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Fuel Volume vs. Fuel Pressure

Posted By: tboomer

Fuel Volume vs. Fuel Pressure - 10/15/15 03:36 PM

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. wave
Posted By: Bad340fish

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 03:46 PM

My thoughts are if you have pressure, the volume is there.
Posted By: sr4440

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 04:18 PM

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
Posted By: DoubleD

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 04:31 PM

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
Posted By: Mr.Yuck

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 04:38 PM

volume is the amount of fuel flowing pressure is just a measure of resistance... like boost.
Posted By: moper

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 06:00 PM

Originally Posted By Mr.Yuck
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.
Posted By: dogdays

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 06:07 PM

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.
Posted By: madscientist

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 06:19 PM

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.
Posted By: dogdays

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 06:25 PM

You just proved you're not a scientist.

R.
Posted By: Cab_Burge

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 07:07 PM

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 scopeIf 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 work shruggy Lots of fuel supply gremlins out there runaway I've fought, found and fixed a few of them shruggy To small of a fuel filter before the pump will starve the pump, even a big pump shock Open flowing a good pump is not a good test tsk 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 scope up 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 realcrazy Lots of potential problems and failures out there shruggyBTW, 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 up
Posted By: AndyF

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 08:14 PM

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.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 08:25 PM

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.
Posted By: BSB67

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 09:18 PM

Originally Posted By dogdays
You just proved you're not a scientist.

R.


haha stirthepot
Posted By: polyspheric

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 10:06 PM

Cab_Burge's test idea: X2
Posted By: 540DUSTER

Re: Fuel Volume vs. Fuel Pressure - 10/15/15 10:23 PM

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

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 01:20 AM



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.
Posted By: Dragula

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 01:23 AM

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.
Posted By: caper

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:00 AM

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
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:25 AM

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.
Posted By: caper

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:47 AM

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.
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:52 AM

Ok. Now do the same test, except increase the water pressure to the house,and don't create a restriction with your finger.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:53 AM

Originally Posted By madscientist
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.


I know what you meant and you're right. More fuel mass in the line has more inertia so it has more of a tendency to stay put during launch, hence the need for more pressure to move it forward.
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:01 AM

Where are you reading the fuel pressure? If you have a regulated pump at the rear, you should still be regulating at the carb, and monitoring pressure there.
You can have pressure and zero flow if reading at the rear, but if you are in a dynamic state(float allowing flow) and you have pressure at the carb inlet you WILL have flow.
Posted By: caper

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:05 AM

You would have more water pressure, but not necessary more flow. The pump will only put out much flow as it is designed to put out at a certain RPM, and the pump puts its most flow out when there is no restriction.
You could increase the voltage (16 volts)to the pump to get it to spin higher and maybe put out more flow.
Posted By: Cab_Burge

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:11 AM

Originally Posted By caper
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.
The original Carter AFB carbs didn't come with that device to pull the floats down, niether did any of the early Carter carbs, 1,2 or 4 barrel WCFBs. I'm not sure exactly when I started seeing those in Carter carb. kits or in the after market over the counter Hi Po AFB and AVS carbs confused As far as restricting fuel flow I did a test before and after on my old pump gas car with the six pak and the Magnafuel 275 pump and then replaced that pump with a Magnafuel 300 pump. It took the exact same time in seconds to fill a 2.5 gallon jug with all three #6AN fuel lines dumping into that jug shock I called Magnafuel to complain and they said try using a rstrictor in the lines like the needles and seats are so that would load the pump like the real world, I hooked one line back up to the rear carb and redid the test with the 300 pump on that car, it filled that 2.5 gallon jug up a lot quicker threw(SP?) two lines flowing into it than it did with all three lines free flowing into it shock No other changes either shruggy
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:19 AM

listen to thumper.
you can run lower pressure with a larger/better bowl /needle/ seat. A stock holley needle seat/ bowl will not flow enough to keep up with the jets on most engines with a gravity feed under sustained load.
Posted By: caper

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:30 AM

If I understand what Thumper is saying is that there is an added restriction to the flow of fuel through the needle and seat and the bowls. He removes the restriction by putting in a bigger needle seat and better designed bowl. Lowering the pressure, allowing more fuel to enter the bowl.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 04:08 AM

Originally Posted By Thumperdart
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.


Which Quickfuel bowls are you referring to? I'm looking for something better than my stock Holley bowls that won't break the bank.
Posted By: Spaceman Spiff

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 04:22 AM

Originally Posted By caper
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


GRAVITY is creating pressure.
Put that fuel jug on the frame rail and see what happens.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 06:16 AM

Originally Posted By 340B5
Originally Posted By Thumperdart
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.


Which Quickfuel bowls are you referring to? I'm looking for something better than my stock Holley bowls that won't break the bank.


Dont have part #`s in ft. of me but it`s a kit that Quickfuel sells for around $105 and comes w/new bolts, nylon washers and gaskets and I try to talk every customer into using em if I can. Just one look at a stock Holley bowl and even the "high end" stuff and you`ll see the wall fuel hits THEN get yer hands on the mentioned bowls, and you will never run a stock one again.........There`s more "science" in carbs than most people think.........
Posted By: poboyengineering

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 12:48 PM

Thumper, is this it? 34-100, comes with aluminum fuel bowls?
It's on their website at $101 and change.........
Posted By: fbs63

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:13 PM

I have always understood this to be a basic rule in hydraulics. Increasing pressure reduces volume and vice versa. This only remains true while keeping the same orifice.
Posted By: 65 Hemi

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:31 PM

In our old TS car we would only run 4.75-5 psi with big needle and seat. You don't want to high of pressure because it can get air in the fuel and/or when your floats let fuel in you don't want the fuel on top of the float weighing the float down.
Posted By: sshemi

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 02:51 PM

Only way to increase pressure is to choke more witch also reduces flow.
Simple laws of physics.
Posted By: sr4440

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 03:25 PM

Originally Posted By fbs63
I have always understood this to be a basic rule in hydraulics. Increasing pressure reduces volume and vice versa. This only remains true while keeping the same orifice.


Doesn't work that way with mechcanical fuel injection. to flow 200 lb/hr takes 20 psi; to flow 400 lb/hr takes 80 psi, so
to get twice the flow takes four times the pressure. Why? If we want to flow twice as much through a fixed hole size, we will have to push twice as many fuel particles through it at twice the velocity, so we will have to do 2 x 2 or 4 times the work. We use the pressure to do this work.

If you want to flow more through an orifice, but keep the pressure the same, then you must use a larger orifice. The flow increases as the area of the orifice increases. Since the area is Pi x diameter squared / 4, the area increases as the square of the diameter, so twice the diameter is four times the area.

Joe
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 04:03 PM

Originally Posted By poboyengineering
Thumper, is this it? 34-100, comes with aluminum fuel bowls?
It's on their website at $101 and change.........


YES........
Posted By: justinp61

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 04:15 PM

I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 04:17 PM

Originally Posted By justinp61
I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.


Post a pic if you can of the fuel entrance for all to see....... thumbs
Posted By: StealthWedge67

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 05:43 PM

It seems to me that if you have pressure at (just before) the carb, then you have what you need to keep it full. Pressure should only be created from the needle / seat restricting what enters the bowl, based on how much it takes to keep the floats in the correct position. I like the inclusion of the bowl design and needle & seat in this discussion because ultimately it may be more important than the pump. Its the damn, whereas the pump is the river.

I only make a little over 500hp, but FWIW: I run dominator style bowls and .120 needles & seats at both ends of my 830 DP. Some would say overkill, but I think it helps keep the floats in the right position. I monitor pressure right at the carb, and generally I see 6psi @ general running conditions, and it drops to a steady 3.5psi through a run. I run a Carter 110 mechanical pump and stock 5/16 line to the pump, 3/8" from the pump to the carb.

Notable: this past year I had a couple of runs on a real hot day where I watched the fuel pressure guage drop to 0 halfway through the run. I waited for the car to nose over, but it never happened. car ran right on its best MPH on those runs. All I can take from that is that even with 0 pressure, if you have a good flowing system within the fuel bowl, you're probably still okay. (???)
Posted By: B3422W5

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 06:51 PM

I ran much quicker and faster than the OP at probably as much weight(3350) with a deadheaded Holley Black.
Upgraded the entire system and picked up absolutely zero anywhere.
Save your money Ted for something else.
ETA....... Insuring good and constant adequate voltage at the pump is very important, and overlooked
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 10:13 PM

Lots of good stuff here! Thanks everyone for the replies! The fuel pump is a Firecore and I can't remember the output on it. I have a Holley filter before the pump and the pump feeds a 1/2" aluminum line up to the Holley regulator. From there I have two #6 lines feeding an 1150 dominator. The engine is a 512 RB with Victor heads and a roller cam. The best 60' was 1.385 or 1.375. It usually is around 1.40-1.41. One thing I do not have on it is a relay for the pump. I will address that in the future. wave
Posted By: caper

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 10:35 PM

If you can , put the regulator in front of the carb, G forces would not effect the pressure.
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/16/15 10:39 PM

It is on the passenger side inner fender. Can't move it.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/17/15 03:32 AM

Originally Posted By justinp61
I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.


X2 Thanks Thumper
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/17/15 06:07 PM

Originally Posted By 340B5
Originally Posted By justinp61
I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.


X2 Thanks Thumper


thumbs Hey Boomer, you really need a rely so it takes the load instead of your signal 12v wire and I run two 30 amp relays tied together per Magnafuels directions and my pump gets full voltage and screams.........literally lol!
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/17/15 10:23 PM

The fuel PUMP is only a small part of the fuel SYSTEM. The biggest baddest pump in the world won't work if the system doesn't. It all has to work together. Bigger lines, hold more volume and the column of fuel is harder to move in a G situation, so you need more pump. Smaller lines help that, but won't supply the volume. More pressure is NOT the answer. Pressure just aerates the fuel, which is NOT a good thing. Your fuel system should supply the volume of fuel you need and not need more than 5 psi at the carb to do it. If 5psi of regulated pressure at the carb, does not supply enough fuel...........you need more volume
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/17/15 11:24 PM

Originally Posted By Monte_Smith
The fuel PUMP is only a small part of the fuel SYSTEM. The biggest baddest pump in the world won't work if the system doesn't. It all has to work together. Bigger lines, hold more volume and the column of fuel is harder to move in a G situation, so you need more pump. Smaller lines help that, but won't supply the volume. More pressure is NOT the answer. Pressure just aerates the fuel, which is NOT a good thing. Your fuel system should supply the volume of fuel you need and not need more than 5 psi at the carb to do it. If 5psi of regulated pressure at the carb, does not supply enough fuel...........you need more volume


I agree w/MOST of what you`re saying Monte but low pressures like the 5psi you mentioned need to have the bigger n&s`s to function properly and a .110 ain`t gettin it like the ones I recently pulled out of a 1050 Dominator that was jacked up. Voltage is a HUGE factor and I crack up when guy`s run a 12 v system w/out an alternator....... tsk
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 12:09 AM

Thanks for the reply Monte! The old rule of thumb used to be 6 1/2#. I know a guy who wrote an article for an on line magazine that turned down the pressure to 5 1/2# and the car picked up. Can you explain that? And Thumpman...Why two relays? I also have an alternator. Learned that lesson the hard way!
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 12:46 AM

Originally Posted By tboomer
Thanks for the reply Monte! The old rule of thumb used to be 6 1/2#. I know a guy who wrote an article for an on line magazine that turned down the pressure to 5 1/2# and the car picked up. Can you explain that? And Thumpman...Why two relays? I also have an alternator. Learned that lesson the hard way!


I assume the two relays carry the load better than one but not 100% sure on that you`ll have to ask Magnafuel. The low pressure/big n&s`s are more consistent and aerate less keeping the bowls full of fuel instead of fuel and bubbles and w/a .130 probably less stress on the pump. Been running 5 1/2 psi for a while now w/a .130 n&s and may even go down to 5 to see what happens since I have a gauge on my cowl, it`s easy to view.
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 12:52 AM

My gauge is also on the cowel. I don't know what is in the 1150. I presume it is stock n&s.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 01:51 AM

Get you some viton .130`s and lower the pressure to 5 1/2 and see what happens but then you still have the "shelf" the fuel has to fight/overcome to get to the n&s`s.......
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 03:34 AM

Originally Posted By Thumperdart
Originally Posted By tboomer
Thanks for the reply Monte! The old rule of thumb used to be 6 1/2#. I know a guy who wrote an article for an on line magazine that turned down the pressure to 5 1/2# and the car picked up. Can you explain that? And Thumpman...Why two relays? I also have an alternator. Learned that lesson the hard way!


I assume the two relays carry the load better than one but not 100% sure on that you`ll have to ask Magnafuel. The low pressure/big n&s`s are more consistent and aerate less keeping the bowls full of fuel instead of fuel and bubbles and w/a .130 probably less stress on the pump. Been running 5 1/2 psi for a while now w/a .130 n&s and may even go down to 5 to see what happens since I have a gauge on my cowl, it`s easy to view.


Makes sense, because over time I'm sure the contacts in the relays get pitted and maybe even heat up causing even more resistance.

If nothing else, it would be nice to know that if one relay failed the other would keep things going.
Posted By: nss guy

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 03:51 AM

FWIW, I run a Magnafuel 300 pump with a return line it started leaking, had to go to my back up aeromotive ss dead head pump. Saw zero difference in performance. I run 2 eddy 750cfm carbs psi set at just less than 6psi.
car runs 10.30's. just info

Attached picture 12068476_1019572638105555_740309623049467653_o.jpg
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 05:17 PM

Originally Posted By nss guy
FWIW, I run a Magnafuel 300 pump with a return line it started leaking, had to go to my back up aeromotive ss dead head pump. Saw zero difference in performance. I run 2 eddy 750cfm carbs psi set at just less than 6psi.
car runs 10.30's. just info


Apparently both pumps are enuff for your combo......call Magnafuel and get a re-seal kit or send it in and they`ll install the seals(or whatever else it needs)for the price of the parts and shipping back to you.......No labor charge.
Posted By: nss guy

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 11:01 PM

Originally Posted By Thumperdart
Originally Posted By nss guy
FWIW, I run a Magnafuel 300 pump with a return line it started leaking, had to go to my back up aeromotive ss dead head pump. Saw zero difference in performance. I run 2 eddy 750cfm carbs psi set at just less than 6psi.
car runs 10.30's. just info


Apparently both pumps are enuff for your combo......call Magnafuel and get a re-seal kit or send it in and they`ll install the seals(or whatever else it needs)for the price of the parts and shipping back to you.......No labor charge.


Did that and got it back, $51 new seals and bearings plus shipping. Great service and price !
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/18/15 11:10 PM

Good deal and I`m takin my junk to a semi-local 1/8 th mile track here soon to either kick out the rear gears or run a 6.teen........ luck
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 12:44 AM

Originally Posted By Monte_Smith
The fuel PUMP is only a small part of the fuel SYSTEM. The biggest baddest pump in the world won't work if the system doesn't. It all has to work together. Bigger lines, hold more volume and the column of fuel is harder to move in a G situation, so you need more pump. Smaller lines help that, but won't supply the volume. More pressure is NOT the answer. Pressure just aerates the fuel, which is NOT a good thing. Your fuel system should supply the volume of fuel you need and not need more than 5 psi at the carb to do it. If 5psi of regulated pressure at the carb, does not supply enough fuel...........you need more volume


Really?
Let me try an analogy, numbers here are arbitrary, you have a 12' tall cylinder water cistern, say its 1/2" in diameter, you measure the water pressure at the bottom, on earth at 1g,, your neighbor also has a 12' high cistern next door, its 12" in diameter, what pressure does his measure at the bottom? You both move to Saturn with your cisterns, gravity is now 4g's, what is the difference in water pressure now between you and your neighbor?

The point is, line diameter has little effect as long as pump can provide needed pressure, and flow for the needed tube diameter, or run a 3" or bigger line, it will not hurt. twocents
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:47 AM

We are not dealing with water cisterns..............we are dealing with moving a column of fuel in a large line, while fighting Gs. Now while I admit I don't know a damn thing about water cisterns, I do know a little about fuel systems
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 12:32 PM

Originally Posted By Monte_Smith
We are not dealing with water cisterns..............we are dealing with moving a column of fuel in a large line, while fighting Gs. Now while I admit I don't know a damn thing about water cisterns, I do know a little about fuel systems


Well then for everybody else, here's another related analogy, say you had a tube the size of a golf ball, tube is any length you want, and its completely filled with golf balls, if you had a golf ball pump that inserted one golf ball in one end, want to ponder how many golf balls would come out the other end, discounting any inertia? Now imagine if the same length tube was much greater in diameter then the diameter of a golf ball and again filled with golf balls, and your pump again inserted one golf ball in one end, know how many golf balls will exit the other end?

I think the confusion here is the weight of the liquid column increases with increasing diameter, but the pump in reality is only acting on a Lbs per inch basis, not the entire column, no matter what its size or weight.

I need to go fill my cistern with golf balls. stirthepot
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 12:57 PM

Pascal's law...
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 05:44 PM

I don't know what a fuel pump has to do with a cistern? But I did talk with a tech from Aeromotive this morning and he recommended The same pump that Jim has on his N/SS car...
Posted By: max_maniac

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 05:48 PM

Originally Posted By tboomer
I don't know what a fuel pump has to do with a cistern? But I did talk with a tech from Aeromotive this morning and he recommended The same pump that Jim has on his N/SS car...


Ted, I'm thinking we can go to Home Depot/Lowe's and get a well water pump when on sale and have plenty of fuel volume!!!! May even be cheaper then a regular ole small fuel pump shruggy
Posted By: madscientist

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:11 PM

Originally Posted By dogdays
You just proved you're not a scientist.

R.


Nice come back.

What exactly did I say that is wrong?

You can have PRESSURE and ZERO flow.

FACT.

Now prove me wrong.
Posted By: 540DUSTER

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:12 PM

I think there is another law that says an object in motion tends to stay in motion UNLESS some force or g-force tends to stop it.
Posted By: madscientist

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:15 PM

Originally Posted By 340B5
Originally Posted By madscientist
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.


I know what you meant and you're right. More fuel mass in the line has more inertia so it has more of a tendency to stay put during launch, hence the need for more pressure to move it forward.



Exactly.

But the keyboard know-it-alls need to have it spelled out for them. Guess I should have spent my time educating them for free.
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:25 PM

Since we are using golf balls, water cisterns and all kinds of other useless crap, in relation to race car fuel systems.........how about this. I don't have any type pump on my house and I have good pressure and volume in the shower.........so hmmm...........hell maybe we don't even NEED fuel pumps.........LOL!!!
Posted By: polyspheric

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 08:33 PM

I did talk with a tech from Aeromotive

To a hammer, everything is a nail.
When has a manufacturer not said "you need a big pump"?
For those of you who still think that the car is faster in direct proportion to the amount of money spent (i.e., billet = power), I'll quote David Vizard (slight editing) on fuel supply requirements, not as line size but in terms of how much must be actually received at the carb inlet.
"Brake Specific Fuel Consumption (as shown in dyno tests): how many lbs. of fuel per hour per horsepower the motor needs; .5 lbs./hr is a safe minimum figure.
.5 lbs/hr/hp × 500 hp = 250 lbs./hr
add 50% safety margin for restrictions, inertia, bends, etc. = 375 lbs./hr
gas = 6 lbs. per gallon
62.5 gallons per hour is more than sufficient for a 500 hp motor."
Sooo... your BG 400 pump is JUST RIGHT for that 3200 hp motor...
Posted By: sixpackgut

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 09:12 PM

Originally Posted By polyspheric
I did talk with a tech from Aeromotive

To a hammer, everything is a nail.
When has a manufacturer not said "you need a big pump"?
For those of you who still think that the car is faster in direct proportion to the amount of money spent (i.e., billet = power), I'll quote David Vizard (slight editing) on fuel supply requirements, not as line size but in terms of how much must be actually received at the carb inlet.
"Brake Specific Fuel Consumption (as shown in dyno tests): how many lbs. of fuel per hour per horsepower the motor needs; .5 lbs./hr is a safe minimum figure.
.5 lbs/hr/hp × 500 hp = 250 lbs./hr
add 50% safety margin for restrictions, inertia, bends, etc. = 375 lbs./hr
gas = 6 lbs. per gallon
62.5 gallons per hour is more than sufficient for a 500 hp motor."
Sooo... your BG 400 pump is JUST RIGHT for that 3200 hp motor...


a BG 400 pump doesn't pump 400 gallons per hour. Neither does a magnafuel 275 pump 275. These are all Barry Grant misleading numbers

a 5/8th garden hose will only flow between 200-300 GPH with no restrictions depending on pressure
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 10:16 PM

Originally Posted By Monte_Smith
Since we are using golf balls, water cisterns and all kinds of other useless crap, in relation to race car fuel systems.........how about this. I don't have any type pump on my house and I have good pressure and volume in the shower.........so hmmm...........hell maybe we don't even NEED fuel pumps.........LOL!!!


Obviously my cistern analogy went over your head. I did however exempt you from the golf ball analogy. And sorry you couldn't form a legit question to my comment I could respond to.
Posted By: John_T_Brown

Re: Fuel Volume vs. Fuel Pressure - 10/19/15 10:51 PM

Originally Posted By Monte_Smith
The fuel PUMP is only a small part of the fuel SYSTEM. The biggest baddest pump in the world won't work if the system doesn't. It all has to work together. Bigger lines, hold more volume and the column of fuel is harder to move in a G situation, so you need more pump. Smaller lines help that, but won't supply the volume. More pressure is NOT the answer. Pressure just aerates the fuel, which is NOT a good thing. Your fuel system should supply the volume of fuel you need and not need more than 5 psi at the carb to do it. If 5psi of regulated pressure at the carb, does not supply enough fuel...........you need more volume


Exactly what has been said here! up
Posted By: justinp61

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 01:25 AM

Originally Posted By Thumperdart
Originally Posted By justinp61
I need to pull one of the bowls off my QF 750 and one off my Biggs 950HP and compare them. Thanks for the info Thumper.


Post a pic if you can of the fuel entrance for all to see....... thumbs


Sorry for the delay Dom, I've been trying to get my short block together. This photo is of the Quick Fuel Bowl, the carb is 10 or 12 years old so it may not be the latest design. BTW the bowls on my Biggs 950HP are the same.

Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 01:28 AM

I meant a pic of the fuel entrance where the supply line hooks up to.......
Posted By: justinp61

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 01:57 AM

Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 02:03 AM

That`s the money shot..........see that nasty wall the fuel has to go through? The QF entries are blended and smooth.....no walls baffles etc......Thankxx man.
Posted By: Spaceman Spiff

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 02:11 AM

Originally Posted By polyspheric
I did talk with a tech from Aeromotive

To a hammer, everything is a nail.
When has a manufacturer not said "you need a big pump"?
For those of you who still think that the car is faster in direct proportion to the amount of money spent (i.e., billet = power), I'll quote David Vizard (slight editing) on fuel supply requirements, not as line size but in terms of how much must be actually received at the carb inlet.
"Brake Specific Fuel Consumption (as shown in dyno tests): how many lbs. of fuel per hour per horsepower the motor needs; .5 lbs./hr is a safe minimum figure.
.5 lbs/hr/hp × 500 hp = 250 lbs./hr
add 50% safety margin for restrictions, inertia, bends, etc. = 375 lbs./hr
gas = 6 lbs. per gallon
62.5 gallons per hour is more than sufficient for a 500 hp motor."
Sooo... your BG 400 pump is JUST RIGHT for that 3200 hp motor...


and he also says a vacuum secondary carb is perfect for a drag race car, because it acts like two carbs in one.
Posted By: Cab_Burge

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 02:55 AM

Next whistling grin devilLet not the pot stop boiling grin
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 05:48 AM

Originally Posted By jcc
Originally Posted By Monte_Smith
Since we are using golf balls, water cisterns and all kinds of other useless crap, in relation to race car fuel systems.........how about this. I don't have any type pump on my house and I have good pressure and volume in the shower.........so hmmm...........hell maybe we don't even NEED fuel pumps.........LOL!!!


Obviously my cistern analogy went over your head. I did however exempt you from the golf ball analogy. And sorry you couldn't form a legit question to my comment I could respond to.
No, it didn't go over my head and I felt no need to ask you a question from that meaningless stuff you posted, because it is not relevant to the discussion at hand. You think it is...fine, I just don't care to talk about theory and equations, because I know what a race car needs and how to properly set up a fuel system that works right. You want to flex your engineering knowledge, fine, knock yourself out. I will opt for proven results that work

As far as regarding Vizards word as the gospel of all things automotive...........I will refrain until he builds or tunes an actual car that runs fast, instead of peppering us with theory and dyno numbers
Posted By: polyspheric

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 06:15 AM

I will refrain until he builds or tunes an actual car that runs fast, instead of peppering us with theory and dyno numbers

That happened about 50 years ago.

I love how people don't trust those "science", "physics", and "chemistry" things, instead they appreciate "real world experience". LOL!
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 06:35 AM

Exactly...........so why do I care about what he did 50 years ago. I don't run 50 year old parts and some of his ideas are VERY dated.

As far as that "experience" thing........yeah, that means a lot to me, because "better ideas" are engineered every day that fall flat on their face..........so laugh all you want
Posted By: Spaceman Spiff

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 02:05 PM

Originally Posted By polyspheric
I will refrain until he builds or tunes an actual car that runs fast, instead of peppering us with theory and dyno numbers

That happened about 50 years ago.

I love how people don't trust those "science", "physics", and "chemistry" things, instead they appreciate "real world experience". LOL!


50 years ago "science" and "physics" said it would be impossible for a piston driven vehicle to exceed 180mph in a 1/4 mile....

I'll take real world experience.
Posted By: Mark Whitener

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 04:40 PM

Having spent a fair amount of time with carbs in the last 7 years I have found out a few things relevant here. Lets assume the pump can supply the volume the engine needs, and enough pressure to overcome g-force. The biggest restriction is almost always the N&S, and the biggest source of having fuel aerate on the bowl. When fuel aerates it makes delivery thru the jets inconsistent, so jetting has to be made larger to cover the inconsistency. This is bad for power. With smaller N&S's you have to try to force more fuel thru, so you increase the pressure. This makes aeration worse. I use .128 N&S on gas 4150's, .140's on Little Bo and Dominators on gas and on all E85 carbs. For methanol I jump to .164's. The second restriction point to address is the regulator, and this can be as bad and in rare occasions more restrictive than the N&S. When I started running E85 I put a new regulator on at the same time. The car ran out of fuel before the end of the track, once I put the old regulator on all was well.

I currently run a large port Magnafuel Regulator, It has supplied enough fuel to run 4.90's in the 1/8 at 5 psi with methanol. You need volume at the lowest possible pressure to minimize aeration. The following videos made by BLP show the reality of it. First is a .150 N&S, second a new design bowl with a N&S around .250.Pressures are 5 psi with the .150, at or under 2 psi with the new design. And the new design has been in the 6.70's in the 1/4 at under 2 psi.

https://www.youtube.com/watch?v=PehQUKwQX8E

https://www.youtube.com/watch?v=FOJKcvTKQAg
Posted By: polyspheric

Re: Fuel Volume vs. Fuel Pressure - 10/20/15 11:18 PM

No, that was an idiot calling his subjective guess "science".

And it was 60 years ago - 200 mph was done in 1960 by Karamasines.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/21/15 12:41 AM

http://www.4secondsflat.com/BLP%20N_S.jpg

Has anybody tried these? I wonder if they help.

EDIT: Just seen where BLP has these too.
Posted By: madscientist

Re: Fuel Volume vs. Fuel Pressure - 10/21/15 01:43 AM

Originally Posted By 340B5
http://www.4secondsflat.com/BLP%20N_S.jpg

Has anybody tried these? I wonder if they help.

EDIT: Just seen where BLP has these too.


Either BLP makes them or 4 seconds flat and BLP gets them from the same place. Probably available from other sources if BLP isn't making them in house.
Posted By: Mark Whitener

Re: Fuel Volume vs. Fuel Pressure - 10/21/15 05:08 AM

Stick with a standard N&S, .140's work well and will supply a lot of fuel. Bottom feeds don't flow as much for the same N&S size.
Posted By: julian2007

Re: Fuel Volume vs. Fuel Pressure - 10/21/15 02:47 PM

I bought a 2007 spitzer dragster from Rick Forish (general manager at Spitzer race cars) When I showed up to pick it up I noticed it had a holly blue fuel pump on it .I jokingly asked him if he was trying to pull a fast one and where was the good pump. He then took me over to his brand new car fresh off the jig and showed me the fuel pump on it holly black.

my car went well into the 6ixes when rick had it (holly blue). I had it go 7.18 (holly blue)

He was at the us nationals when his bg 400 failed him for the third time and all he could find was a holly blue he switched it out at the track and went well over 200 mph (same performance as bg 400)

I have never changed a fuel pump and gained performance do to it being too small. If its plumed properly a 110 pump will go a long way.

Today I have a run a Aeromotive mechanical pump driven off the back of the dry sump pump (use to run alky) however just to prove a point we dead headed -6 lines out of the regulator and put my 1200 alky dominator on a b1572 and it worked fine with a a-2000 pump.

most running out of fuel problems at the big end is do to pi$$ pore pluming rather than fuel pump being too small.

Sit down with a good fuel system company like Aeromotive and design a good system plumed properly and you will be surprised at how small of a pump you can get away with.

Even though we dead headed a system to see what would happen I think all systems should be bypassed out of the regulator back to the tank,after I went to this design my fuel gauge was thought to be defective do to it being so steady. On the race pak graft it is almost a flat line.

one more thing -8 coming out of a pump = -10 feeding it to combat cavitation (very important)
Posted By: fourgearsavoy

Re: Fuel Volume vs. Fuel Pressure - 10/21/15 05:45 PM

I have to agree with all the plumbing comments above. I still use a Carter race pump on my Savoy with -10 inlet and -8 out to 1/2" hard line to the dead head Holley regulator.
Car has been 10.91 at 125 with a 3.54 gear shruggy
I still have a hard time spending $300 on a pump that I don't need twocents

Gus beer

Attached picture my savoy.jpg
Posted By: sgcuda

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 02:32 AM

Originally Posted By Thumperdart
Originally Posted By poboyengineering
Thumper, is this it? 34-100, comes with aluminum fuel bowls?
It's on their website at $101 and change.........


YES........


Hey Thumper,

What's the difference between Quickfuels 34-100 and 34-101? 101 shows "Special fuel chute fuel technology" 100 is $101. 101 is $175. Will the 34-100 get the job done?
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 02:37 AM

Never used the "chute" ones and can`t imagine needing to so I`d just get the regular ones myself..........
Posted By: sgcuda

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 02:45 AM

Cool. Thanks. Running dual 850's on a sheet metal intake. Never thought that the carbs themselves would become a source of fuel restriction. Thanks for the heads up.
If I can get one more piece of free advise from you: How important is it to mount the regulator up front. Never did that before, but then again, I never ran as fast as I plan on running this year.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 02:49 AM

Most of the tunnel rams have em mounted up ft. which just makes sense and even non t-ram carbs do the same although mine`s mounted on the inlet lines hanging on the pass side.......
Posted By: sgcuda

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 02:52 AM

I've run six packs and dual quads before with the regulator to the side of the carbs/motor, but like I said, I don't know how much G force plays into the equation as the cars potential speed increases.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 03:28 AM

Apparently it`s important, just look at Pro-stock or other fast classes and I cant remember NOT seeing em mounted in ft.except on a few occasions.......
Posted By: Cab_Burge

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 06:39 AM

Mount the fuel regulator in front of the front fuel bowl so the high pressure from the pump doesn't get reduce before the needles and seats on the front fuel bowl twocents
Posted By: sgcuda

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 12:58 PM

FWIW, I think this has been a great thread/subject. Lots of knowledge and experience has been thrown around here. This is why I joined Moparts in the first place, and I'm glad that I can participate in it from time to time. Thanks to everyone here.
Posted By: fourgearsavoy

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 03:45 PM

Originally Posted By sgcuda
Originally Posted By Thumperdart
Originally Posted By poboyengineering
Thumper, is this it? 34-100, comes with aluminum fuel bowls?
It's on their website at $101 and change.........


YES........


Hey Thumper,

What's the difference between Quickfuels 34-100 and 34-101? 101 shows "Special fuel chute fuel technology" 100 is $101. 101 is $175. Will the 34-100 get the job done?

I have the fuel chute bowls on my carb and as Thumper has said they do look like they can flow more fuel than other bowls I have seen.
Gus
Posted By: Mark Whitener

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 04:48 PM

The 100's have a 7/8-20 Holley standard thread, the 101's have 8AN boss fittings. Otherwise they are the same.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/22/15 07:28 PM

Originally Posted By sgcuda
FWIW, I think this has been a great thread/subject. Lots of knowledge and experience has been thrown around here. This is why I joined Moparts in the first place, and I'm glad that I can participate in it from time to time. Thanks to everyone here.



Couldn`t agree more and I`ve learned and applied info from here and other sites and learned AND am learning every day which is awesome for all of us..........Thankxx to all who participate in these posts and hopefully it will continue and we can ALL grow together in this awesome sport/hobby we enjoy....... thumbs
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/23/15 05:13 PM

I know I'll be putting on dual relays as well as lowering fuel pressure slightly. Probably go to a .130 N/S too.
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/23/15 09:57 PM

Sure has been a lot of great info in this thread for sure! It sure would save some money to just do a few things to what I have and make it work. I would be really pissed if I dumped 600-700 bucks into something I did not need!
Posted By: JERICOGTX

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 06:22 AM

Ran -12 line from the cell to the Magnafuel500 pump, then -10 line to the regulator, then -8 line to the carb. Wiring to the pump is a often overlooked problem.
Posted By: Jerry Kathe

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 02:33 PM

TBoomer - Monte Smith and Mark Whitener have answered this inquiry.....go back and re-read those posts. Been there, done that.
(FWIW/IMO)
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 03:06 PM

Originally Posted By Jerry Kathe
TBoomer - Monte Smith and Mark Whitener have answered this inquiry.....go back and re-read those posts. Been there, done that.
(FWIW/IMO)



Like:
"Bigger lines, hold more volume and the column of fuel is harder to move in a G situation, so you need more pump. Smaller lines help that...."

Just don't tell your physics teacher. laugh2
Posted By: Jerry Kathe

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 03:40 PM

Its about volume, not pressure.

I don't invest much concern when comparing say a -10 line v/s a -8 line in column reaction to G-forces - but there is some relevance to the general concept and statement.

FWIW - in having a professional education and occupational discipline in the engineering field.....I understand hydraulic physics and dynamics, no need to consult the teacher.
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 04:01 PM

Originally Posted By Jerry Kathe
Its about volume, not pressure.

I don't invest much concern when comparing say a -10 line v/s a -8 line in column reaction to G-forces - but there is some relevance to the general concept and statement.

FWIW - in having a professional education and occupational discipline in the engineering field.....I understand hydraulic physics and dynamics, no need to consult the teacher.

work

I have no idea what you are saying, other then your stated qualifications. To be clear, explain what "relevance to the general concept and statement" means relating to this topic. I would like to hear someone explain how tubing size diameter effects PSI, under g forces. I tried, but everybody? got lost in the weeds, to use another analogy. eyes
Posted By: Duner

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 04:28 PM

I've been making 700rwhp with only a 5/16" fuel line forever.....

I don't think my fuel injectors know anthing about G-forces anyway.


(sorry, couldn't resist)
Posted By: Jerry Kathe

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 04:55 PM

Carburetor.....
you dont want pressure because of a airiation....less is best.

You want volume, this is what maintains the same level of fuel in the bowl even considering gforce efffect.

Fixed displacement pumps will have volume and pressure as a linear effect.

If you use a pump with big gph numbers...you can reduce delivery pressure a bunch and still have adequate volume.

Do this with your small pumps....set the carb pressure at 3.5 psi and make a hit, then set it at 7.5 psi....make another hit and report back.....

Another prior comment about needle and seat size and bowl entry point is important.
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 06:03 PM

Give it up Jerry...........you can't have a legitimate race car discussion with some here. Now if you want to talk about water cisterns, gravity on Saturn and golf balls, you are in the right place.
Posted By: justinp61

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 06:15 PM

Just to throw something else in the mix of needle/seats and bowl entrances, the regulator. When I went to the Magnafuel 275, 1/2" aluminum and 8AN lines I also went to a Holley big port regulator. Looking at the sizes of the inlets and outlets I'm not sure it was money well spent.

Discussion?
Posted By: Just-a-dart

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 06:44 PM

As I read through all of this I am reminded of the mistakes/leasons I have learned about pump placement size/style of the pump, running voltage to the pump, tank placement and g-force. But I am just a dumb electrician, not a rocket doctor.

Some need to remember there is a big difference between a tank at the rear of the car way behind the regulator and carb and a tank ahead of the pump and the rest of the system.

The fuel aeration/pressure discussion is interesting, and I have to think about how some push vacuum referenced regulators and the effect that would have in the fuel bowl.

Thanks for a discussion that is useful
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 07:11 PM

For a vast over simplification of pressure vs volume.........lets relate it to electricity. A 20 gauge speaker wire will carry 12 volts(pressure) and so will a 00 welding cable, but only one of those will crank your car, because only one carries enough volume(amps) of electricity to operate the starter motor. I can crank the pressure(voltage) up on the small wire to 16 volts and it still won't crank the car.

So your motor requires a volume of fuel to run properly. If the pump and line can't supply that volume, no realistic amount of pressure increase is going to overcome the lack of volume.

As for the lower pressure, decreasing aeration of the fuel and the car running better...........that has been proven time and time again on the RACETRACK........NOT on a piece of paper
Posted By: jcc

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 07:31 PM

Originally Posted By Monte_Smith
Give it up Jerry...........you can't have a legitimate race car discussion with some here. Now if you want to talk about water cisterns, gravity on Saturn and golf balls, you are in the right place.


When you label other peoples comments "crap", I would agree about the comment of having legit discussions here, about anything.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 07:54 PM

Considering the conversation has turned to aeration a couple times;

I have a deep (11") fuel cell and have never had a down tube on the return inside. I've always reasoned that the bubbles will float to the top before they get pulled into the inlets. Would it benefit me to use a downtube?

I was planning on finally putting one on this winter.
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 08:13 PM

Originally Posted By jcc
Originally Posted By Monte_Smith
Give it up Jerry...........you can't have a legitimate race car discussion with some here. Now if you want to talk about water cisterns, gravity on Saturn and golf balls, you are in the right place.


When you label other peoples comments "crap", I would agree about the comment of having legit discussions here, about anything.
Here is the thing.........you don't agree with me, that's fine, because I really don't care if you do. I base my suggestions here from things I have tried and KNOW they work, not based from some formula that SHOULD work or is written in a book. So yeah, when you start talking about water cisterns on Saturn and the differences in gravity to prove your point, which is totally irrelevant to the discussion at hand, I zone out and consider that info useless. Nobody care about that stuff. They want to know what will WORK on their race car.

If you and a couple others, think you are the ONLY ones on here with an engineering background, you are sorely mistaken. And if there is one thing I have learned working with other engineers, is that because they can figure things out on paper, doesn't mean they can make anything WORK. Going through that right now, with a self proclaimed "genius" engineer we hired. Nothing he has done for us has worked. So what does that mean........it means a piece of paper is a piece of paper
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 09:07 PM

Originally Posted By 340B5
Considering the conversation has turned to aeration a couple times;

I have a deep (11") fuel cell and have never had a down tube on the return inside. I've always reasoned that the bubbles will float to the top before they get pulled into the inlets. Would it benefit me to use a downtube?

I was planning on finally putting one on this winter.


When my Magnafuel 300 pump died on me the tech at Mag said it had been cavitating and asked about the down tube which I did not use till AFTER I got the pump back. He also said running the cell low and hard braking can uncover the sump and also kill it. He also mentioned foam which I run can also crowd the outlet fittings ALSO causing a restriction. So I now run the down tube, keep the cell at least 1/2 full and will address the foam issue somehow.......
Posted By: dvw

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 10:02 PM

If pressure is being measured directly at the line between the regulator, how could there be inadequate flow to the needle and seat? If there wasn't adequate volume in that line to keep a steady state of fuel at the needle and seat wouldn't the pressure reading go down? As long as the regulator can feed the volume of fuel held in that line with the needle open the pressure will remain constant. Pascals law states; "When pressure on any portion of a confined liquid is changed, the pressure on every other part of the liquid is also changed by the same amount." The needle and seat causes the volume of liquid to no longer be confined. If the needle is open the confined area must be constantly refilled equaling the exiting volume to maintain the same pressure. Obviously flow over time and quality of pure liquid could change and maybe the instruments used to monitor it aren't quick or accurate enough to record the true story. The argument about aerated fuel and using the least pressure necessary makes sense. When we use pressure vs volume maybe it isn't that we don't have adequate flow but the "quality" of the fuel being delivered isn't 100% liquid? Or am I missing something?
Doug
Posted By: sgcuda

Re: Fuel Volume vs. Fuel Pressure - 10/25/15 10:19 PM

So, since I started racing, (back when electricity was first invented, I think) I used 2 Holley blue pumps with Moroso springs, 2 1/2" fuel lines, into 2 Holley regulators tee'd together and into the fuel bowls. I think the Moroso spring and shim kits set the line pressure around 28 psi, and then adjusted the regulators to 5 psi each, which would be 5.5 when both pumps were running. Would lowering the regulator pressure be beneficial as far as aeration or is this a satisfactory setup? Still unsure of a new setup for the new combo. Was thinking leaving the pumps, feed the supply lines into a Y block in front of a single four port regulator. Oh, and the lines off of the fuel cell are -10.
The biggest addition to my new combo will be adding an alternator this year.
Posted By: Cab_Burge

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 12:11 AM

My comments on fuel voulme is that many things in a fuel system can be a potential and actual flow(volume) stopper, like .090 needles and seats on a 800 HP motor with one 1050 Dominator carb. You would have reasonable fuel pressure with insuffeint fuel volume to adequately feed that motor due to the needle and seat restrictions, been there, done that realcrazy
Posted By: Spaceman Spiff

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 12:18 AM

I'm not a smart man.
But you know who I'm going to listen to in a discussion like this?
Guys with real hands on knowledge of making a car go down a track fast.
Guys like Monte, and Thumper. Because they have tried "theories" "formulas" "calculations",
And what ever else a book says will work.
And what usually happens? They don't work. What works on paper, or even a dyno, might not happen going down the track.
Posted By: tboomer

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 12:55 AM

Originally Posted By Spaceman Spiff
I'm not a smart man.
But you know who I'm going to listen to in a discussion like this?
Guys with real hands on knowledge of making a car go down a track fast.
Guys like Monte, and Thumper. Because they have tried "theories" "formulas" "calculations",
And what ever else a book says will work.
And what usually happens? They don't work. What works on paper, or even a dyno, might not happen going down the track.

This!!!!! ^^^^^^^^^^^^^^^^ I could care less about theory. I just want something that works and there has been a lot of good advice here given by people who have been there and done that!
Posted By: TRENDZ

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 03:43 AM

Boost ref regulators maintain the differential pressure in the bowl. Without the ref line to the regulator, you would be very limited on boost pressure.
Lets say base fuel pressure is 5 psi. Since the fuel bowl is vented to the carb hat in a boosted application, you would start to slow fuel delivery as boost increased... The boost pressure would fight the flow of incoming fuel. At 2psi of boost, you would have 3psi of differential pressure, at 5 psi, you would have no differential pressure, and no fuel flow. So, higher pressures are needed with a boosted carb.
At 10# boost, with a ref regulator, you end up with 15psi fuel pressure in the fuel line, but a 5psi differential pressure in the bowl, so fuel isn't screaming in through the needle and seat.
As far as vacuum ref regulators, I see no real need for doing it. Cars that need really high end fuel systems generally make minimal vacuum.
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 03:57 AM

Originally Posted By dvw
If pressure is being measured directly at the line between the regulator, how could there be inadequate flow to the needle and seat? If there wasn't adequate volume in that line to keep a steady state of fuel at the needle and seat wouldn't the pressure reading go down? As long as the regulator can feed the volume of fuel held in that line with the needle open the pressure will remain constant. Pascals law states; "When pressure on any portion of a confined liquid is changed, the pressure on every other part of the liquid is also changed by the same amount." The needle and seat causes the volume of liquid to no longer be confined. If the needle is open the confined area must be constantly refilled equaling the exiting volume to maintain the same pressure. Obviously flow over time and quality of pure liquid could change and maybe the instruments used to monitor it aren't quick or accurate enough to record the true story. The argument about aerated fuel and using the least pressure necessary makes sense. When we use pressure vs volume maybe it isn't that we don't have adequate flow but the "quality" of the fuel being delivered isn't 100% liquid? Or am I missing something?
Doug
When you set a regulator at 5psi flowing, it has 5 psi flowing, because that is what you are telling it to flow. Has NOTHING to do with the volume, the reg is just maintaining the pressure you set it to. I test this stuff everyday on my flow bench. As an example, on the fuel side of my nitrous flow bench, the fuel reg has a .016 bleed jet to bypass fuel and keep the regulator from stacking. So lets say I set that reg to 5psi if that is my test pressure I am measuring fuel flow at. Now, I may be testing a plate system with ONE small fuel jet, or a fogger with EIGHT pretty decent size fuel jets, or just the pump running through the bleed jet. The differences in the VOLUME of fuel I pass, as measured in lb/hr can be quite large......BUT the outlet side of the regulator stays at a steady 5 psi, because that's where I set it. I do this everyday and monitor fuel flow with Rotometers, as well as pressure tranducers on a Racepak, as well as checking pressures about everywhere you can imagine, meaning before and after every piece of the system. I also have a mechanical 8 gal pump that I spin with an electric motor. I can flow a little fuel, or enough for a blown alky setup

So a too small pump can continue to supply pressure at the needle and seat, because it is regulated, but that in no way means it has adequate volume. You want to keep the bowls full, not just enough in there to run on. Which goes back to that aeration thing.

So unless I am missing what you are asking........just look at YOUR car. You know the fuel volume is much greater with the motor at full song. So does your pressure read the same with the car idling, as it does going down the track? It should.

I have proven this to guys by having them clean kill the power and neutral the car at the stripe, with the car under full power. Tow it back to the pits and pull the bowls. Have seen them basically DRY and never be a hiccup in the pressure trace on the logger graph. Not enough volume, but plenty of pressure
Posted By: fourgearsavoy

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 04:33 AM

So I have often wondered what the fuel bypass logs are used for shruggy The circle track guys seem to be using them the most but is this a better setup than a dead head regulator or even a return style system? Or am I completely off base here and they only use them with a high volume mechanical belt drive alky pumps shruggy
I have to change the position of my regulator to conform to the rules so I'm completely re-plumbing my entire system with filters and all. So this thread is very interesting to me up

Thanks for all the "seasoned" wisdom contained in the real world replies bow

Gus beer

Attached picture moria burnout.JPG
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 04:54 AM

It's about Volume, they are trying to run as much volume of fuel as they can by the carb inlets. If it needs it, the fuel is there. That's why they are big.

As I said much earlier, it's not about the pump, it's not about the reg, or any single part.........it's the SYSTEM.

Guys want to save a buck and I understand that, but the fuel system is not where I want to "get by". I want more fuel system than I need and also more electrical system than I need
Posted By: Wedgeman

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 05:01 AM

Originally Posted By Monte_Smith
Originally Posted By dvw
If pressure is being measured directly at the line between the regulator, how could there be inadequate flow to the needle and seat? If there wasn't adequate volume in that line to keep a steady state of fuel at the needle and seat wouldn't the pressure reading go down? As long as the regulator can feed the volume of fuel held in that line with the needle open the pressure will remain constant. Pascals law states; "When pressure on any portion of a confined liquid is changed, the pressure on every other part of the liquid is also changed by the same amount." The needle and seat causes the volume of liquid to no longer be confined. If the needle is open the confined area must be constantly refilled equaling the exiting volume to maintain the same pressure. Obviously flow over time and quality of pure liquid could change and maybe the instruments used to monitor it aren't quick or accurate enough to record the true story. The argument about aerated fuel and using the least pressure necessary makes sense. When we use pressure vs volume maybe it isn't that we don't have adequate flow but the "quality" of the fuel being delivered isn't 100% liquid? Or am I missing something?
Doug
When you set a regulator at 5psi flowing, it has 5 psi flowing, because that is what you are telling it to flow. Has NOTHING to do with the volume, the reg is just maintaining the pressure you set it to. I test this stuff everyday on my flow bench. As an example, on the fuel side of my nitrous flow bench, the fuel reg has a .016 bleed jet to bypass fuel and keep the regulator from stacking. So lets say I set that reg to 5psi if that is my test pressure I am measuring fuel flow at. Now, I may be testing a plate system with ONE small fuel jet, or a fogger with EIGHT pretty decent size fuel jets, or just the pump running through the bleed jet. The differences in the VOLUME of fuel I pass, as measured in lb/hr can be quite large......BUT the outlet side of the regulator stays at a steady 5 psi, because that's where I set it. I do this everyday and monitor fuel flow with Rotometers, as well as pressure tranducers on a Racepak, as well as checking pressures about everywhere you can imagine, meaning before and after every piece of the system. I also have a mechanical 8 gal pump that I spin with an electric motor. I can flow a little fuel, or enough for a blown alky setup

So a too small pump can continue to supply pressure at the needle and seat, because it is regulated, but that in no way means it has adequate volume. You want to keep the bowls full, not just enough in there to run on. Which goes back to that aeration thing.

So unless I am missing what you are asking........just look at YOUR car. You know the fuel volume is much greater with the motor at full song. So does your pressure read the same with the car idling, as it does going down the track? It should.

I have proven this to guys by having them clean kill the power and neutral the car at the stripe, with the car under full power. Tow it back to the pits and pull the bowls. Have seen them basically DRY and never be a hiccup in the pressure trace on the logger graph. Not enough volume, but plenty of pressure


Killing the fuel pump at the end of the track........here is the most simple and obvious way to know where your system is at !

Why didn't I think of that before !


Dan
Posted By: Monte_Smith

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 05:11 AM

Gotta kill, motor, pump and go into neutral all at same time to get an accurate read. Let motor run down against trans with pump off and it will drain the bowls as well
Posted By: dvw

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 05:36 AM

Originally Posted By Monte_Smith
Originally Posted By dvw
If pressure is being measured directly at the line between the regulator, how could there be inadequate flow to the needle and seat? If there wasn't adequate volume in that line to keep a steady state of fuel at the needle and seat wouldn't the pressure reading go down? As long as the regulator can feed the volume of fuel held in that line with the needle open the pressure will remain constant. Pascals law states; "When pressure on any portion of a confined liquid is changed, the pressure on every other part of the liquid is also changed by the same amount." The needle and seat causes the volume of liquid to no longer be confined. If the needle is open the confined area must be constantly refilled equaling the exiting volume to maintain the same pressure. Obviously flow over time and quality of pure liquid could change and maybe the instruments used to monitor it aren't quick or accurate enough to record the true story. The argument about aerated fuel and using the least pressure necessary makes sense. When we use pressure vs volume maybe it isn't that we don't have adequate flow but the "quality" of the fuel being delivered isn't 100% liquid? Or am I missing something?
Doug
When you set a regulator at 5psi flowing, it has 5 psi flowing, because that is what you are telling it to flow. Has NOTHING to do with the volume, the reg is just maintaining the pressure you set it to. I test this stuff everyday on my flow bench. As an example, on the fuel side of my nitrous flow bench, the fuel reg has a .016 bleed jet to bypass fuel and keep the regulator from stacking. So lets say I set that reg to 5psi if that is my test pressure I am measuring fuel flow at. Now, I may be testing a plate system with ONE small fuel jet, or a fogger with EIGHT pretty decent size fuel jets, or just the pump running through the bleed jet. The differences in the VOLUME of fuel I pass, as measured in lb/hr can be quite large......BUT the outlet side of the regulator stays at a steady 5 psi, because that's where I set it. I do this everyday and monitor fuel flow with Rotometers, as well as pressure tranducers on a Racepak, as well as checking pressures about everywhere you can imagine, meaning before and after every piece of the system. I also have a mechanical 8 gal pump that I spin with an electric motor. I can flow a little fuel, or enough for a blown alky setup

So a too small pump can continue to supply pressure at the needle and seat, because it is regulated, but that in no way means it has adequate volume. You want to keep the bowls full, not just enough in there to run on. Which goes back to that aeration thing.

So unless I am missing what you are asking........just look at YOUR car. You know the fuel volume is much greater with the motor at full song. So does your pressure read the same with the car idling, as it does going down the track? It should.

I have proven this to guys by having them clean kill the power and neutral the car at the stripe, with the car under full power. Tow it back to the pits and pull the bowls. Have seen them basically DRY and never be a hiccup in the pressure trace on the logger graph. Not enough volume, but plenty of pressure

So if I understand correctly the gauge at the regulator is set at 5 psi and reads 5 psi flowing (I'm assuming into an open container with no g force restrictions.) A volume of fuel flows into the feed line between the regulator outlet and the needle/seat assy. If fuel flows out through the needle and seat faster than it can be replenished by the regulated system (inadequate volume) then the pressure in the line itself would be lower than regulator set pressure? is this correct?
Doug
Posted By: Just-a-dart

Re: Fuel Volume vs. Fuel Pressure - 10/26/15 07:28 AM

Thank you TRENDZ, I get that even though I do not play with a blow thru.

What I was thinking about was Patrick's (Prosystems) set up. http://www.prosystemsracing.com/frienddom.html

Looks like this could add to fuel aeration issues to me, especially if you start a little high to begin with.
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 12/01/15 04:50 AM



Ordered a set of these Holley Ultra HP bowls. I hope the baffles combined w/ lower pressure will help reduce aeration.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 12/01/15 05:45 AM

Originally Posted By 340B5


Ordered a set of these Holley Ultra HP bowls. I hope the baffles combined w/ lower pressure will help reduce aeration.


Those look nice. Do you have a pic of the fuel entrance by chance?
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 12/01/15 01:49 PM

I'll work on a pic tonight after work, but the entrance looks like the QF bowl pics posted earlier.
Posted By: Thumperdart

Re: Fuel Volume vs. Fuel Pressure - 12/01/15 07:03 PM

Then you're golden.......
Posted By: 340B5

Re: Fuel Volume vs. Fuel Pressure - 12/02/15 02:29 AM

Here ya go.

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