There are five primary elements to the Citroen aftertreatment system Which include : -
The BlueHDi systemis fitted to the majority of newer model Citroen’s and has the selective catalytic reduction (SCR) positioned upstream of the particulate filter to eliminate up to 90 percent of the nitrogen oxides (NOx) released by the diesel engine. This drops NOx emissions down to levels like gasoline powered engineswhile maintaining the diesel engine advantage of lower CO2 emissions and greater fuel efficiency.
The Citroen BlueHDi system has been implemented on select diesel-powered vehicles since 2013. It has been gradually added as standard equipment on diesel models sold as Euro 6 compliant.
BlueHDi technology offers an exclusive combination of a DOC (diesel oxidation catalyst), SCR (Selective Catalytic Reduction) and FAP (additive particulate filter or diesel particulate filter DPF) system, allowing the engine to reduce nitrogen oxide emissions (NOx) by up to 90% and cut CO2 emissions down to as low as 82g/km, while also reducing fuel consumption.
The oxidation catalyst is mounted against the engine, converting unburned hydrocarbons (HC) and CO into water and CO2. The SCR converts NOx into water and nitrogen using AdBlue (a common urea treatment). Its change is its optimization of the tuning of the engine to favour consumption and specific performance. The diesel particulate filter then reduces 99.9% of the particulate number.
Citroen’s line-up of vehicles suffer from EGR valve, cooler and intake soot issues like most diesel vehicles on the market. Throw in DPF issues just for good measure if you are just pottering around the burbs at lower speeds as well. If SCR isn’t properly maintained it can cause grief too!
All Citroendiesel powered vehicles have a DPF fitted to help in the reduction of harmful contaminants being expelled into the atmosphere.The soot emitted by diesel engines is particularly harmful to people who suffer with respiratory illnesses such as asthma, bronchitis and emphysema.
Over time the DPF can become blocked with a residue of ash from the soot trapped in the filter being burnt off in a process called regeneration. Periodic maintenance is required to keep the DPF functioning correctly which in turn will keep the running costs of your Citroen low, maintaining performance and reliability.
Exhaust Clean Australia are your experts in DPF cleaning with our revolutionary, market leading equipment ensuring clean emissions and trouble-free motoring. When you or your mechanic send your DPF to us for a clean please ensure that the sensors aren’t removed as we will clean them as part of the service for no extra charge!
AdBlue is a solution made up of urea and water that’s injected into the car’s exhaust system before NOx leaves your exhaust. After it’s fed into the exhaust, it reacts with the NOx produced by the combustion process and breaks it down into harmless nitrogen and oxygen.
It’s a case of basic chemistry – at high temperatures, AdBlue turns into ammonia, and it’s this process that breaks down the NOx. And this significantly reduces the amount of NOx particles in exhaust emissions.
This process is managed by a Selective Catalytic Reduction (SCR) system. In a nutshell, AdBlue is injected through a catalyst in the exhaust.
Apart from running out of DEF (Diesel Exhaust fluid), there are many other issues that will cause a Citroen BlueHDi equipped vehicle to enter either a limited start, or a no-start mode. This is not to protect expensive components in the exhaust after treatment system but is purely to prevent excessive amounts of NOx from being released into the atmosphere when the SCR system does not work as intended.
DEF is stored in a dedicated tank, and during normal operation of a BlueHDi equipped vehicle, the volume of a full tank of DEF is calculated to last the distance between scheduled services. However, sustained aggressive driving can deplete the supply of DEF at a higher rate.The DEF usage is usually about 1-4% of diesel, so for every 100L diesel used expect to use around 1-4 litres of DEF.
All Citroen BlueHDi equipped vehicles display a visual warning to the driver, which warning clearly indicates not only the level of the DEF tank, but also how many more times the vehicle can be started with the remaining DEF in the tank. If the DEF tank is run dry, the engine will enter a no-start mode immediately, and this mode will persist until the DEF tank is refilled and a system reset is carried out.
To do the reset procedure you need a scan tool with Citreon specific software that can monitor and display Citreon specific live data, as well as perform BlueHDi adaptations and resets.
You need to extract all active and pending fault codes but take note that the codes you find must NOT be cleared. If you clear any codes, the system will enter what is known as “Tamper Mode” and it’ll automatically enter a limited start cycle even if all repairs are carried out successfully.
All high-quality DEF consists of a mixture of 62.5% deionised water and 32.5% high-grade urea, which is the source of the ammonia that converts NOx into water and nitrogen. Every important aspect of SCR systems, such as the injection rate and storage capacity is designed around these percentages; in this proportion, the water and liquid urea freeze and thaw at exactly the same rate, which prevents one component in the mixture separating out of the mix in freezing temperatures.
While freezing temperatures are not an issue in Australia, majority of SCR systems now have a heating element in the tank to keep the DEF at a set temperature. All DEF mixtures sold in the world have the same relative concentrations of water and urea on the one hand and have a maximum shelf life of only 12 months.
Even trace amounts of any contaminant can cause the engine to not start.
Most SCR catalyst faults are the direct result of issues in the DEF injection system. Blockages and leaks anywhere in the system (particularly leaking valves/injection nozzles) cause too much or too little DEF being injected and both conditions can cause issues with the catalyst filter itself requiring it to be cleaned which we can do at Exhaust Clean Australia utilising our patented industry leading machines. It is also recommended for the SCR catalyst convertor to be cleaned at regular service type intervals to maintain optimum efficiency.
SCR systems (BlueHDi included) use upstream and downstream NOx sensors to monitor the efficiency of the catalytic converter, and as with oxygen sensors, the ECU/SCR control module compares the output of both sensors to calculate the efficiency value for the SCR catalytic converter.
However, since NOx sensors are very expensive, all other possible causes must be investigated before any NOx sensor is deemed to be faulty.
Once you are certain that the DEF storage and injection systems are functional, you can use a suitable scan tool to perform a test of the metering valve. This test involves activating the injection pump remotely with the metering valve removed from the exhaust system. The valve should emit a very finely atomised spray pattern consisting of three clearly defined cones, and the amount of the DEF emitted during the test should weigh about 15 grams.
Your DOC is an integral part of the entire after treatment system in converting the nasty by products emitted by your Citroen’s engine into safely breathable emissions that are no longer harmful to us or the environment. Regular cleaning intervals are recommended to ensure perfect operation of the DOC system to prevent costly failures, downtime without your vehicle and expensive repair bills. Exhaust Clean Australia, using our patented Italian made machines will keep your DOC operating like clockwork!!
Catalytic convertors are an important part of the aftertreatment system on petrol powered Citroen vehicles to reduce hydrocarbons, carbon monoxide and nitrogen oxides to drastically reduced levels that are safer for the environment. These by-products of the combustion process are fatal in an untreated state. CAT convertor health and condition is important to ensure your Citroen is operating in a manner designed by the manufacturer to not cause harm to the environment as well as to us as human beings! Exhaust Clean Australia can clean your Citroen’s CAT convertor restoring their efficiency to an ‘as new’ state drastically reducing the risk of costly repair bills, increased running costs and most importantly reducing the damage to environment!
The Intercooler on your Citroen plays a vital role in your engine’s intake system. Cooling the incoming air temperature dramatically increases your vehicle’s performance, efficiency and contributes towards the reliability factor as well. Intercoolers are often overlooked maintenance wise till a problem appears or the vehicles performance has a noticeable drop in output. A dirty, oil filled intercooler will not be anywhere near as efficient cooling wise and if a turbo or other related engine failure has occurred the contaminants may well just be stuck in your intercooler ready to be digested back into the engine causing further possible damage. Exhaust Clean Australia’s revolutionary machines can return your intercooler to full efficiency and like new cleanliness giving you peace of mind trouble free motoring.
The EGR system on Citroen’s vehicles reduces the combustion temperature by diverting a small portion of the exhaust gases back into the intake manifold. The exhaust gases are no longer combustible so diluting the intake air with exhaust gases makes the air/fuel charge less combustible.
The engine management system opens or closes the EGR valve to control the flow within the EGR system. The EGR valve connects the exhaust manifold to the intake manifold. The EGR valve is normally closed and there is no EGR flow when the engine is cold, at idle, or during hard acceleration. The EGR flow is at its peak during steady cruising under moderate load. This has a quenching effect that lowers combustion temperatures and reduces the formation of NOx.
If the EGR system is rendered inoperative because it was disconnected or tampered with, the cooling effect that was formerly provided by the EGR system will be lost. Without EGR, the engine will often knock and ping (detonate) when accelerating or lugging the engine. This can cause engine damage over time.
The EGR cooler and valve over time on your Citroen can become totally blocked with a build-up of carbon, oil and contaminants from the recirculating of the exhaust gases back into the intake system.
Common problems related to EGR system are as follows: -
Exhaust Clean Australia is equipped with industry leading technology to successfully clean and restore your EGR cooler and valve back to its original condition. Savings in fuel economy and the restoration for your Citroen’s performance are the big benefits!! We also recommend having your mechanic perform an intake clean whilst we are taking care of your EGR system cleaning to receive the maximum benefits for your vehicle.
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