1Bad454

Ok I understand what an FMU does and I also understand what a VRFPR does as well. They both raise FP under acceleration (yes I know an FMU refereces boost). My question is do you still need an FMU when you have a VRFPR? Can someone help better explain the reason?

explorer5.0

The fuel pressure reglator raises pressure 1:1, So you can make fuel pressure go up 1 psi for every 1psi of boost. FMU's raise at a much higher rate. A 10:1 FMU will raise fuel pressure 10psi for every pound of boost.


I was reading a while back about using an FMU on TBI engines (because I have a 1993 Z71), and because of the low fuel pressure the TBI uses, they were using just a 1:1 FPR for boosted applications.

whitt1

The vacuum referenced fuel regulator has an adjustable base pressure plus a 1:1 vacuum reference.This allows fuel pressure to be set to any pressure desired and by the use of a boost reference maintain the actual pressure the motor sees as boost goes up.Example if you have to small of an injector you can actually increase their flow by increasing fuel pressure.Also as boost increases the amount of fuel pressure seen by the motor decreases by a like amount thus the need to boost referencing.