I was talking to a tech from Manafuel on the phone a couple of nights ago. He was trying to explain to me the volume and pressure on fuel systems. I told him that my car has run 10.15 at almost 132 with the small 110 or 140 pump on it. He feels that I may be leaving a bit on the table on the top end. I think Jim said my car has about 6 1/2# pressure on the top end. What say ye? He did recommend a 275 and said a 300 would handle anything that I could throw at it.

My thoughts are if you have pressure, the volume is there.

There is some information missing, what size carb, how many needle and seats, what size needle and seat. It would be a lot cheaper to go to a larger size needle and seat that buying a larger pump. It looks to me that he’s trying to sell you a pump.
FYI I ran a 750HP methanol powered engine on the dyno with a 110 pump.

Joe

Based on your MPH - you are not leaving anything on the table at top end - also if you have steady pressure at the stripe - you are good in my mind. I am assuming you do not have a return line in your system - The bigger the pump the more you need a return line from the regulator - if not all you are doing is dead heading the bigger pump and causing cavitation of the fuel. Bigger is not always better in a fuel system

volume is the amount of fuel flowing pressure is just a measure of resistance... like boost.

Like the man said... Volume is the amount of fuel that pump can move with no restrictions (at the outlet). Pressure is the resistance to that flow. So if you have pressure indicated, you may not have flow. I like to free-flow the system into a bucket, float bowls and all, so I can see what it's moving (1 gallon in "x" seconds). That accounts for everything but G force from acceleration.

I agree that he is trying to sell you a pump.

If doesn't matter if there is flow or not, if you are maintaining good pressure as you cross the finish line the system is big enough.

In answer to one of the last posters, if there is a leak at the end of the line (needle and seat) and the fuel pressure is adequate, flow is adequate. If there is a leak at the end of the line and there is no flow, there will be no pressure built up right before the leak. So gauge will read 0.

R.

You can have pressure and ZERO flow. That is why if I have to use a .500 fuel line I want the pressure to the regulator to be 30 pounds or more. A bigger fuel line has more fuel in it, thus more weight. So if you don't raise the line pressure you can have pressure but zero flow. Seen it a bunch of times.

That said, most of the time it shows up in 60 feet.

You just proved you're not a scientist.

R.

The simplest way too find out if you have enough fuel volume is to richen the mixture up at the track enough to slow the MPH down in the 1/4 mile If you can do that you have enough volume, if you can't you need to fnd out why, to small needles and seats will have fule pressure without enough volume to keep the jets immersed in fuel Lots of fuel supply gremlins out there I've fought, found and fixed a few of them To small of a fuel filter before the pump will starve the pump, even a big pump Open flowing a good pump is not a good test Been there done that, inserting a flow restrictor in the line can and will make a really good pump increase the volume in the same time compared to open versus restricted flow I had fuel volume flow issues on my old Duster due to not listening to Magnafuel on the fuel filter micron rating on the filter before the pump Lots of potential problems and failures out there BTW, I have used all three sizes of the Magnafuel pumps for carbs., use them as they recommend and build the fuel system like they recommend and have fun with no problems ever

If you have 6.5 pounds of pressure while going 130 mph then you have enough pump already. You don't know how much safety margin you have which is why it can be a good idea to change the jetting until the car slows down. That way you know that you have some safety margin in the system.

If your pump can really deliver 100 gallons/hour to the engine then that is 600 lbs of fuel per hour which is enough to support 1200 hp. But fuel pump rating is black magic at best and total lies at worst. Hanging the carb bowls in a bucket and running the pump for a minute will give you a more accurate fuel flow rating than the sticker on the side of the pump.

I have ran pretty well w/a smallish holley 150 but stepped up to the 300 Magnafuel and the second half of the time slip came around. Volume and pressure are two different deals and the big pumps return right back into the cell/tank to keep em cool and the pre-set pressures are 28+ lbs. for a reason. I run .130 n&s`s in Dominators and .120`s in 4150`s w/great results and lower pressures combined w/Quickfuel whale mouth(My terms)entrance fuel bowls keep aeration under control. Just look at your stock bowls and check out the "wall"the fuel hits before entering the bowl......not good.

Cab_Burge's test idea: X2

The title of this thread should be: FUEL VOLUME VS. FUEL PRESSURE VS. G-FORCE

The better way to select a fuel pump to use in your fuel system is to consider three factors:
1.How much horsepower your engine will produce.
2.What fuel pressure is required for your engine.
3.How much voltage is supplied to your fuel pump when the engine is running.

1. Horsepower

The amount of horsepower that your engine has will determine how much fuel flow is required to support that engine. As horsepower increases so does the volume of fuel required to support that power. A good estimator of volume to power is approximately 10 hp per gallon or 2.64 hp per liter. For example if your pump flows at 50 gph it should be able to support a 500 hp engine (50 x 10 = 500). However, to actually know the gph you must also consider the fuel pressure required for your engine.

2. Fuel Pressure

Different engines require different fuel pressure. For example a carbureted engine typically requires between 4 to 7 psi whereas a typical GM LS engine runs on about 58 psi. Furthermore, if you are running boost the pressure required for your engine may increase under load.

It is important to know what the max pressure your engine will require because fuel pressure has a large effect on how much flow a pump can produce. A fuel pump will flow at its highest volume when there is no pressure (free flow). As fuel pressure increases, fuel flow decreases. Every pump has a different flow volume at a given pressure. Because of this it is important to look at a flow chart of whatever pump you decide to buy. As free flow, or even flow at a given pressure is only part of the equation.

3. Voltage

Fuel pumps have different flow rates at different voltages. As voltage increases so does the speed of the fuel pump which will increase the flow of a pump at any given pressure. Because of this it is good practice to see how a pump is rated at a given voltage. Most cars will produce about 13.5 volts when running. However, if your alternator does not produce 13.5 volts, or you simply want to plan conservatively simply look at the flow ratings of a pump at 12 volts.

I have found my Mallory regulator was my biggest restriction. I was dropping pressure at the big end....Went from 6.5 to barely 3.5 on the big end...I had replaced the eddy fuel pump last season with a MF275 and still had the same issue. Pulled the regulator apart one day to check for any junk in it, and the poppit was so tiny, its amazing the car ran 9.80's that way.

I switched to a Aeromotive prostock regulator, and 6.5 all the way down the track now....But to my chagrin, no improvement in ET...But the engine, had another issue that was preventing its usual performance.

I would say that the 3.5# pressure was enough pressure to keep enough flow up to fill your bowls in your carb, and also enough to overcome your G forces. A carb does not work on pressure, it works flow of fuel. You can have all the pressure in the world if you don't have flow you have no fuel for your engine.

EX. Lets say your car used just less than a gallon of gas to run the 1/4 mile. You mount a gallon can on top of the engine hood just over the top of the carb. You hook a hose to your carb. The fuel would be gravity feed to the carb bowls, no pressure. The car would run the 1/4 mile with no problem. No fuel pump.
Don't try this at home. LOL

If the carb uses more fuel than can flow through the needle/seat at a specific pressure, you need to increase pressure, or (better solution)increase the flow area of the needle seat/fuel bowl. A gravity feed would not be sufficient in most cars on this board.

Experiment

Go to your kitchen sink, open up the cold water facet, put a gallon jug under it and time how long it takes to fill the jug.
Now put your finger on the head of your facet to cause a restriction (pressure). Time how long it takes to fill the jug up. It will take much longer.

It may take pressure to unseat the needle from the seat on a Holley carb. But what about a old Carter carb. The floats drop pulling the needle of the seat allowing the bowls to fill quite quickly.