國五排放標準實施的具體時間確定，雖然有過渡期，但市場還是掀起了國五熱潮。但國五輕卡比國四的技術升級在哪？我國的排放標準是參照歐洲排放標準制定的。車輛的排放標準及檢測按輕型車和重型車分類，即按車輛最大總質量不超過3.5T（N1類車）或超過3.5T（N2、N3類車，N3屬于重卡）來區分，分別執行輕型汽車GB18352.5或重型汽車GB17691排放標準。其中涉及到輕卡的車型為N1和N2類車型。
目前我國國五技術路線大致有2種，EGR（廢氣再循環）+DPF（顆粒捕集器）+DOC（微粒催化轉換器）技術與電噴發動機+SCR+DOC的技術路線。
根據不同排放標準，不同車型選擇不同的技術路線。N1類車選擇EGR+DPF+DOC，N2類車搭載SCR+DOC技術路線。
其中N2類車的技術難點相對小些，下面小編就從易到難簡單分析下輕卡升級國五的技術難點。
SCR的原理是通過優化噴油和燃燒過程及性能優化標定匹配，盡量在機內控制顆粒PM的產生，實現柴油機比較理想的裸機PM排放，在機外后處理過程，采用尿素溶液對NOx進行選擇性催化還原。
在2種技術路線中，SCR系統相對簡單成熟，因為其技術在國四階段已近趨于成熟，升級國五排放標準只需要調整一下技術參數，對發動機的改變不大，相對的開發成本要低些。而且SCR對燃油品質不那么敏感，可以回避國內燃油含硫量高的問題。
即使SCR系統技術已經相對成熟，但對于輕卡搭載SCR系統升級國五存在著最大的問題—成本問題。
首先購車成本的提高，SCR系統價格昂貴，一套系統大約在10000元左右。而且SCR系統體積龐大，且需要加尿素儲存裝置，對于國內輕型卡車4米多的底盤，造成了布置困難，也使車輛損失有效載荷200-300kg。SCR系統是通過添加車用尿素催化還原的，而車用尿素是消耗品，需要定期添加，百公里尿素消耗量是百公里油耗的5%以上，這就使得用車成本的提高。
N1類車采用的是EGR+DPF+DOC的國五技術路線，EGR+DPF+DOC的技術路線，是通過EGR進行對發動機缸內清潔，提高燃油燃燒率減低NOx，再通過DOC和DPF對排氣中顆粒物進行凈化。除了發動機要改變結構添加EGR閥外，最為關鍵的技術是DPF系統。
作為國五發動機的關鍵，DPF由PM采集裝置、燃油噴射裝置和控制系統組成。當DPF內的顆粒吸附量達到一定限值時，ECU就會開啟燃油噴射系統向DPF噴射燃油，使DPF捕捉到的顆粒充分燃燒完成再生，這能夠有效凈化排氣中70%-90%的顆粒，是凈化柴油機顆粒物最有效、最直接的方法之一。但也存在這三大難點：
1、DPF技術依賴國外
目前我國的DPF的生產都是和外企合作的，成本高。DPF標定技術主要掌握在國外公司手里。標定周期長、費用高、國內車型種類多等，對于國內企業來說都是壓力。
2、DPF標定復雜
DPF技術路線標定工作非常復雜，需要整機臺架標定與整車標定技術的集成與融合，柴油機本身燃燒、再生策略、排氣溫度熱管理、機油稀釋風險、碳載荷與系統背壓關系標定、OBD標定等都是要突破的技術難點。這些技術在行業內都已經得到應用，但由于標定復雜，研發成本很高。
3、DPF需定期清潔或更換
不是裝載了DPF就完事了，由于DPF在使用過程中的顆粒物逐漸增加會引起的發動機背壓升高，導致發動機性能下降的情況。所以要定期除去DPF內沉積的顆粒物，恢復它的過濾性能，質量不高的需要定期更換。這就要產生額外的費用，而且DPF目前單次購買價格高，使用成本又將提高。
面對如何延長DPF的使用期限，成為各生產廠家研究重點，作為在排放系統技術領先全球的佛吉亞排放控制系統一方面致力于DPF產生的本土化，減少成本，一方面開發熱再生TR系統，通過熱量將微粒物氧化燃燒，使得DPF過濾性能再生，保護了環境也使DPF使用周期得到延長，但目前TR系統只在客車或者重卡上使用，在輕卡上還無法使用。
隨州市東正專用汽車，國五排放公告陸續申報中（國五灑水車、國五垃圾車、國五吸糞車、國五吸污車、國五高壓清洗車、國五清障車、國五平板車）等專用汽車公告，最新消息請登錄 http://www.dragonhide.cn
The five standards implementation determine the specific time, although there is a transitional period, but the market is also raised five boom. But the five light trucks than four technology upgrades? China's emissions standard was drawn up with reference to the European emission standard. Vehicle emissions standards and testing according to the light vehicle and heavy vehicle classification, namely according to the vehicle maximum total quality is not more than 3.5 T car (N1) or more than 3.5 T (N2 and N3, N3 belong to heavy card) to distinguish, respectively carry out light car GB18352.5 or heavy car GB17691 emission standards. Which involves the light truck models for N1 and N2 class models.
At present our country the five technical route to roughly two kinds, EGR (exhaust gas recirculation) + DPF (particle trap) + DOC (particle catalytic converters) + SCR + DOC technology with electronic fuel injection engine.
According to different standards, different models to choose different technical route. N1 class car choose EGR + DPF + DOC, N2 class car carried SCR + DOC.
The N2 class car technology difficulty is relatively small, below small make up from easy to difficult simple analysis light trucks upgrade the five technical difficulties.
The principle of SCR is through the optimized fuel injection and combustion process and performance optimization calibration match, try to control the generation of particles PM inside the machine, to achieve ideal bare-metal PM emissions of diesel engine, the closed post-treatment process, selective catalytic reduction of NOx by urea solution.
In 2 kinds of technical route, the SCR system is relatively simple and mature, because of its nearly mature technology in the four stages, upgrade the five standards only need to adjust the technical parameters, the engine of change is not large, relatively lower development costs. And SCR of fuel quality is not so sensitive, can avoid the problem of high domestic fuel sulfur content of the.
Even SCR system technology is already relatively mature, but for light trucks carrying SCR system upgrade the five biggest problems exist - cost problem.
First of all, the rising cost of cars, SCR system is expensive, a set of system about 10000 yuan. Bulky and SCR system, and need to add urea storage device, 4 meters for the domestic light truck chassis, caused the difficult, also make the vehicle loss 200-300 kg payload. SCR system is by adding urea catalytic reduction of automobile, and vehicle urea is consumables, need to add regularly, hundreds of kilometers of urea consumption is the first of the gas mileage by more than 5%, which makes the rising cost of the car.
N1 class car USES is the kingdom of EGR + DPF + DOC five technical route, EGR + DPF + technology route, DOC is clean inside the engine cylinder by EGR, improve fuel combustion rate reduce NOx, again through the DOC and DPF of particulate matter in the exhaust purification. In addition to add an EGR valve engine to change the structure, the key technology is DPF system.
As the key part of the five engine, DPF by PM collection device, fuel injection device and control system. When the particles inside the DPF adsorption amount reaches a certain limit, the ECU will open sprays fuel into the DPF fuel injection system, make the DPF captured particles burn adequately complete regeneration, which can effectively purify exhaust gas of 70% - 90% of the grain, is to purify the diesel particulate matter is one of the most effective and most direct way. But there is also the three major difficulties:
1, DPF technology dependence on foreign
At present, China's production of DPF is cooperation with foreign companies, the cost is high. DPF calibration technology mainly in foreign hands. Calibration models, long cycle, high cost and domestic variety, etc., are pressure for domestic enterprises.
2, calibration of DPF complex
Calibration of DPF technology route is very complex, needs the machine bench and vehicle calibration technology, integration and fusion of burning diesel engine itself, regeneration strategy, exhaust temperature, thermal management, carbon, oil dilution system load and the back pressure relationship, OBD calibration is to break through the technical difficulties. These techniques have been applied in the industry, due to the complex calibration, research and development cost is very high.
3, DPF need to clean or replace regularly
Not loading the DPF is finished, as a result of DPF in motor caused by the use of particles will increase gradually in the process of back pressure increases, resulting in a decline in engine performance. So regularly remove deposition of particles within the DPF, restore its filter performance, quality need to be replaced regularly. This will generate additional costs, and DPF currently single purchase price is high, the cost will increase again.
Face how to extend the use of DPF, become the manufacturer research priorities, as a leading technology in emission system global faurecia emissions control system on the one hand, committed to the localization of DPF, reduce costs and develop these renewable TR system on one hand, through the heat particles combustion, the DPF regeneration, the filtration performance to protect the environment is to extend the lifetime of DPF, but at present, the TR system only used in passenger cars or heavy card, also cannot be used on light trucks.