subynut Posted May 9, 2005 Share Posted May 9, 2005 How do they work? Does the ECU just turn them on for a time then off or is it pulsed? Such as the EGR: The ECU kicks on the solenoid valve after the engine has warmed up, then the throttle body takes care of controlling the EGR valve itself. The purge control valve is opened after the car is warmed up and the engine speed above say 2000 RPM. Am I right? I think that's how I interpret those systems. Please correct me if I'm wrong. Link to comment Share on other sites More sharing options...
subynut Posted May 10, 2005 Author Share Posted May 10, 2005 Hummmm I guess there's no guenius in the house. Link to comment Share on other sites More sharing options...
Ross Posted May 10, 2005 Share Posted May 10, 2005 How do they work? Does the ECU just turn them on for a time then off or is it pulsed? Such as the EGR: The ECU kicks on the solenoid valve after the engine has warmed up, then the throttle body takes care of controlling the EGR valve itself. The purge control valve is opened after the car is warmed up and the engine speed above say 2000 RPM. Am I right? I think that's how I interpret those systems. Please correct me if I'm wrong. Not sure i understand what you are meaning about "on for a time then off or is it pulsed"??? Does the ecu not turn the valve off under WOT conditions? Link to comment Share on other sites More sharing options...
torxxx Posted May 10, 2005 Share Posted May 10, 2005 They are thermo activated I believe. Link to comment Share on other sites More sharing options...
Hank Roberts Posted May 10, 2005 Share Posted May 10, 2005 They are thermo activated I believe. The valve takes some exhaust gas -- very low oxygen -- and routes it back into the combustion chambers, so when the engine is hot, the lowered oxygen to fuel ratio is appropriate. If you're spoofing the EGR system so the engine thinks it's working, you're basically running your engine with the wrong ratio, too much oxygen for the amount of fuel at that temperature. Someone else will have to comment on what that does. But I can remember (in the early days of the latter half of the last century of the previous millenium, when we drove dinosaurs) that it wasn't, um, productive in the long run to forget to push the choke in after getting the truck running. Might be the same thing, basically. Don't trust my opinion -- I don't. Link to comment Share on other sites More sharing options...
subynut Posted May 11, 2005 Author Share Posted May 11, 2005 So, they are kicked on by the ECU at a certain temp. Cool, that means I can just find another 3-way solenoid valve and drive it with another relay that has roughly the same impeadance as the original solenoid valve. Hehe hehe hehe.......the wheels are begining to turn......... Thank you! Link to comment Share on other sites More sharing options...
stephenw22 Posted May 11, 2005 Share Posted May 11, 2005 I plugged off my EGR system and replaced the solenoid with a 68 Ohm, 2 Watt resistor. I haven't noticed any change as far as performance, mileage, or engine temperature goes. All I know is that my ECS light is out, and that there isn't an engine code for the EGR solenoid anymore. It was 'fixed' that way about 4-5 months ago. I also replaced my purge control solenoid with another 68 Ohm resistor. Link to comment Share on other sites More sharing options...
subynut Posted May 11, 2005 Author Share Posted May 11, 2005 Precicely. BUT if I can find a replacement solenoid valve, I would prefer to keep them enabled. Currently, my computer is complaining about the Purge, EGR and the Neutral safety switch. I may just throw those resistors in and see if I can get the ECU to run in closed loop mode. I assume you picked those resistors up at RadioShack, right? Link to comment Share on other sites More sharing options...
stephenw22 Posted May 11, 2005 Share Posted May 11, 2005 I just picked them up at a local electronic parts place in town. Personally, I loathe RadioShack, and I would never go there for parts. Anyways, the 2W rating seems to be working fine. We'll see over the summer how it holds up. You could go with a 5W-rated resistor if you wanted to be extra safe, or use a style with a better temperature rating (I just went with cheap carbon film resistors). I spent $1 per resistor, instead of $90 per solenoid from the dealer. The wrecking yards around here don't get many Subarus, and even less that have decent parts on them. When we take vacations, I always stop at big wrecking yards to scavenge for parts, and my wife thinks I'm a little weird. Link to comment Share on other sites More sharing options...
hooziewhatsit Posted May 11, 2005 Share Posted May 11, 2005 I would think that a normal 33ohm 1/4watt resistor would work just fine, since that's all the resistance that the coil has. subynut: I have two extra Purge control solenoids lying around. if you want one, PM me. Link to comment Share on other sites More sharing options...
stephenw22 Posted May 12, 2005 Share Posted May 12, 2005 I would think that a normal 33ohm 1/4watt resistor would work just fine, since that's all the resistance that the coil has. subynut: I have two extra Purge control solenoids lying around. if you want one, PM me. When you do the power calculation, you find that... Power = V^2 / R = 12^2 / 33 = 4.36 Watts into a 33 ohm resistor You'd make the little 1/4 watt resistor cry. a 68 Ohm resistor puts the power dissipation at just over 2 watts. Link to comment Share on other sites More sharing options...
hooziewhatsit Posted May 12, 2005 Share Posted May 12, 2005 When you do the power calculation, you find that... Power = V^2 / R = 12^2 / 33 = 4.36 Watts into a 33 ohm resistor You'd make the little 1/4 watt resistor cry. a 68 Ohm resistor puts the power dissipation at just over 2 watts. d'oh, my bad! Link to comment Share on other sites More sharing options...
subynut Posted May 14, 2005 Author Share Posted May 14, 2005 I did find a relay that's 62 ohms. I'm gonna try that and see if I can fake out the ECU. If that works, then all I have to do is find a 12V 3-way valve. Else, it's gonna be find a 68 ohm 5 watt resistor. Really want that CEL off. It's buggin' me. Link to comment Share on other sites More sharing options...
Hank Roberts Posted May 23, 2005 Share Posted May 23, 2005 If the EGR system is working -- as I understand it -- it's to change the fuel-air ratio after the combustion chamber heats up, when you want _less_ total percentage of oxygenated air in the mix. When it's working, the EGR system is feeding some already-burned air back in to lower the total percentage of oxygen. (I know this much, if I do, because the persistent EGR code problem I had, which had baffled a year's worth of mechanics for the prior owner, happened because someone had screwed up one hose trying to make the light go off. Result -- both channels in the engine (one leading from the exhaust side to the EGR, the other from the EGR back to the combustion chamber) had packed up solid with carbon because the valve was not being properly operated by the solenoid. So replacing everything outside the engine itself didn't help. Fix was taking the engine apart enough to soak and clean out the gas ports. Twice, because the first guy didn't think or bother cleaning them both out -- didn't understand how it worked or went home early, wtfdik. Meanwhile, the engine had been running with too much oxygen in the combustion mix the whole time it was hot, for a year. The previous owner who sold it to me had had no end of trouble getting it to run well in that condition. Let us know how it works for you if you try it. I don't know how fooling the EGR system compares to just having it totally clogged. I'd guess the same thing is happening in the combustion chamber either way -- overly much oxygen while running at normal temp. Link to comment Share on other sites More sharing options...
subynut Posted May 24, 2005 Author Share Posted May 24, 2005 Currently, I have a good used one in there. So, the idea is on the back burrner right now. Gots other Subarus that want my undivided attention. Link to comment Share on other sites More sharing options...
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