EVAP Charcoal Canister and Purging
 

Hi All,

Recently I have been toying with the Miata EVAP canister system as I get a fuel smell coming from the canister which then wafts under the hood and then eventually finds its way through the air vents and into the cabin. It will happen when its a hot day and the car has been idling a lot in traffic. This is due to the V8 getting the tank and fuel lines very hot and expanding the vapors to the point where they flood the charcoal canister and overwhelm it, thereby letting the gasses "leak" out from the open air vent on the canister. This happens on the standard MX5 as well but nowhere to the degree of the V8 converted cars. Many people delete the evap canister but thats not a smart thing to do as it has an important role to play. From what I could find out, the SCT tuner software that I use to tune my car does NOT have a parameter that allows me to control the duty cycle of the purge solenoid. So I was stuck with whatever the factory duty cycle was for purging, which is no where near frequent enough to evacuate all the fuel vapor gases from the tank and canister. So what I have done to solve this is to use a really cool Multi function Timer that I bought from here:

Buy Multi Functional Timers online | Timers.shop


This timer allows me to setup cycling of the purge solenoid (independent from the ecu) so that the vapors can be sucked into the intake manifold at a more frequent rate. I have currently got it setup to work as follows:

1. Upon Ignition ON
2. Delayed Start for 10 mins (allows for engine warm up)
3. After 10 mins it will activate the purge solenoid
4. The Purge solenoid will work for 8 secs when activated then turn off
5. The Timer sleeps for 10 mins
6. Purge solenoid is reactivated for 8 secs

The Cycle will then repeats every 10 mins until ignition is switched off.

I thought I would share it as its been a bug bear for me for a while now....as people have often complained about my car smelling like its got a fuel leak, and the garage would stink after I parked the car (when hot) in it and and closed it up.

So with all other issues solved this is one of the last (if not the last) one that I have fixed.

Hope that helps :)

Cheers,

Cool. Great idea. Another step closer to perfection.)