EGR/AIR questions.
08-20-2011, 09:38 PM
#1
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Location: Detroit, MI
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EGR/AIR questions.
I have had my car over 10 years and back when I first bought it I made some "modifications" as per the resident LT1 expert. I removed my AIR injection, TB bypass, etc. This brings me to my query...
The charcoal canister/vapor system remains despite the removal of my AIR injection. I have given myself a headache trying to understand the correlation between the two, and recently after I replaced my charcoal canister, purge valve and solenoid due to a code 26, I had an epiphany. Am I right to assume the AIR injection dilutes the EGR hydrocarbons? If so, does this mean that I could be doing engine damage by injecting straight EGR emissions into the engine? And further, is this effecting my air/fuel combustion? I had the EGR tuned out of the computer, but for some reason it still throws a 26 when the vapor system is not functioning properly.
Thanks in advance,
Charlie
The charcoal canister/vapor system remains despite the removal of my AIR injection. I have given myself a headache trying to understand the correlation between the two, and recently after I replaced my charcoal canister, purge valve and solenoid due to a code 26, I had an epiphany. Am I right to assume the AIR injection dilutes the EGR hydrocarbons? If so, does this mean that I could be doing engine damage by injecting straight EGR emissions into the engine? And further, is this effecting my air/fuel combustion? I had the EGR tuned out of the computer, but for some reason it still throws a 26 when the vapor system is not functioning properly.
Thanks in advance,
Charlie
08-20-2011, 10:28 PM
#3
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Re: EGR/AIR questions.
Thank You!
Charlie
08-20-2011, 11:38 PM
#4
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Location: Little Rock, AR
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Re: EGR/AIR questions.
The EVAP is beneficial for dealing with any fumes from the tank. The system has no effect on performance. I don't see any benefit to removing it. MHO.
08-21-2011, 09:40 AM
#6
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Location: Hell was full so they sent me to NJ
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Re: EGR/AIR questions.
AIR, EGR and EVAP are three TOTALLY different systems, each aimed at a particular form of emissions reduction.
AIR - injects filtered air into the exhaust manifolds for the first 2 or 3 minutes from startup, then shuts off. It's only purpose is to put the air into the exhaust to help burn up the excess hydrocarbons that come out in the exhaust, due to the very rich mixture used to start the engine. In burning the HC's in the exhaust manifold, the heat generated helps the cat heat up faster. The cat won't work until it reaches 600*F.
EGR - Dumps exhaust products back into the intake manifold, to help reduce the formation of oxides of nitrogen (NOx). The EGR only flows under engine operating conditions that cause high combustion chamber temperatures. That's when the normally inert nitrogen in the incoming air starts to combine with the oxygen and form the polutant NOx. Does not operate at idle, does not operate at WOT. Does not operate above 3,500RPM. In addition to reducing the formation of NOx, it also helps minimize detonation (knock) when the engine it being lugged at low RPM in the wrong gear.
EVAP - Collects the hydrocarbon vapor being vented from the fuel tank, by adsorbing the HC's on the charcoal. Periodically, the EVAP purge solenoid opens, and allows engine vacuum to pull fresh air through the charcoal canister to strip the HC's from the charcoal, and allow them to be pulled into the intake manifold, and burned in the combustion chambers.
In a practical sense, NONE of these hurts your engine performance. EGR offers the advantages of reduced knock,. EVAP collects the fuel vapor, preventing a gas smell at the rear of your car, and gaining some tiny amount of improved fuel mileage.
In fact, there is really no good reason to delete them. I built an 800HP nitrous 381, and kept all three system totally intact and functional (at least until it became a "track only" car).
AIR - injects filtered air into the exhaust manifolds for the first 2 or 3 minutes from startup, then shuts off. It's only purpose is to put the air into the exhaust to help burn up the excess hydrocarbons that come out in the exhaust, due to the very rich mixture used to start the engine. In burning the HC's in the exhaust manifold, the heat generated helps the cat heat up faster. The cat won't work until it reaches 600*F.
EGR - Dumps exhaust products back into the intake manifold, to help reduce the formation of oxides of nitrogen (NOx). The EGR only flows under engine operating conditions that cause high combustion chamber temperatures. That's when the normally inert nitrogen in the incoming air starts to combine with the oxygen and form the polutant NOx. Does not operate at idle, does not operate at WOT. Does not operate above 3,500RPM. In addition to reducing the formation of NOx, it also helps minimize detonation (knock) when the engine it being lugged at low RPM in the wrong gear.
EVAP - Collects the hydrocarbon vapor being vented from the fuel tank, by adsorbing the HC's on the charcoal. Periodically, the EVAP purge solenoid opens, and allows engine vacuum to pull fresh air through the charcoal canister to strip the HC's from the charcoal, and allow them to be pulled into the intake manifold, and burned in the combustion chambers.
In a practical sense, NONE of these hurts your engine performance. EGR offers the advantages of reduced knock,. EVAP collects the fuel vapor, preventing a gas smell at the rear of your car, and gaining some tiny amount of improved fuel mileage.
In fact, there is really no good reason to delete them. I built an 800HP nitrous 381, and kept all three system totally intact and functional (at least until it became a "track only" car).
08-21-2011, 01:11 PM
#7
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Location: Detroit, MI
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Re: EGR/AIR questions.
Excellent info, thank you. It is amazing how my approach to the car has changed during the course of ownership (10 years). I used to be concerned with the "go" and blindly cut wires, deleted this or that, spray painted things, etc. Now I strive to return the car to stock appearance and functionality and I find myself questioning my practices of old. Thanks again for your help.
Charlie
Charlie
12-20-2012, 11:16 PM
#9
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Re: EGR/AIR questions.
"mess the engine up"..... depends.
It will prevent the EGR system from operating. EGR is used only when cruising below 3,500RPM, and typically when lugging the engine in the wrong gear. That causes high combustion chamber temps, which causes the formation of oxides of nitrogen (NOx) in the exhaust. The PCM opens the EGR valve, using the vauum solenoid, to dump exhaust gas into the combustion chamber and reduce the temperature. Without the EGR, when lugging the engine, you may encounter detonation (spark knock). The PCM will pick that up via the knock sensor, and pull ignition timing to prevent the detonation.
If you frequently lug the engine, and run low octane (regular grade) fuel, you may encounter more detonation than the PCM can prevent, and then you could "mess up the engine". The knock would be audible at that point.
Depending on the year of your car (which you have not indicated), you may or may not get a code/SES light for the non-functional EGR system.
You need to add a "Signature" with basic info about your car - year, model, engine, trans and any major modifications. There are subtle difference from year to year, type of trans, etc. that may affect the answers to your questions.
It will prevent the EGR system from operating. EGR is used only when cruising below 3,500RPM, and typically when lugging the engine in the wrong gear. That causes high combustion chamber temps, which causes the formation of oxides of nitrogen (NOx) in the exhaust. The PCM opens the EGR valve, using the vauum solenoid, to dump exhaust gas into the combustion chamber and reduce the temperature. Without the EGR, when lugging the engine, you may encounter detonation (spark knock). The PCM will pick that up via the knock sensor, and pull ignition timing to prevent the detonation.
If you frequently lug the engine, and run low octane (regular grade) fuel, you may encounter more detonation than the PCM can prevent, and then you could "mess up the engine". The knock would be audible at that point.
Depending on the year of your car (which you have not indicated), you may or may not get a code/SES light for the non-functional EGR system.
You need to add a "Signature" with basic info about your car - year, model, engine, trans and any major modifications. There are subtle difference from year to year, type of trans, etc. that may affect the answers to your questions.
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