When the engine is moving slowly in a higher gear, it makes a knock-knock sound. Because of the extra weight, the vehicle eventually stops. And, sadly, many people who write about cars call it “knocking.”
What It Really Is?
Our vehicles run on millions of explosions. The combustion happens inside the chamber, and the noise is kept to a reasonable level by the exhaust. If the mixture of fuel and air in the chamber explodes before the piston reaches its top-dead-center, the crankshaft will start to turn in the opposite direction. When this happens, the roles of the intake and exhaust pipes switch. Because there aren’t any filters or soundproofing on the side where the air comes in, the sound of that explosion makes a lot of noise in the engine bay.
What’s The Damage?
The blast blows the air filter out of the car and leaves dust in the engine bay. If things get worse, the strong gases could tear the airbox apart completely. But that isn’t even the worst thing that could happen. The reverse pressure could break the pistons, piston rods, crankshaft, timing chain, or all of these.
When you experience knocking for yourself, you’ll be glad it was just the intake plumbing that broke. The explosion is so loud that other drivers may feel like they were hit. When the engine knocks, the driver will feel like he has hit a wall that doesn’t exist.
Why Does It Happen?
First of all, it only works for engines that run on gasoline. Diesels have much higher compression and don’t have the knocking problem.
The mixture of air and fuel will explode just by being squeezed. But it’s hard to know exactly how much pressure is needed for a perfect spark. That’s why spark plugs are used. They blow up the mixture of fuel and air right when we need it.
You must have heard of high-octane or premium gasoline. Price goes up. But it can pack together more than regular fuel without going off too soon. If your car has a high-compression engine, they come in handy. In exchange, these engines make more power.
For example, the KTM 390 Duke has a 373cc engine that runs at 12.6:1. On the Bajaj Dominar, the same engine works at just 11.31:1. This means that regular gas can be used in the Dominar, but only premium gas should be used in the Duke. There is also a clear difference in how much power each one gives off. The Dominar only has 35 horsepower, while the KTM has close to 45 horsepower. Supercars like Lamborghini and Ferrari also have very high compressions and can only run on gasoline with a high octane rating.
Should You Buy Premium Fuel?
Most of the mass-market cars and bikes we get here can run fine on regular gasoline. If that’s the case, switching to premium fuel won’t help you in any way at all. But if you have a high-performance machine, you should use premium. Check your car or bike’s owner’s manual to see if it needs premium, and do what it says.