Article by Justin Pritchard
The inside of a combustion chamber is a dreadful place full of explosions and noise and hazardous metal parts reciprocating at impossible velocities.
Countless times per second, some amount of air and fuel, perhaps half a litre’s worth, is drawn into the chamber – filling the space between its floor and ceiling. An instant later, the ‘floor’ of the combustion chamber – the piston – rises upwards, all but touching the ceiling of the chamber and squashing that mixture into a teensy sliver of space. A spark ignites the flammable mixture, driving the piston downwards and providing the force that ultimately makes your ride move.
Auto Tech: Ultra 94 Gasoline. Click image to enlarge
This all happens faster than you can blink, and in somewhere between four and eight cylinders, maybe more, sitting in close proximity to one another.
Precise timing is absolutely critical. By precisely controlling engine operating characteristics and igniting the precise amount of air and fuel at precisely the right time, engineers create the fuel economy, emissions and performance that shoppers – and governments – demand.
Today, it’s all about meeting modern demands by harnessing one of the oldest bits of science in human history: explosive stuff blows the heck up in the presence of a spark.
But inside the combustion chamber, it’s not only the spark that can set that all-important explosion off. Compression is on the rise in modern engines, because more compression means more heat, which means more power. More heat and compression also means the gasoline used by the engine is more likely to misbehave.
Let me explain.
Gasoline loves to explode. Loves it. In fact, gasoline is pretty much constantly looking for a reason to turn itself from a liquid or vapor into as large a fireball as possible.
Most of the time, gasoline will wait for the spark plug to ignite the desired explosion. But, in the presence of extreme levels of heat and compression, it may not wait its turn – instead being ignited by extremely hot surfaces inside of the combustion chamber before the spark plug says ‘go’.
Ever take your golden retriever to the dog park? He’ll probably wag his tail and spaz out with excited impatience until you open the door to let him out of the car. But, if there’s an alternative – an open window or liftgate, perhaps – Bowser might just climb the seat and go for it.
Bowser’s enthusiasm for the dog park is just like gasoline’s enthusiasm for blowing up. Sometimes, in the right circumstances, waiting isn’t an option.
Ultra 94-Bridgestone Driving Academy. Click image to enlarge
Anyways. Of vital importance to today’s breed of high-efficiency engines is that the fuel supplied to the combustion chamber is ignited by the spark from the spark plug, and nothing else. Reason? That spark is controlled, monitored and optimized by a sophisticated network of computers and sensors that ensure it arrives with impeccable timing. When the timing of the spark and subsequent explosion is perfect, the engine is running at peak and optimal efficiency and performance.
When gasoline misbehaves, attempting to explode before its proper time, the timing isn’t perfect. In extreme cases, the gasoline may explode while the piston is still trying to compress it – thereby forcing down upon the piston while the piston is still forcing itself upwards. This will likely turn your smooth, round shiny piston into what resembles a crumpled-up wad of aluminum foil from last-night’s barbequed baked potato. Congratulations! Your engine is a paperweight, and you’re riding home next to a hairy, sweaty tow-truck driver.