Should I go with -6an or -8an fuel setup
12-21-2005, 03:26 PM
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Should I go with -6an or -8an fuel setup Im having slight trouble putting together an -8an system using my Nasty Fuel Rails, getting all the fittings and inline fuel pressure gauge and special nitrodave connector.
If I do -6an I can get everything right now. But if I go -8an, nitrodaves special quick disconnect fitting is a -6an, so then I have to somehow convert that to a -8an which is a problem.
How much HP will a -6an support? Not to mention as writing this Im thinking why bother with an -8an since the nitrodave quick disconnect is only -6an and techincally I would be bottlenecking it there anyways. Also if I went -8an is it even worth it since the rest of the fuel lines are the stock 2002 z06 fuel line coming from the tank? What would you do?
Dixit
If I do -6an I can get everything right now. But if I go -8an, nitrodaves special quick disconnect fitting is a -6an, so then I have to somehow convert that to a -8an which is a problem.
How much HP will a -6an support? Not to mention as writing this Im thinking why bother with an -8an since the nitrodave quick disconnect is only -6an and techincally I would be bottlenecking it there anyways. Also if I went -8an is it even worth it since the rest of the fuel lines are the stock 2002 z06 fuel line coming from the tank? What would you do?
Dixit
12-27-2005, 06:07 AM
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It is a typical rule of thumb in a flow system that with everything else being equal - the system will only flow as much as the smallest opening. There is a small disclaimer that if the smallest section is short enough in length - it will not have a huge effect on the flow rate.
Therefore, if for example, your entire fuel system was plumbed with -8 and then you have a 2-3' section of -6 (3/8"ID), it would follow that the system would only flow as much as -6 could handle. Shorter the length of the -6 restriction - the better. There are engineering flow calcs. that you can do to get actual #'s - but they are somewhat involved
I don't know off hand the size of stock lines on your vette - but I'm willing to guess that they are not as large as -8. They are probably either 5/16 or 3/8". So if you follow the rule above, adding a 2' section of -8 line to a basically -6 or smaller system will not realize any gains in flow out of your system since enlarged -8 flow area makes up small percentage of entire system.
If you are replacing lines all the way from tank to engine - then go with -8, if you are retaining most of stock system then going from hardline, to -6, to rails, will be fine.
A real quik calculation for Gallons Per Minute can be done using:
GPM=0.0408 x (Pipe Inside Diameter Inches)2 x Feet/Min Water Velocity
This calc. simulates water flow which would be slightly different than gasoline due to difference in gas properties. (note: the pipe dia. is 'squared' in the equation above.)
If you really want to get technical you would have to allow for the Frictional Losses in both the pipe and each fitting - first assuming either laminar or turbulent flow. Typically I use the Hazen-Williams equation for this and one of the following constants for seamless/welded steel pipe material:
Friction Loss Constant (C)
(C) Range - High = 150/Low=100
(C) New/Clean = 140
(C) In-Service = 100
Feet of Head Loss values are subject to the following conditions:
a) Pipes carrying clear water @ approx. 60 Deg F (15.6 Deg C)
b) Pipes are flowing full
c) Velocities of water are generally less than 10 ft/sec.
If you want a good example of why NOT to use sharp 90 deg bend fittings vs. sweeping 90 deg bends in a good flowing system:
The Friction Loss in pipe fittings for a 90 deg street elbow = 3ft of pipe caused by the joint @ a 1/2" ID vs. 1ft of pipe for a 90 deg sweeping elbow
I'm running Racetronix Pnp pump, stock fuel system up to engine compartment, and then -6 line to rails, feeding 42# injectors on my T/A with the #'s in my sig with no problems on the fuel side. Plans for new combo should put me at 500 rwhp range N/A - I will probaly go thru the flow calculations to make sure I'm OK prior to tuning...
-Jay-
Therefore, if for example, your entire fuel system was plumbed with -8 and then you have a 2-3' section of -6 (3/8"ID), it would follow that the system would only flow as much as -6 could handle. Shorter the length of the -6 restriction - the better. There are engineering flow calcs. that you can do to get actual #'s - but they are somewhat involved
I don't know off hand the size of stock lines on your vette - but I'm willing to guess that they are not as large as -8. They are probably either 5/16 or 3/8". So if you follow the rule above, adding a 2' section of -8 line to a basically -6 or smaller system will not realize any gains in flow out of your system since enlarged -8 flow area makes up small percentage of entire system.
If you are replacing lines all the way from tank to engine - then go with -8, if you are retaining most of stock system then going from hardline, to -6, to rails, will be fine.
A real quik calculation for Gallons Per Minute can be done using:
GPM=0.0408 x (Pipe Inside Diameter Inches)2 x Feet/Min Water Velocity
This calc. simulates water flow which would be slightly different than gasoline due to difference in gas properties. (note: the pipe dia. is 'squared' in the equation above.)
If you really want to get technical you would have to allow for the Frictional Losses in both the pipe and each fitting - first assuming either laminar or turbulent flow. Typically I use the Hazen-Williams equation for this and one of the following constants for seamless/welded steel pipe material:
Friction Loss Constant (C)
(C) Range - High = 150/Low=100
(C) New/Clean = 140
(C) In-Service = 100
Feet of Head Loss values are subject to the following conditions:
a) Pipes carrying clear water @ approx. 60 Deg F (15.6 Deg C)
b) Pipes are flowing full
c) Velocities of water are generally less than 10 ft/sec.
If you want a good example of why NOT to use sharp 90 deg bend fittings vs. sweeping 90 deg bends in a good flowing system:
The Friction Loss in pipe fittings for a 90 deg street elbow = 3ft of pipe caused by the joint @ a 1/2" ID vs. 1ft of pipe for a 90 deg sweeping elbow
I'm running Racetronix Pnp pump, stock fuel system up to engine compartment, and then -6 line to rails, feeding 42# injectors on my T/A with the #'s in my sig with no problems on the fuel side. Plans for new combo should put me at 500 rwhp range N/A - I will probaly go thru the flow calculations to make sure I'm OK prior to tuning...
-Jay-
12-27-2005, 10:08 AM
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Jay that was some good info. I knew the -6an fitting would cap off my -8an setup if I went for it. Also as you said the stock fuel lines look like they are no more than 5/16".
I talked to Nitro Dave and he said just go with the -6an setup because Im not planning to push this car past 800whp for awhile. Once the 402 and boosted setup goes in, if I hit 800whp, Im sitting on that for a bit.
Dixit
I talked to Nitro Dave and he said just go with the -6an setup because Im not planning to push this car past 800whp for awhile. Once the 402 and boosted setup goes in, if I hit 800whp, Im sitting on that for a bit.
Dixit
