Q: hello, Teacher Xiong! What should I pay attention to when choosing a car? It is said that the engine is the heart of the car, should we choose the engine with variable compression ratio?
Jiangsu readers: Zeng benefit
A: there is a jingle for choosing a new car: move around slowly to see the appearance, then squat down to check the depression; Open the door and cover respectively, close the sound to check the defects; Front and rear tires and spare tire, the production date is the first choice; it is easy to start at one point, and the idle speed is smooth and noise-free; The acceleration is sensitive and does not stir, and the oil loss does not shake down; The external lights are all normal, and the built-in air conditioner has strong effect; The start is stable and the speed is good, turning the loose plate can return to the right; Running in a straight line does not drift, braking does not shift the plate does not shake; Instrument display should be complete, all functions should be found; Don't panic to pay the money, go out 20% off and then regret.
As for whether to choose the engine with variable compression ratio, you may be wrong. It should be the engine with variable valve timing. Nowadays, cars and SUV are almost the same engine. So far, I have not seen the variable compression ratio engine you asked. The engine with variable compression ratio is still the engine at the conceptual stage, as shown in Figure 1.
The data describes an engine like 1.5L. The working state of compression ratio can vary from 14:1 to 8:1. Its maximum power is 220hP, the maximum torque is 420Nm, the maximum power output is equivalent to the power provided by Peugeot 3.0 liter V6 engine, and its torque reaches the torque output of some V8 engines.
So why on earth does this engine have such good performance? The original mystery is that it uses a new technology of engine combustion control, variable compression ratio technology. This variable compression ratio technology was originally developed by Sabo. At the 2000 Geneva Motor Show, Sabo exhibited its SVC variable compression ratio engine, which shocked the whole industry at that time. Although someone heard of this engine two years ago, what everyone knows is just a concept. Later, PSA cooperated with BMW to develop an evolutionary version of SVC, intelligent variable compression ratio technology VCRi, the variable compression ratio technology used in 407 equipped with a 1.5L MCE5VCRi engine can control the compression ratio between 7.1 and 20.1, and the fuel consumption is only 6.7L for 100 kilometers, the emission of carbon dioxide is 15 8 grams per kilometer, its maximum power is 220hP, and its maximum torque is 420Nm. Its torque reaches some V8 engines (Lu Xun LC200 4.7L V8 maximum torque 410Nm; Mercedes Benz G500,5L V8 maximum torque 460nm; Lu Hu found that 3,4.4L V8 engine maximum torque 425Nm; audi Q7 4.2L V8 maximum torque 440Nm) provides torque performance.
Q: hello, Teacher Xiong! I repaired a Camry 5ARFE(2.5L) naturally aspirated inline four-cylinder engine, the fuel consumption of 100 kilometers should be 7.6L, and the fuel consumption in actual use is as high as 17L. Moreover, the idle jitter of the car, cleaning throttle is invalid, and it is also invalid after replacement. The ignition coil is invalid, and the spark plug is new. We check that the ignition timing is timing mark normal, and the mixing ratio and compression ratio are within the normal range. Where else can I check?
Hubei readers: Wei Ming
A: according to the description, the main problem of the car is high idle speed and high fuel consumption. If we analyze the causes of idle jitter, there are mainly three aspects: first, circuit, leakage will shake, like spark plug leakage, ignition coil and wire leakage will shake; the second is the oil circuit, the mixed steam will shake, but the car's fuel consumption will double, generally not; The third is the mechanical aspect, machine leg loose will also shake, and the valve leakage will also shake. Therefore, it is recommended to use the component test function of fault diagnosis equipment to check the phase change of variable input exhaust valve. For example, when the engine is idle, the intake or exhaust camshaft phase is deliberately instructed to postpone to the maximum value. Under normal circumstances, the engine will stall. If the engine does not respond, the camshaft phase control system does not execute the phase control command issued by the engine control unit. When idling, once the phase exhaust valve of entering the overlap region is too large, it is equivalent to the lax valve closing, which will inevitably cause idle jitter.
The phase change is abnormal, and the fuel consumption must be abnormal. Phase control system check is also very simple, can directly measure the phase control solenoid valve voltage, under normal circumstances, turn on the ignition switch should be 12V, soon it will drop to a few minutes, if 0.34V is the average voltage of duty cycle, it indicates that the control signal of the solenoid valve by the computer is normal, and the problem may lie in the dirt of the solenoid valve itself or the oil passage. Overhaul the variable valve system, idle jitter and high fuel consumption may be eliminated.
Q: does the replacement of new doors after the new car is hit have any impact on the vehicle? How to identify and solve.
(From my WeChat fans)
A: if the new car is hit, if it is simply A car door, the door frame, namely A, B, C column, is not deformed, and the replacement of the original factory car door assembly will not affect the sealing, car door lock, and heavy feeling. Unless the door used is not the original door or homogeneous door, a simple identification method is to weigh or feel the weight of the driver.
Q: A Ma Zida 3 has resonance jitter when the speed is 750~1 250r/min, regardless of speed increase or deceleration. The spark plug has been changed, and the fault is still the same. What is the reason? (From WeChat background of my journal)
(From my WeChat fans)
A: there are generally three reasons for this phenomenon: first, the engine is short of oil or water, and the cylinder is slightly strained; Second, the sensor at throttle gate or accelerator pedal is faulty; Third, carbon deposit, dynamic imbalance caused by machine foot pad or replacement. If the car is not caused by repair and replacement parts, there is no problem with the throttle gate and throttle position sensor. It is recommended to add removing carbon agent to the oil at the same time.
