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TECH-TORQUE! - EGR - The Ugly Truth

Every day, without fail, I get asked about EGR systems (Exhaust Gas Recirculation Devices). I’ve heard some very creative stories that seem to stem from the world of the internet forum warriors. It appears that everybody has completed their google degree on Emissions Control equipment on modern Common Rail Diesel vehicles and has their own solution.

With every customer being just as confused, or misinformed as the last, I have set about writing this article to educate you about the REAL TRUTH behind EGR systems, how they function, what exactly they do, and what side effects they can have to the service life of your rig, and how to prolong exactly that.

So, what is it?

First and foremost, the EGR system is a form of emissions control equipment, fitted to a modern diesel engine from the early 2000’s onwards (in Australia). All vehicles must comply with ADRs (Australian Design Regulations) and emission outputs are a critical part of the criteria manufactures must meet to allow access to the Australian market. The EGR is employed to reduce the amount of NOx (Nitrogen Oxide gases) produced by the vehicle during the combustion cycle of a Compression Ignition Engine (Diesel). These NOx gases are harmful to our environment. The EGR’s job is to take a portion of those spent gases, and recirculate them back through the intake side of the motor, re-introducing them to a secondary combustion cycle to be re-burned, and broken down into smaller elements to produce a smaller carbon footprint… A good thing for our environment, but not so healthy for our motor.

So, you might ask, if it is good for our environment, why is it not good for my motor? Because of the characteristics of a modern Diesel engine, they often “breathe heavy” and will see what is referred to as “Positive Crankcase Ventilation”. This is necessary because an internal combustion engine inevitably involves a relatively small, but continual amount of “Blow-By” which occurs when some of the gases from the combustion cycle escape past the Piston Rings and are trapped inside the crankcase, causing a pressure build up. To regulate this pressure, a PCV (Positive Crankcase Ventilation) Valve is used to vent the crankcase, carrying this pressure, and inevitably, a small amount of engine oil with it back into the intake, much like the EGR does with NOx gases. Each of these alone, taking this path, don’t cause an issue.

What Goes Wrong?

Ever spilled flour when baking cakes with Grandma as a kid? Easy to clean up, right? Ever spilled water when baking cakes with Grandma as a kid? Also, easily cleaned up right? But, ever combined flour and water and spilled them both together? Makes an almighty claggy mess that is hard to clean up! The same goes for your motor when the PCV Valve and EGR System get together and decide to have a party like two naughty kids and cause mischief without you knowing. The combination of NOx Gases and Oil particles when they meet in the Intake Manifold and EGR Valve, causes a claggy, sticky, build-up of Carbon that eventually solidifies over time. It has a similar effect to Cholesterol in the arteries of a human body…eventually blood can’t flow and the result we all know too well… heart attack, stroke, the list goes on. It is the same for your motor. Eventually the carbon build-up becomes so severe, that the air flow that is so critical to a Diesel motor’s operation is so far reduced that it causes rich AFRs (Air-Fuel Ratios) drastically reducing the efficiency of the motor. Symptoms can cause the motor to run unusually hot, fuel economy going out the window, lead the vehicle to produce a “flat spot” or “laggy” sensation during take-off, or simply just a severe lack of power. Unfortunately, and to my astonishment, a lot of drivers don’t feel this happening! But, to be fair, 99.99% of the time it is not due to their own fault, but due to a lack of knowledge!

Left untreated, this build up eventually causes the intake to become so blocked, the inevitable heart attack takes place, and people are left wondering why they have a 40,000km old vehicle, they have spent upwards of the average person’s annual salary on has decided to give up the ghost and requires a new motor. I don’t mean to alarm you, but the prime victims are tradies, and young families that use these around town, as shopping trolleys or mum’s taxi. Reason being; an EGR Valve generally operates at 60km/h road speed or less. The science as to why I can cover in a later article, but it stands to reason; Tradies, mums, and daily tarmac prowlers beware! This IS happening to your rig.

What is the solution? Well, put simply, EGR’s aren’t leaving us. They are here to stay and emissions control laws are getting even more stringent. I have spent a fair amount of time in Europe during my career for one reason or another, and when we see in Australian what they have there right now, most people will be left scratching their heads. Another article for later. My suggestion is to outlay a small investment in your rig in two areas.

●Invest in a Catch Can – Catch Cans have been common place in motorsport for a long time. Now they should be the first, single most affordable investment you can make to your Common Rail vehicle. It traps and separates the oil that the PCV recirculates, preventing it from having that party with the NOx gases we touched on earlier.

●Invest in a De-Soot or Carbon Clean If you fit one of that criteria of tradie, school run mum or daily driver of any description, have your manifold and EGR system inspected, and cleaned. There are several ways to do this, and it is FAR cheaper than a new motor, labour and downtime is FAR less, and I guarantee you’ll thank me for your economy improvements later. Who wants to spend money on fuel anyway? It’s already dear enough as it is!

I hope that answers some of the myths that are floating around the forums now. If I had a dollar for every story I’ve heard, I could’ve produced a skit to air on the nine network at prime time by now. Still curious? Give us a call or drop us a message.

Cheers! JC.

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