Michael Savage Posted April 17, 2016 Report Share Posted April 17, 2016 Several of you have probably seen me post about improving on the fuel system. EVAP system, it has a Paint can full of Charcoal to "store" the Gasoline vapors. Then goes up to the EVAP solenoid which is basically a electric needle valve from what I've read. What is the point of the charcoal in the canister? Wouldn't it be better for mileage/performance to have it empty and just have a flashback arrestor(if the solenoid isn't capable of that) and get a stronger amount of fuel Vapor injected into the system without possibly being compromised by the charcoal? Just a thought I was thinking about. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 From my understanding the charcoal absorbs the fuel vapors and only let's a little out from the Vacuum of the engine when the evap is in open loop. So the charcoal is literally just there to prevent the vapors in a stonger/purer state from entering the engine. What would hurt to replace the charcoal canister with another with the charcoal removed entirely and let the canister contain the fumes? Another question when is the Solenoid open and closed? Can't find much info on why the charcoal is there other than to trap the fuel in the charcoal. From my other research Fumes have a much stonger combustion rate than the liquid fuel. So since the canister is letting in fuel vapors wouldn't more be better than less and make you use less liquid gas since there's no added Oxygen than with the stock setup so it's calculated as running rich and lessens the load on the Injectors making you use less liquid fuel. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted April 17, 2016 Report Share Posted April 17, 2016 the activated charcoal is used as a storage medium to get the vaporized fuel out of otherwise stagnant air. without the charcoal, any fuel vapor that builds up before being purged is going to settle and collect as a liquid on the bottom of the canister, defeating the purpose. when the purge solenoid is opened(earlier stuff tends to need power removed, later stuff needs power applied), it acts as another air path into the engine, which is why there is a filter on the canister itself to prevent dirt/etc from being ingested. OBD2 vehicles have a vacuum switch/sensor(year/application dependent) and another solenoid in the feed line that is used to test for leaks in the EVAP system, the fuel tank itself and even the gas cap. solenoid tends to be closed under low throttle conditions, otherwise idle instability is a serious consideration. opens when there is a decent amount of throttle being applied(in the case of boosted engines, solenoid is shut again with positive manifold pressure to prevent pressurizing the EVAP system). gasoline vapor does burn better than liquid gasoline... in fact, liquid gasoline doesn't burn at all, which has been the push for smaller and smaller injector orifice sizes, better fuel atomization. the fuel that gets pulled from the charcoal canister reaches the engine pretty well vaporized. oxygen(air in general, really since atmospheric oxygen content is ~21%) is added to the fuel vapors via the fact that filtered air is drawn through the canister. the mixture ratio is going to be highly variable and really difficult to predict since estimating the amount of stored fuel vapor would require the PCM to be active at nearly all times, sampling ambient conditions to guess at how much the fuel is evaporating in the tank and being stored by the canister while the engine isn't running. instead, purge only tends to be allowed under closed loop conditions, that way the O2 sensor can just trim the fuel coming via the injectors by whatever small amount necessary. Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted April 17, 2016 Report Share Posted April 17, 2016 I would think if you're going to do that you might as well rip it out completely... At any rate I think mine is plugged/ unworking, now that it's warmer I have to look into it and rid the code Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 Yeah I considered that but the canister adds extra protection from gas sloshing around incase of an accident no fuel(can escape due to its placement. I'm gonna pull the one off my scrap Monte here in a little bit and see how easy it is to rebuild. Read up on the Activated Carbon I think the amount in our old ones is overkill 1tablespoon is equal to close to a football field in surface absorption. Gonna see how it works with less in the canister. Considerably ours are alot larger than most cars, also after 20years I'm sure the one on my car is needing a tuneup if anything. Also mine is the 95 model and only has the purge solenoid and canister. Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 But Robert what would you say gain vs loss would be on minimizing on the Carbon a little or swapping to steel mesh vs standard. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted April 17, 2016 Report Share Posted April 17, 2016 Read up on the Activated Carbon I think the amount in our old ones is overkill 1tablespoon is equal to close to a football field in surface absorption. when you're looking at really, REALLY finely vaporized fuel(down to just a few hydrocarbon molecules sticking to each other), you need all of the absorbent surface area you can get. But Robert what would you say gain vs loss would be on minimizing on the Carbon a little or swapping to steel mesh vs standard. the amount of steel mesh required to equal even half the capacity of what activated carbon can retain would be unreasonable. that and far more prone to dropout since the fuel would only really be attached to the mesh via surface tension rather than absorption(adsorption?). to be honest, I'd leave it the hell alone, GM wouldn't have put that much time/money into it if they didn't need to. the last time I had mine in my hand, I was checking to see if it had any obvious damage and if it had a replaceable filter element(pretty sure it didn't), otherwise it got thrown back where it belonged and continued to do its job. Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 There's a foam filter inside top and bottom that keeps the Carbon bits from falling into the hoses thar need replacing, I'm gonna try to get the one off the other car to take it appart I'll post some pics, gm didn't spend alot of time money or research on the canister itself back then just copied the universal can same ones on about everything the new styles have actually had testing done and are virtually just smaller cans with less charcoal don't think the ones they made had any changes from 81 until 2000+ same ones on the 79 S10 Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 Those regulations they passed in 77? So the design and setup was kinda just thrown together from what I've been reading and supposedly they new style ones are better to use if you can find one with the connections you need on it's Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 this is mine replacing those hoses now btw Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 this is the late 90s model with the gas cap sensor(guessing since there's no other sensor back there) now I'm stumped because this one looks solid sealed Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 17, 2016 Author Report Share Posted April 17, 2016 Besides the point of messing with the can. Is it possible to tune the car to open more/less at different variables? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted April 18, 2016 Report Share Posted April 18, 2016 those are the most critical components of the CCP solenoid operation for 94-95 3100 PCMs. the code actually modifies the solenoid position continuously while in operation, hence the term "initial" for duty cycle. if the valve is commanded open at all, it will continue to open to 100%. if the valve is commanded to close, it will close slowly via the same process. there are also the MAP and IAT modifiers shown and a handful of scalars used to enable/disable based on MPH/runtime/coolant temp/etc. it could be modified to work differently, but it would be a fringe scenario(monster throttlebody) where any kind of changes would really be noticed. Quote Link to comment Share on other sites More sharing options...
Michael Savage Posted April 18, 2016 Author Report Share Posted April 18, 2016 Oh sweet mother lol more complicated to mess with than its worth since it's flash and see if it fails basically. Which I can't do myself. So that'd be rough unless you could find say a new model cars identifiers and check to see what say a evap setup for a late model 3500 Non vvt looks like and see about porting it over. If there's not added in variables from obd2/updated evap system Quote Link to comment Share on other sites More sharing options...
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