Lotus Elan

Charoal canister on a Plus2

PostPost by: prezoom » Fri Dec 30, 2016 5:49 pm

My Plus 2 was a bit of a mashup when I purchased it. Servos removed, charcoal canister removed, wiring issues of course, and a Stromberg head that had been modified (butchered) by welding on a Weber style manifold, including a host of other issues. In the course of the previous mods, a flame wrench had been employed in the area of the exhaust header to provide additional clearance on the chassis. In the process, the vapor recovery/vent line from the fuel tank to the charcoal canister, was severed and not so neatly melted and sealed by the torch. Love quality workmanship......

I am replacing the hacked up TC with a Zetec, equipped with a pair of Webers. The question is: the Strombergs had ports to connect hoses to the charcoal canister, and another hose from the canister was routed to the air intake to the airbox to provide purging air. The air purging hose will not be a problem. However, Webers of course do not have a port to connect the hoses from the canister. Does anyone have a reasonable solution to connect the two hoses from the canister to the carbs when using Webers?
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PostPost by: Gordon Sauer » Fri Dec 30, 2016 6:06 pm

Those are just a emission things that were added along with the emission friendly Strombergs and if you go back to Webers and a different engine I wouldn't think you'd want any of that. There's also a vapor recovery tank above the gas tank that recirculates gasoline vapor but that's just all the emission stuff and I think he would leave it off if you doing Webers and a different motor. But if you stay with it then you can look up carbon canisters and there's a lot of them that you can get with the same input and output points that match the one on the Lotus. Gordon Sauer
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PostPost by: Sea Ranch » Mon Jan 02, 2017 12:54 am

Watching this with interest!

"Just emissions" stuff is of great interest to me because I want to eliminate fuel vapors in my shop/garage. A more than good enough reason to find a way to vent Webers into a charcoal cannister.

Back when I was driving my car, I made up simple plugs for the ends of the large caliber tank vent tubes that exit underneath the car. That helped. I had planned to replace them with 2 way valves with low "cracking" pressure, so the fuel tank could vent on a hot day (positive pressure), and so there would be no vacuum created during operation, with the fuel pump sucking out fuel (negative pressure).

Carry on, Rob :mrgreen:
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PostPost by: mbell » Mon Jan 02, 2017 1:57 am

I am with Roger, I'd dump the evap system.

If you really care about venting you can get special valves that open under a low vacuum or higher pressure designed for the purpose. This allow the tank to replace the fuel consumed with air but prevent fumes being vented unless the pressure gets to a high level then it'll vent to atmosphere for safety.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: Sea Ranch » Mon Jan 02, 2017 2:07 am

Right. I believe I just said that :wink:

But I'd still like to capture the evaporating fuel from the Webers, too. The charcoal canister seems to be the way to go.
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PostPost by: Vic » Mon Jan 02, 2017 3:00 pm

Rob, evaporative emissions are important, to work correctly with Webers is difficult, but could be done. The purpose of the charcoal canister is to store gasoline vapors evaporating in the fuel tank and in the carburetors. Webers lack a sealed float bowl/vent line and lack a ported vacuum port to purge the vapors from the charcoal canister. For carburetor vapors, the open bowl ports into the air box need to be sealed and new vent ports added. Perhaps fittings added to carburetor top plates. For a vacuum purge signal, I would suggest an electrical micro switch added to the carburetor linkage, activating a canister purge solenoid (common on all fuel injected engines). Adjust the micro switch for purge to occur above 1500 to 2000 RPM. Manufacturers also delayed purge until the engine was warm. Up to you if you want to add a temperature switch. You should also consider fuel injection. Carburetor float bowl evaporation goes away. Charcoal canister then only needs two ports, fuel tank and purge line. Computer that controls the fuel injection would command the purge.

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PostPost by: prezoom » Mon Jan 02, 2017 5:29 pm

Thanks Vic, more points to ponder. I had given some thought to routing the lines to the top covers, but not closing off the vents to the air box. Float bowl evaporation is not a concern. The Zetec has no provision for a mechanical fuel pump, so an electric fuel pump would be employed with carbs or injection. I have the carbs and an Electromotive HPV1 ignition left over from racing days. A breast in the hand is worth two in the blouse sort of thing. The cost for injection and the associated required ignition are unneeded expenses, unless all else fails. The other thing is, I love a challenge.
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1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

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