Main Motorcycle: 06 Thruxton
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I'm new here. I recently bought a new Brooklands Green Thruxton which is still to be delivered. It will be fitted with Triumph TOR exhausts.
Does anyone know what exactly the air injection system does?
Thanks guys, for all your replies. That answers my questions.
It's now clear how it works and what it causes. I think I´ll just break in the bike first until the first service, and remove the AI myself after a while.
So after removing it, it's not necessary to remap it?
The concept of AI first began showing up in US cars during the late '60s/early '70s. It may have been used elsewhere before or after, I don't know. US cars often used an AIR (air injection reaction) pump to force fresh air into the exhaust manifold/exhaust port of the head.
The goal was to supply fresh oxygen to the still hot but unburned products of combustion that had failed to completely burn while still in the combustion chamber. With out the AI system, the unburned products of combustion (mostly carbon monoxide and hydrocarbons) would flow through the exhaust system and exit into the air.
Catalytic converters were another way of dealing with some of these problems (albeit by different mechanisms) but were incompatible with the lead used in fuels at the time to improve performance.
The AI system that we have on our bikes is a passive system that uses the drop in pressure at the exhaust port as the exhaust pulse exits the system. A system of check valves allows a small amount of fresh air to be "induced" into the port at the right time to accomplish this purpose.
A side note is that this acts exactly like an exhaust leak at the header joint where the pipe connects to the head. Exhaust leaks, such as this, typically produce popping in the exhaust during overrun. Sound familiar?
The bluing of the header pipes is a result of the additional heat generated by these burning gases, kind of like an after burner. Unfortunately we get no boost in power, just blue pipes.
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