Help me understand how an in-line fuel pump pumps more fuel...

[slow4now]

Originally posted by Osirian:

I run the Wlabro 340M 255lph in-tank pump. Boost right now is in the 17 to 18 psi range and will be approaching - and probably just passing - 20 this year.

 

What is BSFC?

Brake Specific Fuel Consumption.

 

 

You guys are killing me with your theories and calculations that are incorrect!

 

Flowing more fuel means that more fuel is being moved from the fuel tank to the fuel injector. How in the world you guys think that an inline pump can flow more fuel than the intank pump can provide is beyond me! It's physically impossible!

 

 

Here is a paragraph taken from www.fuel-pumps.net on standard pressure vs high pressure fuel pumps, maybe it will help you understand the difference between pressure and flow:

 

Walbro makes the same fuel pumps (as far as mechanical fitment is concerned) in two different styles. These styles are normally referred to as standard pressure and high pressure. This reference is a bit of a misnomer, since either pump will produce approximately the same amount of flow at standard fuel injection system pressures. However, well above the standard fuel injection system pressure the flow of the standard pressure fuel pump will drop off whereas the flow of the high-pressure fuel pump will see less impact. This is important to users who are trying to use higher fuel pressures to push more fuel through their fuel injectors than is normally done at standard fuel pressure levels. While this may be a cost-effective solution it can lead to other concerns, including safety considerations. Fuel-Pumps.net recommends that you use an injector that is able to inject the proper amount of fuel into the engine without requiring the fuel system's pressure to be increased significantly above stock levels.

 

You guys are either over-analyzing or incorrectly applying theories, but whatever the case you are both wrong. smile.gif

[rl]

Originally posted by the Man With No Name:

Brake Specific Fuel Consumption.

 

 

You guys are killing me with your theories and calculations that are incorrect!

 

Flowing more fuel means that more fuel is being moved from the fuel tank to the fuel injector. How in the world you guys think that an inline pump can flow more fuel than the intank pump can provide is beyond me! It's physically impossible!

 

 

Here is a paragraph taken from www.fuel-pumps.net on standard pressure vs high pressure fuel pumps, maybe it will help you understand the difference between pressure and flow:

 

Walbro makes the same fuel pumps (as far as mechanical fitment is concerned) in two different styles. These styles are normally referred to as standard pressure and high pressure. This reference is a bit of a misnomer, since either pump will produce approximately the same amount of flow at standard fuel injection system pressures. However, well above the standard fuel injection system pressure the flow of the standard pressure fuel pump will drop off whereas the flow of the high-pressure fuel pump will see less impact. This is important to users who are trying to use higher fuel pressures to push more fuel through their fuel injectors than is normally done at standard fuel pressure levels. While this may be a cost-effective solution it can lead to other concerns, including safety considerations. Fuel-Pumps.net recommends that you use an injector that is able to inject the proper amount of fuel into the engine without requiring the fuel system's pressure to be increased significantly above stock levels.

 

You guys are either over-analyzing or incorrectly applying theories, but whatever the case you are both wrong. smile.gif

It flows more AT PRESSURE. Its a PRESSURE SYSTEM.

 

2 pumps with 20psi pressure drop WILL flow more than 1 pump with a 40psi pressure drop! My calculations are NOT incorrect. Its all about being able to move fluid at high volumes UNDER PRESSURE.

 

 

He is running 63psi of fuel pressure, that means his ONE pump has a pressure drop of 63psi accross it! Your telling me that 2 pumps, with less of a pressure drop, at the same rail pressure are going to NOT flow more, but RAISE the pressure? Thats horribly incorrect!

 

The ONLY way the inline pump will RAISE the pressure is if there is a RESTRICTION after the rail (ei the regulator and return lines) and it doesnt allow enough fuel to return to the tanks.

 

What adding an inline pump will do is allow him to maintain his 63psi rail pressure while still moving the volume needed (because the first pump will have less of a pressure drop across it as will the second). If he is losing fuel pressure its because at 63psi his walbro pump cant move enough volume. Adding an inline pump WILL fix this, period.

 

I think YOU are looking at it wrong.

 

a high pressure pump is rated to flow more at a higher pressure drop (ie 60psi instead of industry standard 42).

 

The link I posted was writting by a man who was a Ford/roush powertrain engineer for 20 years and has tuned over 3,000 cars in the last 2 years. His calculations are wrong as well? (because they are the exact same thing I posted).

 

smile.gif

 

Flowing more fuel means that more fuel is being moved from the fuel tank to the fuel injector. How in the world you guys think that an inline pump can flow more fuel than the intank pump can provide is beyond me! It's physically impossible!

NO! IF it was a RETURNLESS FUEL SYSTEM then you would be correct but its not, fuel flow is the AMOUNT OF FUEL PUMPED TO THE RAIL, the EXCESS (that is not used by the injectors) is returned to the tank, the pressure is a direct function of the FPR, NOT the fuel pumps on a RETURN system (unless you run OUT of pump like chris is, then pressure DROPS). The FPR restricts the return line to maintain constant fuel pressure.

 

The ONLY way pressure will RISE because of the pump on a RETURN style system is if there is a RESTRICTION in the return (it outflows the FPR or return line).

 

[ 18. February 2004, 02:21 PM: Message edited by: rl ]

[Don 95Vert]

Originally posted by the Man With No Name:

As already stated an inline pump doesn't increase the volume of fuel that is pumped, but it increases fuel pressure thus injecting more fuel per injector pulsewidth.

If that were true, than every time you increase fuel pump size, you'd be running pig rich. It just doesn't happen. On a return style system the FPR trims fuel to keep a constant FP. On a returnless system, a fuel rail pressure sensor measures pressure drop across the injectors and then sends data to the ECU to trim voltage to the FP - on returnless systems you have to use a turbine style FP because they can more accurately vary operation rate. When you add an FMU to the return style system, it raises FP to the injectors by tricking the FPR by a fixed ratio and makes the injectors act bigger. On a normal system, the fuel is controlled by injecor pulsewidth, not inceasing pressure to the injector.

 

I'm sorry, but their calculations are basic engineering facts and are VERY correct.

[slow4now]

I dont have any time to waste at the moment with this thread, but I am happy for you guys as you will be able to make a ton of money building devices that can teleport things from one place to another without any physical interaction. I will revisit this thread later. Amazing. http://forums.offtopic.com/images/smilies/bowdown.gif

 

 

BTW, reducing volume loss at pressure and increasing volume at pressure are not the same thing.

[Don 95Vert]

No offense intended - I was just adding to the good tech in here. No need for the sarcasm.

[rl]

Originally posted by the Man With No Name:

I dont have any time to waste at the moment with this thread, but I am happy for you guys as you will be able to make a ton of money building devices that can teleport things from one place to another without any physical interaction. I will revisit this thread later. Amazing. http://forums.offtopic.com/images/smilies/bowdown.gif

 

 

BTW, reducing volume loss at pressure and increasing volume at pressure are not the same thing.

Have you even been reading the thread? What we have been saying makes perfect sense, and not only that but it is the WAY IT WORKS. What you are saying is not logical in the least. Do you understand how a return style fuel system works?

 

 

Please explain to me in detail how you think a in-line fuel pump simply raises pressure on a return style fuel system without outflowing the regulator or return line.

[slow4now]

Originally posted by rl:

Have you even been reading the thread? What we have been saying makes perfect sense, and not only that but it is the WAY IT WORKS. What you are saying is not logical in the least. Do you understand how a return style fuel system works?

 

 

Please explain to me in detail how you think a in-line fuel pump simply raises pressure on a return style fuel system without outflowing the regulator or return line.

Were YOU reading anything I typed? It doesn't appear that you were. To be honest when you guys stated that an inline pump increases the flow capacity to the injectors, I pretty much stopped reading. tongue.gif

 

[ 18. February 2004, 09:44 PM: Message edited by: the Man With No Name ]

[slow4now]

Originally posted by rl:

Have you even been reading the thread? What we have been saying makes perfect sense, and not only that but it is the WAY IT WORKS. What you are saying is not logical in the least. Do you understand how a return style fuel system works?

 

 

Please explain to me in detail how you think a in-line fuel pump simply raises pressure on a return style fuel system without outflowing the regulator or return line.

First off we need to start with definitions.

 

Rate of flow or "flow" (No I'm not talking about the lunch lady in the cafeteria tongue.gif ) = The amount or volume of a substance (In this instance fuel) that can be moved in a given amount of time.

 

Pressure = a measure of force

 

A fpr increases pressure in the rail by reducing the return flow back into the tank. The fpr is controlled by engine vacuum. It's purpose is to maintain a specific pressure differential between intake pressure and the pressure across the injectors. This is done because of the way ECU's are programmed (I don't want to get into that.) The more vacuum (more load = more vacuum) the more the FPR restricts the return flow back to the tank. More load = more fuel pressure.

Stock fuel pressure regulators were designed around the parameters of the other stock fuel system components. When you upgrade the fuel pump to a higher flowing unit, the fuel pressure regulator doesn't know this. The ECU doesn't know this. Many cars DO run more rich when a higher flow capacity pump is installed, but generally the change is minor unless a high pressure intank pump is installed.

 

Generally pressure is inverse to flow. If you want to increase pressure, you decrease flow. As related to a return fuel system, to increase fuel pressure in the fuel rail/feed line you reduce the flow of fuel back into the gas tank. The flow of a pump eventually drops once the fuel pressure reaches a high enough level.

 

More pressure, less flow.

 

Adding an inline fuel pump to the mix reduces the loss of flow at higher fuel pressures. An inline pump continually pressurizes the fuel system beyond what the intank pump can achieve.

Adding an inline fuel pump to the mix reduces the loss of flow at higher pressures.It does not increase the flow capacity of the fuel system beyond that of the intank pumps capacity! It can only reduce the loss of flow. Therfore an inline pump is not to be used as a band-aid for instances when the intank pump is inadequate at normal pressure levels. This is why an inline pump is necessary when a FMU is used in conjunction with a stock fuel pump, as the stock fuel pump does not maintain it's flow rating at the needed pressure.

 

FMU + Standard pressure fuel pump = wrong

FMU + Inline Pump or high pressure intank = right

 

I hope I typed everything to where it's understandable and my intended point is made. My apologies if not.

[rl]

Originally posted by the Man With No Name:

First off we need to start with definitions.

 

Rate of flow or "flow" (No I'm not talking about the lunch lady in the cafeteria tongue.gif ) = The amount or volume of a substance (In this instance fuel) that can be moved in a given amount of time.

 

Pressure = a measure of force

 

A fpr increases pressure in the rail by reducing the return flow back into the tank. The fpr is controlled by engine vacuum. It's purpose is to maintain a specific pressure differential between intake pressure and the pressure across the injectors. This is done because of the way ECU's are programmed (I don't want to get into that.) The more vacuum (more load = more vacuum) the more the FPR restricts the return flow back to the tank. More load = more fuel pressure.

Stock fuel pressure regulators were designed around the parameters of the other stock fuel system components. When you upgrade the fuel pump to a higher flowing unit, the fuel pressure regulator doesn't know this. The ECU doesn't know this. Many cars DO run more rich when a higher flow capacity pump is installed, but generally the change is minor unless a high pressure intank pump is installed.

 

Generally pressure is inverse to flow. If you want to increase pressure, you decrease flow. As related to a return fuel system, to increase fuel pressure in the fuel rail/feed line you reduce the flow of fuel back into the gas tank. The flow of a pump eventually drops once the fuel pressure reaches a high enough level.

 

More pressure, less flow.

 

Adding an inline fuel pump to the mix reduces the loss of flow at higher fuel pressures. An inline pump continually pressurizes the fuel system beyond what the intank pump can achieve.

Adding an inline fuel pump to the mix reduces the loss of flow at higher pressures.It does not increase the flow capacity of the fuel system beyond that of the intank pumps capacity! It can only reduce the loss of flow. Therfore an inline pump is not to be used as a band-aid for instances when the intank pump is inadequate at normal pressure levels. This is why an inline pump is necessary when a FMU is used in conjunction with a stock fuel pump, as the stock fuel pump does not maintain it's flow rating at the needed pressure.

 

FMU + Standard pressure fuel pump = wrong

FMU + Inline Pump or high pressure intank = right

 

I hope I typed everything to where it's understandable and my intended point is made. My apologies if not.

You are right in the first part of what you said. I ALREADY stated ALL of that. The only thing you have wrong is more load = less vacuum. As the motor becomes more volumetrically eff. the vacuum drops. And they dont do the FP because of the way the ECU is programmed, its basic physics of the system. If there is vacuum at the head of the injector it needs that much less pressure to flow the same as it would with 0psi and normal rated fuel pressure. Same with boost, with 10psi at the head of the injector it needs 10psi more fuel pressure to maintain the base drop.

 

The inline pump DOES increase the overall flow of the system otherwise fuel pressure would STILL drop with the inline pump. If fuel pressure is dropping its because the single pump cannot keep enough volume of fuel going to the regulator for it to maintain pressure. The second pump increases that VOLUME which allows the system to maintain pressure. I PROMISE you that the formulas that I used are 100% correct. That's how you calculate the total flow of 2 pumps inline to each other. The flow of the system does increase.

 

You even said it yourself,

 

Adding an inline fuel pump to the mix reduces the loss of flow at higher pressures.

Just toss the "higher" and you're there.

 

Higher pressures, like Chris is seeing (his stock regulator WILL raise fuel pressure on a 1:1 ratio with boost to maintain the 45psi pressure drop across the injectors, just like every other regulator) so he is seeing 63psi of fuel pressure. His 255lph pump is effectively a 200lph pump at that pressure. Adding an inline pump INCREASES the capacity of the system and allows him to maintain pressure that that volume because the pressure drop across each pump is less and they can both flow more.

 

Same thing with a car running 40psi of fuel pressure and no boost. If you are making more power than the pump can support and FP is dropping off its because the pump cannot meet the required volume at that 40psi. Adding an inline pump will create enough volume to maintain pressure at that power level (because the pressure drop across both of the pumps is smaller and thus BOTH pumps CAN and WILL flow more thus INCREASING the CAPACITY of the fuel system) That's what the calculations I posted showed.

 

Ohh, and for fun, FMU in general = the wrong way.

[excell]

Wow, there is so much stuff in this thread I don't understand.

 

So the general feeling is that an in-line will help my situation? Is there any brand or model that you would reccomend I use?

[rl]

Originally posted by Osirian:

Wow, there is so much stuff in this thread I don't understand.

 

So the general feeling is that an in-line will help my situation? Is there any brand or model that you would reccomend I use?

An inline pump will be the CORRECT fix for your problem provided you are losing fuel pressure, period. A walbro inline 255lph pump is THE best option. Jegs sells one under the holly name brand, go in and ask for a walbro 255lph inline pump.

[Turbo Ben]

Originally posted by rl:

You are right in the first part of what you said. I ALREADY stated ALL of that. The only thing you have wrong is more load = less vacuum. As the motor becomes more volumetrically eff. the vacuum drops. And they dont do the FP because of the way the ECU is programmed, its basic physics of the system. If there is vacuum at the head of the injector it needs that much less pressure to flow the same as it would with 0psi and normal rated fuel pressure. Same with boost, with 10psi at the head of the injector it needs 10psi more fuel pressure to maintain the base drop.

 

The inline pump DOES increase the overall flow of the system otherwise fuel pressure would STILL drop with the inline pump. If fuel pressure is dropping its because the single pump cannot keep enough volume of fuel going to the regulator for it to maintain pressure. The second pump increases that VOLUME which allows the system to maintain pressure. I PROMISE you that the formulas that I used are 100% correct. That's how you calculate the total flow of 2 pumps inline to each other. The flow of the system does increase.

 

You even said it yourself,

 

Just toss the "higher" and you're there.

 

Higher pressures, like Chris is seeing (his stock regulator WILL raise fuel pressure on a 1:1 ratio with boost to maintain the 45psi pressure drop across the injectors, just like every other regulator) so he is seeing 63psi of fuel pressure. His 255lph pump is effectively a 200lph pump at that pressure. Adding an inline pump INCREASES the capacity of the system and allows him to maintain pressure that that volume because the pressure drop across each pump is less and they can both flow more.

 

Same thing with a car running 40psi of fuel pressure and no boost. If you are making more power than the pump can support and FP is dropping off its because the pump cannot meet the required volume at that 40psi. Adding an inline pump will create enough volume to maintain pressure at that power level (because the pressure drop across both of the pumps is smaller and thus BOTH pumps CAN and WILL flow more thus INCREASING the CAPACITY of the fuel system) That's what the calculations I posted showed.

 

Ohh, and for fun, FMU in general = the wrong way.

The inline pump doesn't have to "overcome" the fpr. Under load the fuel pressure regulator is already reducing the flow of fuel back into the fuel tank which increases fuel pressure. The flow of the pump is constantly at it's peak output unless 1)voltage to the pump is insufficient (hence the reason DSM owners re-wire their fuel pumps) or 2) fuel pressure is too great for the pump to overcome. The stock pump doesn't have to "overcome" the flow of the fuel pressure regulator, and neither does an inline pump. An inline pump merely maintains the flow of fuel at fuel pressures where the intank pump cannot by itself. It does not increase the flow capacity of the system beyond what the intank pump can handle.

 

An inline pump cannot create volume. It cannot flow more volume than what it being supplied to it from the intank pump. To be honest, I didn't read your calculations because it wouldn't do me any good as it's probably over my head. However I do not need to know them in order to realize that you cannot produce something out of nothing. If the inlet of a inline pump is recieving 255lph of fuel it cannot flow more than 255lph of fuel at the outlet. Therefore it cannot increase the overall flow of the system, it can only MAINTAIN flow at pressure! There is a huge difference! No mathematical equations will change that!

 

FMU's suck and so do inline pumps. tongue.gif

 

PS This is Ricky, douche bag forgot to logout.

[Hwilli1647545487]

I promised I would stay out of this discussion, but it looks like I broke my promise. I don't want to start any personal attacks. I would prefer this stay on a discussional, adult level.

 

I have read through this thread a few times, and I hope I am reading what everone has said accuratly.

 

Bottom line is, you cannot increase flow when adding a pump inline. a 255 in take pump and a 190 inline pump does not flow 455. It doesn't work that way.

 

A fuel pump is rated at a certain flow rate at a certain preasure. RLs link was an excellent reference, and I am suprised that this argument is still going on after I read it.

 

When preasure in a system increases the efficiency of the pump decreases. So let's say that a 255 pump is rated 255 at 40psi of system preasure (I am almost directly stealing from RLs link BTW). When you increase system preasure, the pump has to work HARDER, so it can't push fuel as fast. That is common sense (at least to me). RLs link has some math to help you figure out what the pump will become rated at at different preassure rates.

 

This is my first point. I hope we all can agree on this. Fuel pump is rated at xxx @ a certian PSI. As PSI increases, pump can push less fluid over time.

 

The purpose of the inline pump is to take stress off of the in tank pump. If you place a pump inline, the two pumps together help to divide the system into preasure zones. Thus making them have to work less.

 

example.

 

fuel rail--------------------inline pump---------------------intank pump

 

40psi.....................................................20psi

 

Using RL's link which states that the preasure between the two pumps is only 20psi. We know it's going tobe less than the system, so it's as good a number as any.

 

The intank pump is rated at 255 @40psi. Since it is only seeing 20psi it is now more efficient (see RLs post/link for the exact math). It can flow more fuel.

 

Normally the preasure in the tank would be ~0. So since the inline pump is being force fed the fuel at 20psi it now becomes more efficient. The preasure difference it is seeing from the rail, and it's supply is again only 20psi.

 

Someone correct me if I am wrong.

 

Also, as far as I know the FPR regulates preasure. Not the pump. Though if the pump can't meet the demands obvioulsy preasure will drop.

 

Good link RL, good math in that link. One problem I see in this thread is that people are failing to articulate their point, and that in itself is causing confusion.

 

Chris, Ricky is 100% correct. Get a FPR gauge on your car so you can identify the problem. Don't just throw parts at it smile.gif .

 

Also concerning the arguments in this thread, I think a little read comprehension, and people being better able to articulate themselves just a bit better could have avoided a lot of the dick swinging.

[excell]

When the car goes back on the dyno next week we will be putting a pressure gauge on it to see if our conclusions are correct. smile.gif

 

I think this is the first informative thread I've ever started!

[rl]

Originally posted by Hwilli:

 

Bottom line is, you cannot increase flow when adding a pump inline. a 255 in take pump and a 190 inline pump does not flow 455. It doesn't work that way.

Thats what you guys are not understanding. Both pumps flow more because they BOTH have to work less, inceasing the volume that the SYSTEM can move, thats what my math shows, thats what it says in the link. Of course you cannot just add the flow of the pumps together, that doesnt work. My math is the CORRECT way to calculate the NEW flow for 2 pumps (note that it IS higher than the SINGLE pump, thus the inline pump INCREASES flow)

 

 

Exactly, the inline pump INCREASES the flow of the system by reducing the pressure drop across both pumps. At less pressure both pumps can move more volume. The amount of fuel at XXpsi that the system can move with one pump is INCREASED when the inline pump is added.

 

 

That is correct, that is why system volume at XXpsi is INCREASED with an inline pump. They both flow more at less pressure.

 

Also, as far as I know the FPR regulates preasure. Not the pump. Though if the pump can't meet the demands obvioulsy preasure will drop.

Thats been my point from the very beginning. The FPR regulates pressure, NOT the pump. If the pump cant supply enough volume of fuel to the regulator to allow it to restrict the rail pressure to XXpsi then pressure drops. The only way to increase that pressure is to increase the volume. How do you do that? With an inline pump.

 

Good link RL, good math in that link. One problem I see in this thread is that people are failing to articulate their point, and that in itself is causing confusion.

Its a possibility smile.gif

 

 

I agree, however I dont see any dick swinging going on. It stayed 100% technical, just trying to get a point across which I happen to know a great deal about.

 

From Jerry W. On mod depot.:

 

In a 350 RWHP car, with a stock intake pump and a T-Rex, there was 20 psi between the two pumps. So, now you take 40/(20+10) to get 1.333. Now I used 20 instead of 39.5 psi because the actual pressure drop across the pump is 20 psi, not 39.5. The square root of 1.333 is 1.155 and then this multiplied by the flow of 190L/hr is 219 L/hr. This is a total of 279#/hr of fuel delivered and with a BSFC of .6, it would support a HP of about 466 at the crankshaft.

Note that the new total flow for the system is much higher than it would be with just the in-tank pump.

 

 

smile.gif

[rl]

Originally posted by Vash The Stampede:

An inline pump cannot create volume. It cannot flow more volume than what it being supplied to it from the intank pump. To be honest, I didn't read your calculations because it wouldn't do me any good as it's probably over my head. However I do not need to know them in order to realize that you cannot produce something out of nothing. If the inlet of a inline pump is recieving 255lph of fuel it cannot flow more than 255lph of fuel at the outlet. Therefore it cannot increase the overall flow of the system, it can only MAINTAIN flow at pressure! There is a huge difference! No mathematical equations will change that!

 

FMU's suck and so do inline pumps. tongue.gif

 

PS This is Ricky, douche bag forgot to logout.

Its a pressurized system! The pumps are rated at 255lph@ XXpsi. At LOWER PSI they flow MORE. When you REDUCE the pressure drop accross the pump (or the PSI it is having to push) then the flow INCREASES. When you add an inline pump you make the pressure BOTH pumps have to push against LESS so BOTH pumps can flow MORE. THAT is how it INCREASES the OVERALL flow of the system.

 

Just think about it for a minute, if pressure is dropping it is because at that pressure the intank pump cant produce enough VOLUME (flow). When you add the inline pump and pressure goes back UP then you have INCREASED the VOLUME (flow) that the system is moving. This is moving more VOLUME (flow) than just the intank pump could thus the inline pump has increased the overall VOLUME (flow) of the system.

 

 

smile.gif

[Don 95Vert]

Sometimes it helps to picture these things in everyday situations. Think of a garden hose delivering water with no restrictions. Then put your thumb over the end, partially blocking it. What happens? The water shoots farther because the pressure is increased. But it's obvious that unrestricted, the hose delivered a higher volume.

[Crash1647545504]

im learning alot, or am i?

[desperado]

He He... around and around we go. I found two things after re-reading this all about 5 times.

 

First is, I can be an asshole. graemlins/asshole.gif

But we all knew that, and to all of you that read all of this trying to dycypher the actual theroy that I clouded with being an asshole, sorry.

 

I do still stand firm on the two pumps thing, and what Don said helps to demonstrate it.

 

If you take a garden hose and hold it with nothing on the end, the water will only go a few feet out. But stick your finger on it, the water goes alot farther, now think about what you have done. You have increased the pressure in the hose, but you have decreased the volume of water flowing in gallons per minute from that hose.

 

Now with watering your garden that's not a problem. In a fuel system decreasing volume is bad because less volume of fuel gets to into the engine.

 

So so increasing the restriction, which would be leaning out the motor, in effect turning down the flow, but not the pressure is bad.

 

Now, a motor needs two things from the fuel system, a certain volume of fuel needs to erach the injectors. But that needs to be at a specific pressure. So everything else being equal, if we want the open hose, to shoot the same ten feet that it will when there is no finger over it. What do you have to do. And Ricky, you are on the right track, you have to increase the pressure in the hose. Now at this point ther seems to be no restriction in the hose, but the hose it's self is the restriction, by itself. Follow this real close (no I ain't being smart assed either)

The internal restriction of the hose, is the injector so to speak, it can't be changed to flow less or there isn't enough fuel in the motor to make the mixture right, even if the volume exists in lph, ot GPH, the pressure is too low. So it is not right, so to make it right. To get the water to come out of the hose and spray ten feet, with out restricting the end with your finger. You have to pump enough water through the hose until the restriction of the hose itself starts to create to pressure necessary to shoot a larger stream of water than the stream with your finger over it (more volume) the same distance.

I wish I come explain this better, I can demonstrate the heck out of it, but that ain't gonna help here. It need to be done in person.

 

Lets leave this alone. It's to the point that we need to agree to disagree and forget it.

[Guest stevil]

Originally posted by Vash The Stampede:

An inline pump cannot create volume. It cannot flow more volume than what it being supplied to it from the intank pump. ....

If the inlet of a inline pump is recieving 255lph of fuel it cannot flow more than 255lph of fuel at the outlet. Therefore it cannot increase the overall flow of the system, it can only MAINTAIN flow at pressure! There is a huge difference! No mathematical equations will change that!

From what I understand of all this, the intank pump will supply MORE than the normal 255 Lph when it's used with another in-line fuel pump. Normally it flows 255 at 40 psi, but if it has another pump helping it, it will flow something like 295 Lph at 20 psi, and the other pump will pass all that along and jack up the psi to 40 or whatever.

 

It's not teleporting magic or anything, but rather a rated pump flowing more than it's rating, because it will be pumping at a lower pressure than which it was rated at. And it does that because it's inline with another pump helping it.

 

I always heard that inline pumps suck, but now I'll consider one in the future since I know how it all works. smile.gif

 

[ 20. February 2004, 04:59 AM: Message edited by: Hoosier Daddy? ]

[rl]

Originally posted by Hoosier Daddy?:

From what I understand of all this, the intank pump will supply MORE than the normal 255 Lph when it's used with another in-line fuel pump. Normally it flows 255 at 40 psi, but if it has another pump helping it, it will flow something like 295 Lph at 20 psi, and the other pump will pass all that along and jack up the psi to 40 or whatever.

 

It's not teleporting magic or anything, but rather a rated pump flowing more than it's rating, because it will be pumping at a lower pressure than which it was rated at. And it does that because it's inline with another pump helping it.

 

That is exactly the point. That is exactly how the inline pump increases the capacity of the system. That is exactly what I have stated over and over and over again. smile.gif

[Nitrousbird]

I haven't read the links, but the concepts are pretty simple. Pumps are rated at X volume at Y pressure, and as Y increases, X decreases (since the pump is now having to work against the pressure in the line). This of course is figuring identical voltages and temps in the pump. The inline pump simply helps decrease that work to push against that pressue, making Y go down. And as Y goes down......X goes up.

 

But I do have a couple other questions. When does the inline pump become a restriction? Eventually it has to, otherwise wouldn't people simply be tossing 3 inline pumps in to keep dropping the pressure?

 

Another thing not discussed was voltage. Lower voltage = less VOLUME the pump can flow. Another item Chris may want to consider is a Boost-A-Pump. Basically, as boost rises, this device increases voltage to the pump up to a certain amount. Of course you can't run a fuel pump at 18V all day long and expect it to last, which is why this voltage box is boost referenced. Good wiring all the way to the pump is also important.

 

IMO, step one is to install a fuel pressure gauge. I've had one in my car for some time now, and IMO is a very essential gauge. Autometer full-sweep electric gauge, mine was about $190, and they also have one w/ a peak pressure reference, which is nice for finding where your fuel pressure tops out. smile.gif The newer units are also more convienent to install than the older unit like I have, which requires a seperate control box and more wiring.

[Dave1647545494]

I didn't read the whole thread , but heres some things to think about. at certain power levels ,and you are coming up on them fast. the stock fuel lines themselves become the restriction. you have a late model GM so the fuel lines are probably 5/16" or the metric equivalent. replumbing the fuel system in -8an or 1/2" may be nesecary. you may even want to run two seperate feed lines that merge at the motor with two seperate pumps this would give you flow numbers around 475 lph. even running one larger fuel line with pressure staying consatnt the volume will increase alot. I've never had much luck with a helper pump, larger fuel lines cost more, but they also provide a larger reurn on your investment.

 

HTH