EGR Delete Basics

EGR Delete Information & Considerations

Exhaust gas recirculation (EGR) is a method of reducing the emissions of nitrous oxides (NOx) by recirculating a portion of exhaust gases through the intake of the engine, lowering combustion temperatures and the concentration of oxygen obtained in the combustion chamber during the intake stroke. The quantity of exhaust gases introduced into the intake manifold is typically controlled by an EGR valve. In diesel engines, some more than others, EGR valves and coolers are susceptible to clogging as a result of soot buildup. EGR systems have been problematic for some diesel engine manufacturers, although modern EGR techniques have greatly improved the reliability of the systems.

The sole purpose of the EGR system is the control and reduction of nitrous oxide formation during the combustion process. "Nitrous oxides", abbreviated NOx, is the industry term for the chemical compounds nitric oxide (chemical formula NO) and nitrogen dioxide (chemical formula NO2). NOx emissions are of concern for several reasons, including:

1) Nitrous oxides are harmful to humans and prolonged exposure can damage lung tissue.

2) Nitrous oxides can cause shortness of breath and difficulty breathing in persons with pre-existing medical conditions, such as asthma and bronchitis.

3) Nitrous oxides react with other organic compounds in the atmosphere to form ozone (chemical formula O3), a potentially hazardous form of oxygen in concentrated exposures.

4) Nitrous oxides contribute to the formation of acid rain under certain atmospheric conditions.

As a result of various NOx hazards and concerns, their emissions are closely regulated in the automotive industry. Today, NOx emissions are primarily controlled by the use of selective catalytic reduction (SCR) equipment, which uses a urea based diesel exhaust fluid (DEF) to neutralize nitrous oxides in the exhaust stream. This is opposed to previous systems, which relied entirely on exhaust gas recirculation to control the formation of nitrous oxides.

The typically EGR system includes an EGR valve and EGR cooler. The flowrate of exhaust gases through the EGR circuit (and therefore into the intake air stream) is controlled by an EGR valve, whose position is dictated by the engine's PCM/ECM based on various operating parameters. Prior to being reintroduced into the incoming air stream, exhaust gases are cooled through an EGR cooler. The cooler is a basic heat exchanger which uses engine coolant as a medium in removing heat from the exhaust gases. This is necessary as cooler intake air temperatures are desirable in reducing the formation of NOx during combustion. Therefore, introducing hot exhaust gases into the engine's incoming air stream is counterintuitive.

The fundamental problem with the EGR system is that it negatively impacts engine performance potential and efficiency. For every quantity of exhaust gases reintroduced, there is an equal quantity of combustible oxygen that is displaced - exhaust gas present in the combustion chamber cannot be converted into usable energy through combustion. Furthermore, diesel engines tend to suffer often significant reliability concerns stemming from the EGR system, primarily do to the fact that all diesel engines produce soot. Soot has a propensity to build up on EGR valves and within the small passages of the EGR cooler. Therefore, it is quite common for EGR systems to require periodic maintenance, cleaning, and repair.

The concept of an EGR delete is simple - block off the EGR circuit so that exhaust gases can no longer be recirculated. As a result, an engine typically runs more efficiently, produces a greater maximum power, and all reliability concerns with regard to the EGR cooler and EGR valve are eliminated. EGR deletes can also contribute to lower exhaust gas and engine coolant temperatures (EGT, ECT respectively).

The flaw in the EGR delete concept is that it is technically considered tampering with an emission control device and therefore illegal for vehicles used on public roads per Federal law. Regardless of personal feelings and/or beliefs with regards to today's stringent emissions regulations, science has proven that NOx emissions can have a significant impact on society. Likewise, it's difficult to ignore overwhelming frustration with unreliable EGR systems and the potential for increased engine efficiency.

EGR Delete Pros & Cons



Improved performance

Not a street legal modification - does not comply with Federal emission regulations




Improved fuel economy

Eliminates reliability concerns with regard to the EGR system

Potentially lower exhaust gas temperatures (EGT)


EGR delete kits are readily available for any EGR equipped Duramax, Power Stroke, or Cummins engine. The modification is particularly popular on the 6.0L Power Stroke, where the poorly designed EGR system has been pinpointed as the root cause of many common problems and reliability concerns. Clogging of the EGR is also common on modified diesels; any soot that exits the exhaust is also cycling through the EGR system, and can cause it to clog or malfunction. As previously mentioned, EGR valve/cooler deletes are only legal for off-road use.