How Navistar solved its EGR problems - Truck News
Tim Shick, vice-president of sales support with Navistar, said most of the problems could be traced to the MaxxForce engine’s turbo air control valve, which connects directly to the engine’s electronic control module (ECM). The ECM, very importantly, would dictate via that connection how much fresh air should be supplied to the engine and for how long, as well as how much hot exhaust should be supplied and for how long, to effectively reduce emissions. “The truck went down the road and the connector moved around due to vibration and wind under the hood and through a process called ‘fretting’ would wear these pins down to the point where it would connect intermittently. The intermittent connection would cause the device to “overfuel” the engine with sooty exhaust, which first went to the EGR valve. Exacerbating the situation, the shaft on the EGR valve was prone to failure, allowing in a free-flow of soot-saturated exhaust. “What usually happens is you get an open flow of exhaust coming in at will, which is full of soot, because the engine is not combusting all the fuel completely and it goes into the EGR coolers,” Shick explained. Next thing you know, the exhaust manifold, valve and coolers inside the EGR housing are filled with soot. Source: www.trucknews.com
