| Nowadays, environment protection and source saving have become the main topic for long term developing. The evaporative HC and VOC coming from vehicle have become the main source of air pollution. The whole world is paying attention to the emission and fuel consumption of vehicle and the regulation and direction to control vehicle evaporative emission are becoming strict more and more. The main point controlling emission has transferred from new type-certification vehicle to in-use vehicle and conformity of production. Our country'emission controlling regulation is becoming stronger, and has been very close to the EU'. Along with the stricter emission regulation, the requirement to control the performance of evaporative controlling system becomes higher and higher. The new challenge to vehicle-manufacturer must be put forward.CATARC is a national vehicle test institution. They will finish 150 times whole vehicle evaporative test using nation 3rd regulation and evaporative and saturating test of some parts. Based on lots of test dada, combining the research at the same time, the concept of evaporation emission is introduced first, and then different type of controlling system and method for controlling evaporation emission is introduced. Last, the evaporative emission of national and international is introduced. Next, the status of national evaporative emission level of light-duty gasoline vehicles as the key point is introduced. Through the analyzing and statistical report, nowadays the national light-duty vehicles (the Gross weight is less then 3500 kilograms) have the evaporative emission level: less then 2.0 grams is 77 percent of all, higher then 2.0 grams is 23 percent. The whole level is good, and some have the bigger space to dead line. But at the same time, there are some very high level emission vehicle, the reason are the poor seal performance of fuel and evaporative controlling system and the poor matching engineering. Classifying the vehicle according the style, the 1st category have the high evaporative emission level, the 2nd category have the low evaporative emission level. It is because the the 1st category have the introducing technology and the 2nd have the national technology for most of them. Nowadays the vehicle industry has agreed that using canister loaded the active carbon is the necessary and only method to control evaporative emission. The active carbon and canister is introduced and analyzed. From inner factor, the adsorption of carbon to HC is a physical progress; the whole construction inside the carbon decides the adsorption and purging capacity to HC. From outer factor, the main factor affecting adsorption capacity of carbon is carbon layer pressure drop, ratio face area, anti-wear capacity, water content of absorbed medium, dust content of absorbed medium, the PH value of absorbed medium. It should be considered for selecting the right carbon. The butane working capacity and gasoline working capacity are the valuable means to value the adsorbing capacity to HC of canister.By the evaporative and saturating test to all the parts that contacting the fuel and fuel steam, the key parts affecting vehicle evaporative emission is given. By analysis, we know that the key parts are: fuel tank, canister, fuel pipe, engine, fuel, ECU controlling and inner decoration. The loading capacity and figure of fuel tank decide the emitting HC steam amount, and the material (metal or plastic) decide the saturating HC steam amount penetrating the wall. For fuel pipe contacting the fuel directly, the contacting area decides the saturating HC steam amount penetrating the pipe wall. Canister is the most key parts controlling evaporative emission, its working capacity, seal performance, venting resistance, anti-vibrating performance and so on decide the HC emission level of whole vehicle. If finishing the matching and selecting test, the whole vehicle HC emission will be below 2.0 grams. Purging controlling is the onboard computer (ECU) driving the purging valve at the right time, dragging the HC absorbed by carbon to the burning chamber of engine through the engine vacuum. The engine burns the HC, and makes the active carbon rebirth. The selecting of purging time and purging flux is very important. We will hold more purging amount, and contribute low disturbing to air-fuel ratio controlling at the same time. And the fuel specialty used by vehicle is very important to the whole vehicle HC emission too. RVP of fuel is the key factor. The test results tell us that the HC steam amount increase in index type while the RVP goes bigger. The inner decoration material, parking time and running odometers and so on have the influence to whole vehicle evaporative emissions.The formula prediction method of key parts is given based the lots of test analysis and statistic. The HC amount produced from fuel system are the combination effect of fuel tank loading capacity and fuel RVP, and the emitting HC amount increase in index type while the fuel tank capacity and fuel RVP goes bigger. The HC amount adsorbed by canister is the difference of HC amount producing from fuel tank and purging amount by ECU controlling, and has relation with canister working capacity and active carbon volume. The HC saturating amount from lastic fuel tank and fuel pipe is relating with the material. Single-layer material has the double emission amount comparing to multi-layer material produced by synchro-extroding method. The inner decoration of vehicle uses a lot of organic solvents, the emitting HC amount is related with the amount of organic solvents, producing time and the environment temperature of vehicle parking. With bigger running odometers, the HC evaporative emission will increase. By statistic analysis, the vehicle after 80 thousands kilometer have the double HC evaporative emission than the 0 kilometer's. Integrating the above analysis and predicting formula, we can export the total HC evaporative emission amount of whole vehicle using national 3rd emission regulation cycle.Lots of canister mass datum, HC concentration datum in VTSHED and test result by canister-fuel tank system evaporative test was collected. At the same time we calculate the result using predicting formula. Comparing the real result with the calculating result, we can make the conclusion that when the whole vehicle have the emission level lower than 0.3 grams, the predicting result have the difference with the real result; when the whole vehicle have the emission level higher than 0.5 grams, the predicting result is very close to the real one. It satisfies the engineering design and matching request.The sum-up to the whole research is given. For satisfying the regulation even the vehicle production line having the big decentralization, the HC evaporative emission amount should be 60% of limited value. It is that it will have 40% remaining capacity in another word. For this reason, the working capacity of canister will be 1.5 times the HC steam amount emitting from fuel tank when selecting the canister absorbing capacity according to the fuel tank capacity and other factors. The seal performance of fuel system is the precondition to decreasing the whole vehicle HC emission. If the whole vehicle has the HC emission higher than 4.0 grams, it must be the poor seal of fuel system. Reasonable matching engineering should be finished based lots of test, consider ting design and appropriate selection of parameters. We will give the right design to satisfying the regulation and to cost much lower at the same time.
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