Speeding lean-burn is unclean says VW
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• Lean-burn petrol engines such as those fitted in Ford Escort vans can meet European exhaust emission standards — but they give clean exhaust emissions only at low speeds, according to a report from Volkswagen.
Catalytic converters, says the report, are the only way to ensure that exhaust emissions remain clean above 96km/h (60mph), and for this reason, Volkswagen will be offering catalytic converters as an option on petrol engines in all its markets by the end 1989.
Tougher emission standards are being adopted by the EC during the next few years. Volkswagen feels that if the testing speeds for exhaust emissions were raised to more realistic levels then lean-burn engine would be hard pressed to comply with them.
The company has been looking at high-speed emissions and says that lean burn has no beneficial effect, expelling more nitric oxide than catalyst converted cars. Volkswagen has identified other problems associated with lean-burn engjnes, including erratic idling and misfiring. Sophisticated ignition, injection and cooling systems could deal with these problems says the company, but they would cost more than a three-way catalyst.
The Volkswagen report is likely to fan the flames of a fierce debate among the major vehicle manufacturers about lean-burn technology versus catalytic converters.
Commercial vehicle operators may think they can escape from this debate by opting for the increasingly popular diesel engines in light vans, but diesels will also become subject to legalisation to control the allegedly carcinogenic particulates they emit (CM 5-11 May 1988).