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From tile by Graham Montgomerie } r 7 8 I 17 )77 I

26th June 1982, Page 58
26th June 1982
Page 58
Page 59
Page 58, 26th June 1982 — From tile by Graham Montgomerie } r 7 8 I 17 )77 I
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ON-BOARD electronic analysis systems have been predicted for a long time for commercial vehicle installation. These could take the form of either of diagnostic checks carried out automatically or as an analysis of the vehicle's performance and productivity.

A half-way house in the latter instance is the tachograph, which when used in conjunction with a computer can provide a lot of information on vehicle utilisation and can provide it quickly.

To date, most tachographs record road speed against time, but instruments are also available which add a record of engine speed to the two parameters already mentioned. The Lucas Kienzle 1314-Series electronic tachograph is one unit where such a function can be incorporated.

The electronic tachograph was developed by Lucas Kienzle in the first place for rear-engined buses where there were problems with the mechanical tachograph due to the great lengths of cable involved. The original electronic design featured a 16pole generator which produced 16 pulses per revolution in sinusoidal wave form thus giving 16,000 impulses per kilometre in contrast to the 1,000 per km of the cable driven type. The current Lucas Kienzle 1314 uses a Hall Effect sender unit (see CM August 22, 1981) which produces a square wave form at eight pulses per second.

With the electronic design there is no technical difficulty associated with recording engine speed as well. With the mechanical tacho there was the problem of engineering a suitable take-off point into the system. But why bother with recording engine speed ...?

Many of the current engine designs are a vast improvement in fuel consumption over their predecessors, but they are extremely sensitive to engine speed. If kept to the manufacturer's recommendations they can be very economical, hence the emphasis on driver training and the use of colour-coded revcounters.

With the engine speed recording option on the tachograph it is possible to have a printed record of the speeds used during the day. As well as recording numbers, the tachograph (as with its road speed functions) will also provide a good indication of individual driving style. The driving patterns thus provide a subjective way of measuring the consistency of the driver.

The chassis manufacturers are interested in the engine speed recording tachographs as typified by the Lucas Kienzle 1314-25 and 1314-26 but as usual there is a cost penalty of 50 per cent over the price for a standard road-speed-only instrument. Chassis manufacturers will fit it if the demand is there, but it is just another example of a typical chicken and egg situation.

As with tOe conventional roadspeed tachograph, a lot of information can be gained by analysis of the chart. Obvious examples are over-revving of the engine whether at high or low road speeds as the engine and road speed readings can be directly cross-referenced.

Racing a cold engine is a cause of high fuel consumption at best and a scuffed piston at worst. Where a few minutes' idling is recommended this will be recorded on the enginespeed section before any road movement is recorded. The same logic also applies at the end of a long motorway journey where a period of idling is again recommended — particularly with turbocharged engines where heat soak to the turbo charger can cause excessivE bearing wear.

Although the obviou: example of engine misuse over-revving, it should not bE forgotten that too low an enginE speed is not conducive to gooc fuel economy as it means thE engine is not operating within it region of optimum efficiency.

Lucas Kienzle claims that thE more professional fleet engi. nears can correlate the results ol driving style not only agains1 fuel consumption but also against the maintenance re.

qUirements of any vehicle. particular While the recording of engine speed is particularly useful when the power take-off is in operation with the vehicle stationary, the possibilities do not end there. The extra stylus on the tacho can be used to show when any extra piece of equipment has been in use, eg the compactor on a refuse vehicle or even a siren on an ambulance.

But that is only half the story. Lucas Kienzle also markets a fuel-consumption meter which when linked to the engine-speed tachograph, is a "marvellous diagnostic tool", according to marketing manager David Michell. This works on the elliptical gear principle and can cope with fuel flow rates of up to 120 litres per hour (26.5gal/h).

The metering unit is mounted ahead of the engine's lift pump in the suction line as shown in the accompanying installation diagram. Fuel is drawn from the tank and passes through a filter and the elliptical gear meter, continuing on through the main filter to the injection pump. So far, the meter can be used only with "conventional" fuel systems using in-line pumps. Rotary pumps have a high spill rate making it necessary to deaerate the fuel before an accurate reading can be attempted. Also excluded are Detroit Diesel and Cummins engines with their distinctive injection systems. The fuel return from the injec tion pump is directed back into the circuit between a non-return valve and the injection pump, so it cannot be measured twice.

The 120-litre flow rate is claimed to be adequate for en gines up to 400 horsepower. The flow meter continually emits electric pulses which drive the separate digital counter, which is electromechanical and thus is not reset in the case of an electri cal failure of the vehicle. The counter can be mounted in the cab and gives the cumulative total on a six-digit display to an accuracy of one tenth of a litre, according to the Lucas Kienzle claims.

The installation time for the flow meter is between four to six hours at a cost of about £350 dependent upon the vehicle. Lucas Kienzle recommends a finer level of fuel filtration than is usual although a by-pass is incorporated in the system. This is only accessible after the filter has been removed.

So far the description of the flow meter could apply equally to many other systems on the market. With the Lucas Kienzle arrangement, however, the fuel consumption can be analysed via the company's computer in addition to being merely measured.

Using the fourth stylus which can be incorporated into the automatic versions of the tachograph, recordings can be made on the chart. The impulses from the cumulative counter cause the stylus to register a mark • which represents two or five litres according to the type of system installed. Similarly at intervals of 20 or 50 litres, a longer mark is made.

The computer can then analyse the tachograph chart in terms of average speed, pro ductivity, etc, as has been possible in the past, but when the fourth stylus is used for mea suring the fuel consumption then this can be related to the various operating conditions as recorded by the tachograph's other functions.

As I mentioned earlier the significance of the fuerflow meter is that it can be linked to the tachograph for a complete analysis of the operational per formance. It does not just say that a vehicle is achieving x mpg. If used correctly it will also

explain why the vehicle is doing x mpg and what action, if any, can be taken to improve this.

Tachograph design has come a long way since the instrument was tagged "the spy in the cab".


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