As one of the oldest and most mature internal combustion engine power, diesel engine has played an irreplaceable role since its birth because of its fuel-saving, energy-saving and high-torque characteristics. There is no power mode that can completely replace diesel engines.
As an excellent and important power system, diesel engines have been widely used all over the world. In China, diesel engines are mainly used for vehicles: equipped with various commercial transport vehicles, including heavy-duty and medium-sized trucks and buses, various special Work vehicles, etc.; there are also marine and industrial applications, etc., but these are beyond the scope of this article.
However, the difference between the Chinese market and the rest of the world is that the popularity of diesel engines in light-duty vehicles—especially household-level passenger cars—is not high, which is a bit similar to that in North America; but the reasons are completely different. Domestic cars in North America do not use diesel engines mainly because gasoline is cheap, and Americans are keen on large-size, large-row vehicles, etc.; while in China, it is mainly due to consumption habits, the ban on diesel engines in many domestic cities, emission regulations, and domestic consumers’ preference for diesel engines. ignorance and other reasons.
Of course, there are also reasons for the bad impression caused by low-quality diesel flooding the market for many years and poor power of diesel engines with backward technology, because diesel engines are not popular; there are very few passenger diesel engine models that have thrived in the Chinese market for many years. Audi wanted to promote it many years ago. Diesel models, but after an Audi, a Passat, and a Jetta, there is no more sound; in addition, diesel engines and gasoline engines can be said to be power systems with completely different characteristics, which directly causes many people in China to have a problem with how to drive diesel-powered models. many misunderstandings
Characteristics of diesel engines:
1. Compression-ignition ignition can also be understood as passive ignition; compared with the active ignition of spark plugs in gasoline engines, due to the different working principles and characteristics, the speed of diesel engines climbs slower than gasoline engines;
2. The speed reserve is limited; the diesel engines used in China, whether they are Japanese or domestic, are basically at the 4000rpm level; low-speed diesel engines have their own advantages in reliability, durability, and economy, but low speed reserves will also result in low power. , has a relative impact on the rapid rise of power during acceleration. In addition, the most fatal problem with low-speed diesel engines is that its speed reserve is indeed limited.
3. The speed of small diesel engines in Europe basically reaches 5000rpm, but there is still a big gap between the 5000rpm diesel engine and the gasoline engine with a speed of 6,000 to 7,000rpm, not to mention that the characteristics of the diesel engine itself are not suitable for high-speed working conditions. It also causes the user experience of the diesel engine to be poorer than that of the gasoline engine under high speed conditions.
4. Maximum torque – the effective speed range at maximum power is very short, which is the root cause of the completely different working conditions and driving methods of gasoline engines and diesel engines.
Typical passenger-grade diesel engine in China: Isuzu’s RZ4E engine; taking this as an example, RZ4E is a diesel engine with relatively good performance in the passenger car-level power currently equipped in China, and it is also the domestic application level in the passenger car-pickup field. It is one of the highest engines, and it has been on the market in China for a period of time, so it is typical to use it as an example;
1. The maximum torque speed range is 1800-2800rpm, and the peak torque reaches 360nm; but we see that the maximum torque range is 1000rpm, of course, its effective entanglement range will be larger, as we can see from the graph.
2. Two upgrades of diesel engine, the maximum power speed is 3600rpm; the maximum power is 120kw; from the data, it is quite good, but there is still a gap compared with the gasoline engine, but fortunately, the power of this diesel engine can be improved after brushing the ECU or adding an external plug-in Not a lot.
3. After exceeding 3600rpm, the diesel engine will have neither torque nor power, and the speed space is already exhausted; this actually means that you should not step on the accelerator above this speed, unless you have very special circumstances, otherwise step on this There is basically no meaning above the speed; in fact, strictly speaking, the advantage of the diesel engine is to output high torque at low speed, so stepping on the maximum torque speed (2800rpm) has already lost the biggest advantage of the diesel engine; at that time you have already regarded the diesel engine as a gasoline engine open.
4. The most effective use range of RZ4E means between 1800-3600rpm, that is, between the maximum torque and the maximum power; this speed reserve is only 1800rpm; compared to gasoline engines, whether it is supercharged or not supercharged The effective speed range of gasoline engines and diesel engines is much smaller.
5. From 1800rpm to 3600rpm, this is the most obvious characteristic area of low-speed high-torque diesel engine; from the maximum torque point of 1800rpm, it has a reserve speed of 1800rpm to the maximum power area. In fact, it can be seen from the data sheet that the RZ4E has 300nm after 1000rpm, so if you want to fully reflect the economy of the diesel engine, it is very important to make full use of the low speed range. In this regard, Aisin’s gearbox is quite good. Yes, mu-x and d-max equipped with RZ4E engine + Aisin 6-speed gearbox can usually maintain a cruising speed of 100km at 1500rpm.
The most important way to drive a diesel engine power: use the gear to increase the speed
1. This is an extremely important point, which can also be said to be the core of making good use of the diesel engine; try not to step on the accelerator hard in the D gear mode in order to speed up the vehicle quickly; in this case, the engine will only increase the speed, but not The gear box will only quickly lower the gear, and the result is the working condition of high engine speed + low gear; this is actually the speed-up mode of the gasoline engine; because the gasoline engine-especially the self-priming gasoline engine can only rely on high speed. own power to quickly increase the speed of the vehicle; in this mode, the diesel engine has become the high-speed working condition that it is least good at. In addition to the loud roar of the engine and the waste of fuel and increased wear and tear, it can give you a good impression and not not much.
2. In most cases, the gear ratio speed difference of each gear of the diesel engine is about 400-500rpm, so if you want to achieve an economical and fast speed increase, the more conservative approach is to reserve the next gear for The speed of the maximum torque output is enough. For example, the maximum torque output of RZ4E is 1800-2800rpm, so the minimum speed of the maximum torque is 1800rpm. We only need to ensure that the speed is at 1800rpm+400rpm when shifting gears, that is, 2200rpm is enough.
3. In fact, the torque of 300nm is enough in general use, so the speed of gear shifting can actually be much lower. For example, the initial point of maximum torque burst at 1800 rpm is actually enough to maintain the power performance of the vehicle when shifting gears.
4. Whether it is a plateau winding mountain road or a multi-bend section, as long as you keep shifting at 2200rpm, you can ensure that the vehicle has sufficient power reserve. This is why we ran the Yunnan-Tibet line, the Yunnan-Tibet new channel, and the crossing of Houzang when we entered Tibet The Himalayas and the Ngari region in Houzang have been fully verified through various passes and winding roads, and there is no problem at all.
5. For an automatic gearbox with manual mode, do not throw away the accelerator when upshifting, just use the manual mode to upshift directly; in this shifting mode, the shifting efficiency of manual transmission is not as high as that of automatic transmission, and The automatic transmission has to interrupt the power when changing gears because there is no manual transmission, which is also very helpful to the speed-up performance of the vehicle, especially when climbing a slope.
6. In manual mode, in order to speed up quickly with automatic transmission, you must watch the tachometer. After meeting the speed of 2200rpm, you should immediately upshift again, and make full use of the low-speed and high-torque characteristics of the diesel engine to speed up quickly; this is because Diesels don’t have that much rev reserve to splurge on, but plenty of torque, so it’s important to remember that aggressive upshifts provide both quick acceleration and fuel economy.
From my own experience in using diesel engines, I highly recommend that you choose the configuration mode of diesel engine + automatic transmission; manual transmission is not bad, but in the face of the characteristics of diesel engines, the only thing that has an advantage is the driver’s inner feeling – can Satisfying my own feeling of addiction; but in fact, no matter which application is used, automatic transmission has an advantage. I have explained this clearly in many previous articles and videos. Of course, some people will regard manual transmission as their own. It’s another matter to keep your hobbies.
The description of this text can be made into a video when there is time to make a more intuitive display.
