What are Ratios? like on an FMU, there 6:1, 8:1, 12:1

and like on gear ratios and stuff..

Can someone please explain them in laymens terms

 

It's just like a fraction, only written a funny way.

For gears, it's how many teeth on each gear, or how fast one shaft turns relative to the other. For example, with a 3:1 gearset, the input shaft turns 3 times for every 1 turn of the output shaft.

For air/fuel ratios, it's how many pounds of air vs. pounds of fuel. For example, 14.2:1 would be 14.2 pounds of air for every pound of fuel.

 

for an X:1 FMU the FMU raises fuel pressure by X lbs for every 1 lb of boost.