Main Fuel line size

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Do the fuel can test then you'll know. 10 second ET needs to fill the can in 25 seconds. 9 sec. need to fill the can in 20

I think you should be good to go.

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9 sec et requires 180 gph , 8 sec et 240 gph , do we tend to over kill on fuel pump flow? , some guys run 400gph pumps , that's 10 sec to fill a gallon can , i realise G force comes into this but i still think it's overkill.

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-12 from the cell to the pump, then -10 to the reg, and -8 to the carb . NO problems.........
Chryco

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x 2

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Lots of people claim too big of a main feed line can be detrimental. More mass of fuel and a larger cross sectional area in the line for the G forces to act on.

Everybody I know personally in SG and SC runs a -12 from the cell to pump; -10 pump to front and -8 if they have a return line. I ran a BG 280 for about 8 years at mid nines in my charger with -8 line to the front and -8 return line back to the cell. Last year I switched to the BG 400 with -12 to the pump, -10 to the front and just the short bypass from the pump to the cell. Never showed any signs of fuel starvation running 8.9 - 9.0

I did the 1 gallon gas can test on my car with no alternator, just 12.4 volts at the pump and it filled the can in about 12 seconds going through the regulators, right at the carb inlets.

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How did it flow down the course ? Did you consider g-force ? Bigger is better here too .
Food for thought.
Chryco

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Lots of people claim too big of a main feed line can be detrimental. More mass of fuel and a larger cross sectional area in the line for the G forces to act on.

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you need to run -10an to the regulatorfrom the pump. i run a -8an back to the cell from the return.

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X2

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Lots of people claim too big of a main feed line can be detrimental. More mass of fuel and a larger cross sectional area in the line for the G forces to act on.

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those people are flat wrong and don't understand the mechanics of fluids. the diameter of the line has no impact on the force imparted by acceleration, the effective length of the line does. the pressure exerted on a column of fluid would be SG (specific gravity) x .433 (PSI exerted by a 12" column of water) x distance from suction to feed x G force. the actual length of the line to some extent doesn't matter. an example would be say you have 15' of hose but 5' is taken up in bends. then the effective length would be 10'. so .725 x .433 x 10' x (say 2G) = 6.28 PSI. this is the pressure the pump would have to overcome to move fluid and is part of the reason to mount the regulator at the engine. most (decent) pumps have the ability to generate a fair bit, probably upwards of 20 PSI or so. i would say the VAST majority of our cars don't pull 2G for any length of time if at all. a TF dragster pulls around 4 off the line but actually pulls harder down track.

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Good points james.
I would think that the most it would do would slow down for a split second, and then this would never effect total amount delivered, let alone effect the generous amount of fuel supply in the fuel bowls, thats waiting to be emulsified.

If you want to worry about loss, look into the amount of friction loss in 90° bends...I forget the amount of loss occurred through that one 90° that can never be gained no matter what size line it runs to...its like 1800+ or something...crazy..

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9 sec et requires 180 gph , 8 sec et 240 gph

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i don't know where these numbers come from.


a general rule of thumb is .5 PPH (pounds per hour) per horsepower. as mentioned the SG of race fuel is around .725. a gallon of water (SG of 1) weighs around 8.35 pounds. 8.35 x .725 = 6.05. so a gallon of race fuel is about 6 pounds. an 800 HP engine will need about 400 PPH of fuel. 400 divided by 6.05 = 66.11 gallons per hour for 800 HP. an actual 180 GPH of fuel will feed 2000 HP.

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The SAE standard on fuel (gasoline) consumption is based on steady state operation, not acceleration of the motor like drag racing, I believe The thing I come back to on fuel delivery(volume) on drag race cars with catburetors is that you don't have enough fuel delivery if you can't richen the mixture up enough to slow the MPH down in the 1/4. We tend to forget that where trying to force (push) fuel thru a .120 size needle and seats, if we buy the good racing size needles and seats Any one ever try to do a fuel flow tests thru the needles and seats into a can I have That is the main reason I recommend using a way bigger fuel delivery system than most people do

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9 sec et requires 180 gph , 8 sec et 240 gph

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i don't know where these numbers come from.


a general rule of thumb is .5 PPH (pounds per hour) per horsepower. as mentioned the SG of race fuel is around .725. a gallon of water (SG of 1) weighs around 8.35 pounds. 8.35 x .725 = 6.05. so a gallon of race fuel is about 6 pounds. an 800 HP engine will need about 400 PPH of fuel. 400 divided by 6.05 = 66.11 gallons per hour for 800 HP. an actual 180 GPH of fuel will feed 2000 HP.

on another note let's face it racers are in love with their fuel systems. big manly pumps, -12 lines, half a dozen regulators...all trying to jam fuel through two (or four for dual carbs) .110" orifices, THAT'S where the restriction is the needle and seat.

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Line size/volume, pressure , restrictions.........all come into play , might dig the mechanal fuel pump out that delivers 80 gph , should be enough to feed the 600" .