Turbocharged turmoil: How improper acceleration damages engines
Drivers sometimes make a basic mistake—they press the accelerator pedal hard during acceleration without first changing gears. This may result from a lack of knowledge, inattention, or laziness. Such a practice fails to produce the desired effects and can damage the engine. Let's explain the mechanism.
During driving lessons, we learn that downshifting is necessary before overtaking. Switching to a lower gear provides greater power and engine torque, leading to better and more dynamic acceleration. Modern turbocharged engines generate a significant amount of torque at low RPM, and when road conditions are favourable, drivers often skip downshifting, which is a mistake.
This method of accelerating takes longer and causes greater energy losses in the form of heat. Worse still, companies like Toyota and Denso have discovered that it can lead to premature ignition. This means the fuel mixture ignites before the piston fully compresses it. How does this happen?
This is a typical situation of high engine load with insufficient power. Without the appropriate torque, the engine unit starts to "rescue" itself by changing the injection parameters. It increases the fuel dosage because it's the only way to generate higher power, especially at low RPM.
Adding fuel to the fire
Excess fuel makes the mixture rich, making it impossible to burn completely. The engine experiences an unexpected power surge, causing significant strain on friction nodes and potentially leading to the breakdown of the oil film. It's akin to adding fuel to the fire because while the benefits are temporary, the consequences only worsen the situation.
Excess fuel also has other consequences. Residual unburned fuel reaches the crankcase through the cylinder walls, where it mixes with the oil. Vapours of these substances reach the breather and then return to the combustion chambers along with gases from the crankcase.
In such a situation, residual oil and fuel accumulate in the combustion chamber, which is flammable and not properly removed with the exhaust gases. This causes the mixture to ignite before the spark plug initiates it in subsequent compression cycles, in a completely automatic manner. This leads to uncontrolled micro-explosions, which are a powerful "blow" to the pistons, connecting rods, and bearings on the crankshaft.
Toyota and Denso have confirmed that the higher the engine RPM, the lower the risk of premature ignition. The article below explains this mechanism in more detail.
Premature ignition can be extremely harmful. The engine is then exposed to enormous forces, which, in the best-case scenario, lead to wear of the spark plugs. In the worst case, it can result in cracked pistons, bent connecting rods, and the need for a major engine overhaul. Worse still, the more the auto-ignition phenomenon intensifies, the more frequently it occurs over a longer period.
