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February
2000
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Exhaust Systems - A Smoky Halitosis Yawn Apart from contributing to environmental damage, poorly maintained exhaust systems contribute to driver fatigue through noise, vibration and harshness. Despite these and other adverse effects, the exhaust systems on many of South Africa's trucks are held together with 'blou draad'. Worse is that some systems on bakkies are literal death traps. FleetWatch advocates that in the South Africa context where exhaust emissions and noise do not rate even a jot in our society, this is an area where operators must employ self policing by paying urgent attention to the maintenance and overall quality of their exhaust systems. While having transport thoughts in the early hours of the morning, I often hear the noisy exhausts of the old trucks on our roads and my thoughts turn towards the driver who has to live with the drone of a badly maintained exhaust.
When we compare the South African situation to that of the source plant countries from where we buy our trucks, it often amazes me how differently we view the agenda for road transport. South Africans spend their time leaping to all sorts of emergency measures to staunch the flow of death onto our roads, while the flow of nitrous oxide, particulates and poisonous carbon monoxide from exhaust emissions go unchecked. We cannot even control roadworthiness and speed, so why should the poison and noise flowing from exhaust systems matter at all? Let us accept the fact: exhaust emissions and noise do not rate even a jot in our society. The fact that one cannot see the poison leaking from petrol engines makes the average citizen believe that diesel engines are the culprits. I will wager a bet that the 126 000 taxis on our roads cause more environmental harm than the 270 000 registered trucks – why?
SA exhaust system regulations I have never heard of any transport operator having serious problems with the authorities over enforcement of exhaust noise and emissions but we do have a set of rules as a benchmark for those who are interested. It is illegal to operate a vehicle with an exhaust system that is:
On April 30, 1999 the requirement was dropped that exhaust systems be positioned so as not to direct gas to the kerb side.
The bakkie death trap A very practical issue for all fleet owners to examine is that of the bakkie fitted with a canopy. Many people are transported to work under the cover of a canopy on the back of a bakkie – as many passengers as the canopy window rubbers can contain! Passengers in this situation have been poisoned and killed by the inhalation of carbon monoxide fumes. Carbon monoxide poisoning is the first choice of suicide victims as it is insidious, starting with drowsiness that leads to unconsciousness and death. The canopy design, accompanied by a draught through an open window and poorly fitted seals, can draw exhaust gas into the back of a bakkie. On a long trip, passengers can be guaranteed to arrive ‘dead on time’. Bakkie canopies must also be maintained and checked:
Modified exhaust systems – an engine death trap All engines respond badly to back-pressure, especially turbocharged engines. Any restriction in the exhaust system will cause the following symptoms:
Silentor South Africa, manufacturers of low back-pressure silencers, claim that a reduction from 8 kPa to 3 kPa in exhaust back pressure will add sufficient power and torque for the driver to stay in a higher gear than previously experienced on the same gradient. Engine manufacturers do not recommend any exhaust system modifications. Even bending a tail pipe can cause back-pressure that can harm the engine. In some cases, a vertical exhaust pipe has allowed hot exhaust gas to be sucked into a stack-pipe air cleaner intake with bad results. I would also like to add one recommendation of my own from observations of used trucks and fleets:
NVH and driver fatigue Noise, vibration and harshness (NVH) contribute towards excessive driver fatigue. The problems of NVH are magnified when exhaust systems are badly maintained and emit noise well beyond an acceptable standard. The mounting points of an exhaust system are designed to account for vehicle flexing and twisting and to insulate the cab from the vibrations and resonance of the exhaust. So why is it that so many exhaust pipes are strapped to truck chassis with ‘blou draad’? Wire strapping will only amplify exhaust NHV. Drivers who are exposed to excessive NVH cannot listen for, or hear, other developing mechanical problems. Some drivers also drive on the exhaust note and do not manage the power train using the instrumentation. Modern trucks from Europe are supremely comfortable to promote driver productivity and must be driven by reading the instruments on the control panel - not by just relying on the tone of the exhaust. The final arbiter – exhaust gas temperature (EGT) One of the most important instruments in an airplane cockpit measures exhaust gas temperature (EGT). In trucking terms, this instrument is called a pyrometer and is fitted to some trucks. Air-cooled engines such as the Deutz, also use EGT to control the hydraulically operated thermostatic engine fan. Apart from the effect on engine life, excessive EGT eats up exhaust systems. Fuel consumption is the link. Drivers who have pyrometers fitted to their vehicles and who drive to achieve low EGT, will achieve low fuel consumption and long engine life. Low EGT is a reflection of driving skill and management of the complete power train. Conclusion Motivating the South African road transport industry, and government authorities to respect exhaust emissions seems to be a waste of time in the current environment. We will also not have ultra-low sulphur fuels available on a national basis for the foreseeable future. Sasol is the only manufacturer of ultra-low sulphur fuel at this stage and this is not available at the coast. Certainly the following is worthwhile and will impact on the environment with an economic payback:
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