. Mine pulls the cap back against the threads of the filler neck when opening. Has done so since the car was new. The check valve in the vapor line is a one way valve that allows vapors to be pulled but no air to enter. I know, I checked it when I removed the evap system. I am no moron and can tell the difference between vacuum and pressurization. And to to clear the air, positive and negitive pressure do make different sounds when released.

 

[PieEyedPiper]

Sure it is. The ECU would almost prefer to burn vapor; it's gasoline in the optimal state for combustion. Injector atomization is, in fact, a synthetic attempt for quick vaporization. Perhaps the ECU doesn't account for purged vapors in pre-OBDII vehicles, but it is taken into account in '96 and later models.

I still think it makes up a fairly significant portion of burned gasoline (~50 miles worth when ~350 miles is the average for a full tank).

Ok, that being said, what kind of metering abilities does this charcol container come equiped with? Like you said there are too many variables to reliabley calculate the amount of gasoline being evaporated. So I would imagine this canister or the hoses leading too and from must have some kind of sensors to tell the ECU how to compensate for, and take into account, these vapors that are suposedly accounted for and used to propel our money-sucking machines down the street.

 

[VelocitàPaola]

You're a little late... I'm not arguing this point anymore; we've already come to a conclusion.

For knowledge's sake, however, the ECU uses engine speed, MAF/MAP, coolant temperature and oxygen sensor data to determine when to purge vapors. It primarily relies on the oxygen sensor to tell it how enriched the vapor flow is.

Vapors leaving the canister, for the record, are more consistent than gasoline evaporation rate and EVAP collection. The EVAP system collects stray vapors without much external logic, however, it releases those vapors in a much more controlled way.

 

[zero_]

well i read all this and i would have to agree more with velocitapaolo it would hurt your gas mileage (they arent going to develop something that has no effect what so ever) maybe not a dramatic amount but it would have some sort of affect on it... and as for the hot soup metaphor when you put soup into a tupperware contain what happens? the vapours condence on the top (and they tend to stay there for a while), and well in the northern states and canada if you have condenced vapours on the side of your tank they may tend to freeze... and if that happens it could be somewhat disastrous... but vapours will tend ignite somewhat faster/easier so there may even be a very minimal power gain (if there would be it wouldnt be too noticeable) but it would most likely allow your engine to run more efficiently... and as for you being able to pass emmisions with out it would be given because it's just the way the fuel vapours are being used, it would still run basically the same to them. sorry i just had to put in my 2 cents

 

[kottyking]

coming from dejon tools website

"Do I need the charcoal canister tube on my new intake pipe?
What is the large hose going to my stock intake pipe (coming from under the battery)?
It's the hose from the charcoal canister. The charcoal canister stores fumes from the gas tank until the car reaches about 3000rpm when a valve opens to send them thru the hose to the intake. At idle and low rpm, the purge valve is closed keeping them from affecting idle.


What happens if I leave it off?
If you remove the hose, direct it to the underside of the car and cap the tube or order an intake without this tube, the fumes will vent below the engine compartment when driving (over 3000 rpm). You will probably not smell anything and drivability / performance will not be effected. However you will be defeating emissions (which is illegal except for offroad use)."
Enjoy.

 

[SprayinGS-T]

....just for kicks

The real argument is that your gas will evaporate away without the canister right? Really just an argument over if your going to have better gas milage with or without this thing. (as nobody is really giving a crap about the environment...) So for an extreme test of this canister real need, take a bucket or something, throw some gas in it, measure how much and then check it in a week, if it hasnt all dissapeared like the scientist up here says it will then you know you can throw your little charcoal can in the trash...

 

[MyBeatGSX]

coming from dejon tools website
If you remove the hose, direct it to the underside of the car and cap the tube or order an intake without this tube, the fumes will vent below the engine compartment when driving (over 3000 rpm). You will probably not smell anything and drivability / performance will not be effected. However you will be defeating emissions (which is illegal except for offroad use)."
Enjoy.

I just stopped listening to anything Dejon Tool has to say. If I heard that correctly, they suggested you vent gasoline fumes under the car, about 1' away from the blistering hot downpipe and in my car the occational spark creating low hanging exhaust.WTF WTF

I have a better idea. Turn that check valve around so that stuff can go in but nothing can come out of the tank. Then cap off the other end so nothing can go in. Problem solved and you don't blow up.

 

[VelocitàPaola]

....just for kicks

The real argument is that your gas will evaporate away without the canister right? Really just an argument over if your going to have better gas milage with or without this thing. (as nobody is really giving a crap about the environment...) So for an extreme test of this canister real need, take a bucket or something, throw some gas in it, measure how much and then check it in a week, if it hasnt all dissapeared like the scientist up here says it will then you know you can throw your little charcoal can in the trash...

Better yet, I'll do the actual experiments in my lab at work. Give me a week or two and I'll report back.

 

[staticbrainwash]

I don't mean to bring this back, but im a little confused. The valve opens at 3k, if thats true, when said valve opens how much "gas vapor" is being released.

Also if you read carefully, the dejon description says to cap the line at the intake and the line comming off of the canister (or thats how i read it).

I highly doubt enough vapor is being released that even if the line is left open it would be a volatile concern. But again it comes down to how much vapor is really being released at 3k plus. I was actually going to remove my canister today (as i don't have lines into my hard intake now).

Another thing i'd like to bring up is how many people who ARE running hard pipes (with no evap return) seem to have no mileage issues or complaints about anything evap concerned.

 

[MyBeatGSX]

I'll be #1 on that list. My gas mileage went UP after I removed it (more than likely unrelated though).

My only complaint would be the blast of gas vapor I get when going to fill up on a hot day. That's definately dangerous so I'm very careful to discharge static first, stay off the phone, etc (which I always did anyway). Although its not any more dangerous than filling up the lawn mower, a gas container, etc.

 

[staticbrainwash]

so you're all for the removal mybeatgsx?

 

[big_eskimo]

Haha, I just read through this entire thread, it's really funny that it started off with quite a noobish question (no offense to the thread starter) and turned out some very intelligent posts. Kind of makes you think what your missing in all the posts on the rest of the site. Anyways, keep us updated on the results of your lab experiment.
R.J.

 

[1gcrazy]

This has been an interesting thread to read. You both do have valid points and I feel more educated from this reading. I know everyone has noted the incredible sportsmanship from both sides. Gotta love it!

YEAH I rock!!!

....just for kicks

The real argument is that your gas will evaporate away without the canister right? Really just an argument over if your going to have better gas milage with or without this thing. (as nobody is really giving a crap about the environment...) So for an extreme test of this canister real need, take a bucket or something, throw some gas in it, measure how much and then check it in a week, if it hasnt all dissapeared like the scientist up here says it will then you know you can throw your little charcoal can in the trash...

Wow, didn't i say this a few weeks back? But NOOOO no one wants to listen to Steve haha
I rock