TR6 TR6 Carbon Can

[erstearns]

While I have the rad out working on the timing seal etc any reason I should consider scrapping the carbon can, its associated hoses and anti run-on valve? Pros and cons of the headaches of getting everything synced without "it"? Nobody here will remember here that in 1973 the Fed's thought it was a good idea.

 

[poolboy]

I removed mine recently. The cannister is just a short term "storage facility" for vapors. While they are in there they are exposed to the cleansing properties of a certain amount of activated charcoal. The lines or hoses have to be dealt with, but if you remove it you are just bypassing the activated charcoal, for all the good that it might do.
You won't notice any change in power, one way or the other, if you handle the hoses correctly.
See this:
https://mossmotors.com/forum/forums/thread/14667.aspx

 

[TR6oldtimer]

They still do....

If your carbs are stock, IMO keep it as it is not a high maintenance item, and the anti-run on feature works well.

 

[TR3driver]

They still do....

Me too.

I'm no tree-hugger, but I have seen first-hand what emission controls have done to clean up the air in the Los Angeles smog basin. The carbon canister doesn't hurt anything, and should help. Might even give you a miniscule (too small to measure) reduction in fuel consumption when the vapors get sucked into the intake. I'm keeping mine.

Note however, that there is a screen in the bottom that may need to be cleaned. If you can detect any change in the way the engine runs with the purge line connected to the canister, your screen may be clogged with rust and dirt. Early units just unscrewed, later ones may need to have a plastic weld broken to get them apart.

Or it should be easy enough to find a suitable substitute from a more modern car. Most of them still use canisters, but they are frequently hidden inside fenders or whatnot.

I'm less enamored of the ARS (all my Triumphs are too old to have one), but again it doesn't hurt anything.

 

[erstearns]

Probably right.....keeping it is the right thing to do. Bracket was a pain when removing the radiator, the ARO wire is broken and the unit is probably trash. Guess as I "rebuild" the PO rebuild (maybe just paint in some cases)might as well do it all piece by piece.

 

[poolboy]

I don't think that you would be putting out any more harmful emissions. The gas tank vapor is still being drawn into the carbs, if you connect the 2 lines together as I did.
Except for when the solenoid in the anti run-on valve opens the cannister to the vacuum in the intake manifold, all the vapors or whatever are drawn into the carbs along with the vapors from the valve cover.
The only difference is that w/o the cannister in the picture there is no exposure to the charcoal before being drawn into the carbs. How much good that did anyway is questionable, at least to me.

 

[RonMacPherson]

And you can replace the "carbon" with aquarium charcoal...

 

[TR3driver]

I don't think that you would be putting out any more harmful emissions.

The difference comes when the engine is not running, but the car is sitting in the sun. Gasoline expands when it gets warm, forcing vapor out of the tank and float bowls. The charcoal acts as a holding area for the gasoline vapor. Otherwise, the fumes back up out the air intake and evaporate. As we were just discussing on the Stag list, they can also cause hard starting if you come out of the store at the wrong time.

Aquarium charcoal is not the same, BTW. At least according to the people who manufacture the stuff. Don't recall his name now, but there was a gent at the 2005 VTR selling charcoal for gasoline, instead of water.

 

[poolboy]

Yeah, I get that Randall. But what mechanism contains the vapors in the cannister while all this expansion is going on? I'm not sure of this, so I wonder if that Charcoal is actually doing all that much purifying. I know that the surface area of the activated charcoal is supposed to trap a certain amount of hydrocarbons, and it has certain deodorant properties.
Despite the purge it might get from the activation of the anti run-on valve as it kicks in when the oil pressure drops, I wonder how long it takes for the granules to become saturated to the point of being ineffective.
I think it's mostly theoretical.

 

[RonMacPherson]

The charcoal for aquariums, is not designed for carbon canisters. BUT if you find the activated kind, and believe me there is plenty out there, it will work. It is a fairly inexpensive, money and time wise, replacement for those that want to replace the charcoal.

AHM used to recommend replacing the charcoal canisters, which is essentialy the same as the TR's every 30K miles. Then they upped that to every 60K miles. Now it is "as required".. Part of that recommendation change is they increased the amount of charcoal in the canister...

The canister is designed to "hold" the vapors in a circuit between the intake manifold and fuel system piping. keeping it insulated from the outer atmosphere. Just like a big vaccum reservoir(only it has charcoal in it). Then when the engine is started the vapors get ingested back into the engine.

If you intend to keep the original intake system installed it does NOT hurt anything to keep it installed. If the system has been modified(my Webers for example) and the car is 30 +years old, as you say it doesn't really help all that much, but it does help some.

 

[TR3driver]

But what mechanism contains the vapors in the cannister while all this expansion is going on?

The process is called adsorption. Basically it's a "partial pressure" kind of thing; the concentration of hydrocarbons stuck to the surface of the carbon adjusts to match the concentration in the air passing through. Thus when more or less pure vapor is going into the canister, it gets adsorbed onto the surface of the charcoal. (The surface is much more than what you see; the "activation" process involves creating millions of tiny fissures in the carbon chunks so there is a great deal of surface involved.) But later when the engine is running, it sucks fresh air through the canister, and the adsorbed hydrocarbons go back into the air and get sucked into the engine to be burned.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] I'm not sure of this[/QUOTE] Well, I'm sure my Dad could give you a much more convincing lecture with examples (he's a retired chemist) but the basic process is used for a lot of things, so I believe it works. It's not perfect, but even if it's only trapping 90% of the vapors (and I believe the percentage is much higher), it still seems worthwhile to me.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Despite the purge it might get from the activation of the anti run-on valve[/QUOTE]Just for clarity, the ARS is not part of the purge process; and in fact most cars (including my Stags) don't have one. The purge happens continously all the time the engine is running; while the ARS is activated only when the key is turned off and the engine is still turning.

What the ARS does is apply vacuum to the float bowls, to starve the engine of fuel so it cannot run-on with the key off. The carbon canister just happens to be a convenient place to do this, since it already has vacuum and the link to the float bowls.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I wonder how long it takes for the granules to become saturated to the point of being ineffective.[/QUOTE]Since they are cleaned every time the engine is run, in theory they never become saturated and ineffective. However, eventually they do become fouled and clogged with dirt and so on carried in during the purge process (which is why most canisters have a filter in the bottom of them that should be changed occasionally). That's also why Triumph recommended the canister be changed every 48,000 miles.

I've heard from several people that have solved "fuel smell" problems in their garages by replacing 30 year old carbon canisters. Must be doing something for them

If you've followed my posts, you'll know that I'm dubious about most of the emission controls from the 70s. They reduce power and increase fuel consumption (and CO2 emissions) with dubious benefit. But carbon canisters are an exception, IMO. They really do help without hurting (except of course for all the hoses & added complexity involved).

 

[achtungeveryone]

Is bypassing this system just a matter of capping of hose fittings? The hose fitting on my anti-run valve is broken and won't hold the hose on. I guess this means I probably have a vac leak there. At 90$ for the part I'd consider bypassing the canister and planting a few trees for a carbon offset. No, really.

 

[achtungeveryone]

poolboy,
I just read info in the external link you supplied, so that should get me on my way. Thanks for posting!

 

[TR3driver]

Worth noting, perhaps, that you can just toss the ARS and leave the remainder alone. Or leaving it as-is with the broken fitting won't hurt anything either. There should not be vacuum at that point, except during the brief moment when you've turned the key off but the oil pressure has not dropped off yet (which is the only time the ARS is activated). An air leak will disable the anti-runon system, but it's usually not needed anyway. And you can just let the clutch out to kill the engine, if necessary.

 

[poolboy]

On my anti run-on valve there are 2 hose nipples. One, the larger of the 2, goes to the carbon cannister with a U-shaped hose.
The other nipple on the anti run-on valve is for attaching the vacuum line from the intake manifold.
The solenoid inside the anti run-on valve housing prevents the manifold vacuum from entering the picture until the process that Randall described (above) occurs.
If it is that nipple that will not hold the vacuum line from the intake manifold onto the anti run-on valve housing, then yes, you will have a big time vacuum leak w/o the effect of the closed solenoid valve.
If it is that line, then you can just cap the nipple fitting at the manifold and remove the hose altogether.
Keep in mind that you won't have a functional anti run-on device, but as Randall said you may not need it.
When I found out that I didn't need it, that's when I started to see what else I could do without.
If you just want to disable the valve like that, it wouldn't affect the cannister plumbing in any way if you decide to keep the cannister.

 

[TR3driver]

Oops, poolboy is quite right. I forgot about the later models having the separate vacuum line to the ARS. As he says, you can just plug that line.

However removing the canister is a bit more tricky, because the float bowls, fuel tank and crankcase have to breathe. Can be done, but you need to figure out which lines to cap, and which to leave open. Different for different years.