Great Wall Motor issued a statement, saying on April 11 reported to three government agencies BYD’s two hybrid models use atmospheric-pressure fuel tanks instead of high-pressure fuel tanks, there is a “whole vehicle evaporative pollutant emissions do not meet the standard suspicion”.
BYD then released a statement, saying the Great Wall’s test report is invalid, and can not be used as a basis. It’s products and related tests comply with national standards and pass certification by national authorities.
BYD said in the interactive platform, BYD DM-i is based on the electric vehicle platform design of dual-motor series-parallel architecture, to achieve the decoupling of the engine and wheels (decoupled connection), in EV mode the engine can be flexibly started, the fuel vapour can be freely decoupled (pumping away the oil vapour in the carbon tank). Together with the synergistic strategy of multiple control units and in-depth research on the characteristics of carbon tanks, BYD has developed its own fuel vapour emission control technology for atmospheric tanks, which can meet the evaporative emission regulations. This technology enables the PHEV to automatically start the engine before the carbon tank is saturated, even if the vehicle is used for a long time in EV mode, and the problem can be solved in about 4 minutes, which neither increases fuel consumption nor noise, but also completes fuel vapour desorption, vehicle power generation and engine maintenance, which is both reasonable and legal.
With the full text of BYD’s response:
Question 1: What technical routes are available for PHEV plug-in hybrid to solve the problem of steam emission compliance?
PHEV plug-in hybrid has two technical routes in the industry, one is based on the development of the fuel car platform, the motor and powertrain superimposed, can not achieve the decoupling of the engine and wheels (decoupling connection), and the engine in EV mode can not be flexible to start the decoupling (pumping away the oil vapour in the carbon tank), so it must be equipped with a high-pressure fuel tank to meet the regulatory requirements of evaporative emissions.
The other is based on the EV platform design of dual-motor series-parallel architecture, which realizes the decoupling of the engine and wheels, and the engine can be flexibly started for desorption in EV mode, so it can also meet the regulatory requirements of evaporative emissions with the atmospheric pressure fuel tank.
Question 2: Can BYD achieve the evaporative emission standard with an atmospheric fuel tank?
Yes, it can. BYD DM-i is a series-parallel architecture with two motors based on an EV platform, which realizes the decoupling (disconnection) of the engine and wheels so that the engine can be flexibly started in EV mode and the fuel vapour can be freely desorbed (pumping away the oil vapour in the carbon tank). Together with the synergistic strategy of multiple control units and in-depth research on the characteristics of carbon tanks, BYD has developed its own fuel vapour emission control technology for atmospheric tanks, which can meet the evaporative emission regulations.
This technology realizes that PHEV will automatically start the engine before the carbon tank is saturated, even if the vehicle is used for a long time in EV mode, and the problem can be solved in about 4 minutes, which neither increases fuel consumption nor noise, but also completes fuel vapour desorption, vehicle power generation and engine maintenance, which is both reasonable and legal.
Question 3: How is fuel vapour generated and how is it removed from PHEV vehicles?
The emission of fuel vapour mainly depends on temperature change and vehicle mileage, for example, in Shenzhen, when the vehicle is parked, 3~5 grams of fuel vapour can be generated in the fuel tank every day, and about 1 gram of fuel vapour can be generated for every 100 kilometres of driving under EV conditions; the generated fuel vapour is adsorbed by the carbon tank, on average, the weight of the carbon tank increases by 4~6 grams a day, if we take the average value of 5 grams/day, the weight of the carbon tank increases by 30 grams after 6 days.
BYD PHEV plug-in hybrid technology is very intelligent, the control system has the ability to monitor and count the oil vapour evaporation in real-time and control the engine start and desorption time according to the judged conditions, and accurately complete the carbon canister desorption (draw-off the oil vapour in the carbon canister). For example, the 1.5L self-priming engine can achieve 40-50 grams of desorption capacity in about 4 minutes, and the intelligent system can monitor in real-time, accurately determine the time point of desorption, start the engine, and easily complete the above case of 30 grams of desorption requirements, ensuring compliance with evaporative emissions.
Specifically in the user’s use scenario, when the vehicle is driven continuously in EV mode for about 6 days, the engine will start when the desorption time point is reached and the vehicle speed is greater than 35km/h, which only takes about 4 minutes, and the noise of the engine running at this time is less than the noise of the whole vehicle, which is senseless to the user. In addition, the engine starts for a short time, and the process of solving the oil and vapour desorption is also generating electricity, which does not increase energy consumption and also realizes engine maintenance.
Question 4: What is the difference between Chinese standards and other countries’ standards?
China is the birthplace of PHEV technology and the largest PHEV market in the world. The Chinese brand represents the advanced direction of PHEV technology in the world, and the Chinese evaporative emission standard is internationally forward-looking and leading. At present, more than 80% of countries and regions in the world are referring to Chinese standards.
The technical standards of a few countries and regions are different from China’s, mainly because their PHEVs are mainly P2 architecture, based on a fuel car platform, which cannot decouple the engine and wheels (disconnected), cannot start the engine at any time in EV mode, and cannot freely desorb the fuel vapour (pumping away the oil vapour in the carbon tank), and can only use high-pressure fuel tank. It is understood that they are also referring to China’s PHEV technology architecture, and will most likely refer to Chinese standards in the future to diversify the technology.
Question 5: Which fuel tank technology solution does BYD use in China and abroad?
BYD has accumulated more than 20 years of PHEV plug-in hybrid technology and has strong independent research and development capability, with both atmospheric and high-pressure fuel tank technology solutions. In terms of application, both domestic and foreign countries are the same, and both atmospheric and high-pressure fuel tanks are used, both of which meet the local evaporative emission regulation standards.
Question 6: What is BYD’s research on evaporative emissions and related patents?
BYD PHEV plug-in hybrid has undergone four generations of powertrain optimization and upgrading since 2005. The third generation powertrain was designed based on the fuel car platform, which could not decouple the engine from the wheels (decoupling), and could not flexibly start the engine in EV mode for carbon tank decoupling (extracting the oil vapour from the carbon tank), so we also used high-pressure fuel tank at that time to comply with the regulatory requirements. 2020 BYD launched the fourth generation plug-in hybrid solution, which is based on the new design of the EV platform and adopts the dual-motor The series-parallel power architecture decouples the engine from the wheels and allows for flexible engine start for efficient decoupling, so the atmospheric fuel tank can also meet regulatory requirements.
BYD has applied for several patents on technologies related to steam emissions over the past decade or so.
The combined solution of BYD PHEV dual-motor series-parallel power architecture and evaporative emission system with atmospheric fuel tank is new, and we have accumulated rich software and hardware solutions for fuel evaporation systems. In order to further promote the development of PHEV, BYD is willing to share the control strategy and principle of our core technology and patent achievements to all automotive peers for free, and also accept the analysis and discussion from industry experts.
