The skinny on EGR's

[sleeperred90tgp]

EGR and EVAP Emissions Systems nonsense

I am sure by now everyone has heard from the old racer down the street that you need to yank all of that emissions "crap" off of your car because it hurts performance and does not have any benefits.  Nothing could be further from the truth.  First off, when functioning properly, both the EGR and EVAP systems are SHUT OFF at Wide Open Throttle.  So exactly how are these systems degrading performance?  The short answer is they don't hurt performance and removing them can cause annoying or damaging results.

The EVAP system is designed to recycle or burn unused gasoline vapors instead of allowing them to escape into the atmosphere from the fuel system.  Gasoline fuels vaporize at room temperature.  At higher temperatures, more gasoline vaporizes and can build high pressures and in greater concentrations.  This can occur even with the vehicle sitting in the hot sun on a summer day!  On most fuel injected cars, the fuel is constantly circulated thru the fuel rails which are mounted on the top of the engine.  As a direct result, engine heat is constantly transferred to the fuel system.  This increased heat causes more fuel to vaporize in the tank which results in a pressure buildup.  All of these vapors have to go somewhere.  If allowed to escape to the atmosphere, at the very least they can present an annoying and smelly problem -- raw gas fumes.  The charcoal canister is designed to store these gas vapors until the engine is operated.  When the engine is operating at preset parameters, the canister is vented to the intake manifold and thus is "purged" of its stored vapors.  Most 96-up OBD-2 equipped vehicles have what is known as an Advanced EVAP system.  Here, a second canister is installed back by the gas tank and its function is to store gas vapors accumulated during refueling.

The EGR system is a little more involved in its function.  The EGR valve and system are designed to introduce INERT exhaust gases into the intake manifold and engine during preset circumstances.  The primary reason for doing this is to cool the combustion event which results in less NOx gas emissions from forming.  There are a few side-effects to having a functioning EGR system present.  First, because the EGR system is cooling the combustion event, less heat is transferred to the engine resulting in less cooling load on the cooling system.  Second, the inert gas present takes up space that would otherwise need to be occupied by more fuel and air.  Therefore, in affect, the engine effectively becomes "smaller" (breathing less) and more efficient using less fuel when the EGR is operating.  A functioning EGR system has been shown to cause slightly better gas mileage compared to an identical engine and vehicle without a functioning EGR system.  Now there is a potentially damaging drawback to removing or disabling an EGR system on a vehicle.  If the computer does not know that the EGR is not functioning, it may be commanding more ignition timing (as it usually does when it commands the EGR system ON) which can result in hotter combustion temps and even detonation.  If you remove or disable your EGR system, you should have the computer reprogrammed to disable the EGR spark advance parameters or significant engine damage could result.

[TGPvsTIII]

amen brother. Finally someone else that wants to burn all the fuel they pay for. On some cars you can use a scanner to open the purge sol. If you can see the pw of the injectors you can watch the computer cut it back with the sol. open
Tim