Safety is an important part of any motorsport - including diesel motorsports. One item that is imperative to have if you run a diesel, is an air shut off device. The theory behind the air shutoff is that any internal combustion engine needs air to run, especially diesels. Diesels are "compression ignition" engines - meaning, they need fuel, air, and heat (compression) to ignite the diesel fuel. In some situations, diesel engines can keep running even when the fuel is shut off. How does this happen? Well, engine oil can be the "fuel" and when combined with enough oxygen and heat, the oil can allow diesel engines to continue to "run". Engine oil can be sucked from the engine crankcase and/or the turbocharger. In some instances, the oil provides enough "fuel" to keep the engine running. Even if the diesel fuel is shut off, the oil can burn uncontrollably, causing the engine to overspeed, which will lead to engine catastrophic failure if not stopped in time. This is commonly referred to as a "runaway" engine. The solution in these instances is to "remove" the air from the combustion process. No air = no combustion = engine will stop. This is where an air shutoff device comes into play. Typically, a gate valve or flap valve is activated to shut off the air flow to the engine. These mechanisms are generally spring-loaded devices that are actuated by removing a pin, which enables the valve to mechanically close off the air flow. Once the airflow is stopped, the engine will shut down. The shutoff devices are usually set up so a pulling sled operator and/or the driver can actuate them.
Many motorsports organizations require air shutoff valves but even if it's not required, it's highly recommended that one is installed.
Pictured below is an example of a "guillotine" type air shut off device. I use this on my diesel garden tractor puller.
