FD Stock Fuel rail setup
02-19-09, 05:04 PM
#1
FD Stock Fuel rail setup
Has anybody reversed the flow direction in the rails so that larger secondaries get the flow first and resistive interconnect hose/pipe is only supporting lower flow primaries?
Yes, I know to do this I would need to flip presure regulator and Damper positions.
I am going under the UIM again and want to get all odds and ends out of the way once and for all. I just purchased all new OEM fuel hardware, sending new injectors out to RC Engin for boring again and purchased both the OEM and Marren Pulsation Damper (maybe i can get it to fit); for what ever reason i want to keep factory fuel rails but have an extra set to modify.
Yes, I know to do this I would need to flip presure regulator and Damper positions.
I am going under the UIM again and want to get all odds and ends out of the way once and for all. I just purchased all new OEM fuel hardware, sending new injectors out to RC Engin for boring again and purchased both the OEM and Marren Pulsation Damper (maybe i can get it to fit); for what ever reason i want to keep factory fuel rails but have an extra set to modify.
03-06-09, 05:36 PM
#4
Answer to my own question:
Just did a fuel system flow calculation of velocity changes as fuel goes from in line to fuel rail to interconnect hose to 2nd fuel rail to regulator. Mazda was not dumb in selecting flow direction Primary before secondary and rail ID's of 11 and 13 mm. As way Mazda set it up velocity in primary and secondary rails is within 4% of each other, whereas reserve flow has a 172% difference.
OEM setup ,in relative velocity units:
Inlet hose before damper 7.5
Primary Rail 1.58
Hose 5.1
Secondary Rail 1.52
Return hose after FPR 1.50
Reverse flow:
Inlet hose 7.5
Secondary Rail 2.21 (40% increase = pressure drop due to losses) ((would need to bore to 14 mm to get vel down to 1.5) not enough material)
Hose 18.0 (350% increase = Big pressure drop due to losses)
Primary Rail 0.81 (47% flow drop .. good but big imbalance between P/S injectors)
Return hose after FPR 1.50
Conclusion best balance is in OEM direction; this works because primary to secondary ID's decrease but so does flow due to primary bleed off. with 650/1220 injector ratio imbalance goes from 3.8% to 5.5% in other direction. To bring back to balance I need to bore primary rail out to 13.5mm (17/32 drill bit). Bringing final up'd capacity flow velocities to 1.57 in primary (down from 1.68) and 1.54 in secondary. Interconnect hose is at 5.21 up from 5.14, not much change however I am making an -6 connect using Goodrige 710 lines w/ 7 mm bore bring velocity down to 3.8 from stock 5.14
Just did a fuel system flow calculation of velocity changes as fuel goes from in line to fuel rail to interconnect hose to 2nd fuel rail to regulator. Mazda was not dumb in selecting flow direction Primary before secondary and rail ID's of 11 and 13 mm. As way Mazda set it up velocity in primary and secondary rails is within 4% of each other, whereas reserve flow has a 172% difference.
OEM setup ,in relative velocity units:
Inlet hose before damper 7.5
Primary Rail 1.58
Hose 5.1
Secondary Rail 1.52
Return hose after FPR 1.50
Reverse flow:
Inlet hose 7.5
Secondary Rail 2.21 (40% increase = pressure drop due to losses) ((would need to bore to 14 mm to get vel down to 1.5) not enough material)
Hose 18.0 (350% increase = Big pressure drop due to losses)
Primary Rail 0.81 (47% flow drop .. good but big imbalance between P/S injectors)
Return hose after FPR 1.50
Conclusion best balance is in OEM direction; this works because primary to secondary ID's decrease but so does flow due to primary bleed off. with 650/1220 injector ratio imbalance goes from 3.8% to 5.5% in other direction. To bring back to balance I need to bore primary rail out to 13.5mm (17/32 drill bit). Bringing final up'd capacity flow velocities to 1.57 in primary (down from 1.68) and 1.54 in secondary. Interconnect hose is at 5.21 up from 5.14, not much change however I am making an -6 connect using Goodrige 710 lines w/ 7 mm bore bring velocity down to 3.8 from stock 5.14
