One of the most important new technical features in Model Year 2002 is the introduction of a vehicle driven by natural gas which is based on the Zafira, with the Z 16 YNG engine.
The abbreviation CNG stands for Compressed Natural Gas.
The Z 16 XE engine was used as a basis for the Z 16 YNG. Modifications to the intake manifold, the piston, the exhaust system, the tank system and the electrics had to be made for operating the CNG.
The driving characteristics of the Zafira Z 16 YNG correspond to those of the Zafira Z 16 XE. The only difference is in the start-up phase, when the engine speed is briefly increased to 2000 rpm immediately after starting.
This increase in engine speed during the start-up phase is generated because the control electronics will only open the injectors for CNG when a minimum engine speed of 820 rpm has been reached.
The Z 16 YNG engine only sucks in air during this phase, which means that opening the injectors for CNG leads to an increase in engine speed to approx. 2000 rpm. This speed is immediately adjusted to the normal idle speed by the electronic control system. Normally, this brief increase in engine speed is hardly noticed.
The idle speed for Engine Z 16 YNG is between 850 – 950 rpm. The engine with CNG has an increased compression of 13.0 : 1. This results in greater efficiency at low engine speeds, which leads to significantly reduced fuel consumption.
The two CNG tank modules, which are fitted to the vehicle underbody in the area of the rear axle, are filled via a modified filler port.
For the fuel supply of the engine these are supplemented by the emergency tank, which has a filling capacity of 15 litres and is arranged between the CNG tank modules.
This permits alternative operation modes – petrol/CNG – to enable the vehicle to be driven to the next petrol station.
| 1 | Pressure reducer with pressure-relief valve | 5 | Tank modules (CNG) |
|---|---|---|---|
| 2 | Modified front muffler | 6 | Modified rear muffler |
| 3 | 15 l emergency tank (petrol) | 7 | Safety valves |
| 4 | Modified tank filler port | 8 | Stainless steel CNG high-pressure line |
The most important features of the Zafira Z 16 YNG
- Modified filler port for CNG/petrol under fuel filler flap
- Gas pipes from stainless steel
- Switch for petrol/gas operation in the centre console
- Pressure reducer for CNG
- 1.6 litre 16V DOHC engine, Z 16 YNG, optimised for CNG
- Modified intake manifold with separate injection systems for CNG/petrol
- Engine electronics with operating functions for CNG and petrol operation
- Knock detection for CNG quality differences to adapt to different CNG qualities
- Two CNG tank modules each with two pressure vessels (front CNG tank module and rear CNG tank module including safety valves, safety frame and protection devices)
- Bleeder and maintenance valve
- Emergency tank with 15 litre tank capacity (petrol)
- Modified rear axle for CNG vehicles
- Modified exhaust system for CNG vehicles
The difference between CNG and petrol operation
The difference is in the type of energy carrier.
Petrol is obtained from oil and CNG is obtained as a by-product during oil drilling. For the vehicle owner, it simply means a different medium when filling up the tank, in all other respects it has characteristics comparable to a vehicle operated exclusively with petrol. In Aftersales, the vehicle is treated like a petrol vehicle.
There is no greater danger from a vehicle operated using natural gas, compared to a petrol-driven vehicle. The same safety, repair and maintenance regulations and the same service intervals still apply. An exception is repair and maintenance operations to the gas system (high-pressure component). In this regard, the extended safety regulations and the special features in the Service Instructions must be observed.
Operations on the gas system must always be performed by specifically trained personnel. Proof that training in accordance with H757 has taken place is necessary.
Exhaust gas characteristics
The Z 16 YNG engine meets the exhaust emissions standard according to D4 or Euro 4.
Nevertheless, the proportion of pollutants in the exhaust gas of the Z 16 YNG engine in CNG operation is considerably less. The emission of nitrogen oxides (NO x ) and carbon monoxides (CO) is reduced by up to 90%, the emission of carbon dioxide (CO 2 ) is reduced by up to 30%. With hydrocarbons (HC), the emission is about 45% less compared to Engine Z 16 XE.
CNG (Compressed Natural Gas)
Most natural gas flowing through German natural gas networks is Russian natural gas (in addition to Dutch natural gas, North Sea natural gas, natural gas from northern Germany). Russian natural gas has the highest quality and has essentially the following composition:
| Carbon dioxide (CO 2 ) | 0.09% | |
|---|---|---|
| Nitrogen (N) | 0.82% | |
| Oxygen (O 2 ) | < | 0.01% |
| Methane (CH 4 ) | 98.09% | |
| Ethane | 0.66% | |
| Propane | 0.23% | |
| ISO-butane | 0.04% | |
| N-butane | 0.04% | |
| ISO-pentane | 0.01% | |
| N-pentane | 0.01% | |
| Hexane | 0.01% |
The octane number of natural gas is 130 – 135 octane.
The Z 16 YNG engine used in the Opel Zafira can therefore be highly compressed (13.0 : 1). 'Super' petrol (RON 95 or 98) can be used as an emergency fuel.
Only high-grade gas flows through the local gas supplies into the gas system in German gas networks (except for a small number).
The difference between low-grade gas and high-grade gas is the percentage of methane contained in the natural gas.
The methane content is approx. 83% in low-grade gas (primarily with Dutch natural gas) and about 98% in high-grade gas (with Russian natural gas).
The high-grade gas flowing through the gas networks is mixed from various gas flows. This gives a mean methane content in natural gas which fluctuates between 87% and 88%. As a result, an almost constant methane content is in the natural gas flowing through the networks.