EGR – can engine work better without it?
 

We have a discussion in our local Mazda forum of one experiment on EGR. Guys (who even have EGR as a whole in good working condition) advisedly “switched EGR Off” by putting a gag between their cars exhaust system and the intake manifold. It can be quite easily done, for instance, by properly sized coin fitted into EGR intake pipe or by a piece of tin at EGR valve so that exhaust gas is not anymore recirculated back into the intake stream. And several guys tell that as soon as they did that the idle RPM became more stable, more engine power and other positive results were noticed!

But other experimenters report that no changes at all or even some negative were observed.

Also, it looks like that original (the manufacturer’s) gags exist to do the above described. For instance, a plate part # JE41-20-301 for Mazda 323 98’ BJ.

I, of course, understand that as the main purpose of EGR is to reduce oxides etc. of emissions this gag does not help to eliminate atmospheric problems. I also think that it is unlikely but I am just curious whether somebody in this forum tried to do such an experiment? If so, did you notice any positive or negative changes?

And, in general, if ERG is eliminated, may it give any improvements in the engine performance? What do gurus here think?

RE: EGR – can engine work better without it?
 

Have not tried this myself on any of my own vehicles Sirob but here is my two cents worth.

EGR system and its effects on performance. First off we need to think about what the EGR does. EGR takes already burnt and spent inert gas from the exhaust manifold and delivers it back into the intake manifold. It does this in order to take up room in the combustion chamber so the combustion temperatures are lower and nitrides of oxygen are less likely to be created.
With that in mind we can look at the most common and practical ways to increase horsepower and performance. By far the most common way for a car maker to increase power is by pressurizing the intake air with a turbo or supercharger. The more oxygen that you can push into the combustion chamber, the more fuel that you can add to it and the greater the increase in power. An intercooler also adds to this as a cooler air charge is more dense with oxygen than a hot one. Aftermarket uses a similar principle with cold air intake or ram air systems. Drawing cooler air or forcing it in with the help of ram air also allows the intake of more oxygen and addition of more fuel for more power.
EGR is working against these very ideas. The inert exhaust gas is taking the place of valuable oxygen in the combustion chamber so you are adding less fuel and getting less power out of the combustion. On top of that the exhaust gas is very very hot and this raises the temperature of the intake charge for a reduction of oxygen density.
For those that do not feel any power increase or decrease, they either do not notice or the manufacturer has skillfully timed EGR to not operate or reduce operation during periods of acceleration and limit EGR flow to cruising or light throttle when it would not be noticed.
Reduction of power by eliminating EGR can happen in two ways. One of the byproducts of EGR and combustion temp reduction is also the elimination or reduction of pinging or pre-ignition in the engine. Pre-ignition will certainly cause a reduction in power as the combustion occurs too early and actually tries to push the piston backwards and down into the cylinder before it reaches TDC. The other power loss from pre-ignition occurs if the vehcile is equipped with a knock sensor. Knock sensor detects engine pinging, sends signal to engine computer which responds by retarding spark timing untill the pinging stops. Retarded or late spark timing causes reduction in power because the combustion process is cut shorter and engine does not get the full benefit of complete combustion cycle. Both of these reductions can be lessened or virtually eliminated by the use of higher octane fuel.
Well enough rambling Sirob. Take it as you will. Only an opinion.