Charcoal Canister

[Toehead]

I've been running the MS from more then a year now, and It is a rock solid platform.

Something has always bugged me about my set up. The charcoal canister has an electrical 'purge soleniod' from the factory that controls when the contents are fed into the engine.

When I went with the megasquirt, I just simply bypassed the valve, and ran it through the pressure activated valve. This way, whenever the engine is running it is pulling in air from the canister.

This has presented me with a rather annoying problem: When it is really hot out, the engine starts to run richer because of the extra fuel vapor.

How did everybody here deal with the evap system on their cars?

[Joe]

I've given this some thought as well and have never come up with a good solution.

I have been thinking the following.

Use an extra channel to control the solinoid (Fidle or warmup LED) for hardware control. Thats the easy part.

I have never been able to find real good data on when the purge should be applied. All I have seen is "When the engine is able to use additional fuel" it purges the evap canister. I was thinking of leaning out my decel and using a conditional for the evap solinoid-

if RPM > 2000 and TPS < 10 enable the purge solinoid. My thought is for a brief moment on a coast down purge a little out of the canister. Never actually followed through, I moved on to other things. I am curious as well what others have actually used. Pro's and con's.

Once the hardware is wired. Enough tweeking with the conditionals should get good results with minimal impact on drivability.

Just my thought-

Joe

[Toehead]

That may be the correct time to to it.... It is also the time of the highest vacuum , and it would be the most effective.

[neil85ae86]

I've always been trying to figure out what stinks when I run the MS ...maybe this is the cause, smells really rich sometimes at a stoplight.

I too bypassed the factory solenoids.

Since my engine is boosted I ran a vacuum activated valve so that the canister doesn't get pressurized.

..but this is obviously not sufficient, alot of folks remove it altogether, I may have to look at doing that myself.

Neil

[Mad Medicine]

the original ecu usually don't leave it open all the time while running like you're doing. they usually only open up for a brief time when the conditions are right. I believe its usually when you're decelerating or not giving any load, but not idleing. but that can differ from car manufacturer. anyways you just have to remember that you only need to purge once in awhile, and let the pressure build up. you could try programming your output to just drive the solenoid when decelerating.

[Toehead]

I really should.

I could get a vac switch that is triggered by low vacuum (18kpa), seeing as how I already used all my outputs.

Does anybody know of such a switch?

[devastator]

I see several at Summitt Racing, but there is very little info about them.

[bleoh]

My computer feedback carb had one. This is pretty much the same system used in AMC vehicles from the mid to late 80's with the 4.2L straight six and the carter feedback carb.

http://home.sprynet.com/~dale02/vacuum.htm