AN-6 or -8 for My Fuel System (SBF)

[Bill Edgeworth]

Originally Posted by Chad Rhodes

I've never seen too much fuel system slow a car down.

I have, if I get some time a little later in the day I will explain.

[FED 387]

also while we are at it depending on the type of material your float is made of you just might not have the float set at the correct level causing improper engine performance due to lack of fuel-- look into it its something that does happen from time to time

[FireSale]

Current wish list.

-10 braided line
MagnaFuel filter
MagnaFuel Quick Star 275 pump
MagnaFuel regulator
Holley pressure gauge
Summit 15 gal aluminum fuel cell and straps
AN hose cutters and Koul AN installation tool for -10

Total damages: $1,044

The pump maxes out at 18psi which is twice what a carb motor needs. It's rated to feed up to 700 hp and I hope for around 500. It's also been used on the street, so I wouldn't worry about burning it out driving to the strip this year towing a small trailer.

There seem to be two return systems, one from the pump and one from the carb feed. One is a closed pressurized line at the carb and the other is a loop back to the tank. Most big pumps return from the pump. Any preferences here?

Thanks for all the feedback and well thought out PMs.

Dale

[HandOverFist]

Ours has -10 from tank to regulator and -8 from there to carb. Using a BG 280 pump it shows 14psi on the high side then goes thru a big body Holley regulator which is set to 6-1/2psi. I have not seen it drop pressure down track as of yet. Recently added a gauge on the cowl to confirm this...who knows if it is really accurate/responsive enough to show tho.

[FireSale]

Originally Posted by HandOverFist

Ours has -10 from tank to regulator and -8 from there to carb. Using a BG 280 pump it shows 14psi on the high side then goes thru a big body Holley regulator which is set to 6-1/2psi. I have not seen it drop pressure down track as of yet. Recently added a gauge on the cowl to confirm this...who knows if it is really accurate/responsive enough to show tho.

Thanks for the input. I really hope you can keep your rig up and running for the season and beyond. Reading your build thread has been painful.

Dale

[V M Kauffman]

You need 7.5 lb of pressure to move the column of fuel for each G of acceleration this is just to move fuel forward if the fuel cell is in the rear

Originally Posted by FireSail

Thanks for the input. I really hope you can keep your rig up and running for the season and beyond. Reading your build thread has been painful.

Dale

[FireSale]

Originally Posted by V M Kauffman

You need 7.5 lb of pressure to move the column of fuel for each G of acceleration this is just to move fuel forward if the fuel cell is in the rear

I read that too. Lateral acceleration doesn't translate well into G forces which are a pull against gravity. A Top Fuel car will pull something like 4 G so a 10,000 hp engine would need something like a 40 psi pump.

If the line was empty at launch, then there would be a force working against the pump, but since the system is fully pressurized I don't think this is that much of an issue. The force of launch could actually aide the pump. The fuel would be pushed to the back of the tank and out the exit line towards the pump forcing fuel into the system.

Dale

[Bill Edgeworth]

Originally Posted by Bill Edgeworth

I have, if I get some time a little later in the day I will explain.

I have seen a couple things that I would deem as problems created by oversized fuel systems.
Hot fuel on systems with real big lines. If you are using real big lines on a low horsepower application the flow velocity is quite low. So when you throw a #10 system on a lets say 350hp motor the fuel takes a long time to get from the cell to the carb. Most of that time its spent in a fuel line that is probably routed through areas exposed to a fair amount of heat either radiated from the ground, exhaust or engine compartment. All I can say on this issue is if you insist on putting a system in your car that could support 1000hp make sure it’s well insulated. I should also add putting in way too big a pump generates heat in the fuel.
Another example of better isn’t bigger is a problem a friend faced on his modified car a few years back. He decided to freshen his carbs and afterwards had a huge problem with the car stumbling after the launch. During the freshen on the carbs he figured what the heck he might as well get all the good stuff from Brasswell. He spent big bucks on their bowls and needle and seats. Figured bigger was better. Turned out (and I understand C-25 is especially bad for this problem) as the floats dropped and fuel started to flow after the launch the inrush into the bowl was so great that it causes spill over into the boosters. Not sure if it was foaming or just the flow being so high that it pushed the fuel into the boosters. Moving the floats up or down did not help. He took the big Brasswell needle and seats out and put the smaller stuff back in and the problem went away. Guess the lesson here is don’t use Pro Stock carb parts on a 300 inch motor.
I know in my car running 11 teens in H I used to just run a Holley blue pump with no problems the data recorder showed no fuel pressure or O2 issues. I decided to upgrade to the Magnafuel 300 when the Holley was getting a little noisy and immediately started having problems with the hydraulic shock at start up overpowering the regulator and the Q-Jet. Took a bit of work and a real light regulator spring from Magnafuel for the bypass on the pump to solve the problem.
Adger touched on the subject talking about orifice sizes; there is not much point in having fuel lines 20x the size of the flow orifices in your pump, regulator or needles and seats. The system needs to be big enough to not cause excessive pressure drops but way bigger could possibly cause you some grief.
My .02

[FireSale]

Originally Posted by Bill Edgeworth

I have seen a couple things that I would deem as problems created by oversized fuel systems.
Hot fuel on systems with real big lines. If you are using real big lines on a low horsepower application the flow velocity is quite low. So when you throw a #10 system on a lets say 350hp motor the fuel takes a long time to get from the cell to the carb. Most of that time its spent in a fuel line that is probably routed through areas exposed to a fair amount of heat either radiated from the ground, exhaust or engine compartment. All I can say on this issue is if you insist on putting a system in your car that could support 1000hp make sure it’s well insulated. I should also add putting in way too big a pump generates heat in the fuel.
Another example of better isn’t bigger is a problem a friend faced on his modified car a few years back. He decided to freshen his carbs and afterwards had a huge problem with the car stumbling after the launch. During the freshen on the carbs he figured what the heck he might as well get all the good stuff from Brasswell. He spent big bucks on their bowls and needle and seats. Figured bigger was better. Turned out (and I understand C-25 is especially bad for this problem) as the floats dropped and fuel started to flow after the launch the inrush into the bowl was so great that it causes spill over into the boosters. Not sure if it was foaming or just the flow being so high that it pushed the fuel into the boosters. Moving the floats up or down did not help. He took the big Brasswell needle and seats out and put the smaller stuff back in and the problem went away. Guess the lesson here is don’t use Pro Stock carb parts on a 300 inch motor.
I know in my car running 11 teens in H I used to just run a Holley blue pump with no problems the data recorder showed no fuel pressure or O2 issues. I decided to upgrade to the Magnafuel 300 when the Holley was getting a little noisy and immediately started having problems with the hydraulic shock at start up overpowering the regulator and the Q-Jet. Took a bit of work and a real light regulator spring from Magnafuel for the bypass on the pump to solve the problem.
Adger touched on the subject talking about orifice sizes; there is not much point in having fuel lines 20x the size of the flow orifices in your pump, regulator or needles and seats. The system needs to be big enough to not cause excessive pressure drops but way bigger could possibly cause you some grief.
My .02

Makes a lot of sense. Efficiency is important.

Thanks.

Dale

[FED 387]

Bill H--- his problem was not the float or fuel level it was something else--- doing just what he did to correct it was a band aid approach its what most people do to remedy this but it never really totally solved the problem--- it "sorta" cured his problem but the problem is still there and his performance is still not all it could be if he had really corrected the cause of his excess fuel running over into the carb-- if you know how to correct his situation it is very easily correctable and his performance should pick up from where it is now==== FED 387