EAC Telford Exhausts Systems

About Exhausts

Your exhaust system is effectively a series of pipes and boxes specially designed to channel emissions away from the front of the vehicle, reduce engine noise and maintain optimum fuel efficiency.

The importance of maintaining a healthy exhaust system and the impact a faulty exhaust system can have on the environment is not something people automatically think about.

All exhausts produce 6 gases as emissions; of the six three are less harmful (nitrogen, carbon dioxide and water vapour) and three are toxic (carbon monoxide, nitrogen oxide and nitrogen monoxide). The job of the exhaust, catalytic converter and its monitoring system is to maintain the correct balance of emissions, check the engine is running efficiently and move the emissions away from the vehicle occupants.

Under existing regulations a Police officer can warrant the removal of any vehicle from the roadways on the suspicion that it is producing excessive amounts of pollutant gases from the exhaust. Also, if your vehicle exhaust system is broken and noisy your vehicle will come under police scrutiny. Your vehicle will also fail its MoT test if the exhaust system has a fault resulting in incorrect emissions levels being recorded.

A vital part of today’s exhaust systems are the ‘Catalytic Converters’. These change the properties of noxious gasses produced by the engine combustion chambers in to a more environmentally friendly emission. All petrol cars manufactured from 1993 have catalytic converters fitted and all diesel cars from 1997.ecorded.

The gas emission level for your vehicle is set by the vehicle manufacturers and enforced at the time of a MoT test; however there has been much debate within the European Commission about whether these settings should become mandatory. If a mandatory level is to be underpinned by law the result could be further regulatory controls to ensure all motorist keep their vehicle emissions within a specified tolerance level.

For best practice and to keep your vehicle in ideal condition, EAC Telford recommends you have your vehicle emission and exhaust system checked at least twice a year for cracks, leaking joints, broken hangers, worn rubber mountings, corrosion, failed gaskets and high levels of pollutant gasses.

We want to help you maintain a healthy exhaust system so please don’t wait until your next vehicle MoT test or service is due, call EAC Telford on 01952 585511 for a free inspection without obligation.


The exhaust emissions standards for new cars have effectively required fitment of a DPF in the exhaust of diesel cars since 2009 when the ‘Euro 5′ standard came into force. In fact, many cars registered before 2009 will have had one fitted too in anticipation of the change in standards.

Standards aim to deliver an 80% reduction in diesel particulate (soot) emissions but the technology’s not without problems – AA patrols are regularly called to cars with the particulate filter warning light on indicating a partial blockage of the filter.

Even if your driving isn’t mainly urban/stop-start, changes to driving style may be required to get maximum benefit from these systems.

If you’re buying a new car and plan to use it mainly for town-based, stop/start driving it would be wise to avoid a diesel car fitted with a Diesel Particulate Filter (DPF) because of the possible hassle of incomplete ‘DPF regeneration’.

How do they work?

Diesel Particulate filters (DPF) or ‘traps’ do just that, they catch bits of soot in the exhaust.

As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance. For a DPF this process is called ‘regeneration’ – the collected soot is burnt off at high temperature to leave only a tiny ash residue.

Regeneration is either passive or active

Passive regeneration

Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Because many cars don’t get this sort of use car manufacturers have to design-in ‘active’ regeneration where the engine management computer (ECU) takes control of the process.

Active regeneration

When the soot loading in the filter reaches a set limit (about 45%) the ECU can make small adjustments to the fuel injection timing to increase the exhaust temperature and initiate regeneration. If the journey is a bit stop/start the regeneration may not complete and the warning light will come on to show that the filter is partially blocked.

It should be possible to start a complete regeneration and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.

If you ignore the warning light and keep driving in a relatively slow, stop/start pattern soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights come on too. At this point driving at speed alone will not be enough and you will have to take the car to a dealer for regeneration.

Expensive repairs

If you continue to ignore warnings and soot loading keeps increasing then the most likely outcome will be that you will have to get a new DPF costing around £1000.

DPF additives

The most commonly fitted type of DPF has an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be hot. This heat means that passive regeneration is possible.

There’s not always space close to the engine so on some models, across a wide range of manufacturers, a different type of DPF has been used which can be located further from the engine. These rely on a fuel additive to lower the ignition temperature of the soot particles.  Many newer models are managing without the fluid because the dpf has been relocated nearer to the engine.

The additive is stored in a separate tank and is automatically mixed with the fuel whenever you fill up. Only very small quantities are used though so a litre of additive should treat around 2800 litres of fuel – enough to cover 25,000 miles at 40mpg.  No, lasts about 72000 miles and is replenished during a service – at extra cost

You will have to pay to get the additive tank refilled at some time in the car’s life – expect to pay between £150 and £200 including fluid and labour

Don’t be tempted to ignore a warning light showing that the additive tanks need refilling.  It’s absolutely essential this tank is refilled as without it regeneration is unlikely to be successful and a new DPF may be needed – at significant cost.  Fuel consumption can increase as a result of failed regenerations too.

AA experience

We’re seeing some evidence of DPF systems failing to regenerate even on cars used mainly on motorways.

On cars with a very high sixth gear the engine revs may be too low to generate sufficient exhaust temperature for regeneration. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases.

With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn’t notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

There’s no evidence in AA breakdown data that the problem’s going away – newer car models seem just as likely to sufffer DPF problems if not driven ‘correctly’ as those built when DPF’s were introduced.

Check the handbook

If you buy a car with a DPF fitted it’s important to read the relevant section of the vehicle handbook so that you understand exactly what actions to take if the warning light illuminates and how, if at all, your driving style may need to be adjusted to ensure maximum DPF efficiency and life.

(updated 26 September 2012)

DPF Health Check

We are offering a DPF Heath Check for only £49.95 which includes 2 visits per year for a DPF & Vehicle Heath Check. With in that check we your DPF system and refill with a special DPF addative FOC

DPF Problems – Diesel particulate filter cleaning made easy. Problems with the Diesel Particle Filter (DPF) that are fitted to all Diesel cars since 2007 can frequently lead to bills of £1500 and more. These problems are normally not covered by warranty. Protect yourself from DPF Problems NOW with DPF Heath Check.


Driving behavior, particularly short distances, prevents the diesel particle filter from getting hot enough to completely burn the soot particles contained in the filter. Additionally the automatic regeneration – where more diesel fuel is injected into the combustion area to

reach a higher combustion temperature – will be reduced by city or stop and start motoring.


Excessive soot particle build up causes the filter to clog.


Failure indication from the OBD-system to the driver (Warning Light). Power Loss, increase in fuel consumption, leading to the total breakdown of the vehicle.


We are offering a DPF service for only £49.95 which incluides 2 visits per year for a DPF & Vehicle Heath Check with in that check we your DPF system and refill with a  special DPF addative FOC.

More details at:


Speak to an EAC Telford representative directly about your service enquiry or request a quote.