Exhaust/codes???
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Joined: Nov 2004
Posts: 2,475
From: Garland, tx
bypass AIR EGR??? also knock module bypass???
heres the question soon going to put on pacesetter LT with true duals w/o x or hpipe...so it sounds real good with cam later...the qeustion is i want to block off AIR AND EGR and if i do will i throw any codes??? and can some1 explain more in detail wat theses are and wat they do i think i understand AIR is just an air pump that pumps clean air into the exhaust for emissions...is this before or after the o2 censors...sor a 94Z...i kno there b4 the cat soi not worried about that...thanks
Daniel
also forgot does anyone know how to bypass the knock module...ive heard of this being done with a resister in the line does anyone know the details of this or have a site that shows this, know the resister size???
Daniel
also forgot does anyone know how to bypass the knock module...ive heard of this being done with a resister in the line does anyone know the details of this or have a site that shows this, know the resister size???
Last edited by Daniel6718; Nov 28, 2004 at 04:57 AM.
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From: Hell was full so they sent me to NJ
Re: bypass AIR EGR??? also knock module bypass???
The AIR pump runs for about 3-4 minutes at startup. The air that it pumps into the exhaust manifolds (obviously, before the O2 sensors) combines with unburned hydrocarbons (HC) and carbon monoxide (CO) from the rich startup mixture, releasing heat that helps the catalytic convertor and the O2 sensors heat up faster, and start working. Deleting the system has no affect on performance.
In an OBD-I setup (93-95), you can totally delete the AIR system, and there will be no code set as long as you insure there is a good fuse in the power supply circuit for the AIR pump. OBD-II has additional ldiagnostics, and will almost always set a code.
The EGR system allows a small amount of burned exhaust gasses to be recycled to the combustion chambers. That gas displaces oxygen, and reduces combustion chamber temperatures, reducing the formation of the pollutant "oxides of nitrogen (NOx). The sytem only works at part load, generally when lugging the engine in too low a gear. Never works at idle, never works at WOT or over 3,500rpm. Removing the system has no affect on performance. It could be argued that the EGR system help reduce the potential for detonation when the engine is under certain part throttle loads. A leaky EGR valve can cause rough idle, stalling and surging, so eliminating it and properly blocking the system eliminates this possibility.
In the OBD-I cars, there is a diagnostic routine used to determine if EGR is flowing when it is supposed to be. The diagnostic does not seem to be very sensitive/accurate, and 90-95% of the people who delete the EGR in OBD-I cars do not get a DTC code, but it is possible. OBD-II diagnostic is much more sensitive, and will almost always set a code. There is a way to trick the PCM into thinking the EGR is still there, using a switch and resistor on the MAP sensor.
Why do you want to "bypass the knock module". The module is a filter in the PCM that filters out "false" knock. Most people upgrade to the LT4 knock module because it is a more selective filter and does a better job of eliminating false knock signals.
You may be confusing the knock module with the knock sensor, screwed into the side of the block. That can be "desensitized" wiht a circuit involving resistors, but there is no reason to do that unless you have determined that you are getting excessive knock retard as a result of false knock. Desensitizing or bypassing the knock sensor is simply adding risk of engine damage.
In an OBD-I setup (93-95), you can totally delete the AIR system, and there will be no code set as long as you insure there is a good fuse in the power supply circuit for the AIR pump. OBD-II has additional ldiagnostics, and will almost always set a code.
The EGR system allows a small amount of burned exhaust gasses to be recycled to the combustion chambers. That gas displaces oxygen, and reduces combustion chamber temperatures, reducing the formation of the pollutant "oxides of nitrogen (NOx). The sytem only works at part load, generally when lugging the engine in too low a gear. Never works at idle, never works at WOT or over 3,500rpm. Removing the system has no affect on performance. It could be argued that the EGR system help reduce the potential for detonation when the engine is under certain part throttle loads. A leaky EGR valve can cause rough idle, stalling and surging, so eliminating it and properly blocking the system eliminates this possibility.
In the OBD-I cars, there is a diagnostic routine used to determine if EGR is flowing when it is supposed to be. The diagnostic does not seem to be very sensitive/accurate, and 90-95% of the people who delete the EGR in OBD-I cars do not get a DTC code, but it is possible. OBD-II diagnostic is much more sensitive, and will almost always set a code. There is a way to trick the PCM into thinking the EGR is still there, using a switch and resistor on the MAP sensor.
Why do you want to "bypass the knock module". The module is a filter in the PCM that filters out "false" knock. Most people upgrade to the LT4 knock module because it is a more selective filter and does a better job of eliminating false knock signals.
You may be confusing the knock module with the knock sensor, screwed into the side of the block. That can be "desensitized" wiht a circuit involving resistors, but there is no reason to do that unless you have determined that you are getting excessive knock retard as a result of false knock. Desensitizing or bypassing the knock sensor is simply adding risk of engine damage.