I'm self tuned on haltech with a custom catalytic converter at the end of my stock header. I have advanced scavenging (gernby/urge style) so I can run more timing and more fuel. Every cell of the throttle opening and RPM table is custom tuned to be as lean and as powerful as possible. I don't have any reduction in power programmed into the haltech when the temperature start to rise. The stock Honda ECU dramatically reduces power when the temperatures rise, which is why stock cars have variable power levels.
Yes I have a return system and yes it is heating up the fuel in the tank. By dramatically reducing under hood temperatures, it reduces the tank temperature.
I'm opening the gas cap under special circumstances just because I know it's so hot it's going to fill up the entire vapor canister and begin flooding the intake. Only happens maybe once or twice a year when I'm out in the mountains, never when I'm returning home.

 

Ohhh right, because you have the vapor canister plumbed back into the intake. That makes more sense now. I thought it was just venting to atmosphere.

 

So I’ve got a question about the valve. Mocal says that the valve will open either way depending on the amount of pressure being exerted on it.



Does this mean that I can just cap off one of the hoses and use only one of them as both the breather and the vent? Sorry in advance if this is a stupid question.

 

This is a copy/paste from my build thread. I'm just adding it here to help all the people who are trying to deal with the fuel smell like I did after following the steps outlined in this thread.

Once I had the new pressure relief valve and filter installed I ran into a few issues. Summers are very hot here in Arizona, and I was experiencing very strong fuel smells coming from the car. Similar to what sometimes happens with completely stock S2000s, but it was happening all the time. It was hot enough outside the garage would start to smell very strong of fuel, and at stoplights with the windows down I was getting strong whiffs of fuel as well. Basically the new EVAP system was working as designed. The tank could build a bit of pressure (so it's not always just open), but when it releases that pressure it's pushing fuel vapor out which is where the smell is coming from.

I had been looking for a way to incorporate a charcoal canister into the system somehow to help reduce the smell. I had been searching on an off for the past couple of years to try and find some OEM or aftermarket system that would fit in the spot that the factory EVAP system used to live. My concern was that without a strong vacuum source there really wouldn't be a way to purge the system and that it would eventually fuel soak and need to be replaced. I ended up searching Google again and stumbled across some billet charcoal canister that wasn't there the day before. I started looking into it and it looked like it fit the bill. Fairly small, and straight forward, serviceable so I could open it and replace the material should it ever get soaked with fuel, and it was billet. It looked like a quality part. As I started looking into it I found a phone number on their site and realized the area code was from here in Arizona, and then found out their shop was located just a few minutes from my house. I ended up give the company a call, spoke with Tim and explained everything I was trying to do. He seemed to think that the canister would work perfectly for my set up and offered for me to swing by and see what we could do.

I initially elected to go with a 6in version as I wasn't sure how I was going to fit it, but I've since revised it to the 8in version. It's a pretty simple design, it's a billet tube with end caps that hold several mesh filters and O rings in place. You can use their fittings or add some -6 ORB fittings to make it work for your set up. I tried a few different layouts and ended up fitting it by laying it in the old EVAP tray that bolts to the OEM rear tie bar. The only modifications I did to the car were all two holes to that tray so that I could secure the D clamps. It rests on the tray, doesn't vibrate or make noise, and has eliminated the fuel vapor smell. Now when the pressure relief valve needs to vent rather that let it out into the atmosphere it vents it into the charcoal canister, which then vents out right in front of the air deflector for the driver side rear tire. The big concern from the Vapor Trapper team was that I might get some liquid fuel depending on how the S2000s fuel tank worked. To test that I completely topped off the S2000 with gas, took it to the track, and then the next day took the canister back to them and we opened it up and poured out all the charcoal from the inside. It was bone dry.

This thing works perfect and is another piece I'm going to recommend to everyone who is trying to reduce the fuel smell when running an aftermarket ECU or who no longer utilized the OEM EVAP system. It's excellent. It just works and completely solved the problem for me. Full disclosure I paid full price for my canister but the people at vapor trapper let me swap it out for a larger one, and thew in a few fittings to help me mock everything up as I was trying to figure out how to fit it. They also drilled out the holes for me on my EVAP tray as I didn't have a drill press at home. If you are running the set up from the EVAP thread I linked above you owe it to yourself to check these things out.

Charcoal Canister: https://www.classicperformancerestor...-vapor-trapper

 

I can confirm that the valve opens either way. I tried it with my mouth with I first got it to see how much pressure it would take to open the valve and I was able to get it to open both directions. I don't think that you want to cap the other line though. I have seen/heard people having issues properly filling the tank with one or both of the lines capped. I believe the larger line is for that or to let air into the tank when necessary. Just buy the recommend filter and dremmel out some of the rubber like I did to get it to fit over the OEM plastic connector.

 

Good writeup on using the billet charcoal cannister that gives another good option for those that are still having the fuel vapor issues in those super hot climates.

On a side note... I wonder why the S2k has such a problem with the fuel vapor smell? What is so different with the S2k fuel tank that causes this and why don't we hear of this issue with other platforms, like the Civic or others? Or maybe they do and I just haven't noticed....

 

Yes. I connected the end to an aftermarket charcoal canister, which then is connected to the stock intake vent lines.
Very hot engine bay with return fuel system so the tank gets very hot and the fuel boils after you turn off the car. I had to install a big charcoal canister and also a hood vent to keep things cool. I rarely hear my car "fart" anymore when the valve activates.

When I'm in the mountains and I beat on my tuned car for hours on hills, if I stop without 5+ minutes of specific cool down, you can hear the fuel being angry and it overwhelms the canister after a short amount of time. I crack open the fuel cap when I part it hot. The stock ECU reduces power when the engine bay is hot, my Haltech doesn't do that.

 

My pressure relief value would just give off this low level hum when it was open, which led me to believe that it was venting only bit of pressure. My fuel system has been converted to returnless though, so it's closer to an 06+ set up than it is anything else.

 

Recently bought an s2000. Previous owner completely removed the evap system and added those filters under the car. Can someone explain to me what reason would you want to do this? Car has a check engine light on because of it. I took the car to a pretty reputable shop to see if they’d could put a charcoal canister back on the car but they refused to do it and recommended that I get the car tuned.

 

For people using a standalone ECU - it renders the entire evap system inop. Eventually, because it isn't properly purging the vapors anymore, the charcoal canister ends up getting inundated with vapors to the point where it saturates and just starts filling with fuel. My logic was simple - When I chose to mod my car and go boosted, I knew I wasn't going back. Therefore, I removed any and all systems that were now virtually dead weight, but at the same time, I wanted to maintain some semblance of original function in terms of allowing the fuel tank to be able to breathe properly. Sure, that can be accomplished by just leaving the lines open, but for a small cost and not much effort it can be done properly.

Really happy with this thread. What started out as an idea has evolved quite a bit. Really really like @Feezy 's charcoal canister solution! I'd looked into some of that stuff myself but never went that far. Glad others are taking initiative and tossing ideas around! That's how the dream works.