Engine/Transmission (1998.5 - 2002) -8 fittings compared to stock banjo's

[JPLB22]

I am not very educated in pressure and flow, so I hope someone can help me out !



I would like to know the difference in flow at the same pressure, between the stock banjos, and -8 fittings with 3/8 fuel line ?? It doesn't need to be exact, just a close estimate.



I am wondering because, I have replaced all banjos and fuel line with -8 fittings and 3/8's line. Now before the switch my personal limit on fuel pressure was nothing lower than 10 psi for freeway cruising. But now that I have larger fittings, the same 10 psi means more flow, right ?? So I'm just wondering what my safe zone is on fuel pressure now ?? I installed a brand new LP when I changed the fittings and line, but it must be a turd right out of the box. My pressure is already starting to drop after about 9000 miles. I change my fuel filter every 7500 and use addative every tank. So I will be swapping another LP long before I planned to , I just need a good idea of what my new limit for low pressure might be.



Thanks



Jeff

 

[Ncostello]

In theory... the bigger fittings at the same pressure will flow more. In reality the VP44 will only flow a certain amount of fuel. You cannot force any more through it and adding bigger lines does not instantly mean a large increase in flow.



Your providing the available volume if its needed. Your ensuring the VP44 doesn't pull small lines dry. Will this help the lift pump live longer or do its job better too? For me the jury's out on that (and have been for a year). If the Carter was a normal pump... then plenty of clean fuel would be good for it. BUT... since this particular fuel pump has a very unpredictable life span... there is no telling.



To me 12 psi is low. I want 15 psi and I want it pretty much all the time. Simple... yet so very hard to do with a stock lift pump. Chrysler figures 8 psi is a good minimum pressure. But to me thats just saying someone is willing to accept the fact that the pump is on its way out and there is some arbitrary cut-off point to replace it. The thing is on a death spiral and using some minimum cut-off just minimizes their cost to replace.

 

[jjohn]

Hey Jeff

I did the -6An 3/8" line first then a added pusher pump. Before the the pusher I saw a gain of 5psi WOT. This due to the unrestricted flow supplying demand without sucking down the pressure in my mind.



You mentioned using -8AN and 3/8th. -8AN accepts 1/2 fuel line unless there is an angle out there I havn't seen yet? Just curious.

 

[BJMarshall]

-8 is 7/16 ID and -6 is 11/32 ID

 

[Ncostello]

Of all the AN sizes I've encountered... -6 is 6/16" or 3/8... and -8 is 8/16ths or 1/2". I was told its always the number of 16ths of an inch.

 

[BJMarshall]

You are right. It is supposed to be in 16th's. Nearly all of the hose sold that is not FAA-PMA approved are nominal dimensions. Any hard line you buy will be the right ID, but most all hose is a little shy of the proper dimensions unless you buy actual aircraft parts.

 

[JPLB22]

I have the Wildcat Max Flow Kit. It came with 3 compression fittings 90* elbow, one straight hose barb fitting, and one strait compression fitting. It also came with enough S. S. braided line to hook everything up. But I have since replaced the S. S. braided line with rubber fuel hose ( 3/8 ). I'm still using the Wildcat fittings, but instead of using the brass ferring and compression nut, I just slid the rubber hose over the end of the fitting and clamped it on. It is a lot easier to work with !! I thought the Wildcat fittings were -8, but I may be wrong ??



Jeff