Save fuel

Press, 11 July 1980, Page 9

Save fuel

A badly tuned car wastes fuel and runs badly but with regular emission testing this can be corrected. With proper maintenance and tuning of the vehicle the resuk is an improved fuel economy and reduced pollution. Emission testing is done quickly and cheaply and if repeated about every six months, will monitor the normal gradual deterioration of engine tune and alert the responsible motorist to have corrective work done. The maximum levels allowed in the analysis of the exhaust gas as .suggested by the Ministry of Energy — TOO parts per million (P.P.M.) of hydrocarbons (H.C.) and 4.5 per cent carbon monoxide (CO) — have been determined in an effort to allow the majo'rity of New Zealand vehicles built since 1965 to qualify. Any vehicles emitting an excess of either CO or HC are out of tune and wasting both fuel and the motorist’s monev.

It should be possible for vehicles built since 1972 or so, to be adjusted to levels much less than the existing standards with resultant gains i> economy for the motorist. This is because later model vehicles have been designed with better ignition systems which help in reducing hydrocarbon levels and more sophisticated carburettors which are capable of better mixture 'control. Not all -ehicles will show similar emission characteristics. This is the result of individual design factors of the engine itselrf itself and will vary from make to make.

Emission tests are carried out with the engine running at idle. Engineers are aware that tests at idle do not neces-

sarily reflect the situation that may exist during cruise or high speed operation; but a badly adjusted or malfunctioning engine at idle does indicate a degree of neglect which is sure to affect the engine’s power and economy over a wide engine speed range. The cost of correcting a faulty engine will vary but tests ha. - shown that the majority of vehicles can be corrected with minor carburettor adjustments for between $5 and $lO.

Tune up costs vary depending on the type of vehicle and number of cylinders and in particular the parts required, such as plugs, points, filter, gaskets and may be between $l5 and $5O. All vehicles covering more than 8000 km a year should be tuned at least once a year.

Of course some engines may require more extensive repairs such as valve grinding a" 1 re-ringing but their numbers are low (lesss than two per cent) and although the cost of rectification would be relatively high, the fuel consumption on these inefficient engine- is extremely high.

Free emission tests are carried out in the Ministry of Transport’s testing stations in Christchurch and by some automobile associations, oil companies and service stations on a trial basis. The exhaust emissions analyser is without doubt one of the most useful instruments for testing and adjusting the fuel efficiency of a spark ignition engine. By sampling the gases emitted from the exhaust, a quick and accurate check of the efficiency of the carburettor and ignition system can be made. These analysers are capable of telling at a glance how rich the air-fue’ mixture is before entering the cylinders and how well this mixture is being ignited and burnt within the cylinders. Too rich a mixture of fuel-to-air will cause fuel wastage through insufficient oxygen being available to mix adequately with the fuel to enable it to burn completely. Too lean a mixture can also cause high levels of unburnt fuel to be emitted from the exhaust system. This is brought about by what is known as “lean mixture misfire.” Correcting the problem of high hydrocarbon emissions will lower the vehicle’s smog-forming emissions, improve vehicle performance and improve fuel economy. —