Cars & Motorcycles
Car Mechanics

Car Mechanics October 2019

Car Mechanics is the UK's only car magazine with essential advice on maintaining and repairing popular makes and models. It’s an invaluable motoring resource that appeals to both the DIY car enthusiast and the more experienced motor trade professional. Car Mechanics has helped save money for our readers every month since 1958. Each issue includes a wide range of in-depth features written in a clear, straightforward manner: • Readers’ motoring-related problems answered for FREE • Real-life motoring dilemmas from our man in the garage trade • Electronic diagnostics delves inside a different modern vehicle each month to explain its management system • Survival Guide looks at new and used component prices for a particular vehicle • Used Car Focus is an in-depth buying guide on a specific make and model • Service Bay covers a full service with close-up images and comprehensive descriptions • Project cars are a major part of the structure of the magazine as we buy, fix and sell different vehicles over a period of months So if you're into saving money and being a home technician, Car Mechanics will help you out - guaranteed!

United Kingdom
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in this issue

1 min.
mot testing equipment changes

▶ Changes are being introduced at MOT testing stations throughout the UK. From October 1, newly-installed roller brake testers will be linked directly to the MOT testing service, sending results via broadband, instead of the MOT tester having to input them by hand on their computer. When an existing MOT testing garage’s rollers wear out or become uneconomical to repair, they will need to be replaced by the new ‘connected’ model, and any test station opening from this date will need to have installed the upgraded equipment in order to be legal. The DVSA is also working with manufacturers to develop other connected test equipment, including: ▶ diesel smoke meters ▶ exhaust gas analysers ▶ decelerometers ▶ headlamp beam testers It is likely that the connected models of these kinds of machines will also become…

1 min.
wrong figures

▶ In Your Letters in the September 2019 issue, John Waldron wrote in to respond to a query we had about hybrid vehicles using solar panels and the figures that John predicted would be gained from fitting them. Unfortunately, we interpreted John’s figures wrongly, so he wrote in again to explain our error. John writes: “ In my email to you (‘Panel Beating’ CM Sept 2019), I notice that my ‘kwhr’ was published as ‘Kw/hr’. Now kwhr is a measure of capacity, while kw/hr is a measure of how many kilowatts are used per hour – not the same thing! As an analogy: a 12-volt lead acid car battery may be sold as having a capacity of 60Ah (ampere hours) – this means it could produce a current of 1 amp…

12 min.
working on exhaust systems

In the early days of motoring, a typical exhaust system was responsible for not only carrying toxic emissions away from the passenger compartment but also reducing the noise caused by the gases escaping the engine at high velocity. “Today, these are not the only functions,” says Doug Bentley, technical head of research and development at Klarius Exhausts of Cheadle, Staffordshire and our technical adviser for this feature. “Aside from influencing engine efficiency, the modern exhaust system is crucial to pollutant control and curtails the emissions of hydrocarbon (HC), nitrous oxides (NOx) and particulates (PM).” The times they are a-changin’ A vehicle’s original exhaust system is designed to complement the engine, enabling it to meet the emissions requirements set by the Euro Standards of Whole Vehicle Type Approval. It also influences performance and fuel…

1 min.
why you should buy a type approved exhaust

▶ Considering their importance to our environment, it’s unsurprising that replacement catalytic converters and DPFs must be Type Approved. This ensures that they perform to the same standards to the car manufacturer’s own replacement parts and have been tested independently. Selling a non-compliant part is illegal. While European countries require the remainder of the exhaust system (ie, the pipes and silencers) to be Type Approved, this is not mandatory in the UK. As fitting a non-Type Approved exhaust can result in a significant reduction in efficiency, with higher emissions, a potential MOT test failure and a shorter life expectancy for not only the exhaust but also the engine and other ancillary parts, Klarius is the only UK aftermarket exhaust manufacturer that has its products certified. Doug explains how this is done:…

1 min.
diesel particulate filters (dpfs)

▶ The function of the DPF is to trap soot particles emitted by the engine and stop them from being expelled into the atmosphere, because they are carcinogenic. We provided a comprehensive overview of how they work in the February 2018 issue of CM. The DPF empties itself by super-heating the soot, causing it to vaporise, leaving a trace of ash behind. This process is called regeneration and it occurs naturally with high exhaust temperatures, such as those resulting from a high-speed run, or by the engine’s fuel injectors initiating a post-injection on the exhaust stroke, which causes diesel fuel to enter the exhaust system, where it combusts, raising the exhaust temperature within the DPF and burning the soot. This process is initiated automatically by the vehicle’s ECU, where a number…

1 min.
diesel pressure differential sensors

▶ Hollow tubes are fitted to either end of the DPF to transmit exhaust gas pressure to an electrical pressure sensor, which tends to be mounted on the bulkhead. Based on the two pressure inputs, a degree of DPF blockage is calculated and communicated back to the engine ECU. These sensors can develop faults and it is not unknown for even new replacements not to work properly, or have incompatible software. So, prior to condemning the DPF, check your live diagnostics for pressure readings to see if they are realistic and test the sensor. This is explained in more detail within the February 2018 issue of CM. Should you need to remove the DPF, these pressure tubes, as well as a temperature sensor, will need to be removed. Consider also that…