Pressing the pedal without downshifting risks engine damage
Drivers sometimes make a fundamental mistake: they press the gas pedal hard during acceleration without first changing gears. This might be due to a lack of knowledge, inattention, or simple laziness. Such a practice not only fails to achieve the desired effects but can also damage the engine. Here's an explanation of the mechanism behind this issue.
During driving lessons, we learn that it's necessary to downshift before overtaking. Switching to a lower gear provides greater power and engine torque, resulting in better and more dynamic acceleration. Modern turbocharged engines generate significant torque at low RPMs, and when road conditions seem favorable, some drivers skip downshifting, which is a mistake.
This method of accelerating takes longer and results in greater energy losses in the form of heat. Even worse, companies like Toyota and Denso have discovered that it can lead to premature ignition. This means the fuel mixture ignites before the piston has fully compressed it. How does this happen?
This is a typical situation involving high engine load with insufficient power. Without adequate torque, the engine attempts to "rescue" itself by adjusting the injection parameters. It increases the fuel dose because that's the only way to generate higher power, especially at low RPMs.
Adding fuel to the fire
Excess fuel makes the mixture rich, making it impossible to burn completely. The engine receives an unexpected power surge, causing significant stress on friction nodes and potentially leading to the breakdown of the oil film. It's like adding fuel to the fire: 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. Vapors of these substances reach the breather and then return to the combustion chambers along with gases from the crankcase.
In such situations, 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, completely automatically. 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, leads to the 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.
