Carbon Canister and evap. system on Gas RTV?

[kmelander]

Can I delete this system and simply vent the fuel tank like normal, simple lawn tractors do? Do other SxS's use fuel evap. systems? It truly seems overly complex for this little ~450cc engine and 5 gal fuel tank. Seems like a good idea since I don't know much about them, other than 95% of the vehicles I've owned have had some sort of problem with, and triggered an CEL, due to the evap. systems.

That little "check valve" seems sketchy.

 

[lugbolt]

people have removed them but the downside is that wherever you store the machine, you WILL have fuel fumes building up. That's what the canister does, it uses activated charcoal to absorb the fumes instead of venting the fumes to atmosphere. EPA stuff so removing it is tampering with emissions devices which may not be legal. It doesn't hurt anything to leave it.

lawn mowers use them, SxS's use them, cars have used them since, gosh, early 1980's?? A LONG time. Possibly 1970's. People take them off all the time then they gripe about gas fumes. Well duh.

 

[wendol]

Not a RTV, but same dilemma on a Scag Zero Turn. I didn't realize it had a set of charcoal canisters until after the purchase, and then to learn the down side of having them.........i.e. being careful to not over fill the tank, using a hoist to raise the mower to clean the deck, mowing slopes, etc. could create problems with gas in the canisters.

After more research I found that Ferris (using the same identical engine) did not use the canisters, therefore I removed mine. Engine runs great, with no noticeable fumes when stored in the shop.
FWIW.....just my experience.

 

[fried1765]

Not a RTV, but same dilemma on a Scag Zero Turn. I didn't realize it had a set of charcoal canisters until after the purchase, and then to learn the down side of having them.........i.e. being careful to not over fill the tank, using a hoist to raise the mower to clean the deck, mowing slopes, etc. could create problems with gas in the canisters.

After more research I found that Ferris (using the same identical engine) did not use the canisters, therefore I removed mine. Engine runs great, with no noticeable fumes when stored in the shop.
FWIW.....just my experience.

I don't think that my zero turn, SCAG Liberty Z (21HP Kawasaki) has any canisters.

 

[kmelander]

people have removed them but the downside is that wherever you store the machine, you WILL have fuel fumes building up. That's what the canister does, it uses activated charcoal to absorb the fumes instead of venting the fumes to atmosphere. EPA stuff so removing it is tampering with emissions devices which may not be legal. It doesn't hurt anything to leave it.

lawn mowers use them, SxS's use them, cars have used them since, gosh, early 1980's?? A LONG time. Possibly 1970's. People take them off all the time then they gripe about gas fumes. Well duh.

It's just too many components and too complex for the application, IMO. It could conceivably cause issues if it malfunctions. A vacuum leak? In fact, once the weather cools off a bit, I'll be doing some testing to see if capping off that vac source from the TB has any effect on how the machine is running.

 

[lugbolt]

It's just too many components and too complex for the application, IMO. It could conceivably cause issues if it malfunctions. A vacuum leak? In fact, once the weather cools off a bit, I'll be doing some testing to see if capping off that vac source from the TB has any effect on how the machine is running.

on a lot of cars the ecu compensates for the slightly "richer" mixture when the purge valve is opened. I can't speak for mowers, I do not know their ecu strategies, although I would assume it would be similar.

 

[kmelander]

on a lot of cars the ecu compensates for the slightly "richer" mixture when the purge valve is opened. I can't speak for mowers, I do not know their ecu strategies, although I would assume it would be similar.

good point. in fact, I've been researching aftermarket ECU possibilities, just to know whats out there and learn more about the topic. Have you ever heard of Speeduino? I never knew it existed and it looks very interesting...and cheap. I spent thousands on a Holley Terminator system for my project car. Speeduino looks like it can be done for about $150 plus the sensors. I think, based on my research so far, there would be some challenges on this little Subaru engine. Primarily the TPS, or lack of one currently, and possibly the crank sensor. Sure would be nice to have a window into what the hell this troubled little engine is experiencing. Maybe I'll get lucky and find this evap system is the culprit. At least I have a couple more things to check before I'm completely vexed. If it winds up being the crank sensor, I'll explore the Speeduino solution more seriously in an effort to avoid removing the engine to replace the oem sensor. Id have to replace the throttle body with one that has a TPS and figure out a crank sensor solution. Something custom on the accessory drive side of the engine I imagine. Hopefully it doesn't come to that, but I'm prepared to go that far if necessary to fix this little bastard.

 

[lugbolt]

good point. in fact, I've been researching aftermarket ECU possibilities, just to know whats out there and learn more about the topic. Have you ever heard of Speeduino? I never knew it existed and it looks very interesting...and cheap. I spent thousands on a Holley Terminator system for my project car. Speeduino looks like it can be done for about $150 plus the sensors. I think, based on my research so far, there would be some challenges on this little Subaru engine. Primarily the TPS, or lack of one currently, and possibly the crank sensor. Sure would be nice to have a window into what the hell this troubled little engine is experiencing. Maybe I'll get lucky and find this evap system is the culprit. At least I have a couple more things to check before I'm completely vexed. If it winds up being the crank sensor, I'll explore the Speeduino solution more seriously in an effort to avoid removing the engine to replace the oem sensor. Id have to replace the throttle body with one that has a TPS and figure out a crank sensor solution. Something custom on the accessory drive side of the engine I imagine. Hopefully it doesn't come to that, but I'm prepared to go that far if necessary to fix this little bastard.

yeah I've heard of it. Performance automotive enthusiasts have tried it, and haven't heard any good feedback from it either.

megasquirt is another option, and probably a much better option. I have some experience with MS3X and PiMP.

any efi requires a crank sensor so you're gonna have to figure that part out. ECU needs to know where the crankshaft position is, so it knows when to fire the spark plug and injector(s). There are some things on the 360 deg parallel twins that can be "fudged" such as waste spark, which makes it slightly easier to "time" the engine's spark advance. Just fire both plugs at the same time. One is on exhaust stroke, other on compression. The one on exh stroke, don't matter if it's firing the plug or not-won't ignite anything. Pretty common setup even in OE applications (inline 4's come to mind....)

 

[kmelander]

I deleted the canister with no improvement or issues to the operation of the engine. I just T'd the 2 vent ports on the tank together and ran the vent line up to where the plastic check valve originally was. Similar location to the transaxle vent location. I found a rubber cap to seal off the vacuum port on the throttle body.

 

[Russell King]

I deleted the canister with no improvement or issues to the operation of the engine. I just T'd the 2 vent ports on the tank together and ran the vent line up to where the plastic check valve originally was. Similar location to the transaxle vent location. I found a rubber cap to seal off the vacuum port on the throttle body.

Reading through your other postings on your engine problems…

Is there anyway that plugging the vacuum port is causing the too rich fuel mixture? What did the port connect to and does it allow air movement or just vacuum pressure?

 

[kmelander]

Reading through your other postings on your engine problems…

Is there anyway that plugging the vacuum port is causing the too rich fuel mixture? What did the port connect to and does it allow air movement or just vacuum pressure?

I deleted the canister as a possible remedy and it made no difference. I think it does allow the fuel vapor to flow when the fuel tank pressure is above atmospheric somehow. I believe it's the small check valve that makes it all work.

 

[N3BP]

Not familiar with your SxS, but regarding the system, they are used on all fuel injected gas engines due to it being a pressurized system. The primary function is to direct and collect built up gas vapor, then spit it back into the engine to be combusted during specific times.
It does prevent nasty gas vapors if you park in a garage. Humidly and temperature will increase the pressure in the system and cause the smell.

I went through this when I was swapping a LS6 into MY RX-7. I didn't want to keep the system because it created excess weight and clutters up the engine bay. I was ultimately convinced to keep the system and in hindsight, glad it did. Guys that deleted the systems installed a "Rollover Valve" at their tank and reported mixed results.