I know, I know - not another fuel tank breather thread! I've renewed all the connectors and have a new t-piece and one open ended 7mm pipe and am just considering how to connect it to the air filter. I'm already connecting the crank case breather to a t-piece and have that to go to both filters on my twin 40 Webers, and was going to connect the tank breather to just one air filter. Is this ok? Is there any risk if there's a backfire through a carb that the vapour in the breather pipe will ignite? Do the condensers act as flashback arrestors? Can somebody put my tired little brain at ease please?
Good questions. Not sure of the answers but I used a modified Bugpack aluminium breather box to split the engine breather and to take the fuel breather.
If a pipe is full of pure petrol vapour it cannot burn as there is too low an air fuel ratio . Its why the gas main cant blow up when you light the gas at home, and every Calor bottle cant blow up as you put on the kettle. It will burn where the air/fuel ratio is correct - at the end of the pipe where there is enough air. At worst its a candle.
I thought I might be worrying too much. It's just the thought of an open pipe with petrol vapour in it being in contact with a backfire that worries me. I don't know what's inside the condenser behind the air-vent or whether it protects from this. Maybe a charcoal box of some sort in series would help?
Both of those have flash-back arrestors though and there is a constant positive pressure. With the fuel tank breather pipe system there is no positive pressure, so I was thinking the flame could travel back down the pipe unless the condenser prevents that?? I would think the petrol vapour in the pipe is mixed with air too. The fire triangle needs fuel, air and fire to burn - all three would be there, wouldn't it?
Looks great! Where does the fuel breather go - can't see it. Think I might go this route as I'd only have to put one pipe into each air filter. Where can you buy one if these and how did you modify it?
Can’t remember where I bought it. One of the usual suspects, probably VWHeritage. It was about 20 quid special offer. It comes with hose and all fitting for three pipes and for air filter tops etc. I made an extra hole for the fuel breather with a screw in Union I found at work, same as Snotty has done to his air filter top. The simple mod was to the breather box lid to make it a sealed unit instead of breathing in to the engine bay.
I spent forever looking in to all of this too. Started a thread and followed the advice (echoed on Samba) to just pipe Fuel Vapour to one of my Carb Air Filters. I used a threaded pipe connector (similar) to one of the above pics. Only reason I opted out of using an additional box was because I’d have to get help taking the engine out. Good luck. I did 1,000miles not even knowing I didn’t have a System in place Sent from my iPhone using Tapatalk
OK my uber-paranoid little brain is at rest. That's a super-tidy job. Think I may use a box - haven't decided yet.
I’d vent it into the carbs. Breather boxes tend to fill up with oil. Or...use a box that doubles as an oil filler.
