EGR 101

Lately I’ve been reading a lot about EGR systems, how they work, and how they’ve changed over the years.  Generally speaking, it’s a controvertial subject and has generated quite a bit of debate over the years.

What is EGR?

EGR stands for Exhaust Gas Recirculation, and is a system designed to reduce combustion temperatures under moderate load (anything but idle and full throttle).  In a nutshell, an EGR system takes exhaust gas and recirculates it through the engine in an effort to reduce NOx gases.

A little history on EGR systems:

In the 1970′s, emissions laws began to pass and a new age dubbed the “Malaise Era” began.  Emissions control was an imprecise science, akin to a religion.  At first, performance suffered (considerably) due to the crude systems implemented and some misunderstandings about what the chemical results would be.  As vacuum sensors gave way to electronic control modules, emissions controls became more strict and engine performance blossomed.  Since the early 1990′s, EGR systems often contribute power gains, mpg gains, engine longevity, and decreased harmful exhaust gases.  Great strides are being made even now with engine management systems, and I whole-heartedly applaud the efforts of modern car manufacturers toward these goals.

Why remove it?

The only real reason to remove an EGR system is to clean up an engine bay, or to replace it when it doesn’t work.  They’re a good idea.*

Why keep it?

Although you may be inclined to lump this into the “Emissions equipment is bad for performance so I don’t want it” category, resist the urge.  There are a gaggle of reasons to keep your EGR system maintained and installed on almost any engine.

1. It lowers combustion temperatures, increasing the longevity of your block, rings, and pistons.
2. It reduces harmful NOx gases.
3. It helps warm up your engine more quickly (in some situations).
4. It reduces the chance of pinging (preignition, where combustion happens too soon) by lowering combustion temperatures.
5. It allows for more aggressive spark advance.
6. Most ECU modules require it.
7. It’s legally required for smog tests.

What else can I read?

Excellent article by Henry Guzman (a little dated, but holds true):  http://www.asashop.org/autoinc/nov97/gas.htm

Mandatory wikipedia article:  http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

Howstuffworks article:  http://auto.howstuffworks.com/fuel-efficiency/hybrid-technology/exhaust-heat-recovery-recirculation2.htm

Last but not least, a hard-to-find article often referenced by Ford gurus to their young apprentices:  http://www.fordscorpio.co.uk/egr.htm

1. The valve was sticky and I couldn’t free it.
2. I live in one of the most consistent climates in the United States.
3. The air pump was frozen.
4. I don’t have (or want) the belt to the air pump.
5. The stock EGR system on the l24 is an inefficient, inconsistent vacuum system with an air pump.
6. The engine is easier to tune without EGR in the mix.