The geeky part
Exhaust Gas Recirculation (EGR) Valves
The EGR system's role in managing engine temperature helps prevent overheating, which can extend the life of critical engine components. A malfunctioning EGR system can cause drivability issues such as rough idling, decreased power and increased turbo lag.
You should service an EGR valve to ensure your vehicle runs smoothly, meets emissions standards and achieves optimal fuel efficiency by preventing carbon buildup that can hinder its proper functioning. Essentially, a clean EGR valve helps to maintain the intended reduction of harmful emissions by recirculating exhaust gases back into the engine.
The average cost of replacing an EGR valve varies but can cost as much as £650.
Key points about servicing an EGR:
Emissions compliance: A properly functioning EGR system is crucial for passing emissions tests as it helps reduce the amount of nitrogen oxides (NOx) produced by the engine.
Fuel efficiency: By regulating the air-fuel mixture, a clean EGR valve can contribute to better fuel economy.
Engine performance: Carbon buildup on the EGR valve can disrupt its operation, leading to symptoms like rough idling, decreased power, and potential engine knocking.
Preventative maintenance: Regular cleaning of the EGR valve is considered a preventative measure to avoid potential issues down the line.
When to service an EGR:
Engine light on: If your check engine light is on, particularly if related to EGR system malfunctions, get it checked.
Poor engine performance: Noticeable decline in acceleration, rough idling, or unusual engine noises could indicate a problem with the EGR.
High mileage: As vehicles age, carbon buildup on the EGR valve becomes more likely, so consider cleaning it during regular maintenance intervals.
Selective Catalytic Reduction (SCR) Systems
SCR is an emissions control system that uses a urea-based Diesel Exhaust Fluid (DEF) called AdBlue to reduce harmful emissions. AdBlue is injected into the exhaust pipe of the diesel engine and once the exhaust reaches the appropriate temperature the urea in the AdBlue releases ammonia. The ammonia reacts with nitrogen oxides in the catalytic converter to form nitrogen and water. Its primary purpose is to reduce nitrogen oxide (NOx) emissions.
Impact of a clogged / blocked SCR
Increased NOx emissions: A clogged SCR cannot effectively convert NOx meaning that more is released into the atmosphere. NOx is a major contributor to smog and acid rain.
Reduced engine power: As the engine struggles to push exhaust gases through the clogged SCR, it can experience decreased power and performance.
Reduced fuel economy: A malfunctioning SCR can negatively affect fuel efficiency due to the engine needing to work harder to compensate for the exhaust flow restrictions.
Ammonia smell: In some cases, a clogged SCR can emit a noticeable ammonia odor from the exhaust, indicating an issue with the DEF injection system.
Higher maintenance costs: Cleaning or replacing a clogged SCR can be expensive, requiring professional service.
Diesel exhaust systems (and certain components in petrol engines) need to be cleaned regularly, as both generate a large amount of particulate matter that over time can restrict and ultimately block filters and units within the exhaust systems. Diesel engines in particular generate a large amount of soot and ash.
Initially, this will start to reduce engine performance, decrease fuel economy and increase exhaust emissions. If left unchecked, the increase in backpressure created by the blocked components can cause damage to the turbocharger and cylinder head gasket and if left unchecked could lead to catastrophic engine failure.
What is a DPF and why does it need to be serviced?
A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter in the form of ash and soot from the exhaust gas of a diesel engine. Soot, a byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter, making the engine work harder and less efficiently.
As the filter becomes more and more clogged, the engine will lose power, fuel consumption will increase and the engine will be placed under increased strain generally.
DPF filters undergo passive and active regeneration as part of normal engine operation and the effectiveness of these processes are determined by engine load and vehicle drive-cycle. However, when the filter particulate builds up too much, particularly the ash component, neither passive nor active regeneration is effective leaving only two options.
Option 1 - replace the DPF filter at a minimum typical cost of £750 ranging to several thousand pounds
OR
Option 2 - the filter must undergo forced regeneration in order to remove the soot and ash build up and restore the DPF efficiency to around 98% of its original performance.
Once the DPF filter has reached this point, it must be removed and professionally refurbished.
Otto Particulate (OPF) Filter for Petrol Engines
The Otto particle filter is an exhaust gas aftertreatment system that filters particles from the exhaust gases of petrol engines. It works similarly to a diesel particulate filter (DPF) and was introduced to meet emissions standards.
An OPF needs servicing because, like any filter, it can become clogged with particulate matter over time reducing its effectiveness in cleaning exhaust gases and potentially leading to decreased engine performance, increased emissions and potential warning lights on your dashboard. Regular servicing involves cleaning or replacing the OPF to maintain optimal emission control and engine efficiency.
Replacing an OPF (Otto Particulate Filter) can cost anywhere between £200 to £1,000 or more depending on the car make and model.
Key points about servicing an OPF filter:
Clogged filter impacts performance: A clogged OPF restricts exhaust flow, causing the engine to work harder and potentially reducing power and fuel economy.
Regeneration process: OPFs have a built-in regeneration process where trapped particles are burned off at high temperatures, but this can be disrupted by frequent short trips or driving conditions that don't reach the necessary temperature for regeneration.
Emissions compliance: A failing OPF can cause your vehicle to fail emissions tests, leading to legal issues.
Diesel Oxidation Catalyst (DOC) Filter
A DOC filter is a component in a diesel engine's exhaust system designed to convert harmful pollutants like carbon monoxide (CO) and hydrocarbons into less harmful carbon dioxide (CO2) and water vapor, essentially cleaning the exhaust gases before they are released into the environment. It acts as a catalytic converter specifically for diesel engines.
Its primary function is to oxidize harmful pollutants in the exhaust stream, not to trap particulate matter like a DPF (Diesel Particulate Filter).
DOC filters should be serviced regularly because over time, deposits can build leading to decreased fuel efficiency, increased emissions, and potential engine problems if left unaddressed. A clean DOC ensures optimal emissions control and engine performance.
Key points about servicing a DOC filter:
Cleaning necessity: While the DOC doesn't get physically clogged like a DPF, its catalytic coating can become contaminated with deposits over time, impacting its efficiency.
Impact of neglect: A dirty DOC can result in higher emissions, reduced fuel economy, and potential engine issues.
Maintenance schedule: Consult your vehicle manufacturer's recommendations for the appropriate cleaning intervals, which usually involve cleaning the DOC alongside the DPF during routine maintenance.