Engine speed and vehicle speed is not a simple positive correlation relationship, but related to gear, torque, transmission form, transmission ratio and other factors, and fuel consumption and speed is not absolutely positive correlation, not high speed fuel consumption is necessarily high, the function relationship between the two is very complicated, but for ordinary car owners, we can simply measure real-time fuel consumption through speed. Ordinary family cars, 120km/h cruising engine speed between 1500-4000 rpm are normal values, so the high-speed 120 engine speed of 3000 rpm, depending on your specific model.
Models with high speeds
1. Manual transmission model
First of all, to give you a formula, the speed = 0.377 * speed * tire radius / transmission ratio. So this means that the smaller the transmission ratio value of the 5th gear, the lower the speed. The following is the gear ratio of Toyota's 5-speed manual transmission.
According to this transmission ratio, the speed is about 120km/h, the engine speed is about 3000 rpm, if you don't feel sorry for the car, you can even hang 3 gears to run to 120km/h, but at this time your speed will be as high as 4500 rpm or so.
2. Small displacement self-priming engine
Generally, the high-speed speed of the small displacement self-priming engine is relatively high, in fact, the reason is very simple, because the displacement is small, the power of the car is also small, and it is necessary to increase the power by pulling the high speed to achieve the set driving speed. For example, the 1.2-liter naturally aspirated engine is equipped with a combination of 4AT or 5MT.
3. Models equipped with high-speed engines
A very typical example is the very famous Honda's "god machine" K20A, this red-headed engine displacement of 2.0L, maximum horsepower 220ps, maximum torque of 196 Nm, maximum speed of 8600 rpm, equipped with Honda's special I-VTEC technology, the maximum torque to 6100 rpm, easy to rev 7000 rpm. To this day, many honda earth dream engines still maintain a tendency to high speed.
4, pay attention to low-twist car
Like vans, light trucks, low speed must have strength, in order to pull goods or passengers, so the low-speed gear radius of the van is often adjusted to be relatively large, so that the low-speed torque is stronger, feeling very strong. But as soon as you get on the high speed, the stuffing is exposed, the engine roars and does not speed up, like a 1.2L displacement van, the speed of the engine speed of 80 per hour will reach 3000 rpm.
Run models with lower high speeds
1. Powerful, maximum torque platform wide model
The old driver has always stressed that when buying a car to see the power, we must look at the maximum torque platform, and only the powerful model cannot run high speed and low speed, and must be the model with the maximum torque platform width. For example, the maximum torque of the same 250 Nm, running 120 km / h, usually the turbo engine is lower than the speed of the self-priming engine, the reason is that the maximum torque of the turbo engine comes earlier, and there is no need to pull the high speed to achieve sufficient speed-up capacity.
2. Models with more gears and a wide range of transmissions
The gear ratio of the transmission is crucial to the engine speed, for example, the highest gear ratio, Toyota's 5MT is 0.775, Volkswagen DQ200 is 0.795, ZF8AT is 0.667, GM and Mercedes-Benz's 9AT is about 0.6, ZF's 9AT is 0.48. As long as the minimum transmission ratio of about 0.6 is reached, the endurance speed of 120km/h can be controlled below 1700 rpm.
3. Low-speed engine
The speed of the engine can be understood in this way, the same is to a water tank to load water, someone uses a large bucket, a dozen liters of water at a time, running once although slow but loaded with more water. Some people use small basins, less water, but more runs. The low-speed engine reduces the speed by increasing the stroke and generating more power at a time. Many of Audi's large-displacement engines are such a logic.
Automobile development to today, with the increasingly stringent emission policy, high-speed engines have gradually withdrawn from the domestic historical stage, low-speed small displacement turbo engines have become the mainstream of the domestic market, so although it is not strict to measure the quality of a car with speed, we can also see that high-speed cruising engines with low speed are either engines with low torque and strong, or more gearbox gears, so if your car, high-speed 120km/h cruising speed is less than 2000 rpm, It can be said to be a good car.