Powerstroke 162,
Hope you did not take that as an attack. I know the point you are trying to get across. My issue is I think most or at least judging by the comments I see do not understand how these things work or just simply have chosen not to think it thru.
But if you need a lift pump for a siphon then you need it for the sump as there would be the same condition. Adding a sump without changing orifice size has little effect. 5/8" fittings and hose 1/2 ID is the same in both so no change. Now if you are comparing stock to sump sure but then that apples and oranges. Then the same could be said for sock vs 5/8 PU systems.
The issue is people are changing way to many variable and so they are IMO coming to less than accurate conclusions.
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Originally posted by V-Ref:
New Orleans needs a Sump.
Someone finally flush that toilet.......twice
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I threw those question out back in my other post to try and get some people thinking about it. The fact not one seemed to pick up on them I guess is a sign ignorance is bliss. :shrug:
I think many are not thinking about siphons correctly or do not realize the level flows rates a siphon has at given hose diameters and height offsets or how it compares to the amount of fuel our pumps are flowing at.
To be very clear: ONCE A PROPER SIPHON IS PRIMED IT WILL FLOW FLUID WITHOUT ANY NEED FOR A PUMP OR ANY OTHER OUTSIDE FORCES NOT ALREADY PRESENT.
Lets look at this from the fuel system flow rates performance we as a group could need for our engines.
Lets setup some standards looking at average maximum:
Pressure: 70%
Flow rate: 100 GPH (overkill for most all setups)
Orifice/hose Inside Diameter: 1/2" ( this would be the ID for 5/9 -10an hose and fittings)
What do we want ideally for there to be no vacuum or better yet some positive pressure at the inlet of the pump.
Pumps Flow Rates @ 70 PSI:
* Bosch 68386 (99-04 SD OEM) : 20-25 GPH
* Walbro GSL392 / Dual = Bosch 68386 : 40-45 GPH
* Fuelab 41401 @ 60% PWM: 60 GPH
* Fuelab 42401 @ 60% PWM: 80 GPH
* Bosch 044: 80-85 GPH
* Dual = Walbro GSL392: 80-90 GPH
* Aero A1000 / Fuelab 41401 @ 100% PWM (not recommended for DD): 90-100 GPH
* Fuelab 42401 @ 100% PWM not recommended for DD): 135 GH
The formals and data points to calculate positive flow rates of a siphon system are the same for calculating a bottom drain sump system. A siphon system flow rate is dictated by the height difference of the fuel level versus the pumps inlet. This is the same for the sump as well.
For those that would like the run numbers themselves the basic formula for calculation fluid flow rates for siphons drains sumps is called the "Bernoulli's equation" Its more basic as it does not take into account friction loss from the inside hose surfaces etc.. For our comparative purposes this is really not needed as they are very close to the same for both system so itsa wash. If you want to run your own figures for this just use a .85 to the output of the "Bernoulli's equation" will get you close enough IMO.
As many are comparing the factory Siphon/Pick up systems I will post those flow rates as well. I think it will help show why some are having issues.
Now for both the sump and siphon the height of the fuel in the tank in relation to the height the pump inlet is what effects flow rate. The pump location is static but the fuel level is always changing as we use fuel. Given that I am posting up the flow rates for the changes starting at 12.00" down to 0.25" so you can see what you are dealing with. Again this effects both sump and siphon. If the pump inlet is higher than say the fuel level in the tank when its at a 1/4 level then there will be no positive flow without the pump energy pulling it either system. For both systems as long as the pump inlet stays below the tanks fuel level height it will have positive flow.
(You may very well have a pump mounted higher than the fuel level at all times in which case you are not getting any positive flow to it period. The pump has to pull it. But its energy needed will still be a factor of height difference.) I hope this is starting to get people to see flow rates differences are now what people may think
As stated earlier the typical 5/8" system is really a 1/2"/0.50" system when you measure the inside diameter of fitting orifices and hose. If you are using a "street" 90 or angles fittings I recommend you swap it out as these are restrictive comparatively to smooth curve JIC/-an fittings or the hose ID. They also significantly increase turbulence that can increase pump and injector cavitation.
Looking at the stock system it measures around 0.30" for its tightest location. The 5/8 as said is 0.50" While this does not on its face seem like a huge difference its not diameter but surface area that is actually needed. As you can see that is rather significant is size and when calculating flow this has a significant effect of flow rate output.
Formula for area from diameter: area = PI * (diameter / 2) * (diameter / 2)
.50" ID hose = .196" area
.30" ID hose = .071" area
1/2" / 0.50" ID
Height difference: flow rate in GPH
* 12" : 295gph
* 11" : 282gph
* 10" : 269gph
* 09" : 255gph
* 08" : 240gph
* 07" : 225gph
* 06" : 208gph
* 05" : 190gph
* 04" : 170gph
* 03" : 147gph
* 02" : 120gph
* 01" : 085gph
* 0.75" : 074gph
* 0.50" : 060gph
* 0.25" : 043gph
3/10" / 0.30" ID (stock system)
* 12" : 106gph
* 11" : 101gph
* 10" : 097gph
* 09" : 092gph
* 08" : 087gph
* 07" : 081gph
* 06" : 075gph
* 05" : 068gph
* 04" : 061gph
* 03" : 053gph
* 02" : 043gph
* 01" : 031gph
* 0.75" : 027gph
* 0.50" : 022gph
* 0.25" : 015gph
As you can see when you go and change to a larger pump and are wanting anything over stock levels of fuel the system at times is going to have the pumps working both pulling fuel and pressurizing it.
This is the issue when you have pumps claiming flow levels significantly greater than stock yet are telling you to use stock lines from the tank to the pump setup. One of two things are true:
Either they do not understand simple flow rate or know the size of the stock systems they are building setups for or the pumps they are offering do not actually flow rates that exceed what the stock systems can handle (meaning less than advertised) or it could be a combination of both.
But now lets look at a sump. Still the same relative sizes and distances of hose outside the tank, only difference is no need for a siphon and the pluses and negatives that come with the physical differences. Its not always a great think to have a hole in the bottom a tank used for toxic flammable liquids..
A sump works off the same calculations you have the height of the fuel in the tank above the drain hole location. You have the height were the pumps inlet is location in relation to that fluid level. You have the inside diameter of the system which is the same @ 1/2". Honestly this would not matter as you can build either to whatever size you would want to get the flow rate you want.
So knowing that anyone want to take a wild guess what the flow rates are going to look like for a sump like this?
Its for our purposes the same thing. Don't you get it. Its the same hydro pressures differences same gravity same orifice sizes. The only dif will be that technically depending on where you located the pump you have the more hose because of the in-tank section of siphon tube (Pick up) and the friction loss from that extra piece of tube. But that is literally nothing you could not even measure it without some very precise setup or large volumes.
Just to be sure I was not crazy here I did a small experiment in my kitchen. Wife is asleep.
Took a jug that had a spout( nipple) on the end. Cut the other end off. So I have a jug with a open top and a drain at the bottom just like a tank with sump. I filled it up with a specific amount of water. Took a hose that was a bit smaller than the outlet so the hose is the restriction point so it will be accurate to use the same type of hose for the siphon setup to compare rates. I set the jug on my counter (fixed height) and the receiving jug on a chair (fixed height) so I would have fixed ratio of between their heights. Using a stop watch on my SGIII I timed how long it took the water to drain to the bottom jug. I then refilled the top jug. But this time plugged the bottom port and took hose and dropped it in from the top creating a siphon and cut it to a length that has it stop at the same height in the bottom jug as the sump version had. Timed it again. The difference was a tenth of a second which is likely operator error as I had to lock the clip I used to hold the prime so I could make sure it was even.
Anyone wants to check that has a full tank of fuel, pull the hose off the pump inlet or water separator if they have one between the two and just watch how fast that fuel flows out of that hose. Some of us have had this happen by accident when working on them. No fun :fustrate:
So IMO what it comes down to is using the correct size fittings hose etc for the flow rate of your pump. If you use the same size in each system you will get for our purpose the same performance is flow rates. Where you are mounting your pump in relation to your tank matters as well.
The real issues you run into when you do exceed the flow rates of the tank-pump setup is higher draw on the pump so heat but also and likely equally if not more damaging, cavitation. LReiff mentions this in his post above.
Two different forms of cavitation for pumps as I understand it from reading: (Just regurgitation what I read here)
Suction and Discharge
But with both the issue is bubbles: vapor or air. When they are exposed to significant changes in pressure vacuum or positive you have the makings for cavitation. Diesel already tends to have about 10% entrained air. Anything that pulls this out of solution is going to create issues from the pump to the injectors. Fuel temperature also has a significant effect on cavitation from what I have read. The warmer it is the easier it will cavitation. (yet another reason I am glad I run a fuel cooler.)
Add a higher volume pump to a stock system designed/sized for lower volume and you are going to have issues. Add a filtration setup between the pump and tank it was also never designed or sized for adds yet more restriction and thus more vacuum pressure which only exacerbates the situation that much more.
Its not whether you have a siphon or sump drain but that its the proper size to flow the correct amounts based on where the pump is located. Set your pump up in the top of the engine bay and you are going to have an issue unless you are getting large enough pump that it can handle both the inlet and outlet work.
I agree fully with Dennis (Strictly Diesel) in I would choose the original supplemental or lift pump Air dog setup over the ADII. The ADII is just giving you the same thing that everyone else has but adds a small amount of air separation. The issue is you are still creating a issue of possible cavitation just like with any other system. With the ADI or anyone that would run a separate lift pump you have the duties separated. Sure you could run a pump that is strong enough to handle both duties but this would IMO mean a very large pump that uses some type of PWM board to control the pump speed so you only flowed what you needed or a gear/belt driven pump similar to our power steering pumps. This has become somewhat popular with the cummins and dmax guys. It could be driving off the crank or other accessories or off the HPOP gear bolt. To me it sure seems that the easiest and least costly is to just add a low pressure high volume pump between your tank and main HP pump. Make sure its set regulated (meant for deadhead use) and has a flow rate that is greater than your HP pumps. You can then mount your main pump and filters anywhere you want without any regard to tank to pump flow rates. I think running two pumps in a stages scenario has worthwhile benefits. I run two.
Sumps positive is they do allow for sure every last drop of fuel to get taken. But the condition of that fuel at that level I do not think I would want it running thru my $2K-$3K worth of injectors and pumps. Now for comp setups etc things might be different and a sump has a number of benefits but for street trucks not so much.
What I really think has gotten more people into installing them if we really want to be honest is the new C plate versions out there now. You hardly saw but maybe a small handful on all the trucks let alone 7.3 using these specific sumps before it. Come on, people like the idea of not having to drop their tanks. LOL So while they would have normally done a 5/8 PU they are willing to spend 5-8x the amount for a sump and make themselves feel better by telling themselves its the better performance choice. LOL Come on who doesn't want to do less work.
One last thing I thought of while typing this up. You know how when you drain a tube or sink as the level gets low you get that vortex or whirpool effect and air starts to get sucked in with the water because of this. I do not see why the same would not be happening with a bottom drain on a tank. Maybe something about pressure from the pump might negate it but I do not know. I do know that if it does do this the LAST thing I would want is to have that happen and run thru my pump and injectors. I guess what it comes down to is I do not think I would ever want to run any tank below 1/8 tank given the fuel height level and return. So should it really be seen as a benefit?:shrug: Again I am not sure this actually happens on a tank as I have not tested it. Maybe someone on here can answer this and put it to bed.
