"At 60 mph, the loudest noise in the latest Rolls-Royce comes from the electronic clock." This is a copy written for Rolls-Royce by Ogilvy founder David · Ogilvy in 1959, also known as one of his most famous works.
Why do top luxury cars spend a lot of money to promote quietness, instead of the 100 kilometers of acceleration, top speed and other indicators that many people think. There is a proverb in English: Quietness is best, which also indicates that quietness is actually a very luxurious experience. In the NVH quietness list of Dr. Zheng Barton, a third-party evaluation platform, the Ideal MEGA won the first place at speeds of 40km/h, 80km/h, and 120km/h, surpassing many million-level luxury models. Why is it that at present, China only has ideals, while other brands rarely specialize in NVH?
It's not that you don't do NVH, it's that it's too difficult to do NVH
In fact, most car brands also do quietness, but they only reach the passing line and do not go deeper. Because it is too difficult to do NVH well, it is a huge systematic project. Indicators such as acceleration of 100 kilometers and top speed have clear technical routes that can be improved, such as increasing engine displacement or motor speed. Among the more than 10,000 parts of the car, more than 30% are related to NVH, which cannot be solved by plugging sound-absorbing cotton; Moreover, there are many scenarios that need to be developed for NVH, including various driving dynamics, environment, temperature, weather, etc.; In addition, everyone's hearing and body perception are different, and sensitive people will perceive noise that ordinary people cannot feel, which is very subjective.
To put it simply, doing indicators such as 100 kilometers of acceleration is like doing a math problem, there is a formula, and doing NVH seems to be step-by-step, but in fact, it needs to integrate various factors, have intention, depth, and breadth. In addition, NVH investment in R&D is large, and the effect cannot be seen immediately after investment, so many brands do not regard NVH as an important indicator. In fact, as to why not do 100 kilometers of acceleration, some industry media have also asked the ideal person in charge, and the answer is "Will you take your family to drag racing?" ”。 Positioning determines the product, so for Li Auto, providing a quieter and more comfortable environment for the user's family is far more meaningful than what 3-second or 2-second club and brushing New North.
Many people only see the first achievement of Ideal MEGA quietness, but few people know that behind the NVH research and development of Ideal Automobile, from Ideal ONE to Ideal L9, there are actually many unknown twists and turns.
As the first model of Li Auto, Li ONE has ranked first in China's medium and large SUV consumer market for 14 consecutive months, and won the 2021 China medium and large SUV sales champion. But Ideal ONE has a great regret in the heart of the Ideal NVH team. The Ideal ONE was a pioneering product at the time in terms of space, power, and intelligence, but the NVH quietness ranked 15th in Dr. Cheng Barton's list at 40km/h, 22nd at 80km/h, and 29th at 120km/h. Such a ranking is unacceptable to the ideal team, and it has become the biggest regret, and this regret has not been completely eliminated until the ideal L9.
On the first day of the new year, a military order was issued, vowing to solve the problem of the roar of the L9 range extender
Later, from the Ideal ONE to the early stage of the development of the L series range extender, the Li Auto NVH team was very confident that the experience accumulated in the Ideal ONE would definitely avoid many problems. But early in development, the team received a message to adjust the target. The boss hopes that the power generation of the range extender system will be increased by 20kW compared with the previous one, so that users can experience better power retention performance, and try not to encounter power feeding and continuous power loss in hybrid mode. But this will add a lot of difficulty to NVH development. Since Li Auto raised its power target in mid-2021, the NVH team has spent half a year optimizing the structure-borne noise of the range extender system, which is the engine roar that everyone usually hears. By the end of the year, the team thought that the NVH of this set of range extender 2.0 was already in very good condition and had exceeded the industry standard, so they asked Li Xiang and other management to review it the day before the New Year's Day holiday.
On the day of the test, many members of the team came to the company with suitcases, ready to go home after the review. However, the results of the review gave the team a slap in the face, and the low-frequency pressure still existed, and it was from the engine that it was. Li Xiang's expectations for the L9 were particularly high, and the team was very shocked by such test results. So on the first day of the new year, the team leader made a military order, and if he didn't solve the problem, he would leave after the year.
In the past month, the team has made further optimizations in terms of hardware and software. In terms of hardware, the structure has been optimized around the intercooling box and pipeline, and the vibration isolation pads and brackets of the new structure have been replaced; In terms of software, the calibration strategy of the XCU was fine-tuned again, so that the noise of the range extender and the vehicle speed were better matched to mask the noise. The review a year ago was on the 28th of the lunar month, and it was the day before the holiday. At that time, many people were as nervous as they were on the day they went to the college entrance examination. The final result was satisfactory to everyone, and the whole team had a happy year. Looking back, Li Auto's NVH's almost paranoid optimization of the range extender system is definitely worth it. Today, range extension has become the driving method chosen by many car companies, but it may not be until it is actually developed that they will not realize the technical content behind the range extension. The range extension 2.0 system on the L series of Li Auto comprehensively considers power performance, energy consumption, power retention performance, and NVH, and its performance is a whole generation ahead of the industry.
The battle for the ideal L9 resonant block: user experience always comes first
When the development of the ideal L9 was nearing the end, when Li Xiang himself drove the L9 test car again, he found that the road noise on the rough asphalt road was very obvious, and the sound was not as calm as that of the BMW X7. The team immediately went to run that part of the road, but none of the NVH team members could feel the difference in sound, and it was not until later that after the NVH hearing threshold sensitivity test experience, it was found that Li Xiang's personal hearing was more sensitive than ordinary people in terms of high frequencies.
In fact, in the early stage of research and development, the NVH goal of the L9 was to benchmark the BMW X7, and 85% of the NVH indicators were not inferior to the BMW X7, and the NVH team also achieved 65% of the indicators to exceed the BMW X7, and 20% of the indicators were the same as the X7. However, Li Xiang himself was very dissatisfied with the noise of the L9 on the rough asphalt road, and insisted that "the NVH index of the L9 should exceed the X7 in an all-round way, not just meet the 85% level". So, this problem has to be solved. For two weeks, the team spent almost every day on the road to Science City doing tests, collecting data, and modifying the plan. Finally, based on factors such as vibration damping performance, weight, reliability, cost, time, etc., the best solution was given, which was the resonant block that we saw later.
Over the course of two weeks, the team worked on an hourly basis, and the durability test personnel worked from three shifts to four shifts, conducting road tests 24 hours a day to ensure the reliability of the solution. Although the team believed that the effect of this solution would definitely solve the problem of road noise, in the end, the decision on whether to use resonant blocks or not was still very tangled. At that time, the team's biggest concern was not performance, nor time, but public opinion pressure, because the resonant block was installed in a prominent position on the upper wishbone and was likely to be caught and attacked by the good guys. Fortunately, in the end, Li wanted to make a decision, he thought that if this problem was not solved, L9 could not be sold at all.
Looking back today, Li Xiang's choice at that time was indeed correct, although it is true that L9 has suffered a lot of public pressure, but its performance in NVH today is absolutely undoubted. In fact, in the same industry, such as BMW X7, the old BMW X5, Audi A8 and other models can be found on similar resonant block design, these cars have the industry's first-class chassis tuning level, in the same level of models are the benchmark for stable performance. In fact, many models do not consider using resonant blocks because they do not value NVH, but instead add resonant blocks to excavate the last trace of optimization space because they do not attach importance to NVH, but instead add resonant blocks to dig out the last trace of optimization space, which is the most reasonable solution in a comprehensive way.
The small stones on the road should also be managed, and the ideal is to overcome the problem of NVH overclass
In addition to optimizing NVH from in-vehicle components such as range extenders and resonant blocks, the Ideal NVH team also specializes in optimizing the impact of rocks bouncing on the road on NVH. In fact, this is a problem that Tang Jing, the leader of the ideal NVH team, discovered when he was driving personally. He found that L9 was parked in the large parking lot of the ideal headquarters, and noticed that the sound of small pebbles collapsing and smashing on the bottom of the car was particularly obvious. However, this problem is difficult to determine, because the small stone bullet up, at first it felt like a particularly random event, and it was difficult for the R&D team to determine the distribution of the impact position after the stone bullet was raised, but it was impossible to add additional guards or sound insulation materials to the entire chassis.
Later, the NVH team found a way to deal with it, by adding a layer of coating to the bottom of the car, the coating will leave special marks after being hit by stones, so it only takes a few more rounds of testing on the actual car to know where the most affected by stones is. With this highly effective method, the NVH team has also extended it to different vehicle speeds, different weather conditions, such as rainy days, and even different sizes of stones. The results of the final test showed that the trajectory of the boulder was indeed regular, and the most dense was the position under the threshold, as well as the position of the wheel cover. Subsequently, by adding additional guards under the threshold and making wheel covers of unequal thickness, thickening the most impacted places and maintaining the original thickness in other positions to control the weight of the material. After optimization, even when the L9 is driving on complex road conditions such as gravel, the interior of the car is very quiet and safe.
Li Xiang discovered the hiss sound that the engineer couldn't hear
As mentioned in the story above, Li Xiang himself has a very sensitive sense of hearing, and can often help the NVH team find some particularly subtle problems. When developing the L9, Li Xiang also found a small problem with the air conditioner. In June 2022, when Beijing had just arrived in the season of turning on the cold air conditioner in the car, Li Xiang found that the trial car he drove home would have a particularly noisy high-frequency noise after the air conditioner was turned on, and he felt that it was similar to the sound of the central air conditioning at home. At that time, the time of L9 mass production was actually very close, and the team urgently went to the car to test and analyze this problem, and found that there was indeed a hiss sound, and the frequency band was actually very high, distributed between 4000hz and 8000hz, and it was very slight, in fact, most colleagues in the NVH team basically could not hear this sound. Eventually, by optimizing the refrigerant expansion valve in the thermal management system, the team was able to optimize the sound. This optimization scheme will increase the cost of more than 140 yuan for each car after the Ideal L9 begins mass production. But the team made a quick decision, and although a bunch of engineers couldn't hear it, the younger they were, the more sensitive they were to high frequencies, and children could hear it. So the team resolutely passed this plan, and the cost of adding more than 140 yuan per car is also worth it.
No one is perfect, but on the road to perfection, the spirit of never giving up is perfect. As football commentator He Wei said, "How to face failure and divide people into different looks." Some people will be knocked down by failure, and some people will get up and move on. "As for Li Auto, the Li ONE is a very successful model, but the initial NVH ranking performance is like a defeat in the eyes of their team. Until the Ideal L9 was in Dr. Zheng Barton's NVH list, in addition to its own products, as well as the million-level top luxury models of Audi and Mercedes-Benz, it was far ahead of other models with an absolute advantage, completing the self-redemption of the once Ideal ONE, and making the Ideal L9 a product that makes the Ideal Auto proud.