Gear bound likely has no technical definition."Gear bound". Is it possible to get a definition for that term?
It is a term used by mostly oval racers to describe a condition as shown above.
My belief is this is caused by our single circuit carburetors providing excess fuel when demand for torque drops off.
Automotive carburetors have a power enrichment circuit which supplies more fuel as indicated by vacuum in the intake system.
When vacuum drops below a predetermined level, the system shuts off the fuel flow from this circuit, leaning out the mixture, allowing for continued acceleration.
Our system only allows for a single circuit, (the idle circuit also flows during the entire time the main circuit is flowing, effectively making it a single circuit), so no top end leaning out is available.
As the load demands drop, the system becomes too rich, dropping available torque even further. The engine simply ceases to accelerate the kart.
There are 2 solutions to this problem.
Lean the entire system, compromising low end torque, (which got you to where you are now), or increase torque demand, (add more load through a gearing change.)
While we may be able to overcome torque loss with more rpm, other factors in the engine limit rpm potential. Air flow limitations, and valve train control are a couple.
Last edited: