What is the intake form of a CNG engine?
3 Answers
CNG engines adopt a naturally aspirated intake method. A CNG engine consists of components such as a high-pressure fuel shut-off valve, high-pressure reducer, low-pressure fuel shut-off valve, and electronically controlled pressure regulator. Advantages of CNG engines: 1. Fuel-efficient; 2. Low emissions; 3. Good power performance; 4. High operational efficiency; 5. Durable. Working principle of CNG engines: High-pressure compressed natural gas exits the storage cylinder, passes through a natural gas filter for filtration, and then enters the high-pressure reducer via the high-pressure solenoid valve. During the pressure reduction process, the high-pressure natural gas expands and requires absorbing a significant amount of heat. To prevent the reducer from freezing, engine coolant is used to heat the gas within the reducer.
I've been driving a CNG vehicle for six or seven years. The intake system typically mixes air and natural gas externally before entering the engine, meaning the two are thoroughly blended before reaching the intake manifold for combustion. The advantage of this design is significant cost savings on long trips—fuel expenses can be reduced by 30-40% monthly—while also being environmentally friendly, with notably lower pollutant emissions. However, if the mixing ratio is uneven or dust accumulates in this intake system, it can easily lead to unstable idling or reduced power output. That’s why I always remind myself to replace filters frequently to maintain smooth airflow. During summer highway driving, noticeable power loss warrants an immediate check, while winter starts may be slightly sluggish but normalize after warming up. During modifications, tuning the mixer position is crucial for optimization; otherwise, it’s a waste of money and resources. In short, this intake setup is simple and reliable, but neglecting maintenance can backfire on efficiency—regular upkeep is key.
With over a decade of repair experience, CNG engines mostly adopt hybrid intake systems. Simply put, a gas mixer is installed at the intake manifold where compressed natural gas mixes with air before entering the combustion chamber. This design offers fewer advantages but lower maintenance costs compared to direct injection systems prone to sensor issues. However, drawbacks include rapid carbon buildup in intake passages, especially on dusty mountain roads, requiring timely nozzle cleaning and filter replacement when power drops. The most common complaint about slow cold starts relates to intake mixture temperature control, which can be improved by adding preheating components. Daily CNG vehicle operation demands close attention to gas line sealing to prevent leaks and ensure safety. Overall, these systems are cost-effective and durable but require meticulous maintenance.
