We continue with the topic “What’s wrong with modern engines.” Start here via this link.
Direct and Combined Injection: Reliability Challenges
In the early days, distributed fuel injection appeared in the intake manifold. A spray of atomized fuel reached the intake valve, helping to clean oil deposits and, as a side effect, aiding combustion.
To boost engine performance, automakers introduced direct or direct injection. Fuel is delivered under high pressure directly into the cylinders, enabling better mixture control and the possibility of running leaner air-fuel ratios. This improves fuel economy.
However, these systems bring a set of challenges. The primary concerns include stricter requirements for fuel quality and octane, frequent fuel-filter replacements, and the risk of premature wear on expensive high-pressure fuel pumps and injectors if standards are not met. Engine operation can become unstable, and starting can be difficult, particularly in cold conditions.
Engine oil must be carefully selected to minimize carbon buildup, which can compromise protection against wear. Cleaning of the intake valves is recommended at intervals around 100,000 km; without this maintenance, the engine may suffer from restricted air flow. If valve cleaning is rushed or improper, a valve could remain open or become bent.
A flushing system paired with a pump instead of a thermostat: maintenance and reliability are challenged
There has been a shift from simple thermostats to thermostats with heating elements and toward systems that no longer rely on temperature-sensitive components for control.
Coolant flow is increasingly managed by purge mechanisms driven by electronic commands. The overall system has become more complex. The user typically notices only that the engine warms at varying rates, while the furthest effect is seen in the control architecture itself.
A coolant-pump with integrated temperature control is now as common as a small motorcycle engine. When failures occur, the entire assembly may need replacement.
Plastic suction pipes and plastic valves: durability concerns arise
Variable-length intake pipes can improve performance, yet plastic intake manifolds often risk blockage from plastic mufflers. Over time the wear of moving joints in carbon-rich and dusty environments can cause dampers to sag, reducing control accuracy and allowing unclean air into the engine.
Start-stop: durability considerations
Many drivers dislike the start-stop feature that shuts the engine off during brief stops and restarts it when movement resumes. The additional starts place more load on the starter and battery, and friction increases as shafts rely on hydrodynamic bearings, creating a delicate oil wedge that minimizes wear during operation.
When the engine stops, the oil wedge disappears and the shafts settle, sometimes pressing against the housing. The crankshaft settles under weight, and camshafts are influenced by valve springs. The result is temporary metal wear as the system resumes operation, potentially accumulating damage over time.
Dual-mass flywheel: durability concerns
Many modern cars with manual transmissions and high-powered engines, including most diesel models, use dual-mass flywheels. They smooth starting and reduce vibration, but their service life is often shorter than the life of the clutch disc. There have been cases where dual-mass flywheels failed unexpectedly. A broken unit makes driving unsafe and replacement costs can be substantial, sometimes reaching tens of thousands of dollars depending on the model.
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WHAT IS THE RESULT? The discussion does not cover every issue facing modern engines. The automotive design landscape has shifted with computer-aided engineering enabling precise life estimates for motors, sometimes at the expense of a built-in safety margin. The peak era of reliability is generally viewed as the 1990s, a time when European engine builders were not chasing ultra-low emissions, Japanesemakers built dependable cars for global markets, and American manufacturers relied on large displacement engines with straightforward solutions like robust camshafts. Today many manufacturers appear less concerned about post-warranty operation. The emphasis often leans toward encouraging owners to replace vehicles as warranties expire, rather than ensuring long-term reliability. This reality makes thorough diagnostics essential before purchasing recent-year cars with high mileage under warranty terms. Hence, a cautious approach is advised when considering late-model, high-mileage vehicles, paired with comprehensive diagnostics to avoid costly, time-consuming repairs. |
- Five issues found in popular engines from Lada, Renault, and Nissan — more details here.
- The American Cyclo automotive chemicals and SUPROTEC additives help maintain vehicle components in good condition.
- Guidance on proper car maintenance can be found in the publications of the publishing house “Behind the Wheel.”
- “Driving” can also be read on Viber.