Jazsun

Thinking about getting it tuned out just because my pcm is getting tuned. Is there any advantage? Does having it help gas millage? Does having it tuned out help?

My car already has no cats so I don't care about emissions.

69gto96z

As far as I know it doesnt, but I could be wrong. I don't have EGR, AIR, or cats on my car anymore and with good 02 sensors I was pullin an average of 20 mpg with that being about 50/50 highway/city and with all mods in sig.

jsetzer

It does not help or hurt performance.
It may help with detonation issues having it.
It does free up a little room and is one less thing to unhook when ripping stuff apart.

Most will say there is no reason to remove it, but I did.

speed_demon24

Only at part throttle, the egr shuts off at WOT.
I took mine off since it saves alot of time working on the car and pulling the manifold. + It won't do anything if you have a cam since it has alot of overlap already, and its 1 less thing to worry about breaking.

mourningyou

If it works, and you're still worrying about gas mileage, there's no reason to remove it. It lowers combustion chamber temperatures at idle/low load. If you DO remove it, make sure you take your time and block all of its ports carefully, because a vacuum or exhaust leak WILL ruin your gas mileage.

69gto96z

To block mine off, I just took some aluminum and cut it into shape and bolted it between my manifold and my EGR. I wanna pull it off completely but that is not on the top of my priority list...

Wild1

EGR will not affect performance since it is closed on WOT. It only opens on part throttle to cool the combustion chambers and reduce NOx emissions. It wouldn't affect mileage.

SS RRR

only the EGR port (drivers side) needs to be blocked off.

shoebox

My EGR operates when the throttle is open (part throttle), not closed. I think you have it backwards. There is no real need to cool the chambers during deceleration.

Wild1

Shoebox, you are right. I'll edit my post. EGR is open at part throttle. Thanks for catching the error.

Injuneer

The use of EGR displaces fuel and air in the combustion chamber, reducing the effective displacement of the engine..... isn't it sort of like "displacement on demand"

km9v

Exhaust gas recirculation
From Wikipedia, the free encyclopedia

Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.


EGR in Spark-Ignited (SI) Engines

In a typical automotive SI engine, 5 to 15 percent of the exhaust gas is routed back to the intake as EGR (thus comprising 5 to 15 percent of the mixture entering the cylinders). The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in an SI engine can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. Contrary to popular belief, EGR actually increases the efficiency of gasoline engines via several mechanisms:

* Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.

* Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.

* Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC, rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is relatively minor compared to the first two.

EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.

EGR in Diesel Engines

In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, where there is otherwise a very large amount of excess air).

Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines (see above). However, exhaust gas (largely carbon dioxide and water vapor) has a higher specific heat than air, and so it still serves to lower peak combustion temperatures; the diesel engine's efficiency is still improved by reduced heat rejection and dissociation.

Implementation of EGR

Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet manifold, which is called external EGR. A control valve (EGR Valve) within the circuit regulates and times the gas flow. Some engine designs perform EGR by trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke, which is called internal EGR. A form of internal EGR is used in the rotary Atkinson cycle engine.

EGR can also be used by using a variable geometry turbocharger (VGT) which uses variable inlet guide vanes to build sufficient backpressure in the exhaust manifold. For EGR to flow, a pressure difference is required across the intake and exhaust manifold and this is created by the VGT.

Other methods that have been experimented with are using a throttle in a turbocharged diesel engine to decrease the intake pressure to initiate EGR flow.

Early EGR systems were relatively unsophisticated, utilizing manifold vacuum as the only input to an on/off EGR valve; reduced performance and/or drivability were common side-effects. However, modern systems utilizing electronic engine control computers, multiple control inputs, and servo-driven EGR valves typically improve performance/efficiency with no impact on drivability. In the past, a meaningful fraction of car owners disconnected their EGR systems. Some still do either because they believe EGR reduces power output, causes a build-up in the intake manifold in diesel engines, or because they feel the environmental intentions of EGR are misguided. Disconnecting an EGR system is usually as simple as unplugging an electrically operated valve or inserting a ball bearing into the vacuum line in a vacuum-operated EGR valve. In all cases, the EGR system will need to be operating normally in order to pass emissions tests.