fluid dynamics experts please chime in
11-26-2014, 12:32 PM
#1
fluid dynamics experts please chime in There is nothing but confusion on this topic so please clear it up for everyone.
Bends aside, will one length of line of about 40 centimeters at 5/16" diameter, out of about 400 centimeters of line at 3/8" diameter still ONLY LIMIT maximum flow to the fuel rail to as much as can flow through the 5/16" section?
I'm using small line as an example but basically does the restriction along the line limit the total flow or does more of the fatter diameter line alleviate some of the restriction of flow that the small line created?
This stems from fuel pump outlets of 5/16" but people using -8AN and -10AN lines after this tiny point.
Bends aside, will one length of line of about 40 centimeters at 5/16" diameter, out of about 400 centimeters of line at 3/8" diameter still ONLY LIMIT maximum flow to the fuel rail to as much as can flow through the 5/16" section?
I'm using small line as an example but basically does the restriction along the line limit the total flow or does more of the fatter diameter line alleviate some of the restriction of flow that the small line created?
This stems from fuel pump outlets of 5/16" but people using -8AN and -10AN lines after this tiny point.
Last edited by foxsl; 11-26-2014 at 01:07 PM.
11-26-2014, 09:32 PM
#3
The flow capacity of a line is not based on 1 limiting restriction, but the sum total of all restrictions in the system. A given line size will produce a certain pressure drop per length of line.
That is why an intank pump will flow 255lph of fuel thorough an opening less than 1/4" in dia, but your car would not have enough flow at the engine if you used a 1/4" fuel line. 1 inch of restrictive length at the pump outlet is proportional to the 150 inches of line to the front of the car.
It is all based on frictional losses. The higher velocity created by a smaller line will have more pressure drop than a larger line.
That is why an intank pump will flow 255lph of fuel thorough an opening less than 1/4" in dia, but your car would not have enough flow at the engine if you used a 1/4" fuel line. 1 inch of restrictive length at the pump outlet is proportional to the 150 inches of line to the front of the car.
It is all based on frictional losses. The higher velocity created by a smaller line will have more pressure drop than a larger line.
11-26-2014, 09:55 PM
#5
The flow capacity of a line is not based on 1 limiting restriction, but the sum total of all restrictions in the system. A given line size will produce a certain pressure drop per length of line.
That is why an intank pump will flow 255lph of fuel thorough an opening less than 1/4" in dia, but your car would not have enough flow at the engine if you used a 1/4" fuel line. 1 inch of restrictive length at the pump outlet is proportional to the 150 inches of line to the front of the car.
It is all based on frictional losses. The higher velocity created by a smaller line will have more pressure drop than a larger line.
That is why an intank pump will flow 255lph of fuel thorough an opening less than 1/4" in dia, but your car would not have enough flow at the engine if you used a 1/4" fuel line. 1 inch of restrictive length at the pump outlet is proportional to the 150 inches of line to the front of the car.
It is all based on frictional losses. The higher velocity created by a smaller line will have more pressure drop than a larger line.
Last edited by foxsl; 11-26-2014 at 10:01 PM.
11-27-2014, 03:55 PM
#6
So if you are working on a foxbody with a 5/16" feed and 1/4" return coming out of the fuel tank hat.....and from the tank hat feed line to the fuel rail you have -8AN line and from the rail to the return on the hat you have -6AN line, are you going to have major issues or will you still see over 80% of the advantage of using the larger line over a greater distance because there is only one point of restriction per line?
My biggest worry is the 1/4" return. I have seen many cars have high idle pressures due to a restrictive return. You should upgrade this if possible with -6 back to the tank.
