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Opel Zafira 1.6 CNG (Compressed Natural Gas)

FOR RELEASE: April 16, 2002

Clean Power from Natural Gas for Versatile Seven-Seater

Opel Zafira 1.6 CNG

  • Low consumption and emissions, reasonably priced fuel
  • Monovalentplus concept guarantees unrestricted mobility
  • Additional gasoline tank for an operating radius of up to 500 kilometers
  • All the versatility of the Zafira with no loss of interior space or payload
  • Parking in underground garages is permitted

Russelsheim. Another Opel model in addition to the 'Eco' versions of the Astra and Corsa that's particularly kind to the environment is the Zafira 1.6 CNG (Compressed Natural Gas). Its engine, based on the 1.6-liter ECOTEC gasoline unit, is described as 'monovalent', in other words it is optimized to run on natural gas although gasoline can still be used. Thanks to this innovative concept, which has been named "monovalentplus", this seven-seat vehicle is entirely suitable for day-to-day use and provides the same driving pleasure as the comparable gasoline-engined model, though with reduced exhaust emissions and also significant advantages in its running costs. This Opel compact van, has four underfloor gas tanks, a 14-liter gasoline tank for use in emergencies and a total operating range of about 500 kilometers – not to mention the same remarkably versatile interior design as the conventional Zafira, thanks to the Flex7 seat system.

Among the significant advantages of natural gas fuel are high environmental acceptability and economy. The pollutant emissions compared with gasoline and diesel engines are in some cases 90 percent lower; the CO2 emissions are only 145 grams per kilometer. Similar benefits become clear in connection with fuel costs: at a consumption of 5.5 kilograms of natural gas per 100 kilometer, the Zafira 1.6 CNG can be run at about 30 percent lower cost than the Zafira with 2.0 DI ECOTEC turbocharged diesel, and as much as 50 percent more cheaply than the Zafira with 1.6 ECOTEC gasoline engine (taking German fuel prices as the starting point).

The Monovalentplus concept: Maximum Efficiency when Using Natural Gas

Unlike 'bivalent' vehicles, which are optimized to run on gasoline and incur a power loss of about ten percent when supplied with natural gas, Opel has adopted a "monovalentplus" concept for the Zafira CNG, with maximum efficiency available in the natural gas operating mode. Since natural gas has an octane number of up to 130, it is distinctly more knock-resistant than gasoline and the engine's compression ratio can therefore be raised to increase efficiency. This in turn yields performance figures equivalent to those obtainable from a gasoline engine. The engine developed and built by the engineering staff of Opel Special Vehicles GmbH (OSV) together with the Special Vehicles department at Opel's International Technical Development Center (ITDC) in Rüsselsheim (ITEZ) is rated at 71 kW (97 hp) with a peak torque of 140 Nm, values that are only slightly below those of the corresponding gasoline engine. The 'natural gas van' has a top speed is in the region of 170 km/h and it accelerates to 100 km/h from a standing start in 15.5 seconds.

Compared with the gasoline engine, the engineers modified the fuel injection system, pistons, valves, valve guides and valve seat rings for the Zafira 1.6 CNG. Unlike other vehicles designed to run on natural gas, it has a double-bank injection system, with four injector nozzles for natural gas and four separate ones for gasoline. The advantage of this is that natural gas injection also takes place sequentially – a feature that helps to maximize efficiency and reduce exhaust emissions. A pressure regulator in the engine compartment maintains the injection pressure at the high constant figure of 8 bar. Special pistons have permitted the compression ratio to be increased to 12.5:1.

Action Radius: Up to 500 Kilometers before Refueling

The four underfloor gas tanks have a total capacity of 110 liters, which permits the vehicle to be driven for up to 350 kilometers. If the reserve supply of gasoline in a separate tank is brought into use, the Zafira 1.6 CNG can cover up to 500 kilometers before refueling. The Zafira 1.6 CNG is the only monovalent natural-gas model on the market that is also able to run on gasoline. This is beneficial if the level in the tanks gradually drops but there is no natural gas refueling point nearby. The driver can then continue the journey safely by switching over to gasoline by means of a switch on the center console. The system changes to the appropriate pressure or gasoline level indicator at the same time, so that the gauge always displays the remaining fuel level whichever operating mode is in use. Since the Zafira 1.6 CNG's engine has been optimized to run on natural gas, its torque and power output are reduced when using gasoline.

Safety: Each Gas Tank is Subjected to Thorough Testing

The Zafira's compact linked trailing arm rear suspension provides plenty of space for the fuel tanks. Two gas tanks and the reserve tank for gasoline are located ahead of the axle, two further CNG tanks behind it. In the event of a crash an installation frame made from high-strength steel protects these pressurized vessels, which contain the natural gas at a pressure of up to 200 bar. All four tanks are tested individually at 300 bar pressure before they are installed. Each of the pressurized vessels, which have a designed pressure rating of 450 bar, has its own solenoid valve that shuts off the gas flow as soon as the engine begins to rotate at less than starting speed. In the event of a crash, additional mechanical flow limiters come into action automatically to interrupt the gas flow. Should fire break out, a special fusible plug on each valve blows off the natural gas at a controlled rate when the temperature exceeds 110 degrees Centigrade. A burst-pressure safety device is also incorporated, to allow the gas to escape in a controlled manner if pressure inside the gas tank should rise to an unacceptably high level.

Since natural gas is lighter than air, it does not settle at ground level if the system develops a leak – for instance after a severe accident. Unlike vehicles that run on liquefied natural gas, which is heavier than air, CNG vehicles such as the Zafira are permitted to enter multi-storey and underground car parks. Furthermore, the ignition temperature of natural gas is higher, at 650 °C, than that of gasoline or diesel oil. Filling up with natural gas is a simple matter: a well-developed system with standardized delivery and filler unions ensures that operating errors are ruled out. The tanks are filled by a gas compressor; this takes about the same time as filling a tank with liquid fuel. The Zafira 1.6 CNG also has a unique pattern of filler union that can be connected to natural gas supply systems of different design in other countries, for instance in Italy, without having to use an additional adapter.

Space: The Natural Gas System does not Reduce the Size of the Interior

The natural-gas version of the Zafira retains all the practical advantages that have helped to make Opel's Compact Van such a success. The tanks are accommodated in a space-saving way, so that the van's remarkably versatile interior layout and its high load-carrying capacity can still be utilized. The Flex7 seat system with which the Zafira can be converted in a very short time, without removing any seats, from a seven-seater into a two-seater with a load capacity of more than 1,700 liters is still available for the Zafira 1.6 CNG. In place of the spare wheel that is normally carried under the floor at the rear, the 'natural gas van' has Dunlop's 'Fill & Go" tire repair kit: a can or special sealant and a small, high-performance compressor that can be connected either to the cigarette lighter socket or to the 12-Volt socket in the right rear side compartment of the load area ("Comfort" equipment specification or above). The Zafira 1.6 CNG is also available with the same full range of optional extras as the gasoline-engined model.

In most respects the Zafira 1.6 CNG's service and inspection intervals are the same as for gasoline-engined versions. Like these, the natural-gas Zafira only needs inspection by the Opel workshop every 30,000 kilometers or once a year. The only exception is a spark plug change, which is needed every 30,000 instead of 60,000 kilometers. The gas tanks only have to be tested for gas-tightness every ten years.

Profitable: Natural Gas Incurs Lower Taxes in Many European Countries

In many countries of the European Union, natural gas enjoys a tax concession until 2009 when used as a fuel. This is reflected by low prices at the filling stations. For this reason, and also because both vehicle tax and insurance premiums are distinctly lower in some countries, the additional cost of 1,420 Euro charged for instance in Germany for the Zafira 1.6 CNG compared with the Zafira 2.0 DTI is recovered in as little as 1.6 years if the vehicle is driven for 20,000 kilometers annually.

The Environment: Natural Gas has a Favorable Eco-Balance

The monovalent natural gas engine also has a very satisfactory ecological 'balance sheet', starting with the way in which the fuel is produced. Depending on the source, natural gas consists to a greater or lesser extent of pure methane (CH4) and can be converted into a fuel at much lower effort and energy outlay than gasoline or diesel oil, which have to be obtained from petroleum spirit. The complex refining process, itself a potential environmental hazard, is unnecessary. Movement of natural gas through a network of underground pipes is also an environmentally acceptable procedure. The energy content of one kilogram of natural gas is approximately the same as 1.5 liters of premium (Super) grade gasoline.

A further advantage: Thanks to the high hydrogen and low carbon contents of natural gas, it creates far fewer pollutants than the gasoline or diesel engine. Emissions of carbon monoxide (CO) are as much as 90 percent lower, those of carbon dioxide (CO2) about 30 percent and those of hydrocarbons (HC) 45 percent lower. Also down by 90 percent are the emissions of oxides of nitrogen (NOX), which greatly reduces the formation of ozone in the earth's atmosphere. Furthermore, natural gas is almost completely free from sulfur and burns without soot formation. The Zafira 1.6 CNG has no difficulty in complying with the tough D 4 exhaust emission limits and therefore qualifies in Germany for a tax exemption of up to 307 Euro. Preparations are in hand for certification according to the Euro 4 limits.

Availability: Natural Gas Filling Stations are Becoming More Widespread

The number of vehicles running on natural gas has increased rapidly in recent years. Worldwide, about one and a half million CNG vehicles are currently registered with the authorities. Most of these are in Argentina (630,500 vehicles) followed by Italy (370,000). In both these countries, efficient gas distribution networks already exist (with about 350 filling stations in Italy). Switzerland and Sweden are promoting 'biogas' as a vehicle fuel. This has a composition equivalent to high-quality natural gas and can therefore be used without problems in the Zafira 1.6 CNG. In Germany about 12,000 automobiles with natural gas as their fuel are currently registered, but as a result of new models being introduced and steady improvements to the infrastructure the total is expected to rise rapidly. The German Gas and Water Industries Federation forecasts that the number of natural gas filling stations in Germany will go up from about 265 to 300 by the end of this year and that in no more than ten years natural gas will be available reliably throughout the country from more than a thousand filling stations.

A Team of Experts: OSV - Opel Special Vehicles GmbH

The natural gas version of the Zafira is built in Rüsselsheim by the company known as Opel Special Vehicles GmbH (OSV). In addition to the compact van, OSV's specialists plan to convert other Opel models too to run on natural gas; for instance, the Astra Caravan will be available with underfloor gas tanks by the end of 2002. Among the business activities of this Adam Opel AG subsidiary company, which has about 260 employees, are the conversion of vehicles for public authorities and the production of special models, the customizing of automobiles and the production of exceptionally sporty, high-performance versions of standard Opel models – the OPC program.

Opel Zafira 1.6 CNG: Technical data summary

Number of cylinders, layout4, inline
Bore79.0 mm
Stroke81.5 mm
Displacement1598 cc
Compression ratio12.5 : 1
Max. power output71 kW (97 hp) at 6000 rpm
Max. torque140 Nm at 3800 rpm
Battery12 V, 44 Amp/h (55 Amp/h with air conditioning)
Alternator70 Amp
Top speed170 km/h
Acceleration (0-100 km/h)15.5 s
Fuel consumption (acc. to 93/116 EC) Urban: 6.8 kg/100 km
  Extra-urban: 4.6 kg/100 km
  Total: 5.5 kg/100 km
CO2 emissions145 g/km
Exhaust emission category D4/Euro 3
Fuel tank capacity Natural gas: 19 kg (110 l)
  Reserve gasoline tank: 14 l
Distance before refueling (total)app. 500 km



Dimensions and weights

Number of seats2 - 7 (Flex7 system)
Overall length4317 mm
Overall width (including mirrors)1999 mm
Height (at unladen weight, including roof rails)1704 mm
Height of loading edge607 mm
Wheelbase2694 mm
Track, front/rear1470 mm / 1487 mm
Turning circle (between walls)11.2 m
Wheel size / tire size6 J x 15 / 195-65 R15
Load volume (ECIE) 2-seats in use (loaded to roof
level): 1700 l
 5 seats in use: up to 600 l
 7 seats in use: 150 l
Unladen weight (incl. 75 kg for driver)1570 kg
Gross weight limit2115 kg
Payload545 kg
Trailer load (on 12 % test gradient) Braked: 1035 kg / unbraked: 600 kg

The performance figures quoted here refer to the use of natural gas with a methane content of 97 percent (GUS H-gas). If L –gas with a lower methane content is used, performance and fuel consumption may deteriorate. The consumption and power output data refer to a standardized average blend of gas with a high and a low methane content. The performance, consumption and emission data shown here are provisional. All values relate to the basic model to EU specification with standard equipment level. Performance figures were taken at the vehicle's unladen weight according to 70156 EEC, plus a payload of 125 kilograms.