Engine/Transmission (1998.5 - 2002) What is the fuel flow in a 3/8" line?

[RADdodge]

I have a question or two for any of you who have replaced all or part of your factory fuel lines with larger line (AN) along with the banjo bolts.



What was the volume of diesel fuel you calculated that would flow through the stock fuel system (3/8" line, banjo bolts, and bends) at 15psi? At 8psi? (or whatever nominal pressure you used)



I'd even be interested in a simple calculation for just the 3/8" line.



Someone must have already calculated this. I’d like to know myself before going to the trouble and expense of replacing my fuel lines.



Thanks in advance.

 

[Gary - K7GLD]

I'll take a shot - and guess you're REALLY wondering/asking if the expense and effort to install fancy fittings and lines in our fuel systems is really worth it... .



NO!



The VP44 has been shown to flow a MAXIMUM, at full load, of less than 50 GPH - including the amount returned/bypassed back to the tank - and I'll flat out GUARANTEE you that with the supplied lift pump operating properly, that's WAY less than the supplied pump and lines are completely capable of in stock form...



SURE, you WILL get more flow and pressure capability with fancy fittings and lines - but unless yer planning an all out drag or pulling machine, it's overkill - much like putting a 10 inch exhaust system on yer engine...



Yer engine can only CONSUME a certain amount of fuel, depending on load, regardless of fuel line size and fancy fittings...

 

[15w40]

I have looked into calculating the frictional losses in the fuel system. For a 3/8” pipe, running 8 psi, the flow velocity is 36 feet per second for water. Diesel fuel will be somewhat less than water and much less then water when cold. The real problem is not the flow in the straight pipe but the flow in the fittings. An AN -6 90* fitting is equivalent to about 3 feet of pipe. When you have 4 of them, that’s equivalent to 12 feet of pipe.



The stock banjo fittings that came with our trucks have got to be a lot worse. When you think about how the fuel flows into the banjo fitting at the input to the fuel filter, it goes something like this. Fuel is fed to an annular ring around the banjo bolt from a tube. The fuel is restricted at this point by the small dimension of the annular ring grove. Fuel then must turn 90* to enter one of the 4 drilled holes in the banjo bolt. The fuel then turns 90* again to flow out of the banjo bolt, threaded shaft. All of the direction changes in fuel flow will really hurt flow. I know that when measuring flow, laminar flow is desirable for maximum volume and turbulence will reduce flow. The banjo bolts are “Turbulence City”.

 

[juicedcummins]

Thats putting it in black and white 15/40.



It´s the pushers that are overkill if left with the stock lines to feed through.



All electric lift pumps fail so why burn out 2 at a time, when you can keep the 2. nd as a spare.

 

[Gary - K7GLD]

For any REALLY curious, all ya hafta do is disconnect the fuel line at the VP44, power up the LP, and see how long it takes to fill a 1 or 5 gallon container... That'll tell ya what the ACTUAL flow is - no guesswork... Wouldn't be much more work to provide the restriction of yer choice at the outlet, while monitoring pressure to simulate load, and do the same...



*I* already KNOW my stock LP all by itself will provide a MINIMUM of 12 psi WOT right at the INLET of the VP44 - all with those "horribly restrictive" 3/8 inch lines and nasty stock banjo fittings - so exactly WHAT do I potentially GAIN with fancier ($$$) stuff?



I saw exactly ZERO, ZIP, NADA change in supplied PSI at the VP44 when I upgraded to the Comp - even at WOT up 8% grades towing my buds 14,000+ 5th wheel when he blew the transmission on his Ford - so again, WHAT would *I* have gained with bigger, fancier fuel lines and fittings?



ZIP, ZERO, NADA! That's what!



The added pusher some of us install is NOT to provide MORE pressure to the VP44, but rather, to provide backup in case the stock LP fails or loses pressure, and for the doubters, when/if YOUR LP dies, all the fancy lines and banjo fittings in the world won't protect yer VP44, will they!



Fact is, *I* have a brand new Carter 4600 sitting at my elbow as this is typed, experimenting with a moderate bypass system and overall PSI reducer to LOWER my average fuel pressure because I think its TOO high for comfort with my added pusher as it is currently installed - maybe I should just install a few more banjo fittings instead...



Hey - spend yer dough - help the economy - but it's not likely fancy fuel lines and banjp bolts will in the slightest safeguard yer LP or VP44 - but man, will you be PROUD when ya lift the hood and show yer buds what ya did...

 

[HVAC]

Gary

QUOTE:



"The VP44 has been shown to flow a MAXIMUM, at full load, of less than 50 GPH -including the amount returned/bypassed back to the tank - and I'll flat out GUARANTEE you that with the supplied lift pump operating properly, that's WAY less than the supplied pump and lines are completely capable of in stock form... "



Whom have you quoted here? What horsepower level is this figure commensurate with?

 

[J.R. Adkins]

Gary,



Put some REALLY LARGE injectors in and see what your FP is. Yep thats right 0. With a injector that flows a extreme amount of fuel you will see 0 psi with the stock set up.







J. R.

 

[Vaughn MacKenzie]

Gary's probably got some crud in his gauge line, I'll bet it reads 12psi even when he's shut down

 

[JR2]

With RV275 injectors and a Power Edge (the first fueling box edge made) I would see "0" psi at WOT. With DD3's and and edge drag comp and fancy fuel lines (stock lift pump moved to the rear) I see a minimum of 8 psi at WOT. It may not be worth it to you Gary, but to some other guys it is a worth wile investment.



Remember you don't have to use $tainless $teel lines and Aeroquip fittings. You can do the same thing with rubber hose and some brass fittings (with adapters).



Its also not just the banjos and 3/8's line, the next time you change your fuel filter pull the line that runs between the lift pump and filter... its tiny and very very restrictive.





JR2

 

[Gary - K7GLD]

Nowell - do a search on this website on lift pumps and VP44 - look for the input on flow testing done in connection with Bill Kondolay's shop - all the numbers are there...



J. R. and a couple of others say:



"Put some REALLY LARGE injectors in and see what your FP is. Yep thats right 0. With a injector that flows a extreme amount of fuel you will see 0 psi with the stock set up. "



YOU guys must have some serious reading disorders - or purposely overlooked THIS part of my qualifying statement:





"SURE, you WILL get more flow and pressure capability with fancy fittings and lines - but unless yer planning an all out drag or pulling machine, it's overkill - much like putting a 10 inch exhaust system on yer engine... "



I'm not too bright (my wife keeps me pretty up to date on THAT subject), but even *I* am smart enough to realize that serious engine upgrades will also increase fuel demands - honest!

 

[J.R. Adkins]

Gary,



Yes i saw that portion of the post. I have seen supermentals pull the stock system down. These are not all out injectors. Just up from the threes right?





J. R.

 

[Gary - K7GLD]

FOR Nowell and others - here's a pointer on fuel flow rates and the VP44:



http://216.235.147.117/forums/showthread.php?s=&threadid=11672&perpage=15&highlight=VP44&pagenumber



Another good read, is the thread "the ultimate VP44 thread" also on this board... Read those 2 threads, and you'll probably learn all you really will need to know about fuel flow rates and the workings of the VP44 - though there ARE some other great threads on the subject as well...

 

[John Berger]

The pumps, lines and whatnot thread is one of the more informative threads I've ever read as a TDR member. When it comes to discussions on fuel pressure, lift pumps and BOMB's, this thread is rarely, if ever referred to. Glad to see it has not been completely forgotten.

 

[Mark_Kendrick]

Well, after reading most of this... .



I have very big injectors and a stock lift pump. I have eliminated the banjos though.



with a PE Comp and DD3s I saw big changes in fp at wot. on the order of 13-14 down to 10-11.



when I axed the banjo bolts I gained 1psi of constant pressure and WOT never dropped more than 2psi.



My FP sits around 10-11 most of the time right now because I have a lift pump with a failing overflow valve. volume is still more than sufficient but max pressure is diminished and I still see about 1psi drop at WOT.



I have been running the same lift pump since 35k. I am now at 54k. The first one went bad under warranty.



SO... yes the factory pump is sufficient but the factory lines seem to be a big limiting factor.



the lift pump that we use is the same on pusher buses and RVs even up to an 8. 3L. The difference is they use much larger supply lines and fittings. The pump itself is identical the inlets and outlets are more similar to the carter P-4601HP that folks like to use as a replacement.



FWIW,

Mark

 

[Gary - K7GLD]

I haven't seen the inlet/outlet sizes of the stock LP on our trucks - and I'm talking about the actual PORT out of the pump chamber, not whatever fitting sizes they come with - but the actual port sizes on the Carter 4600 commonly used in pusher apps, looks like THIS:



#ad






NOW, if THAT is also typical of the one used by DC in the stock LP location, and we accept that the total system flow will be greatly influenced by the SMALLEST restriction in the system, well...



Keep in mind, the above is a 8 psi, 100 gph pump, and the threaded IN/OUT fitting seen is a 3/8 pipe thread...



Some are installing larger lines and banjos - but the ABOVE is what the fuel MUST pass thru to get to the VP44 - and has anyone seen what the actual inlet port size is on the VP44, regardless of fitting size? is it any bigger than what's seen in the pump above?

 

[Mark_Kendrick]

The one used in the DC application uses the Banjo fittins and they are nowhere near that big or flow that well.



-6 AN seems to flow enough to atleast meet the demands of the vp44 in the VERY high HP applications.



-6 is eqivalent to 5/16" fuel hose.



The -6 90s flow a heck of a lot more than any banjo ever thought of for the simple reason that the fuel doesn't change directions but once and that's at 90* not 180* and does it through a smooth radius.



Later,

Mark

 

[JR2]

Gary,

Sure I read your post... . and I said my FP got hammerd with RV275 injectors in... these are not shower heads. Go back and have a look at the signature of the guy who started this thread. He has DD3's and I would guess he was asking about flow rates through 3/8 fuel line because he does not think its big enough. I think your guess about him adding differnt bajos was way off base.



Let me add that if it was me, I would tear the stock fuel system out of a bone stock truck and replace it just on the fact that the stock system is full of restrictions and flow disruptions that can not be good. I remember a post by Ted J. that said he had seen a performance gain on the track by redoing the fuel system... . people guessed that is was because he got rid of the entrained air in the fuel.



John

 

[HVAC]

Entrained Vapor

Now there's another angle, one that I can't help but think about. The idea is that a system under negative/or low pressure will develop some vapor within the delivery system. Vapor will disrupt the function of the injector. It compresses and delays and/or disrupts the timing and/or spray pattern of the injector. This is potentially another reason to streamline the fuel supply system. I noticed a gain on the dyno after revamping my fuel supply system. My revamp in late 2000 included relocating the pump next to the tank. That and larger fuel lines.



The actual "fuel preporator" is used on OTR long haul trucks. They are documenting an improvement in mileage. It's small but when multiplied by a million it becomes formidable. The site is preporator.com I think.

 

[Gary - K7GLD]

"I would tear the stock fuel system out of a bone stock truck and replace it just on the fact that the stock system is full of restrictions and flow disruptions that can not be good. "



YUP - and one of the biggest restriction STILL remaining, even AFTER your installation of bigger lines and fittings, will be the LP itself, just like in the pictire I posted further above...



I've given my reasoning, provided pointers, and supplied pictures - not much else I can provide to support my line of debate on the subject...



I think we CAN agree, as with many other things in life, "bigger IS better", and for sure, larger lines and fittings won't HURT!

 

[JR2]

Gary,

You hit the nail on the head... one of the biggest restrictions is still remaining..... Yes it is, but removing every restriction you can is a good thing that helps. If I knew of a better pump with bigger inlets and outlets that would last as long as a stock pump I would be running it. If I knew of a better filter system (that included a heater and WIF sensor) I would run it. As it is now my system is adequate for my HP. I am going to try a carter HP4061 (the high press version of the stock pump) and see if it gives me any beter press at WOT and if it effects my mileage.



John