EGR is short for ‘Exhaust Gas Recirculation’. EGR works by recirculating a portion of an engine’s exhaust gas back into the clean air inlet side of engine cylinders. This dilutes the oxygen in the incoming air stream.
The purpose of the EGR system is to reduce nitrogen oxide emissions which contribute to air pollution at certain engine speeds and temperatures. The downside is a reduction in performance and economy and the carbon build up with higher mileage vehicles. With the introduction of the EGR valve system on diesel engines, there has been a noticeable and documented 3% drop in engine efficiency, which means an additional 3% more diesel is being consumed and burned to generate the same amount of power.
If 3% more diesel is being burnt, that means there’s also a 3% increase in all the pollutants that are generated. While emission controls are clearly a good thing, it isn’t clear if the EGR valve is causing more good than harm by burning off the trace amount of nitrogen oxides by simply burning more fuel. Also, it may not be good for the diesel engine itself. The process is as follows: As the diesel fuel is mixed with the incoming air, the mixture is burned in the combustion chambers of the engine. Most of the exhaust is expelled out the tailpipe of the vehicle, however, diesel engines equipped with the EGR system divert some of the exhaust off the manifold, re-mix it with fuel and incoming air so that it can be re-burnt. While this does help reduce the oxide pollutants a small amount, it has negative side effects on the diesel engine itself.
Firstly, you will get slightly worse fuel economy. Exhaust gases don’t re-burn all that well because it contains very little that is “useful” to the combustion process. So when you reintroduce exhaust back into the diesel engine, you are displacing fresh air that has more oxygen with exhaust gasses that don’t. As a result, the engine doesn’t burn the fuel as well because there is less oxygen.
Next is the problem that diesel exhaust by its very nature has pollutants in it, including soot in the form of carbon. By re-introducing the untreated exhaust back into the combustion chamber, soot will start to build up in the oil and on other internal engine parts, including the intake turbo.
EGR Blanking Kit – Buy Now
Below is a classic example of the carbon build-up caused by the EGR valves on a modern diesel car. This photo is from a 2009 Discovery 3 2.7 TDV6 with just 89,000 miles. The EGR valves were not faulty but had caused a considerable build of carbon and oily deposits like gritty Marmite on the inlet side of the engine, restricting the airflow and performance.
The EGR’s were blanked and deleted via a remap and the inlet manifolds carefully cleaned off the carbon residue. The build-up is made up from a ‘soft’ deposit of carbon and oil and whilst very sticky will not cause any internal damage to the engine.
This cannot be a good thing, but it’s debatable how bad it is. Surely, the cleaner the air going into the engine, the better it will run and the fewer problems you’ll have in the long term. This is the whole reason why vehicles have air filters. The EGR system does not pass the exhaust back through the air filter because there is too much soot which would clog the air filter in a matter of minutes. So if the EGR process is too dirty to pass the exhaust through a filter, think of all that black soot that is going directly into the engine!
Also, because exhaust gases are hot, it must first be cooled prior to re-mixing it with new air. Piping 700°F gasses into the engine is a recipe for disaster. Therefore, an EGR cooler is needed. It is basically a second radiator that reduces the exhaust gas temperatures before they are re-burned. If the cooler fails, the temperatures in the engine can skyrocket quickly causing permanent damage.
Is the EGR valve needed?
The short answer is no, the EGR provides no benefit to the diesel engine and can be “removed” with no ill effects. In fact, many have reported that their diesel engine runs better with it removed.
How hard is it to remove the EGR?
An EGR Delete Kit can be purchased from JGS4X4. This physically removes the butterfly valve, the hose, and blocks off the incoming ports where the EGR cross-over exhaust return pipe directs the exhaust back into the intake turbo for re-mixing with outside air. Because the exhaust gas return port is completely blocked off, no exhaust gasses re-enter the engine.
On some models and years, the engine management light will illuminate after the EGR valves are blocked. This can be turned off with a software remap, here at JGS4X4 we offer EGR deletes at ECU level, so that you no longer have to suffer from a troublesome EGR valve!
Find out more about Remaps and EGR Deletes
Please be aware that from May 2018 the MOT rules in the UK changed!
Amongst the stricter rules are new legislation regarding emissions including DPF’s and EGR systems. Any modifications/removal to emissions related devices, this includes DPF’S and EGR’s is now a major fail.
During an MOT test, the tester can only do a visual check of the emissions systems, the MOT tester is not permitted to remove covers or guards to make an inspection.
You as the vehicle owner need to be aware of this before removing or modifying any emissions related devices on your car.