Engine/Transmission (1998.5 - 2002) Banjo Bolt and Fitting Differences

[Ncostello]

I haven't played around with fuel systems since I moved my lift pump and installed Stanadyne FM100 filters. I got curious again and want to experiment some more so here goes. I found a 2002 filter canister to study and compare to my 1999 canister (which I no longer use). Nothing big on that... but I did notice some strange differences in the banjo fittings used on the 2002 canister... more specifically those two banjo fittings between the lift pump and the filter on a 2002.



The pictures kinda tell the story. Its hard to imagine that all the fuel supplied to the mighty cummins ISB, and likewise the vulnerable VP44, comes through 4 small holes in a banjo bolt. But Cummins engineers believed it sufficient so OK. Whats more disturbing is the fact that in the previously mentioned fittings on a 2002 setup... the fuel has to go through the banjo fitting hose barb neck... which has an inner diameter equal to only one hole drilled in the banjo bolt. Thus aftermarket high flow bolts might dramatically increase flow rates (4 larger holes) but the fuel must still pass through the same fitting necks using that one small hole. You can see in the photos that the fitting hole itself is a very restrictive part of the total system. Maybe thats why bolts themselves do not improve much. The fittings are more restrictive than the bolts at least on the 02.



Perhaps Cummins thought the fitting necks being straight would be OK while the bolts (which make the fuel turn 90) needed the extra 3 holes due to the restriction created when changing directions. I'm just guessing more or less. But its nice to see whats really under the hood. They really skimped on this stuff. And not all ISB's got equal treatment. 98. 5 and 99's seem slightly better overall when looking at the fittings. Cummins couldn't have payed a whole lot of attention when specing the fittings. They all seem to be different sized in some way or another. I believe they should have been more consistent. If one size is sufficient for an engine... how could a smaller size be OK for the same engine? (by size I mean the ID of the inlet ports or holes to the round fittings themselves). Oh well... food for thought. Nothing new but perhaps some motivation for owners to do something better like get rid of all those fittings. I was just amazed at the diameter of this one point in the system. Looks like the diameter of the fuel line on my 5HP lawn mower.



The photos are plenty bright if your screen settings are normal. And I got the high flow bolts from Wild Cat Diesel. They look and feel very high quality. Threads are perfect. And holes obviously large.



02 fitting and aftermarket high flow bolt



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High flow versus stock bolt



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02 fitting left (LP outlet), 99 fitting right (LP inlet)



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[jungledave]

Just think about the tiny, tiny little holes that are in an injector that feed that mighty cummins.

 

[Ncostello]

I've thought about those too. And they operate at pressures above 15,000psi. I'm talking about the 15psi (usually less) low pressure diesel flow that keeps those hungry things fed and the injection pump cooled and lubricated... all of which goes back to the tank if not burned. That flow path is a critical life line to this engine setup. It's alot more than just supplying the fuel to the injectors.



Much of this is probably well known. I just like to post stuff as I find out. There have been other great posts regarding similar findings.

 

[OPoole]

just go with AN fittings... no more small holes than just good flow

 

[Ncostello]

I've built my system using all straight 3/8" hose fittings and one AN -6 90 degree. I agree they flow way better. I'm just taking a closer look at what is going on with the other 95% of these trucks on the road who are having lift pump problems too often. I'm not trying to say "whats better"... . just "what is".

 

[Hohn]

I have the wildcat max flow kit on order. The size difference from the stock banjo to their -8AN is astounding. Not to mention that the flow goes straight through it.





Let me ask this: why use a banjo fitting at all? There seems to be nothing but drawbacks to them, and they aren't that common on other vehicles i have seen (except for transmission fittings).



I am curious what benefits there are too a banjo other than being cheap and saving a little space.

 

[Gary - K7GLD]

OK - OK - Reality check time here... .



First, DC doesn't give a HOOT about us guys planning vast HP increases with these engines - they supposedly provide what the STOCK engine is sold as, and hopefully a SMALL amount of overhead...



Past flow testing has proved SEVERAL times that the absolute MAXIMUM flow thru a stock VP-44 is about 45 GPH - which will support FULL HP output from the engine (stock), and still allow about 15 GPH for pump cooling - and we know precious FEW of us are running our trucks at full power for hours at a time!



SOOOoooo - the REAL question is, will the standard lines and fittings as supplied PROVIDE 45 GPH or not at proper LP pressure?



ANSWER THAT question, THEN we can discuss the "need" for bigger lines and fittings - but we can't reasonably expect DC or Cummins to provide those lines and fitting that VASTLY exceed the power THEY expect the engine to be operated at!

 

[Gary - K7GLD]

Here's more reading on the subject - especially note the posts made by "Mopar Muscle" about halfway thru the thread...



https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=11672&highlight=lines+and

 

[Ncostello]

I am not trying to tell anyone that banjo fittings and/or bolts are in anyway better than larger AN type fittings or any other kind of fitting, kit, or device you might use for fuel supply. This is just all information only.



I've read the tests by Mopar Muscle and all the pump, lines and whatnot threads there are here many many times over the past year and a half.



There are drawbacks to banjo fittings and I'm pointing them out as I see them. I've been studying the stock system just for fun and am continuously finding what I consider flaws and posting that information for anyone who wants to read it, especially new members.



I'm aware DC dont give a HOOT about banjos and HP increases... much less alot of other things. Then again DC most likely didn't have a single thing to do with such components on this engine. Its Cummins I'm talking about. If they knew this injection pump lived and died by fuel flow... then they should have oversized this stuff. They sure oversized alot of other things like the connecting rods didn't they... or maybe they too are just barely adequate (not )



I'm just having fun posting info... not trying to make definate claims. Since you've got a pusher Gary, you must have already determined the stock system isn't capable of 45GPH right?

 

[Lama]

Gary,

The French AStar helicopters we have burn 46 GPH of Jet-A, every hour, every flight, like clockwork.



They have 1/2 I. D. fuel line running from the fuel tank, thru a fuel filter (filter very similar to a CTD), to the fuel control (an expensive injector pump). and they use Banjo bolts.



They use a 4 to 6bar (don't have my metric to psi conversion chart) lift pump (we call boost pump) to supply fuel to the fuel control.



So I would say that those Frenchie aerospace engineers figured out that when pulling 46GPH you need a 1/2" I. D. fuel line with a boost pressure of roughly 5bar to feed their $35,000. 00 injector pump.



Kinda' rough figuring, but it does somewhat apply.

 

[Gary - K7GLD]

"They sure oversized alot of other things like the connecting rods didn't they... or maybe they too are just barely adequate (not )



I'm just having fun posting info... not trying to make definate claims. Since you've got a pusher Gary, you must have already determined the stock system isn't capable of 45GPH right?"



FIRST, these ain't helicopters, and this ain't the military - second, there's absolutely NOTHING wrong with oversizing fuel lines, AS LONG AS others don't begin to get the impression this is a needful activity on a relatively STOCK system, and thirdly, Cummins uses their 5. 9 in stuff with lots more power than WE get outta them, which pretty well explains the over-built cranks and rods - wonder what injection pump and lines they use in marine and other higher power 24 valve applications?



*I* installed a pusher PURELY to guarantee continued flow thru my STOCK lines and fittings in case the stock LP quit on me out in the boonies - which it DID on our last RV trip 350 miles from home due to failed contact at the LP plug. The pusher, even at reduced PSI easily took our 15,000 GCWR up over the Tehachapies as though nothing had happened, just as I designed it to do - my fuel pressure varied from 10 PSI at idle, down to around 5 PSI over the hills instead of the usual 23/15 PSI...



NOT knocking fancy lines and fittings in the least, or those who like them - I just have better ways to spend my time and money!

 

[A Johnson]

Most higher horse stuff runs a #6 or #8 line up to the lift pump, from there its pretty much the same as Dodge. I have checked restriction at the lift pump on a few stock Dodge engines and it runs @ 6"Hg, max spec by Cummins is 4" Hg at the lift pump inlet.



1Bar= 14. 5PSI so 4-6BAR = 58-87PSI



A Johnson