Fuel lines

pelky350 · May 25, 2018

my buddy with a Cummins keeps going on about how a "big line kit" is gonna make him soo much power. My question is, is he even right about adding any power? He says by replacing the stock lines from the tank to the lift pump with a larger diameter line it will make fuel flow better and therefore he can get more fuel in his motor or something. I plan for now temporarily replacing my fuel lines and only running my front tank till I replace my rear tank and i belive I have possible air intrusion in the system and I want to know for sure by replacing the lines. Can I use just fuel rated rubber lines from parts store for this? Or is there a better solution? Should I get larger diameter fees line? Or what size are they now? Return and feed

gandalf · May 25, 2018

I'm not sure I see how just a larger diameter fuel line would increase your power. You have a choke point at either end which will allow only a set amount of fuel through at any given pressure. You have the pickup line and associated metal section at the tank end, and you have the fuel filter and associated metal line at the engine end. Both of those will restrict and limit fuel flow at any given pressure. Now, perhaps if you increased the pressure...

Having said that, let me tell you about a boat, "Uncle's UFO" (you can google that name). Uncle Andrew was running a Mack E9, getting about 1000 hp from all I'm told. He claimed to get an increase in power when he increased his fuel line to 1 inch. I have no idea what else he might have changed along with the fuel line.

snicklas · May 25, 2018

It will only increase power if it comes with a sticker.......

A bit of apples to oranges, but on the later IH Cub Cadet garden tractors, the fuel line from the tank to the carburetor is a 3/8 fuel line,and most of us put an inline filter in it. IH uses the same size line on the 8 hp engine as they do the 16 hp engine. I would think if line size mattered in power the 16 would have al larger line than the 8.

Now what is different is the carburetor at the end of the line... so the carburetor, or in the case of the diesels, the IP is going to control the fuel flow... now if he was going from a 1/4 to a 1/2 in line, for example, the power gain would be from removing a restriction, but going from 1/2 to one inch shouldn’t make a difference.....

Think about how many times we see “I replaced my fuel filter now it feels like a new truck”, that’s removing a restriction, not making the line bigger.....

I bet this buddy has a huge C sticker that takes up almost the whole back glass, and tow mirrors flipped up.......

79jasper · May 25, 2018

They do have a choke point with the stock lines near the engine.
So depending on if/what other mods he has, he could see a potential increase in power.
I don't know why you're worried anyways, not like a idi is going to out tow/race even a lightly modded cummins anyways. Lol

Sent from my SM-G892A using Tapatalk

franklin2 · May 25, 2018

I personally would not run rubber lines. They do not last that well, and just do not look that good. You can run steel lines from the parts stores easily. The copper nickel lines are super easy to run, almost like running wiring it bends so easy and does not rust. I did a truck a while back and if I remember, it did not take me but two long lines to get to the switching valve, with a coupler at the engine crossmember where it crosses from the driver's side to the pass side. They have these lines in the store already made up with the flared ends on them. And they sell the couplers also. They bend easily with your hand, just make sure to put some radius to the bend, not too sharp. If you want a sharper bend, they sell benders cheap also.

pelky350 · May 25, 2018

@snicklas C sticker yes, tow mirrors also yes lol what's the best option on re doin girl my fuel lines? I have a huge tank I will instal later on but for now I want to just run off my front tank. And want to eliminate the selectors valve. I have air intrusion I belive and want to replace my old lines. It's probably at a connection point Im guessing. Constant haze while driving and acts off sometimes. It would be pre lift pump to have it while driving since rest of system isn't under pressure it wouldn't affect driving just starting. It's very minimal but I think it's causing my temperamental driving issues with power up and down differences every day. My entire fuel system is basically new besides tanks and lines. Parts from r and d and typ4 so I'm assuming they are all good

icanfixall · May 26, 2018

Not a chance of this working ever... Our engines sent about 80% of the fuel back to the tanks thru the return lines. Remember this fuel is used for lubing and cooling the injection pump and the injectors in the heads.

Thewespaul · May 26, 2018

The db4 hybrid pumps for our trucks require larger fuel lines...

Macrobb · May 26, 2018

The way you know if you need bigger lines or less restriction:
With your pump of choice, measure the pressure after the lift pump. If it droops under load, you need a better setup.
This could be a bigger pump, possibly bigger lines etc.
It really depends on whether your lines are pressurized or suction(like in our case). You will be able to get more flow out of a 3/8 line with a pump at, in, or near the tank than one sucking from the engine bay...

At our levels of flow, well, it's not something to worry about(as long as the lines aren't clogged). If a stock mechanical lift pump can supply a RD2-110 at WOT and maintain 3.5 PSI(4.5 at idle)... that's more than good enough - as long as the pressure is positive post-filter at all times, and the total pressure variation(idle to wot) is minimized, everything will be fine.

Here's a decent rundown: http://ipgparts.com/blog/fuel-line-sizing-what-size-do-i-need/

Another page with useful info: https://www.sbmar.com/articles/understanding-fuel-line-sizes-vs-fuel-supply-restriction/

pelky350 · May 28, 2018

Okay so I don't need bigger lines, what kind of lines should I run to My front tank for now until I complete my rear tank set up I'm gonna finish building, I plan on running a single large tank later on, got the tank but need a way to make a fuel send for it and straps of some sort

gerlbaum · May 30, 2018

I used 3/8 brake line. It's like $6 for a 6 foot length at Autozone/O'Reilly etc. I cut it with a pipe cutter for square ends. I used a harbor freight tube bender to make the bends and tried using as little fittings as possible. I got fancy and used an compression fittings but you could use hardware store brass fittings. A dab of goop ensures they won't come loose (or apart lol) ever. Then some of the rubber lined p clamps sandwich 2 together and they make a perfect vibration clamp for the to and return line. $50 in total and won't ever fall apart like rubber or rubber ss lines.

pelky350 said:
Okay so I don't need bigger lines, what kind of lines should I run to My front tank for now until I complete my rear tank set up I'm gonna finish building, I plan on running a single large tank later on, got the tank but need a way to make a fuel send for it and straps of some sort

gerlbaum · May 30, 2018

FYI insulated p clamp. Put the ends with the holes together and 1 bolt will hold both the fuel and return line.

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Hagan · May 31, 2018

I hate using steel brake line as fuel line. It's terrible to bend where you need it because its too strong. I used aluminum fuel line on 2 of my Cummins powered Ford trucks. On my crew cab I used a 38 gallon tank and used an electric pump to pump out the 17 gallons in the front tank to the back tank. I used 3/8" feed and 5/16" return. I flared the ends and used a hose clamp.

https://www.summitracing.com/parts/sum-g2538

genscripter · May 31, 2018

+1 on the aluminum lines. Much easier to deal with.

Also, increasing the fuel supply radius won't increase HP. The amount of fuel delivered into the IP is pretty minuscule even for the largest of IDI IP's. Like the previous commenter said, if the fuel pressure dips, them maybe a radius upgrade is necessary, but that's really unlikely.

I'd say the only thing that a larger fuel-line radius might do is provide more lubricity and cooling for the injectors and IP. The larger radius would provide slightly cooler fluid for the injection system to pull from. That doesn't equate to greater HP, but maybe it would extend the life of your injection components. But I'm sure the temperature delta is minor from 3/8" diameter hose to something larger.

gerlbaum · May 31, 2018

Lol that is true about the steel lines. It put my harbor freight $17 bender on it's knees. I was 50/50 on steel vs aluminum because I was worried about kinking the aluminum too easily. I actually considered 3/8 PEX. It's not rated for diesel and only rated to 180 degrees but a lot of the bio fuel guys run it for several years with no issues. Just not good for an engine bay or near hot exhaust parts.

I think the Cummins p pump guys move to 1/2 lines when they are really pushing fuel out that pump. I think the db4 150 cc pump doesn't even require larger lines and a p pump Cummins can push MUCH more fuel than 150 cc pump.

Hagan said:
I hate using steel brake line as fuel line. It's terrible to bend where you need it because its too strong. I used aluminum fuel line on 2 of my Cummins powered Ford trucks. On my crew cab I used a 38 gallon tank and used an electric pump to pump out the 17 gallons in the front tank to the back tank. I used 3/8" feed and 5/16" return. I flared the ends and used a hose clamp.

https://www.summitracing.com/parts/sum-g2538

Fuel lines

pelky350

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gandalf

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snicklas

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79jasper

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franklin2

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pelky350

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icanfixall

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Thewespaul

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Macrobb

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pelky350

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gerlbaum

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Hagan

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genscripter

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gerlbaum

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