ABCs of EGR

On the inlet side, the crossover pipe “tees” into the pipe from the charge air cooler, and there’s a new injection pump that raises the fuel pressure in the common rail that runs along beneath the inlet manifold runners, with short high-pressure pipes up to the overhead.

Early reports about EGR promised that recycling hot exhaust gases back through the engine would place huge loads on the cooling system. Some suggested there might be up to 40 per cent more heat to dissipate through the radiator, especially during harsh conditions-high loads, extreme temperatures, and high altitude, all concerns for many Canadian fleets.

A solution is to use Auxiliary Emission Control Devices (AECDs), hardware and electronic control strategies that allow an engine to stray outside the regulated 2.5-gram per brake horsepower-hour NOx+NMHC limit. NMHC+NOx is non-methane hydrocarbons and nitrogen oxide, a contributor to greenhouse gas.

AECDs turn off EGR and allow the engines to exceed the emissions limits temporarily. Without them, completely new cooling systems to handle the infrequent occurrence of the extreme conditions would be needed. The result: expensive redesigns of truck hoods, radiator openings, and grilles. Along with this, fuel economy losses could result in more pollution from the additional fuel consumed, negating any incremental gain that outlawing the AECDs would achieve. That’s why EPA has said it will allow limited use of AECDs.