The Disadvantages of an EGR Delete: Engine Damage

Learn the disadvantages of an EGR delete: Little-to-no power gain and engine damage

An Exhaust Gas Recirculation (EGR) system is an essential component in modern engines designed to reduce nitrogen oxide (NOx) emissions by recirculating a portion of the exhaust gases back into the combustion chamber as ballast. Some vehicle enthusiasts and tuners opt for an EGR delete, convinced that they’ll get more power from the engine. But the truth is that an EGR delete has many disadvantages, including lower performance and possible engine damage. This article delves into why an EGR delete doesn’t improve performance nearly as much as claimed by the kit manufacturers and why removing the EGR can cause engine damage.

The people who recommend EGR deletes don’t fully understand how an EGR system helps your engine run more efficiently by reducing pumping losses. They misconstrue the effects of air/fuel dilution. If you’re thinking about performing an EGR delete on your engine, read this first.

What an EGR valve does

Most modern engines use a leaner air/fuel mixture to improve MPG. Engineers use a variety of methods to ignite the lean mixture, including better vaporization techniques and swirl chambers in the cylinder head. However, once a lean mixture finally ignites, it’s not uncommon to see a combustion temperatures in the 2,500°F range.

At that temperature, inert gases become reactive, creating oxides of Nitrogen (NOx), one of the main components of smog. NOx is an eye and lung irritant.

Just as important as the emissions aspect of a leaner mixture, the extremely high combustion temperatures can cause pre-ignition, where combustion begins before the spark plug fires. This results in multiple flame fronts colliding in the combustion chamber, causing ping.

Engineers use exhaust gas recirculation (EGR) to lower combustion temperatures, stop pre-ignition, and reduce NOx formation. EGR is one way to accomplish both goals.

EGR valves also cool the air/fuel mixture in diesel engines. Some diesel engines use an EGR gas cooler to remove heat from the incoming exhaust gas to further reduce combustion temperatures.

Summary:

• A lean burn engine improves MPG but results in higher combustion temperatures
• Higher combustion temperatures create oxides of Nitrogen (NOx)
• High combustion temperatures result in pre-ignition and ping.
• To reduce NOx and meet emissions standards and to reduce pre-ignition, engineers had to either:

a) Richen up the mixture to reduce burn temperature, or
b) Reduce combustion temperatures by adding a non-combustible ballast gas, something that would take up space in the combustion chamber but not burn.

It’s important to understand that the EGR valve doesn’t operate in the high-power band.

If the engineers allowed exhaust gas recirculation at idle or low RPMs, it would cause a rough idle and stalling. So, the EGR valve is fully closed at startup. Once the engine warms up, enabling EGR operation, the valve opens at low speeds at partial throttle. By introducing exhaust ballast at low speeds, the engine can handle the EGR dilution while also reducing the peak combustion temperature.

However, diluting the air/fuel mixture also reduces power. That forces you to open the throttle wider to add more air while the fuel injection adds more fuel. That’s an advantage because opening the throttle at lower speeds reduces pumping losses (the power lost when the piston has to suck against a closed throttle plate during the intake stroke). In other words, by adding exhaust ballast at low speeds and forcing the driver to open the throttle, the engine actually becomes MORE efficient. This point is ignored by the companies selling the EGR delete kits

At higher speeds, where more power is needed, the EGR valve is closed, cutting off all ballast and allowing for a full air/fuel mixture delivery. In other words, the EGR valve isn’t operating when you’re putting the pedal to the metal.

Here’s what happens when you delete the EGR valve

The disadvantages of an EGR delete are unmistakable!

• You raise combustion temperatures back into the 2,500°F range— You create NOx emissions and increase cylinder head temperatures.
• You get pre-ignition and lower power— The cylinder head temperatures stay above normal, causing pre-ignition, which, by itself, reduces power. In addition, the pre-ignition events are noted by the knock sensors, causing the ECM to retard ignition timing which reduces engine power even more, totally defeating the intended purpose of an EGR delete.
• You create a higher heat load on the cooling system— The hotter combustion temperatures transfer more heat to the cylinder walls and valves, thus reducing the amount of energy available to produce mechanical work.
• You create the conditions for burned exhaust valves— The higher heat transfer to the cylinder walls and valves, erodes the exhaust valve faces and seats, causing misfires which can only be fixed by performing a valve job.
• Overall, performing an EGR valve reduces engine life and provides little to no power boost since the EGR only works at low throttle, where you really aren’t looking for performance.
• It’s illegal— But you already knew that

©, 2020 Rick Muscoplat