Dieseling. A mysterious term that you may have heard before, and maybe heard that airguns do, but what is it?
Airgun dieseling is the name given to a process that happens when an airgun compresses heat so fast that it gets hot enough to burn flammable liquids like lubricating oils. This quick ignition boosts the energy output of the gun, but not by much.
This topic is actually quite interesting, and the name of this has some reference to the man who invented the diesel engine, for obvious reasons that we will soon get into.
What is Dieseling, and Why do Airguns do it?
Waaaaayyy back in ancient days, like before people had cell phones, a man by the name of Rudolph Diesel invented an engine type that was soon named after him. His engine worked by compressing air so much that it gets so hot that when fuel is injected into the hot, compressed air, the fuel burns, forces a piston down, and keeps the engine going.
Mr. Diesel’s late 1890’s invention went on to change the world, but the machine employs a simple fact of physics: when a gas is compressed, it warms up. When a gas expands, it cools down.
Your refrigerator and your ac unit take advantage of this too, compressing a gas, running that compressed gas through a cooling system, then, once the gas is at ambient temperature, allows it to expand, which cools it down, and in turn cools you down.
So, you can probably put two and two together and figure that when the oils used to lubricate a springer airgun get caught in the compression chamber, things might get… explosive.
Well, they usually do. In fact, because all springer airguns depend on a rapid compression of air to move the projectile, they always create a massive amount of heat that exists for a brief moment.
The more powerful springers will almost always get to the point where they diesel, burning the oils that are used to lubricate the spring as it scrapes against the walls of the chamber. This will happen whether the manufacturer intended for it to do that or not, and will boost the energy that your gun outputs, but not my much.
Detonation is similar to dieseling, but happens when there is too much oil in the compression chamber, and all of it ignites when the gun diesels. This is not good for your gun and can be avoided by being careful with how much you oil your gun.
Your airgun will not be able to diesel without your knowing it, as it will leak trails of wispy smoke out of the barrel. I was really confused the first time that, but now I know. Dieseling is not ideal for your airgun, but also is not terrible. Any springer over 600 fps will diesel every time, so it is just a fact of airgunning life. Just avoid detonation.
Dieseling will almost never happen on an airgun that is not springer. A multi pump just won’t compress air fast enough, and there is little room for dieseling to happen on a PCP, with the only plausible time that it could happen being when you fill the tank, but even then, only antique PCP’s might have a chance of that happening.
