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• 346.

  Why are GDI engines noisy?

  GDI stands for Gasoline Direct Injection, and certain characteristics of the engine may result in increased noise compared to conventional port fuel injection (PFI) engines. Here are some reasons why GDI engines may be considered noisy:
  ① Higher fuel pressure: GDI engines run at higher fuel pressure than PFI engines. Direct injection of fuel into the combustion chamber requires higher pressure to effectively atomize the fuel. This increased pressure results in greater injector operation and combustion noise.
  ② Injector noise: The direct injection process involves injecting fuel directly into the combustion chamber under high pressure. The rapid opening and closing of the injectors can create a clicking or knocking sound that adds to the overall engine noise.
  ③ Combustion characteristics: GDI engines usually operate at higher compression ratios, resulting in more efficient combustion. However, higher pressures and different combustion characteristics may result in increased noise levels, especially under certain driving conditions.
  ④ Combustion chamber design: Compared with traditional engines, GDI engines usually have different combustion chamber designs. The shape and layout of the combustion chamber affect how the air-fuel mixture ignites, which affects noise levels.
  ⑤ Turbocharging: Many GDI engines use turbocharging to improve efficiency and power output. While turbocharging can improve performance, it also introduces additional noise, especially when the turbocharger revs up.
  ⑥ Engine management strategy: GDI engines rely on complex engine management systems to control fuel injection, ignition timing and other parameters. The dynamic adjustments made by these systems can cause fluctuations in noise levels.
  ⑦ Engine size and configuration: Smaller GDI engines, especially those with a higher number of cylinders, may produce more noise than larger engines. The size and configuration of the engine will affect the level and character of the noise produced.
  

  
  
• 347.

  Does transmission fluid dry up?

  Technically, transmission fluid doesn't "dry out" like water evaporates. However, over time, transmission fluid can change and degrade, affecting its performance.
  Here are some factors that can cause transmission fluid to change over time:
  ① Heat and oxidation: The gearbox generates heat during operation, and over time, exposure to high temperatures can cause oxidation of the gearbox oil. Oxidation causes the breakdown of the fluid's molecular structure and reduces its effectiveness as a lubricant.
  ② Contamination: Contaminants, such as particles from normal wear and tear, may accumulate in the transmission oil. These contaminants can affect the fluid's ability to provide proper lubrication and cooling.
  ③ Hygroscopicity: Over time, transmission oil will absorb moisture, especially in environments with fluctuating temperatures. The presence of moisture can cause fluid degradation and corrosion within the transmission.
  ④ Additive consumption: Transmission oil contains additives that enhance its performance, including anti-wear agents, detergents and friction modifiers. These additives become depleted over time, affecting the fluid's ability to protect and lubricate transmission components.
  ⑤ When transmission oil undergoes these changes, it does not "evaporate" like water. Instead, its quality gradually deteriorates and its ability to perform basic functions diminishes.
  ⑥ To maintain the health of your transmission, you must follow the manufacturer's recommended maintenance schedule, which may include regular replacement or flushing of the transmission fluid. Routine maintenance helps ensure your transmission fluid remains in optimal condition, providing effective lubrication and cooling of internal components.
  
• 348.

  How does transmission fluid get low without leak?

  Due to a number of factors, transmission fluid levels can drop without obvious external leaks. While visible leaks are a common cause of low transmission fluid, there are other potential causes that may cause the fluid level to gradually decrease. Here are some reasons why your transmission fluid may be low but there is no obvious leak:
  ① Evaporation: Over time, transmission oil will evaporate, especially when the vehicle is at high temperature.This is a slow process and the damage may not be immediately apparent. However, over a long period of time, evaporation can cause the liquid level to drop.
  ② Wear: As the vehicle ages, the seals and gaskets in the transmission may wear. This can cause a gradual internal leak, allowing fluid to escape without forming a visible puddle or drip underneath the vehicle.
  ③ Transmission cooler problem: Some vehicles have a transmission cooler integrated into the radiator. If the cooler leaks, the coolant may mix with the transmission oil, causing the fluid level to gradually decrease. This type of leak may not be immediately visible.
  ④ Incorrect fluid level at last service: If the transmission fluid level was not filled correctly during the last service, over time this may result in insufficient fluid level. This emphasizes the importance of accurate fluid level checking and filling during routine maintenance.
  ⑤ Internal problems within the transmission: Internal problems within the transmission, such as a faulty torque converter or pump failure, may cause fluid circulation problems and cause fluid levels to drop.
  
• 349.

  Do CVT transmissions need to be flushed?

  Continuously variable transmission (CVT) maintenance requirements may vary depending on the manufacturer, so be sure to check your vehicle's owner's manual for specific recommendations. Generally speaking, CVTs have a different design than traditional automatic transmissions, and they may not require regular fluid flushing in the same way.
  Here are some things to note about CVT fluid maintenance:
  ① Inspection: Some vehicle manufacturers recommend periodic inspection of CVT fluid rather than periodic flushing. During these inspections, mechanics check fluid levels, condition, and may perform other diagnostic tests to evaluate the overall health of the CVT.
  ② Lifetime transmission fluid: Some CVT systems use what is called "lifetime" or "long-life" transmission fluid. In these cases, the manufacturer may not specify regular fluid changes or flushes, but they still recommend periodic inspections.
  ③ Sealed system: Many modern CVTs have sealed drivetrains, making it challenging for owners to perform fluid changes without specialized equipment. In this case, fluid maintenance can be performed by trained technicians during scheduled service intervals.
  ④ Manufacturer Recommendations: Always follow the maintenance guidelines outlined in the vehicle owner's manual. If the manufacturer recommends changing or flushing the CVT oil regularly, these recommendations must be followed to ensure optimal performance and longevity.
  ⑤ While some manufacturers may suggest that CVT fluids are designed to extend the life of the vehicle, it is important to consider factors such as driving conditions, maintenance history and the specific requirements of the vehicle.
  If you are unsure about your CVT's maintenance needs, consult your vehicle manufacturer or a qualified mechanic for guidance.
  
• 350.

  Can dirty transmission fluid cause poor acceleration?

  Yes, dirty or contaminated transmission fluid can cause poor acceleration and overall transmission performance. Transmission fluid performs several critical functions in an automatic transmission, including:
  ① Lubrication: Transmission oil lubricates various moving parts in the transmission, helping to reduce friction and prevent wear.
  ② Cooling: Helps dissipate the heat generated during the operation of the gearbox. Excessive heat can cause accelerated wear and damage.
  ③ Clutch engagement: Transmission oil helps the transmission clutch and gears to engage smoothly, ensuring correct shifting.
  If the transmission fluid becomes dirty, contaminated, or loses its effectiveness, it can cause several problems that may affect acceleration:
  ① Increased friction: Dirty liquid may contain particles or debris, which will increase friction between moving parts. This extra friction results in reduced efficiency and slower acceleration.
  ② Heat accumulation: Contaminated fluid may not be able to dissipate heat effectively, causing the temperature inside the gearbox to rise. Excessive heat can cause components to wear out faster and affect overall performance.
  ③ Clutch slipping: The presence of contaminants or degraded fluids will interfere with the normal engagement of the clutch, causing slipping during acceleration. This slippage results in a noticeable drop in power and acceleration.
  ④ Poor shifting: Contaminated fluid may affect the hydraulic characteristics of the transmission, causing delayed or violent shifting. This affects the vehicle's overall drivability and acceleration.
  If you experience poor acceleration or notice other symptoms of transmission problems, such as slippage, difficulty shifting, or unusual noises, it's important to address the problem immediately. Regular maintenance, including regular transmission fluid changes according to the manufacturer's recommendations, can help prevent these problems.