Charcoal canister/bvsv question

[7M4EVR]

I'm looking for some good reading on how the charcoal canister/bvsv works exactly. Excuse the newbish question, but I can only get bits and pieces from previous threads and was wondering if someone can point me in the right direction to a full read of the system.

My current thinking: the charcoal canister vents through the bvsv and at a certain coolant temp it will release the gases to the throttle body.

Couple of the reasons I'm interested in this info... Because I need to replace my bvsv and it has me wondering how exactly it works, and also I have excess pressure when I open my gas cap and want to figure out how this happens.

Thanks,

 

[jetjock]

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=6

That pressure is supposed to be there. Controlled by a check valve in the evap canister.

Other questions, ask....

 

[IndigoMKII]

JJ, is there a safe way to remove the charcoal canister? Reason I'm asking isn't because of want that superfly hellaclean engine bay, I've noticed that my downpipe is hitting the charcoal canister mount. I'm really not interested in snapping off my wideband sensor because the charcoal canister is in the way.

 

[7M4EVR]

Indigo, from what I have been able to gather so far, I would just re-locate the canister. I'm sure there are ways of safely removing it, but you would want to come up with some other way to properly vent your gas tank for emissions and safety reasons. Some people have tried vented gas caps, but something else to think about is the stock TCCS (US) accounts for that "fuel vapor" to be re-circulated back into the throttle body so if it isn't there it will cause leaner conditions.

 

[7M4EVR]

By the way, thank you JJ.

 

[jetjock]

JJ, is there a safe way to remove the charcoal canister?

Well, putting aside the emissions thing easiest method is to route down to a draft tube. Better to do what 7M4EVR said though.

By the way, thank you JJ.

You're welcome, padawan...

 

[IndigoMKII]

Indigo, from what I have been able to gather so far, I would just re-locate the canister. I'm sure there are ways of safely removing it, but you would want to come up with some other way to properly vent your gas tank for emissions and safety reasons. Some people have tried vented gas caps, but something else to think about is the stock TCCS (US) accounts for that "fuel vapor" to be re-circulated back into the throttle body so if it isn't there it will cause leaner conditions.

I'm aware that the TCCS is accounting for several things, the charcoal canister being one of them. I might be able to move the charcoal canister over a touch until I can get a standalone. ProEFI is looking more and more tasty, its such a shame I can't afford a MoTeC M600..

 

[supraguy@aol]

I've heard of people going with a smaller cannister.
I think the 1JZ powered supra's had a smaller version.

 

[suprarx7nut]

I have mine in the same location, just mounted to a homemade aluminum bracket that orients it a little differently and gets rid of the bulky factory bracket underneath the canister. I've had a hard time finding a similar canister, that's smaller, that has an integrated check valve with a pressure break point (probably not the right terminology) like the factory one.

I'd love to see some other options. I've been meaning to come up with a solution, but haven't been able.

Technically, I believe it is illegal to change it at all. Regardless, I'd like to clean mine up from a functionality standpoint (currently, it's in the way and mounted very close to the turbo) and aesthetically (the stocker is big and ugly).

 

[IndigoMKII]

I will look around a little bit and report back on my findings.

 

[3p141592654]

the canister is located near a heat source for a reason.

 

[suprarx7nut]

the canister is located near a heat source for a reason.

Really? I haven't read that anywhere. Do you have any more info on this? I'd like to relocate mine, but I don't have any intention of making it less effective.

Was the JZA70 located near a heat source? I could have sworn I'd seen systems with the evap canister outside the engine bay, away from any heat source.

 

[3p141592654]

Different markets have different emission requirements. If you want to meet the JDM standard of the day, then use the JDM canister. If you want to meet the USDM spec, then you need a bigger canister, and you need to get it hot during the purge to maximize the adsorptive capacity of the charcoal when the engine is shut off.

 

[atmperformance]

I'm just going to throw this out there that newer toyotas have the can next to the tank where i'm pretty sure they don't see much heat. maybe it's a different design but that might be a starting point for a replacement.

 

[suprarx7nut]

Different markets have different emission requirements. If you want to meet the JDM standard of the day, then use the JDM canister. If you want to meet the USDM spec, then you need a bigger canister, and you need to get it hot during the purge to maximize the adsorptive capacity of the charcoal when the engine is shut off.

Hmm.. I thought heat allowed gas to be desorbed from activated carbon.

The gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell.

I suppose you could say it might help adsorption on cool down because the heat desorbed much of the vapors that were in the tank previously. In effect, cleaning the filter for the next round.

There are charcoal canisters that are located nowhere near a heat source, though, correct? I'm talking US models. My friend's 97 Pathfinder, I thought, had the small reservoir in the gas tank area under the car in the back. Maybe I'm unaware of another critical piece of those systems which allow that placement. :dunno:

 

[BryanDyer]

Just saying, I removed my canister and put a vented gas cap on and it has had no effect on my AFR. I'm untuned at the moment but my afr is 14.4-14.7 cruising and 10.7-11.0 WOT....

 

[3p141592654]

Newer systems cannot be compared as they have active purge systems with vacuum pumps and solenoid controlled valves. The Supra setup is very old school, with engine vacuum used for purge. And yes, the point of the heat is to get the canister empty so it can hold as much vapor as possible when not running.

The effect of the purge will not show up on your AFR gauge. You need to look at your HC in the stream, but even then if done right it will be compensated for. The trick with the purge is to feed the gas plume to all cylinders uniformly.

 

[IndigoMKII]

Okay so, this cannot be relocated nor deleted until what conditions are met to compensate?