Fuel System
| 1. Fuel pump | 4. Capless refuelling |
| 2. EVAP intake manifold | 5. Canister |
| 3. FTIV (Fuel Tank Isolation Valve) | 6. Fuel tank |
The fuel tank for the Twin Engine holds 50 liters and is not ventilated. This means that it is not allowed to breathe through the canister as in normal tanks, which is why the pressure in the tank increases when the temperature increases.
The main differences in the fuel tank between the Twin Engine and the XC90 (16-) with conventional driveline are as follows:
- rounder tank shape
- more internal reinforcements in order to maintain tank shape in the event of increased internal pressure
- FTIV (Fuel Tank Isolation Valve)
- higher opening pressure (50 kPa) for the non-return valve in order to compensate for the overpressure that may arise in the unventilated tank
EVAP (Evaporative Emission Control System)
| 1. EVAP valve | 4. Leakage detection pump | 7. FTIV (Fuel Tank Isolation Valve) |
| 2. Intake manifold; canister for internal combustion engine | 5. Atmosphere | 8. FTIV to tank |
| 3. Canister | 6. Air cleaner (ACL) | 9. Fuel tank |
The purpose of the EVAP system is to prevent unpermitted amounts of hydrocarbons entering the atmosphere.
The Twin Engine is equipped with an FTIV (Fuel Tank Isolation Valve) on the pipe, which is connected to the canister and the fuel tank. The function of FTIV is to prevent ventilation as well as to regulate the pressure in the fuel tank in the Pure drive mode or when leakage diagnosis is carried out (USA/Canada).
FTIV (Fuel Tank Isolation Valve)
| 1. Vacuum valve | 4. Connection to canister |
| 2. Pressure sensor | 5. Relief valve |
| 3. Solenoid valve | 6. Connection to tank |
To meet the emission requirements in TZEV, the fuel tank must be completely closed to the surrounding environment and the canister in the Pure drive mode. The function of FTIV in the Pure drive mode is to prevent ventilation of the fuel tank, as well as equalize, via the canister, any pressure that may arise in the fuel tank. FTIV is located between the fuel tank and the canister, and is activated during leakage diagnosis and refuelling, as well as in the event of a vacuum or overpressure.
FTIV consists of two valves that mechanically regulate predetermined levels for pressure and vacuum. The vacuum valve (1) can be controlled by means of a solenoid valve (3) that is activated before refuelling when the driver activates fuel filler flap opening or when the car performs leakage diagnosis via ECM.
The pressure sensor (2) measures the overpressure or vacuum created in the fuel tank in order to ensure that the tank pressure remains at atmospheric pressure level before the fuel filler flap is opened. The relief valve (5) opens at pressures lower than -11 kPa or higher than 31 kPa.
When the fuel tank is not vented, the gases form a pressure in the system. How high or low the pressure becomes depends on ambient temperature, atmospheric pressure and the fuel's vapor pressure.
FTIV can be replaced as a separate part. ECM controls FTIV.