Diesel EGR Service
Diesel EGR Service
For independent automotive repair shops, diesel exhaust gas recirculation can be a boost to the bottom line.
Tony Martin/Motor Age — Exhaust gas recirculation (EGR) is an emission control system that we love to hate. On the one hand, EGR tends to reduce both power and fuel economy. EGR systems have also become more complex over time, making them more challenging to diagnose and service. However, EGR has made it possible for diesel engines to meet strict government NOx emissions regulations, leading to an improvement in air quality in our major centers.
For independent automotive repair shops, diesel EGR has been a boost to the bottom line. Enough goes wrong with these systems that EGR has turned into a good revenue source for shops that offer diesel repair services. Getting some training in diesel EGR service basics can pay off quite nicely for both the technician and the shop owner.
A Little History
Exhaust gas recirculation systems have been in use in gasoline engines since the mid-1970s. Automobiles were identified as a significant source of oxides of nitrogen (NOx) emissions, which were bad enough by themselves but were also an ingredient in the formation of ground-level ozone and smog. EGR was an effective method of preventing NOx from forming in the engine cylinder, but tended to decrease engine efficiency. It was a common belief in pre-OBD days that maximizing power and fuel economy were far more important than what came out of a vehicle’s tailpipe. Thus, it was common practice to disable a vehicle’s EGR system despite Environmental Protection Agency (EPA) warnings against tampering.
Most diesel engines in the U.S. didn’t use EGR in these early years, despite the fact that they produced a great deal of NOx. The diesel emissions regulations of the time were such that the required NOx reductions could be achieved using methods such as charge air cooling (CAC) and injection timing adjustments. The bar was gradually being raised, however, and in the 1990s all eyes were on the EPA 2004 regulations that required a major decrease in diesel NOx output. It was quite likely that EGR was going to have to be utilized to meet EPA 2004, but engine manufacturers were planning on crossing that bridge when they came to it.
The situation changed in 1997 when the EPA discovered that most of the major diesel engine manufacturers were “dual mapping” their on-road engines. This meant that the engines were calibrated to meet EPA emissions standards when run on the 20-minute certification test, but would revert to a different calibration when operated under highway driving conditions. According to the EPA, some manufacturers had been engaging in this practice since 1990, resulting in millions of tons of illegal pollution being produced. The charges led to a settlement that cost the engine manufacturers hundreds of millions of dollars and, more significantly, moved the timeline to meet the EPA 2004 regulations to October 2002. The diesel engine manufacturers were now under the gun, and many adopted cooled EGR as the technology to use for meeting the accelerated standards.
Source: Motor Age