fuel: how far will -6 get me?

[greathuskie]

in other words, will -6 ever become a restriction? even if someday id like to take this car very seriously as far as my turbo and whatnot goes (already started with teh head/motor..), or should i just go with -10 right now and never worry about it again?

how much power will push -6 over the limit

 

[Mirage2LTurbo]

You're talking about the difference is maybe $1/foot for the line. The fittings might be more if you have to get adapters fittings, but I'd say go ahead and suck up the few extra bucks and run -10 feed, -6 return and be done with it. Here's a few pics of my setup.

Note: I ran a -10 return only because I got a deal on the line and fittings. It really doesn't matter how big your return line is, because the regulator is only going to let out a certain amount of fuel. I wouldn't run any smaller than a -6 return.

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[greathuskie]

i realize i might just as well get bigger, but i already ordered an autoalchemy kit that uses a -6 filter and line and fittings for the inlet fuel side, now that i need to order a regulator i dont know what i should use or if going bigger then -6 would be pointless since that is what i have on my inlet side

 

[Mirage2LTurbo]

Well, if you ordered the kit, then it wouldn't make any sense to buy larger line. If you're pieceing it togather, it would make sense.

 

[greathuskie]

what i want to know is at what point will 6an become a restriction

 

[terefic181]

My $.02, regarding AN size per HP rating, I'm not sure you'll get a definative answer but I would bet there are a number of 4>500hp cars with stock or -6 size lines with larger pumps. Just remember the larger the line, the lower your (fuel pressure) will be. I would say -6 AN or -8 AN at the largest. -10, -12 your getting into gardenhose sizes. Not to mention the fittings and hoses get quite a bit more expensive the larger you go.

Good luck,

 

[Mirage2LTurbo]

If you are going to a -10, you probably need to be on a large external or twin pump setup in order to maintain pressure in high boost.

 

[myblack98gst]

A local guy made 550 whp on stock fuel lines, filter, & filter-rail line.. so 6-an will carry you a long way..

 

[kooka]

A local guy made 550 whp on stock fuel lines, filter, & filter-rail line.. so 6-an will carry you a long way..

and there you have it.

 

[4geze63]

im also getting the 6an line to and from the tank its more then enough for my goals

 

[NOSLO2PT0]

Well, people have gone lo 10's on the stock fuel filter, stock lines, stock return lines, so how fast do you plan on going?

 

[Kevin Jewer]

Unless I'm way off, increasing line size wont lower the pressure. Line pressure will be a function of the pump flow rate/pressure, consumption rate, and the restriction at the end. In this case, the regulator. Having too small a line may cause some pressure drop due to restriction, especially at high flow. Fuel is not compressable like air is, pressure will be the same at all points (with low restriction).

 

[greathuskie]

well, if i remember science correctly, it is sort of like a garden hose, when the water comes out normal it just sorta spikes out the end with little pressure, but if you hold your thumb over half of the tip the pressure behind the wateer will go up much higher then normal, hence the reason i think he said that -8 or -10 will give you lower pressure

but with fuel i dont think it will matter because im not sure if enough fuel will flow through it at a given point and time to make a difference......maybe im way off too who knows

 

[92redman]

Somebody directed me to a site that gave instructions on building an AN- supply line. The guy flow tested the -06 setup and said it would supply enough volume for 1000cc injectors. Now that is just what the lines will support, you will need a high flow fuel pump to supply that much fuel.

 

[djsven]

Hi,

I ran -6an all the way around from fuel tank outlet back to fuel tank inlet. If you go with the -10an lines your pump will get overworked with bigger injectors, that need a certain higher pressure and the pump can only flow a certain amount of fuel at a specific pressure. To compensate the flow and hold the same higher pressure you will need to upgrade to a higher flowing fuel pump. That will at cost. I am looking to achieve 500whp with this setup that I have and maybe upgrade when I want to go higher.

Sven

 

[GYDTalon23]

Somebody directed me to a site that gave instructions on building an AN- supply line. The guy flow tested the -06 setup and said it would supply enough volume for 1000cc injectors. Now that is just what the lines will support, you will need a high flow fuel pump to supply that much fuel.

is this it?? this is what i am using to upgrade my fuel line system.

http://www.stevetek.com/R-FuelSys.html

 

[bastarddsm]

-10!! are you crazy? most all out race cars only use -8. -6 will get you far enough where fuel lines will be the least of your worries.

 

[psychlow]

A -6 fuel line is INSANELY larger than stock. The stock lines are what, around 3/16''? Not to mention removing the stock fuel filter/banjo bolt assembly.

 

[Kevin Jewer]

Stock lines are around 3/8ths. 2g return line is 1/4, 1g return is alledgedly 3/8ths. 3/8th is about the size of 6an. Thin wall aluminum 3/8th line like I run is a little bigger than the ID of rubber 8 an line. Remember that AN designations give you OD, not ID

If you go with the -10an lines your pump will get overworked with bigger injectors, that need a certain higher pressure and the pump can only flow a certain amount of fuel at a specific pressure.

Increasing line size does not require more flow. The motor still only consumes as much fuel as it needs. Again, once the line is filled, fuel flow will only be what the injectors use and what the regulator bypasses. The garden hose example doesnt apply either becauase this is a closed system.

 

[Blue92]

I used the stevetek "solution" on my car and it is great. According to them -6 will supply 1000cc injectors. That's a lot of fuel.

 

[terefic181]

Garden hose example:

With a larger fuel line are you not pushing a greater (mass/weight). Therefore decreasing the ability of the pump to push this mass and resulting in either decreased pressure or thrashing the pump, do to it's overwork?

I'm no engineer, and maybe one will step in, but I think filling the fuel line is one thing and the pumps ability to push against that greater mass of fuel is another.

 

[Blue92]

Well, lets take a walbro 255lph pump for example. It pumps 255 liters/hour. Lets break it down to cc/min for injector purposes. (255 l/h)*(1000 cc/l)*(1/60 h/min) = 4250 cc/min
Then divide by 4 injectors to get 1062.5 cc/min per injector. So basically a walbro 255lph pump can supply enough fuel for 1000cc injectors at full duty cycle.

With that said, the pump is pumping that much fuel constantly. As most of us do not use all that fuel, there is a considerable amount being returned. Thus if you have a fuel line setup like the -6 AN line, that is reported by Stevetek to support 1000cc/min injectors, the pump can keep up with the flow through the lines as it is within its flow range. Now I am unsure of the exact flow of the -6 AN lines, but if you use for example -10 AN and big enough injectors to devour a ton of fuel, then the Walbro 255lph pump will not be sufficient, thus causing low pressure/flow.

Obviously, you can't use more fuel than your pump can supply. The lines will fill and pressurize, and as long as your engine consumption doesn't outflow the pump you should be alright with your fuel pressure. Sorry for the book.

 

[terefic181]

I guess my point still is that pressure goes down because of the added mass having to be pushed in the line. I'm talking about pressure not volume. I think that a pump can push x amount of fuel at a specified pressure, but that pressure does go down when it has to push x plus an additional amount. There may be a very marginal difference between stock, -6, -8 lines. I don't know, but I do think the pressure goes down to some degree, the larger you get with lines.

The figures below were quoted to be from walbro for a 190LPH pump, I don't have the figures for a 255. As you can see, as the volume goes up the pressure goes down. At 190 LPH, the pump is only putting out 10-20 lbs of pressure. Using stock injectors your looking at what, 37lbs as a general rule. So using the the 40lb range on the chart the LPH goes down to 144. So it looks as if a 255 LPH pump is probably not going to be putting out 255LPH at a very substantial pressure.

Blue92, plug these figures in and see what you come up with.


Walbro 190LPH pump
Flowrate
PSI GPH LPH
0 55 208
10 52 197
20 48 182
30 43 163
40 38 144
50 33 125
60 29 110
70 24 91
80 18 68
90 9 34
100 0 0

 

[Kevin Jewer]

It doesnt matter how big the lines are. Your motor is using a certain amount of fuel and thats it. Lets say you are using 4 lbs/min of fuel. Is the motor going to consume more fuel just because you increased the feed line size? Not at all. Flow wont cange. Pressure wont change. Nothing will change. Except there will be lower restriction at higher flow rates with the larger lines. And that of course, is a good thing.

 

[Blue92]

terefic181
I see your point, but your are basing that on full consumption and possibly higher pressure. Like 95GSXracer said, you will should never use all the fuel that is being supplied to the engine.

Your data is a little wierd, I pulled this off a fuel pump website,"With a 12 volt power source, these pumps flow 190 ltr/hr at 0 psi, 155 ltr/hr at 40 psi." Those numbers look a little off to me, but I don't make pumps for a living. I also found that, "255 ltr/hr pump was born. These pumps flow 255 ltr/hr at 40 psi, and 285 ltr/hr at 0 psi." This was pulled off the same site.

Click on the Technical under fuel pumps to get to the right page. Tons of info here.

fuel pump info

So basically try to avoid pumping at a pressure out of the flow range that you need and you will get sufficient flow. The pump will still make the pressure in the line though, to answer your question.