Does anybody know when the purge solenoid activates in an OBD2a Integra?

The Helms makes it seem like its always on when the AC is on and the ECT is above 155. But it seems weird to me that it would always be purging whenever the AC is on.

 

If I had to guess, although guessing gets people into trouble...
I think I would put my money on deceleration I think there would still be enough engine rpm to be able to pull a slight vacuum in the gas tank, although when car reached normal idle speeds that evap would close so if the gas cap was off you wouldn't have a fluctuation of idle... as I don't believe hondas have a CEL based off the gas cap missing?? I could be wrong..

I would wire up a volt meter to the evap purge solenoid and wait for it to go from 0v to 12v... and if you have any obd2 loggers try that, then maybe you can tell us when it opens..

whats the point of your question anyway?? curious now.

--Aaron

 

It's because I'm NepTuning an OBD1 ECU in my OBD2a GS-R right now, and I'd like to be able to run the evaporative emissions system somewhat normally (trying to be environmentally friendly and all).

I can configure NepTune to send a purge signal under some fairly sophisticated conditions, so I'm just trying to do the best I can.

I've heard of people purging during decel but I'd like to burn the lost fuel if I can. I figured even though the ignition system is running on decel there wouldn't be enough fuel in the purge to actually ignite, and even then it wouldn't be giving power.

What I'm thinking I'll do is this:

Purge only under closed-loop conditions (when the ECU can pull fuel to compensate), and only in 2nd gear. That way I get purges fairly often, but not all the time, and not when I'm idling or romping on it.

From what I can tell the Integra OBD2a purge is set to go with ECT>155 and AC on, but I just can't imagine it runs all the time in those conditions. I figured those just activated ECU purge control, and then the ECU 'decides' whether to purge and when and for how long.

Right now I've got it set for always off while I'm tuning. I'm OBD1 now so no codes to worry about.

 

Well evap really does nothing for emissions, its suppose to keep the engine bay from smelling like gas... I don't run one and it does not smell like gas, so I'm not really sure.

If you are concerned with emissions run 2 cats!

you could simply remember to always leave the gas cap on and run a slight vacuum in the gas tank all the time and be just as good.

honestly... its not a horribly big deal.

--Aaron

 

Fuel always evaporates into the air spaces in the fuel tank. The most volatile hydrocarbons (like CO, CH3) evaporate most, and particularly when weather is warm. To prevent pressure buildup (or fuel tank collapse due to vacuum) the system is pressure controlled, which means that gasses vent out into the atmosphere.

Until 1977, systems were entirely open, and evaporated fuel escaped into the atmosphere constantly, 100% of the time. It's been estimated that 20% of auto HC emissions are due to evaporation, so it's a big deal. To fix the problem, we designed fully sealed fuel systems where pressure was controlled by regulators.

Carbon canisters at the vent location are installed to catch fuel vapors and prevent excess loss during venting. The PCS system draws a vacuum through the carbon canister to dry it out and introduce the 'lost' fuel into the intake manifold, where it can be burn along with the injected fuel. If you disable the PCS system, the canister will foul, and stop working, putting your car back (in some sense) to pre-1977 emissions standards. It has no effect on the tailpipe emissions, but cars with disabled PCS systems are still big-time polluters.

Getting the PCS working is painless, it protects the environment, AND it recovers evaporated fuel, meaning your fuel economy will improve, particularly if you only drive occassionally or spend a lot of time idling. It's a win-win. I just want to make sure I'm setting it up correctly and not using it excessively.

I know that converting to OBD1 sets the car back and worsens it's emissions. A car performance hobby is a hobby that has some inherent contradictions. Putting performance mods to work on the street is often dangerous and illegal, and modifications also often have environmental impacts. Being responsible hobbyists means being aware of those contradictions and making good decisions while still pursuing our hobby. If we can't do that, then there's not much future for auto modification in the coming decades.

I think more people should be aware of this problem since fixing it correctly is so easy with a system like NepTune.

 

Neptune has the ability to activate available output pins when certain conditions are met so I'm sure you could figure out some combination of items that would meet your needs.

Post something like that on the Neptune forum

 

Will do

 

I removed the charcoal canister and line running to the front all together. The line that used to run to the front I have from the little solenoid thing running out the back. On a hot day you see gas fumes but nothing crazy. Dangerous? IDK maybe but gas doesn't actually spill out and all offroad vehicles use a vented gas cap with no problems.

 

Vented gas caps are one-way, and they relieve vacuum. They rely on the evaporative emissions system to handle positive pressure in the fuel tank.

The problem is not really one of safety, but of unnecessary pollution (and fuel loss).