When does a bigger main feed line help flow vs hurt flow? You may be surprise to discover bigger is not always better. I have racers always calling me wanting a 8 AN feed line on smaller tune up applications because they were told it would increase flow. So today I am going to provide you with a comparison flow data of -6 AN VS -8 AN.
The direct port intake that we are using for comparison flow data has .122 Nitrous solenoids and .187 fuel solenoids feeding SBT nozzles.
The only thing we will change when swapping to an 8AN feed line is the Y and the feed line. To get a definite answer we conducted an apples-to-apples flow comparison on the intake above. Changing ONLY the feedline from -6AN to -8AN we flowed several jets at 850psi and recorded our data. As we expected on smaller jets (.036 and smaller) the -6AN feedline flowed more than the -8AN line did, but with jet sizes larger than .040 the larger -8AN hose proved beneficial.
.026 Jet = 792 PPH 30 PSI Drop
.036 Jet = 1360.8 PPH 59 PSI Drop
.041 Jet = 1706.4 PPH 58 PSI Drop
.057 Jet = 2642.4 PPH 93 PSI Drop
.026 Jet = 691.2 PPH 36 PSI Drop
.036 Jet = 1245.6 PPH 51 PSI Drop
.041 Jet = 1778.4 PPH 74 PSI Drop
.057 Jet = 2692.8 PPH 103 PSI Drop
Just in case your not sitting right next to a -6AN and -8AN here is handy eye test to give you an idea in the size difference: