EGR Maintenance

" I would say for anyone to clean the pipe every year."

The EGR pipe is just the tip of the iceberg (so to speak...). The entire EGR circuit must be cleaned. If that pipe is cruddy, the cooler is probably worse...

 

Based on the pics, the whole circuit will be packed.

Be prepared for the whole circuit to require the cleanse.

Pressure washer works good for the cooler and will save having to buy a spare .

Good luck and keep us posted.

 

How many miles on the patient?

 

My understanding of the necessity of an EGR circuit is a bit different. It is a method for controlling the temperature of combustion in each of the cylinders by the metered introduction of exhaust gas. Any inert gas could be used for this, because all it does is displace oxygen in the induction charge. Exhaust gas is readily available and already pressurized, but it contains soot from unburned hydrocarbons which build up in the passageways and slowly reduce the efficiency of the process resulting in higher combustion temperatures and eventual failure of the head gasket. Just a side note, and I don't want to say this too loud as my Prius might be listening. I have 245K on my 2011, 98% highway miles, and I have not checked my EGR at all. I am getting ready to trade in though, as that kind of mileage brings other worries.

 

not really....


"In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NO
x) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. This dilutes the O2 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. NOx is produced in high temperature mixtures of atmospheric nitrogen and oxygen that occur in the combustion cylinder, and this usually occurs at cylinder peak pressure. Another primary benefit of external EGR valves on a spark ignition engine is an increase in efficiency, as charge dilution allows a larger throttle position and reduces associated pumping losses.

In a gasoline engine, this inert exhaust displaces some amount of combustible charge in the cylinder, effectively reducing the quantity of charge available for combustion without affecting the air-fuel ratio. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture.[1] Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates. Gases re-introduced from EGR systems will also contain near equilibrium concentrations of NOx and CO; the small fraction initially within the combustion chamber inhibits the total net production of these and other pollutants when sampled on a time average. Chemical properties of different fuels limit how much EGR may be used. For example methanol is more tolerant to EGR than gasoline.[2]"

 

Below is pretty key for Prius. If you monitor EGR valve position you'll notice it considerably open at highway speeds and moderate to heavy acceleration. It tapers some if you stomp on the gas pedal but cruising at 70 and then starting to climb a slight grade the engine relies heavily on EGR.

 

In the Prius.....the egr is to reduce NOx formation and increase engine efficiency through reduction of pumping losses. As it is in other gasoline-engine cars.

Gen 3 Prius also has an exhaust-heat recovery system. It's way further down the exhaust. Coolant hoses flow to it and back. Not any part of the EGR. Probably what AzusaPrius is thinking of with the "speed up the warm up cycle" business.

 

I cleared my 2013 @ 97K. The Pipe didn't look that bad, but the EGR Cooler look worst than your pipe.