Hi!

Im trying to get my head around understanding liquid under pressure, and how it is with resistance, size of fuel lines etc...

I have bought an upgraded fuel pump, and on banzai racing site they say you must upgrade stock feed and return lines.... I meassured the stock lines and they are inner diametre 5mm(0.5cm).
Then i meassured the walboro pump outlet... its same as stock, 5mm(0,5cm). I then meassured the fuel rack pipes.... same, 5mm(0,5cm)....
In my head, its the smallest passage that will be the biggest obstacle.. but that is the walboro pump outlet.. and the same from there to the engine.. so WHY do i then have to upgrade the stock feed and returnpipes, if its the same all the way? In my head there will be no varible pressure difference or obstacles after the pump outlet anyways, until it hits the FPR? So why upgrade the feed and return? Is it just a universal notification for cars with smaller feed and returns than the FD?

Thanks for putting it in easy form for me if you answer

cheers, and enjoy your weekend

 

We do not say that you must, we say you should. http://www.banzai-racing.com/store/walbro_pumps.html

This pump is meant for modified vehicles with over 500HP. Vehicles in which this pump is to be installed in should have upgraded supply and return fuel lines, upgraded pump wiring to support the increased amp draw, and upgrades to the vehicles fuel pressure regulator.

You can run it on the stock lines, but expect a huge amount of pressure at the pump. This could cause premature failure. It is similar to running dual pumps, it is a lot of fuel to squeeze through a 5mm hole.

 

Hi! Thanks for the reply. I see you are absolutely right about that regarding the text on the page. I blame my memory, age and english not being my main language

BUT, still, my question still hangs, if the outlet of the pump is 5mm, how can it matter what dimension the pipes are after the pump outlet as long as its the same as the outlet of the pump? In my head, if the pump outlet is 5mm and the rest was 4, you would have increased velocity on the fuel, and more resistance, just like a river speeding up when narrowing the river withness..
If its 5mm all the way, it shouldnt matter.


please sort out my logic, halp

 

I've been running something similar to this on my car for about a year. If I'm running a stock tune, would you still recommend that I upgrade the fuel lines?

 

think of it like this guys, You know thos super think coffee straws.. trying blowing into it hard and see how long it takes you to get all the air out your lungs/mouth then keep doing it.. its hard for you just imagine how the fuel pump is while its constantly doing that. Thats how i think about it atleast

 

If the pump outlet matches your fuel lines, it's fine. It's only when your pump outlet is larger do you really need to worry about upgrading your lines. And even then, only if your volume of flow at your peak pressure dictates it.

 

The stock hardlines become a restriction around 500 rwhp. Before that there is not much benefit upgrading them. Sounds to me like you don't need that pump. Put in a supra pump and be done with it.

 

While you are right that the most restrictive size remains 5 mm, resistance is a summation so a longer line of a dia will be more restrictive than a larger dia. Line of same length, likewise a bend at 6 mm will be less restrictive than a 5 mm dia bend. Same principle as wire and resistance.

 

no point replacing the lines if the rails also only have a max diameter of 5mm.

i'm assuming this is for the newer walbro 400 pump? otherwise waste of time upgrading the lines. even with the walbro 400 i haven't seen any issues running it on the stock diameter lines with one of my customers who has been running it for a while now at 500whp.

 

Hmm good info.

 

I think it was hinted at above but i believe this to be absolutely true.... any bends or twists will increase restriction... so the same size line with a few bends will have much more restriction... also the length of line. i believe (not 100%) that the side of the pipe/line may cause more restriction at higher speeds/psi. The cohesive properties of liquids will make the fuel in contact with the outer edges want to stay there.... So in effect the faster the fuel goes the smaller the tube gets for the fuel that is actually moving at the fastest speed. Also you never really want smaller return line that feed just as a safety... if they are the same you should be ok... otherwise the return could cause a pressure greater than the feed and make a pressure spike.... basically if you can afford to upgrade do it. anything that puts less strain on the fuel pump is good! This is one thing on a rotary that you don't want to fail...I have a 255 lph and 3/8 feed /return... will be upgrading pump to aero 340 or walbro 400 probably next year and use probably -6 or -8 an and push loc or ss braided lines..