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An improbable ally in the fuel-saving stakes

8th January 1983, Page 26
8th January 1983
Page 26
Page 26, 8th January 1983 — An improbable ally in the fuel-saving stakes
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runs (with one driver whenever possible and documented to indicate when weather or traffic conditions had an effect) were accurate enough to make some meaningful comparisions and to give him some base figures.

He then began to compare various demonstrators and inservice vehicles over his route and experimented with different rear-axle ratios, always using at least five or six runs around the route to obtain a mean mpg figure.

This particular exercise made it clear, for example, that Air Products' Seddon Atkinson 400Series tractive units with a 4.57:1 rear-axle ratio used less fuel than those with the 5.47:1 ratio when hauling fully laden 32,000 litre (7,000gal) tank semitrailers.

In early 1982 Air Products began to use the Bracknell route to test a DFL (Dallas Fuels and Lubricants) "fuel saver", first on a Volvo F10 and later on Seddon Atkinson 400 and 401-Series tractive units.

The results of these tests has convinced Brian Dixon of the worth of the devices. Three have been bought and 12 more are soon to be delivered.

The DFL device is American designed but is now being built under licence in Bolton by Green and Hodkinson. It is quite simply a fuel warmer which uses heat from the engine's liquid coolant to raise the temperature of the diesel in a heat exchanger before it enters the injection pump. The makers claim that it improves fuel consumption "by at least six per cent".

The device consists of an aluminuum alloy canister inside which is a coiled pipe through which the diesel fuel passes. Hot water from the engine's cooling system is fed through the alloy canister and warms the diesel in the coil, increasing its volume by between 21/2 and 4 per cent, says the makers.

The canister is encapsulated in polystyrene insulation held in place by an outer layer of sheet aluminium.

None of this, of course, is revolutionary in any way or makes the DFL device any dif ferent from other fuel warmer on the market. But none of th other fuel warmer manufactui ers claims its device will say fuel.

Green and Hodkinson say that what makes their fue warmer different is a mysteriou spiral within the coiled fuel line They will not reveal wha material this spiral is made of.

The cost of the Dallas Fue Saver is £275, ex works. Brial Dixon reckons that with hi vehicles covering an averag. 8,000 miles a month he need only a two per cent fuel ecc nomy improvement to recove the cost of the DFL device withil 12 months, and he is confider of doing much better than thai except perhaps on Cummins-en gined vehicles.

This is because the Cummin PT fuel system has an unusualll high rate of flow in its return 13 warm fuel to the tank and so thi fuel there is at a higher tempera ture than on other vehicles.

Green and Hodkinson recom mends that the heat exchange should be fitted as close as pos sible to the injection pump and i is also important that the fue and water connections an plumbed in correctly, so that thi fuel inlet is close to the wate outlet and vice versa in orde that the fuel leaving the can iste is as warm as possible. Gree and Hodkinson says that th water temperature drops b. about 10 degrees as it passe through the heat exchanger.

Before accepting the devic, for use in the Air Products fleei Brian Dixon had to be sure it wa completely safe. His tests hay, shown that the maximum tem perature the fuel reaches in thi filter of a Cummins-enginei DFL-equipped vehicle is 32°C well below the fuel's flash point.


Organisations: US Federal Reserve
People: Brian Dixon

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