when is a FMU needed?

i've never had to use one before, but then again, i'm not from the import world.

 

sorry for adding questions to your thread, but what is an FMU?

 

fuel management unit.

 

when you get into turbo or the need for more fuel under load than is handled by the stock system.

 

Basically what Vince said. To add to that though, 1. you don't need to raise fuel pressure unless your injectors are running too high of a duty cycle or you are otherwise unable to flow enough fuel. and 2. They work off boost pressure, so unless you're running positive boost pressures (a la forced induction) they're pretty much just useless. Someone may correct me on that, but I'm pretty sure it's accurate.

 

I concur with andrew.

 

Just to sound smart....

I concur...