Plumbing fuel system

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DriveWFO · #1 Post by **DriveWFO** » Sun Jan 29, 2006 10:20 pm

I'm going to be installing a new mechanical fuel pump and need to run new fuel line from the tank. I'm going to run 8AN braided line from the tank to the fuel pump. Do I need a pump with 1/2" fittings? Most pumps I've seen have 3/8" fittings, so I thought that would defeat the purpose of running 8AN line???

Also, should I run a return line from the pump and use a dead-head regulator or should I plug the return line fitting in the pump and use a return-style regulator?

#2 Post by **John_Heard** » Mon Jan 30, 2006 12:42 pm

Well a 1/2 Line with 3/8 fittings should out flow a 3/8 line with 3/8 fittings, but of course a 1/2 line with 1/2 fittings would flow even more.

Typically most peopole don't use return line setups with a mechanical pump, they just dead head it at the regulator. I guess I have never seen a mechanical with a bypass like you're talking about. Is this one of those new style mechanical pumps or something?

DriveWFO · #3 Post by **DriveWFO** » Mon Jan 30, 2006 1:11 pm

Beyond wrote:Well a 1/2 Line with 3/8 fittings should out flow a 3/8 line with 3/8 fittings, but of course a 1/2 line with 1/2 fittings would flow even more.

Typically most peopole don't use return line setups with a mechanical pump, they just dead head it at the regulator. I guess I have never seen a mechanical with a bypass like you're talking about. Is this one of those new style mechanical pumps or something?

I got this information from http://www.centuryperformance.com/fuel.asp. I'd rather not have to run a return line.

I'd like to run two regulators in parallel so I can run more psi for the fuel solenoid.

ytnova · #4 Post by **ytnova** » Mon Jan 30, 2006 3:52 pm

I would use a return for the fuel selenoid regulator, probably by just using one of the other ports in that regulator. You will also probably have to run a fixed orifice in that line, nothing big, just something to bleed a little air and warm fuel back to the tank. My thought is two fold, one being my past experence with electric pumps (I know yours is mechanical) on a nitrous only fuel system, the pressure seems to creep up slightly before I activate the kit making the kit rich and soft on the bottom end and second, I would want to make sure there is a full column of fuel in front of the selenoid, so there is no delay in fuel delivery when the kit is flowing, this is even more important the bigger the tune-up is.

DriveWFO · #5 Post by **DriveWFO** » Mon Jan 30, 2006 3:57 pm

ytnova wrote:You will also probably have to run a fixed orifice in that line, nothing big, just something to bleed a little air and warm fuel back to the tank.

What is that exactly?

#6 Post by **John_Heard** » Mon Jan 30, 2006 7:32 pm

The way most people make these is to use a #3 AN male fitting and grind the tip off of it. If I remember right you have to drill it out a little too. Then a Nitrous style flare jet will insert right into the fitting. You want a pretty small jet, like .025 or smaller. Aeromotive has told me that even a .010 orifice is large enough to bleed air out of the system in their testing. If you don't want to make your own, contact http://www.nitroussupply.com or http://www.koehlerinjection.com and they can make one of these for you quickly.

Really on a mechanical pump setup that isn't going to be generating a lot of pressure at the pump, at the worst it will creep up to the pump pressure which will be something like 7 or 8 psi I'm guessing, which won't be that big of a deal as you're going to be probably be using a 5-6psi setting at the nitrous regulator. Large electric pumps on the other hand can cause pressure creep far in excess of a low pressure nitrous tune up and would likely be more of an tuning issue.

Back to the pump setup, I don't think on a mechanical pump setup you need to worry about a bypass like the schematics you linked to. Those are more geared to high volume electric pump setups. For now a good hi volume mechanical pump and the two dead headed regulators should be adequate.

DriveWFO · #7 Post by **DriveWFO** » Mon Jan 30, 2006 10:19 pm

Ok, so far:

1) 8AN from tank (modifying sending unit with 1/2" line)
2) into 8AN inline filter (where should this ideally be placed?)
3) into more 8AN line
4) into mechanical pump
5) into 6AN line
6) into Y-block
7) into two (2) 6AN lines
8) one 6AN line into regulator "A", one 6AN line into regulator "B"
9) 6AN out of regulator "A" to carb (with pressure gauge in 1/8" port)
10 6AN out of regulator "B" to fuel solenoid (attach Hobbs switch to this as well as external fuel pressure gauge to mount on cowl)

How's that sound?

#8 Post by **John_Heard** » Mon Jan 30, 2006 10:38 pm

Ought to work fine for now. A complete second fuel system for just the nitrous (small tank in the front) would be nice and be a step up from your described system, but probably overkill at this time. You can always add that later when you want to step up again.

DriveWFO · #9 Post by **DriveWFO** » Tue Jan 31, 2006 9:29 am

Beyond wrote:Ought to work fine for now. A complete second fuel system for just the nitrous (small tank in the front) would be nice and be a step up from your described system, but probably overkill at this time. You can always add that later when you want to step up again.

John, thanks for your feedback!

ytnova · #10 Post by **ytnova** » Tue Jan 31, 2006 1:48 pm

On step five and 6, you might want to run a #8 instead of a #6 from the pump feeding the y block.

DriveWFO · #11 Post by **DriveWFO** » Tue Jan 31, 2006 10:48 pm

[quote="ytnova"]On step five and 6, you might want to run a #8 instead of a #6 from the pump feeding the y block.[/quote

Any reason for doing that?

jones_performance · #12 Post by **jones_performance** » Wed Feb 01, 2006 12:19 am

a numer 8 will better feed those 2 number 6's

ytnova · #13 Post by **ytnova** » Wed Feb 01, 2006 9:22 am

That is what I was thinking.

#14 Post by **John_Heard** » Thu Feb 02, 2006 8:13 am

Dave here's a picture of that fuel bleed setup I found over at wilson manifolds

ytnova · #15 Post by **ytnova** » Thu Feb 02, 2006 9:35 am

I have done it two different ways, originally I just welded a #3 fitting shut, then drilled it. Thae second time I just used spare nos #3 plate fittings and just used nos jets for the disired size. What do you think if you just ran a return off the nitrous regulator and teed it into the pump inlet?

Plumbing fuel system

Plumbing fuel system

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