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Brief description

Brief description

Legal requirements

ORVR, Onboard Refueling Vapour Recovery, is a legal requirement that comes into force in the USA from M98. The requirement regulates emissions of hydrocarbons while refueling.

LEV: From M00, all LEV (Low Emission Vehicle) cars are equipped with ORVR.

The difference compared to LEV from earlier ORVR systems is the software in T7. The CHECK ENGINE lamp comes on cars intended for markets with legal requirements on tank integrity but not on cars intended for other markets, although a DTC will be generated. The tank integrity diagnosis on LEC cars must be able to detect a leak corresponding to a hole with diameter 1 mm.

Applies to all: Hydrocarbons that vaporize while refuelling must be dealt with in the car and not released into the atmosphere. Max. 0.2 g hydrocarbon per gallon of fuel may escape while refuelling 15-38 litres (4-10 gallons) of fuel per minute. The tank must be able to be filled at 15-38 litres (4-10 gallons) per minute to 95% of its total volume without the fuel nozzle shutting off too early so that subsequent topping up is required.

Leakage larger than that caused by a hole corresponding to a diameter of 1 mm (0.040”) must be detected by the system.

System description

Fuel is poured into the filler pipe and is then passed through a non-return valve down to the tank. The filler pipe functions as an ejector. The fuel flowing down draws air with it from outside into the tank, Preventing the fuel fumes escaping into the atmosphere through the opening in the filler pipe. The fuel being filled presses out the gaseous hydrocarbons and air that is drawn into the tank through the float valve and on to the evaporative emission canister. The hydrocarbons are absorbed in the evaporative emission canister and the air escapes through the shut-off valve.

At a certain level (approx. 95%), the float valve closes and the pressure in the tank increases. The fuel now rises in the filler pipe and the fuel nozzle closes when the fuel reaches it. The non-return valve in the filler pipe prevents ”back-spit” when the nozzle closes.

The pressure remaining in the tank passes slowly through the rollover valve and into the evaporative emission canister. As the fuel level decreases, the fuel runs in from the filler pipe until it is empty.

When the engine is started, the evaporative emission canister is gradually purged as air is sucked into it through the shut-off valve. The hydrocarbon/air mixture passes through the EVAP canister purge valve and into the engine where it is burnt.

LEV: Diagnosis of LEV cars is divided into two variants, normal and special, depending on the engine coolant temperature and intake air temperature. This is to eliminate the affect of evaporating fuel as far as possible.

An evaporative emission canister fitted by the tank is used on ORVR cars to store approx. 130 g hydrocarbons. The canister is filled with approx. 70-90 g hydrocarbons during normal refuelling. This is subsequently purged while the car is being driven so that it is normally empty the next time the car is refuelled.