AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

It's enough to make you turn to drink

21st June 1980, Page 46
21st June 1980
Page 46
Page 46, 21st June 1980 — It's enough to make you turn to drink
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

lems affect the cold starting of an ethanol engine to the extent that it is impossible to start at temperatures below 15°C (60° F).

To get round this. Volkswagen calls on the assistance of petrol whereby a small amount is added to the intake air as the engine is cranked over by the starter.

As soon as the engine fires and the starter is disconnected, the supply of petrol is shut off; but by this time there should be sufficient heat in the combustion chamber for the engine to continue running on straight ethanol.

Volkswagen developed its ethanol engines from two of its current petrol-powered units: the water-cooled 1500cc (91 cu in) in-line four used in the Passat and the familiar air-cooled flat four of 1300cc (79cuin) used in the Transporter and the Beetle.

Because of ethanol's superior knock resistance, it proved feasible to raise the compression ratio of the Passat engine to 10.5 to 1 by increasing the height of the piston crown.

Theoretically, it would have been possible to go even higher on compression ratio, but VW thought that the gain in efficiency would have been too small to justify the possible risk in durability.

The carburettor had to be recalibrated with particular attention to idling and full load enrichment.

To combat the vaporisation problem, the inlet air was heated by ducting it over the exhaust manifold. Further modifications included the addition of a water jacket for the inlet manifold which was fed with hot water directly from the cylinder head.

With the air-cooled engine, the compression ratio was raised to 10 to 1. The main difference from the watercooled engine is in the mixture preparation.

A single carburettor as used in the petrol version required long intake manifolds due to the flat four construction of the engine.

With the ethanol-fuelled version, two carburettors were used which resulted in very short intake passages between the carburettors and the cylinder heads which, in turn, made it possible to dispense with any intake manifold heating as the inlet air was warmed up sufficiently by passing it along a tube around the exhaust pipe. A temperature-control valve was necessary with this engine to change the inlet air supply at full load from hot to cold. Without this control, the intake air would be heated far too much, with the result being severe knocking at full load.

Certain material changes were necessary with the ethanol-fuelled cars because the materials and coatings which have proved successful in their resistance to petrol were not necessarily going to be equally resistant to such factors as corrosion with ethanol.

Thus for the experimental vehicles, the fuel tank was coated on the inside with a special plastic protection, the fuel lines were made of ethanolresistant plastic, and the fuel pump and carburettor were pro-. tected by an anti-corrosive coating. No corrosion problems were found in the engines themselves.

Obviously, fuel consumption varies with road speed and introducing another variable, like a different fuel, makes comparison complicated. But on average, the fuel consumption of the alcohol cars ranged between 15 and 25 per cent higher than the petrol versions.

However, if alcohol can be produced from easily replaceable vegetable sources, then this gives it one supreme advantage over petrol.

The unfortunate part of the petrol /ethanol comparison is that it is not possible as yet to do a comparison on cost because the relatively new fuel is artificially taxed.

It seems likely that Brazil will introduce financial incentives to swing the user towards alcohol — or rather financial disincentives to swing him away from petrol!

Turning to exhaust emissions, the ethanol engine is cleaner with regard to carbon monoxide and hydrocarbons (substantially so in the case of .00). The NOx level is slightly higher, but this is only to be expected because NOx production is very much dependent on a high combustion temperature and this is exactly what is necessary to ensure effective vaporisation with ethanol.

However, even this slight disadvantage could be eliminated, according to Volkswagen, when fuel injection is introduced in place of carburettors, as the extensive pre-heating requirements could be reduced.

In co-operation with Texaco Brasil SA, a lot of tests were carried out on engine lubrication. These tests, which have been running for over two years, have given great encouragement as, for example, the oil viscosity has remained practically constant and the low level of wear metal in the oil has backed up the engine durability trials, which also showed little measurable wear.

Such is the enthusiasm of the Brazilian government for the ethanol project that it persuaded ANFAVEA (the Brazilian equivalent of the SMMT) to enter into an agreement to produce a minimum number of ethanol cars over the next few years: 250,000 this year, 350,000 in 1981, and 400,000 in 1982.

Volkswagen research and development in the field of alcohol fuels will certainly not do the company any harm, as Volkswagen do Brasil has over 50 per cent of the market.


comments powered by Disqus