Just a lot of hot air?
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MONTH OUR sister magMotor tested another two e fuel economy devices. was fitted to a Datsun a and the other to a Re 9 and both cars were cted to "before and after" g on the Mira track and in al road use.
device on the Datsun proI a 3.3 per cent improve in overall fuel consumpwhich would mean that ) miles would have to be ed before the cost of the 3 was recouped. A stagger'5,0 00 miles would be !d to pay back the cost of avice fitted to the Renault managed only a 2.5 per onsumption improvement. .?,r "economy" device pro1 any concrete improve; in performance either.
or reasonably pointed out he improvement in both was well within the 5 per nargin that it assumed for imental error. In short, the )s did not live up to their lecturers' claims and could yen justify their purchase in the short term.
se were just the latest in a me of failures that Motor !corded in its tests of such ;es and the magazine lded that "the credibility )s widened a little further". 3 n it comes to fuel eco devices for lorries with engines it is reasonable to t that this credibility gap I be rather narrower since
are greater potential js. With a 32/38 tonner lg fuel at five times the ía car, even small per cen-nprovements in economy )rth far more.
benefit is then multiplied lorry's — say 50,000 miles • instead of a car's 10,000 — another five-fold oppor tunity for the economy device to prove itself. And finally with tractive units costing £25-35,000 the cost of the device is a considerably lower proportion of the vehicle's price.
So there are grounds for even the most sceptical, hard-nosed commercial vehicle fleet engineer to view the concept of a fuel economy device in a more favourable light.
Having said that, the manufacturer of the Gefarator exhaust aspirator is at pains to stress that it is not called an economy gadget — "It is a combustion efficiency device" — no doubt anxious to by-pass the credibility gap rather than bridge it. The distinction is at best a fine one; the Gefarator is claimed to improve the engine's combustion and this improvement can be used either to increase performance or decrease consumption.
The Gefarator is made by Applied Water Energy (AWE) of Glasgow, a small company that works on the design of combustion systems, in particular for industrial water boilers. The name Gefarator is derived from the name of its inventor, G. F. Hare, and the word aspirator. George Hare invented the Gefarator in the early 1960s and sold it in a small way via mail order.
AWE took over the reins just over three years ago and has since refined the product. It has been test-marketing the Gefarator with fleets for the last 18 months and is now looking for a wider audience.
Over 2,000 have been sold to date but AWE director Patrick Jones told me that he has a "realistic target" of 200,000 being sold next year. On what do these high hopes rest?
To look at, the Gefarator appears disarmingly simple and comprises just three components which screw together. At the base is the condenser; then there is the venturi tube made of cadmium-plated copper and about 50cm (20in) long, and completing the assembly is the valve section.
Installation is equally simple. A 14mm hole must be drilled and tapped in the exhaust manifold in the area of "maximum turbulence", although Patrick Jones said that the precise position is not over-critical. The condenser section of the Gefarator is screwed into this and the venturi tube emerging from the top of the condenser is then bent to suit the particular engine so that the valve section on the end is positioned in the air flow around the engine.
Unlike many other economy devices the Gefarator works on the exhaust side of the engine rather than the inlet side to achieve better combustion, and is claimed to work equally well on petrol, diesel or LPGpowered engines. AWE maintains that all internal combustion engines suffer from an inherent combustion weakness called exhaust gas pollution due to valve overlap — the short period of the firing cycle when inlet and exhaust valves are open together.
The majority of the exhaust gases expelled from the cylinders will be emitted into the atmosphere via the exhaust manifold and system but AWE says a significant amount of gas will find its way back into the com
bustion chambers because of the valve overlap i.e. exhaust gas pollution.
This "reverse surge" of exhaust gas pollutes the incoming charge of fuel vapour and air and reduces its oxygen content. The burnt hydrocarbons and byproducts from the fuel additives generally soot up the valves and spark plugs or injectors.
That, says AWE, is the problem that the Gefarator aims to tackle by means of "scavenging", the timely introduction of a surge of fresh air into the exhaust manifold. This fresh air has to be introduced at just the right time so that it, and not the exhaust gas, is the subject of the reverse surge into the combustion chamber before the next firing charge.
In its descriptive literature AWE says the principle is not new and has been used on large marine diesels; the Gefarator's achievement is simplification so that the same results can occur in small engines. It does this (and again I quote, since CM has not tested the Gefarator) "by harnessing the energy in the pressure pulses of the exhaust gases."
These pressure pulses are caused by the emission of the exhaust gas into the manifold in regular surges, giving a high pressure instant in the manifold followed by an instant of low pressure in its wake.
The Gefarator is designed to act as a metered air intake into the exhaust manifold and the timing of this injection of fresh air is crucial. AWE claims that because the Gefarator's action is controlled by the engine's own manifold pressure pulses it is inherently correct.
The Gefarator also acts as a type of steam injection. Its rawmaterial is the water vapour content of the exhaust gases and Patrick Jones said that by a process known as steam reformi n g the water vapour is converted by the Gefarator to its constituent hydrogen and oxygen. These supplement the fresh air introduced via the Gefarator valve head.
Apparently, the most important part of the Gefarator is the valve head and in particular the material from which the valve diaphragm is made. Patrick Jones would not reveal the type of material used and said that attempts to open up a valve head will mean that the reassembly will not be perfect and the device will almost certainly have a detrimental effect on the. engine.
The consequences of all this clean combustion are claimed to be a cleaner engine, less pollution and more power which can then be used to boost performance or lower consumption. I asked Patrick Jones if AWE is willing to quantify these improvements? He said a 10-20 per cent improvement in fuel consumption can be expected, provided that the extra performance is not used. This improvement is allegedly attainable on all types of internal combustion engines — diesel, petrol or LPG — but AWE says the exact result will depend on the particular engine's level of exhaust gas pollution. This in turn is dependent on cylinder head design, cam profiles and the setting and position of the valves.
In April this year AWE commissioned a commercial engine testing laboratory to carry out comparitive tests on a car with and without a Gefarator. A Ford Escort 1,100cc Mark II that had covered 53,000km (32,950 miles) was the subject of the test.
In the report that was produced after the tests a graph of engine power (in bhp) across the rev range with the Gefarator fitted reveals an increase in power of 0.75-1.5kW (1-2bhp) from around 1,300rpm up to the 5,000rpm limit.
The level of hydrocarbons emitred from the exhaust showed a more dramatic reduction. At a mid-range 3,000rpm the level was down from 330 parts per million to 210ppm. The carbon monoxide emmission levels showed little change.
Fuel consumption tests were conducted on the roiling road using thefamiliar ECE standards to give figures for the urban cycle, steady 56mph and steady 75mph. On the urban cycle the Gefarator-equipped Escort showed a worthwhile increase in economy with the figure rising from 9.41/100km (30mpg) to 7.81/100km (36mpg), a 20 per cent improvement.
But when it came to the constant speed tests the results were far less conclusive. The 56mph figure rose from 6.81/ 1 0 0 km (4 1.5mpg) to 6.61/ 100km (43mpg), while the steady 75mph figure improved from 11.21/100km (25.3mpg) to just 10.91/100km (2 6mpg). These constant speed results translate into improvements of just 3.6 per cent and 2.8 per cent respectively — almost negligible. They would also seem to be in keeping with the marginal increase in the Escort engine's power, so I asked Patrick Jones how he explained the 20 per cent economy improvement in the urban cycle.
He told me that in the periods of deceleration in the urban cy cle combustion is particularly poor, with larger quantities of unburnt fuel being emitted.
Therefore, if the problem is worse the solution has more to offer.
Laboratory tests have not been carried out using a diesel engined commercial vehicle. Instead AWE supplied a sample of results which are said to be typical of those obtained from operators who have fitted Gefarators in their lorries. The figures, which are mostly the result of brim-to-brim readings and so of unknown accuracy, are from a varitey ofivehicles and include vans, rigids and 32 ton artics.
The majority of the 45 results supplied fall within the 5-15 per cent economy improvement range, with a preponderance around 7-9 per cent. The pres ence or lack of turbocharging and/or exhaust brakes did not seem to have any consistent effect on the results.
Some of the larger diesel engines were fitted with two Gefa rators. Patrick Jones said that if it is a vee formation engine or the exhaust manifold is in two separate castings then two Gefa rators are used. Until now, exactly the same Gefarator has been fitted to all engines, irres pective of size or type. But now AWE admits that there appears to be a cut-off point for diesel engines above 4.5 litres in capa city, when the Gefarator is t means so beneficial. So now working on a larger city model for these biggel sel engines, which shoul available in about six ma time.
The price of the existing rator is between £50 and depending on volume disc This includes fitting which i ried out by one of AWE' agents. Alternatively, oper can fit them in their workshops. AWE is curr looking for more fitting ai around the country. Oper would be wise to check thz validity of an engine' vehicle's warranty is not ha by the fitment of the Gefai AWE has approached n facturers but has encoun the credibility gap menti earlier. Patrick Jones said ft does not blame them for attitude — they cannot a that the massed forces of research and developmen partments have failed to up with something so sir However, AWE claims to b tering into a project with o the car and commercial nfacturers, which may enh the reputation of the Gefara Patrick Jones has been in to address Institute of Transport Engineers mee this winter and is hoping audiences will listen wit open mind and not m dismiss the Gefarator as another gimmick that doe: work.