inline fuel pump

[Ken(Bone Breakin Chevy)]

is it hard to change to this? im pretty sure mine is on its way out, id rather get an inline so that i dont have to worry about it next time. or would i be better off replacing the in tank one. what happens to the in tank one? help would be appreciated.
-ken-

[Injuneer]

If you mean can you just add an inline pump to "replace" a failing/failed in-tank pump.... NO. You need a healthy in-tank pump before you can add an inline pump in series. The inline pump will not "pull" efficiently through a dead or dieing in-tank pump. You could go to an "outboard" main pump, but that would require a sump to be added to your tank.

[N20LT4Bird]

I have been thinking about running an inline pump to bump the nitrous up to a 175 shot. DO I need to do this and if so, can anyone recommend a good pump? How much $$? Would I wire it so that it is only on when the nitrous is armed?

[Ken(Bone Breakin Chevy)]

good question, and an idea at the same time, im not to familiar with this, i didnt know i could run both actually, but if you could, i dont see why you couldnt have a switch right next to your nitrous switch

[KnightFire]

Originally posted by N20LT4Bird
I have been thinking about running an inline pump to bump the nitrous up to a 175 shot. DO I need to do this and if so, can anyone recommend a good pump? How much $$? Would I wire it so that it is only on when the nitrous is armed?

Are you looking to create a stand alone fuel system, just for the N2O? Or just something that give a shove to the current fuel system?



KnightFire

[Injuneer]

If you install an inline pump, it has to run all the time. You don't want the in-tank pump pushing through the inline pump.... it just over works the in-tank pump, reducing flow. You wire the inline pump through a relay, and take the relay activation signal for the inline pump off of the gray wire in the stock fuel pump harness. That way they both go on and off at the same time.

There is no problem running it that way. The stock FPR can handle the extra flow and control the pressure. I ran my NOS inline pump for 5 years.

Whether you want an inline pump sort of depends on the type of N2O system you are running. For a dry system like the NOS 5176, you need 85-90psi when you spray. The best way to do that is an inline pump. For a wet system, if you are going to 175HP, you could use an inline pump... or you could just replace the in-tank pump with a larger one.

I run two pumps, but they are in "parallel".... one in the normal in-tank position, and another taking suction off a sump added at the rear of the tank. They both pump into the branches of an NOS "Y" fitting before the fuel filter. Actually, you don't need a full "sump"... you can just weld a -10AN fitting to the bottom/rear of the tank, and put an internal screen and stilling well inside the tank. I don't think it cost very much to do it.... I can't remember though. With parallel pumps, you can run NA on the in-tank pump, and only run the second pump when the nitrous system is "armed".

[N20LT4Bird]

Interesting....a few more questions:

What is the advantage to the parallel pumps over running the pumps in series and having them on all the time?

Also, with the 175 shot, on my motor, do you think the diameter of the stock fuel lines will be restrictive? At what point did you upgrade your fuel lines??

[Injuneer]

My fuel lines are -6AN, which is essentially the same size as the stock supply line, and slightly larger than the stock return line. The fuel system is good for 1,000flywheelHP.

The only thing I have changed is to "split" the supply flow at the back of the rails, to feed them in parallel, and take the return off the diagonal crossover pipe. That gives you a larger flow capacity on the fuel rails, and minimizes the fuel pressure differences from injector to injector. In a stock setup, the entire flow of the fuel pump flows in the back of the passenger side fuel rail, and then each injector uses what it wants.... so each injector sees a slightly lower fuel pressure..... from #8 to #6 to #4....... to #1 to #3.... to the end at the fuel pressure regulator. The inside diameter of the stock rails is large enough to make this pressure difference small for a stock fuel demand, but once you go over 500HP (my estimate) you might start to see pressure differences from injector to injector that will affect your tuning. So you "split" the rails to reduce the flow volume through each rail and minimize the pressure loss.

The "series" vs. "parallel" comes down to whether you need "high" pressure, and what the "curve" (flow vs. oressure) for your fuel pump looks like. With the NOS 5176 kit, they want 90psi. With all pumps, there is a flow curve, that will show it will flow a huge amount with no pressure in the system, and very little flow at real high pressures. Some pumps won't even flow at the real high pressures. So for a high pressure situation, you either get a new pump with high flow at high pressure, or you use the stock flow to feed an inline pump. Doing that basically "adds" the two pump curves together, so now you have a system that can get high flow at high pressure.

For an NA setup, you don't need these high pressures.... stock is 43.5 (3bar) and a lot of high end setups run at 4bar (58psi). And if you are running a wet N2O system, you can jet it for virtually any fuel pressure, so there is no need for "high" pressure. In these cases you want "high" flow at "medium" pressure. That's when you go to a single large pump, or two medium sized pumps in parallel. If you have the pumps in parallel, and they are big enough, you only need the 2nd pump for nitrous (or blower high boost... whatever) so you only run it when you have to.

Here's a site that has flow vs. pressure data for a few popular pumps:

http://www.fwdmopar.com/sites/dennis/fuelpumpinfo.html

[N20LT4Bird]

Thanks.