The 12:1 FMU is standard in many Vortech systems. It is suitable for most applications running with original equipment injectors to maintain an air-to-fuel ratio of approximately 10.8 to 11.5:1 under boost. The pump utilized needs to provide sufficient flow to deliver the fuel pressure required in proportion to boost.
The 10:1, 8:1 and 7:1 FMUs are for Vortech applications that require less fuel pressure to maintain safe air-to-fuel ratios. The 6:1, 4:1 and 3:1 FMUs were designed for high-output custom applications where larger than stock injectors have been employed. For example, the 6:1 FMU can be used on Mustangs using either 30 or 36 lbs. per-hour injectors. The 4:1 unit was designed for either 38 or 42 lbs. per-hour injectors in the same application. Vortech FMU Recalibration Kits include a new ring, washer and fluorosilicone diaphragm.
Recommended calibrations for commonly used injector sizes:
12:1 - 19lb./hr Injectors
10:1 - 24lb./hr Injectors (Cobra)
8:1 - 24lb./hr Injectors (GT/LX)
6:1 - 30lb./hr Injectors
4:1 - 38/42lb./hr Injectors
3:1 - 50lb./hr Injectors
For conversion from CC injectors, divide by 10.5 (i.e. 440cc injectors = 42lb./hr)