Investment in Prevention

Cars change at a staggering pace, which means their required service may also change rapidly. For example, EGR systems are ancient yet remain largely misunderstood. Matters have been made even worse by a radical evolution in EGR systems.

To understand the differences in newer EGR systems you must know what EGR is and what it does. EGR stands for Exhaust Gas Recirculation. Engines have used EGR valves for years to redirect some engine exhaust back into the engine where it combines with incoming fuel and air.

Recirculated exhaust gas lowers the temperature of burning fuel inside an engine. Using hot exhaust to cool combustion may seem like a contradiction but it isn’t. Although it’s extremely hot, exhaust gas is much colder than burning fuel, which can exceed twenty-five hundred degrees. However, when fuel-burning temperatures exceed twenty-five hundred degrees the engine pings and NOX (Oxides of Nitrogen) emissions increase dramatically.

Here’s what we know; EGR is recirculated exhaust gas and it’s needed to keep NOX emissions in check and to prevent pinging. In early EGR systems exhaust gas came through an EGR valve and was dumped into a common chamber inside the intake manifold. Here it haphazardly mixed with incoming fuel and air before entering the cylinders. Acceptable then, but not today.

Today’s tighter emissions requirements necessitate EGR be precisely distributed to each cylinder. To this end many newer engines are using internal tubes leading to each cylinder instead of a common dump-point and catch as catch can distribution. Now each cylinder has its own dedicated EGR supply from a common EGR valve.

That’s good but not without a downside. The downside is you need to take better care of your EGR system. Lack of maintenance causes one or more of the individual cylinder tubes to become clogged with carbon and soot from the recirculated exhaust gas. As tubes become clogged two things happen. The cylinders with clogged tubes get no EGR and cylinders with non-clogged tubes get too much EGR.

You’ll probably know when you’ve ignored the EGR system too long because your engine will ping and probably run rough during acceleration. It may also fail emissions or the Check Engine light may illuminate. Whichever problem afflicts your car it guarantees an unpleasant, costly experience.

Here’s how it happens: let’s say poor maintenance on a six-cylinder engine has caused two of its six EGR tubes to become clogged. Now two cylinders will get no EGR and the remaining four will be saturated by EGR intended to treat six cylinders. The cylinders with no EGR run hot and ping while emissions soar, the cylinders with too much EGR run lean and ping. Not convinced? Extreme or prolonged pinging can seriously damage or destroy an engine therefore EGR service should not be taken lightly.

Fortunately there are new EGR service programs employing specialized equipment and chemicals to keep EGR passages clean. EGR cleaning, using equipment, should be performed at intervals of not more than thirty thousand miles. Without periodic cleaning, concrete-like carbon deposits close-off EGR passages. If this is allowed to happen the cost to remove the carbon can exceed your “investment-in-prevention” by a factor of ten.

© Copyright 02/13/03 Pat Goss all rights reserved


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