Self added EGR, effect on emission?

[TheNeedForZ]

I was wondering what effect will it have if a car that doesn't have EGR is modified to recirculate its own exhaust? What will it do to the emissions?

 

What if the exhaust pipe is a little "plugged up" so there is even more exhaust pollution in the intake charge? What will it do to the emissions?

 

Thanks

[SpeedRacer]

Don't do it because EGR really isn't a good thing. Exhaust Gas Recirculation introduces "inert" gas (exhaust) back into the intake manifold which lowers Oxides of Nitrogen (NOx) by lowering combustion temperature. BUT, you want higher combustion temperature as it generates more horsepower and improved fuel economy.

 

The auto manufactures have to walk a thin line because emissions are somewhat like a seesaw. Both unburned Hydrocarbons (HC) and partially burned Hydrocarbons (CO) go down as cylinder temperature goes up but NOx goes up as cylinder temperature and pressure goes up. So, they introduce some exhaust gas back into the intake manifold when the engine is under light load to help reduce NOx.

 

SO, fuel economy as well as HC and CO emissions will probably be better on a properly tuned engine. NOx will be higher but its primary (although there are others) pollution effect is that it causes ground level Ozone - visible smog.

[rudypoochris]

I was under the impression that exhaust gas is not combustable. For this reason by adding it into your intake mixture it should decrease the effective amount of displacement making your engine equivalent to that of a smaller mechanical displacement. I think that is supposed to reduce emissions, fuel consumption, and combustion temperature. Of course power is less but then again EGR disables at WOT so it doesn't really matter (until you get a leak).