AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

FAST

15th March 1986, Page 38
15th March 1986
Page 38
Page 39
Page 38, 15th March 1986 — FAST
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?

TURN

ROUND

Bill Brock looks at what goes wrong with turbos and sees how one company has built up a sizeable business remanufacturing them

IF the supply of air to an engine is pressurised by turbocharging, more fuel may be injected. This will give improved combustion efficiency and power output. Turbocharging can increase the power of an otherwise normally aspirated diesel engine by as much as 30 per cent. And with correct fuelling overall economy is improved and emissions reduced.

Modern turbochargers work by harnessing the waste exhaust gas to drive a turbine and, in turn, a compressor wheel, which sucks in air and forces it into the cylinders.

Although the principle of turbocharging has been recognised since the early 1900's, it was only with the advent of the jet engine that suitable materials were developed that could withstand the high temperatures involved. And it has been only in the past 10 years that turbocharging has become the norm on commercial vehicles.

UK demand for turbocharging is said to be worth as much as :.18-20 million this year. The prospects are for growth in the market as turbochargers could give the new generation of small directinjection diesel engines performance closer to their petrol equivalents. And their excellent fuel consumption and low exhaust emissions are just too important to ignore.

But, like any other components. turbochargers are prone to failure sooner or later. When they do it will probably put the vehicle off the road until the unit is fixed or replaced. It is no wonder, therefore, that in a commercial vehicle circles turbochargers are classified as 'distressed' components.

The five most common reasons for failure are lack of lubrication, contamination of lubricants, oil breakdown, foreign materials in the exhauster and poor materials or workmanship. The turbocharger revolves at speeds as high as 100,000rpm, so oil is needed not only to lubricate thrust journal bearings, but also to stabilise the rotating shaft joining the turbine and compressor wheel and, perhaps just as important, to act as a coolant.

The oil supply comes from the engine. If it is not changed regularly along with filters it becomes contaminated, accelerating bearing wear. High temperatures in the engine can cause oil to break down forming tarry and acid elements. This can result in the formation of sludge, which may be carried into the oil ways where, at best, it will restrict flow and, at worst, cut it off altogether.

As well as contamination from tiny metal particles produced by wearing components within the engine, foreign matter such as dust is drawn into the combustion chambers through the air intake system. Such matter cannot do any good if it enters the engine, but for the delicate precision-built turbocharger it can be a disaster.

It has been estimated that about 40 per cent of troubles are caused by foreign naterial passing through either the urbine or compressor. An equal .roportion of failures are due to abrication inconsistencies.

IN EUROPE the aftermarket accounts for about 400,000 replacement units a year out of a otal market of four million units, of vhich two million have heavy-duty liesel application.

In commercial vehicles 400,000 to i00,000km is the first-life expectancy for urbochargers, but if they are serviced 'Initially they may be expected to last onger.

Turbochargers produced by the big lames such as Holset and KKK are built to the American Schwitzer design. In the UK Turbospares is the sole distributor of Schwitzer turbochargers and spare parts; its subsidiary, Turbocentre, handles die remanufacturing/service exchange market.

Turbocentre is based in the heart of the New Forest at New Milton, I Iampshire. It has been going four years and operates through a network of 267 distributors in the UK. Some are independent, others are well-known national factors.

Using Securicor delivery services, Turbocentre claims to he able to place a unit within 24 hours of receiving an order. The company carries a large stock valued at around i:0.5 million and boasts a 98 per cent off-the-shelf availability from the in-house stock of loll different types of unit held at any one time. Its IBM computer system aids prompt order processing, with orders staying within the system until final invoicing.

In its %manufacturing operation, Turbocentre uses a total systems approach. The operation is split into three operations of equal importance — stripping and cleaning; inspection and remachining; and assembly and packing.

A major factor in the successful remanufacturing of turbochargers is cleanliness — first with the product and, secondly, in working conditions. A recent investment by Turbocentre is a £30,000 Keolene Kb plant in which molten oxidised salt at 454°C removes all contamination so thoroughly that shotblasting and degreasing have become practically obsolete. Another benefit is that parts, such as those with narrow passages, can be salvaged; previously they were difficult to reclaim.

Initially surface paints, carbon and other organic materials are burnt off. Then, with further soaking, all organic matter in passages, nooks and crannies is oxidised.

On average about 50 per cent of components need to be replaced and always include seals, bearings, piston rings, shaft nuts, studs and gaskets. Ocher components which may need to be replaced include the shaft and wheel, bearing housing, turbine housing, compressor wheel and compressor housing.

Now that the Turbocentre has built up a substantial volume of business, it intends to issue an all-makes applications manual. This should be far more comprehensive than anything offered to date. If it is, it will compensate for the usual omission of turbochargers from manufacturers' vehicle specification sheets owing to multiple sourcing, continuous vehicle development and because of the large number of engine options often available.

Tags

Organisations: Ku Klux Klan
People: Bill Brock

comments powered by Disqus