What is the fuel tank - isolation valve assembly?
The automotive fuel tank isolation valve assembly (FTIV) is an electronically controlled cutoff device installed between the high-pressure fuel tank and the carbon canister, consisting of an electromagnetic valve and a mechanical pressure relief mechanism. Its primary function is to seal the fuel vapor and prevent it from leaking out when the engine is off, and to open and conduct when the engine is running or under overpressure to balance the pressure or introduce it into the combustion process.
Core Definition and Function
Essentially: It is a key safety and emission control valve in the fuel evaporation control system (EVAP), often a standard component of the high-pressure fuel tank system.
Main Functions:
Isolation Locking: Automatically closed when the engine is not running, locking the fuel vapor within the fuel tank (with a pressure resistance of typically 35-40 kPa), preventing direct entry into the carbon canister or the atmosphere.
Dynamic Conducting: Opened when the engine is running, guiding the vapor into the intake manifold for combustion; or actively opened based on pressure sensor signals to relieve pressure and prevent damage to the fuel tank due to overpressure or negative pressure in extreme conditions.
Safety Redundancy: Equipped with an automatic pressure relief mechanism upon power loss or a mechanical overpressure opening mechanism to ensure safety during refueling and system integrity in extreme conditions.
Working Principle and Logic
Off/Brake State: The electromagnetic valve is de-energized to close the main channel, and the mechanical structure is sealed to achieve "fuel and air isolation", reducing the load on the carbon canister and meeting strict emission standards such as Euro 6b + RDE.
Operation State: The ECU controls the opening of the electromagnetic valve, with the fuel vapor being drawn into the engine for combustion through the carbon canister or directly (depending on the system design).
Abnormal/Refueling State: When the pressure sensor detects overpressure (such as intense heat exposure) or receives a refueling command, the valve is forced to open to relieve pressure, balancing the internal and external pressure differences to ensure safety.
Application Scenarios and Composition
Main Application: Plug-in hybrid (PHEV), extended-range electric vehicles, and fuel vehicles meeting high emission standards (as these models have frequent engine startups or shutdowns and are prone to oil and gas accumulation).
Physical Composition: Typically includes a valve body housing, electromagnetic coil assembly, armature/valve core, spring reset mechanism, seals, and an optional mechanical pressure relief valve or pressure sensor integration module.
This component is different from the traditional carbon canister electromagnetic valve (located between the carbon canister and the intake manifold). FTIV is specifically designed for the fuel tank outlet and is the core indicator to distinguish between low-pressure fuel tanks and high-pressure fuel tank systems.
The core function of the automotive fuel tank isolation valve (FTIV) is to cut off the fuel tank and carbon canister connection when the engine is off or in electric mode to seal the fuel vapor and meet evaporation emission regulations, and to automatically relieve pressure in case of overpressure or negative pressure to ensure the safety of the fuel tank structure. Core function
Evaporation emission control: Automatically shuts off when the engine stops or when the vehicle is in pure electric mode, locking the fuel vapor in the high-pressure fuel tank to prevent direct discharge into the atmosphere, meeting strict emission standards such as Euro 6b/RDE.
Pressure safety balance: When an excessively high positive pressure or negative pressure is generated inside the fuel tank due to temperature changes, it opens as a mechanical/electronic safety valve to release extreme pressure and prevent the fuel tank from deforming or rupturing.
Refueling safety assistance: Before or during refueling, it detects and releases the residual pressure in the tank to prevent fuel splashing and ensure safe refueling.
Working logic and application scenarios
Normally closed sealing mode: Connected between the high-pressure fuel tank and the carbon canister, it is default closed (or controlled closed), blocking the flow of oil and gas to the carbon canister, reducing the load on the carbon canister and avoiding the emission of unburned oil and gas.
Active pressure relief mode: Receives pressure sensor signals or relies on the mechanical diaphragm structure, forcibly opens the ventilation when the pressure exceeds the threshold (such as >35-40 kPa) or is below the safety value.
Mainly equipped vehicles: Widely used in plug-in hybrid (PHEV), extended-range electric vehicles, and fuel vehicles with high-pressure fuel tanks, as these types of vehicles have frequent engine startups and stops, special mechanisms are needed to solve the accumulation of oil and gas during shutdown.
This component is a key safety component of the fuel evaporation control system (EVAP), different from the physical "partition" inside the fuel tank that prevents oil and gas from shaking, it is an electrically controlled or mechanical valve device in the pipeline system.
If you want to know more, keep reading the other articles on this site!
Please call us if you need such products.
Zhuo Meng Shanghai Auto Co., Ltd. is committed to selling MG&MAXUS auto parts welcome to buy.
