a crazzy dual fuel system

[DTanklage]

where does the stock inlet go?

what does it feed?


where is the return?

[ford69557ci]

i think the stock inlet feeds to the vane pump and the vane pump feeds the rest of the pump???and the return well thats self explanitory

[seeker1056]

hmmm

I think maybe this is going a little backwards

In any other kinda race engine you figure out the fuel requirements in lbs per hour per projected hp, or gallons per minute if you will.

So if you only need by calculation 3/4 of a gallon in one minute, why would you be trying to be supplying 3 or 4 gallons per minute and bypassing most of it back to the tank?

Bigger line is NOT always better, and for our needs 3/4 inch would be rediculous in the extreme, if you could even keep pressure up in it.

Fact is 1/2 inch is almost too big for the actual volumes required, from what I see in the posts from people who are actually makin big hp numbers.

Why - It takes one hell of a pump to make several gallons per minute flow and keep line pressure up.

If you do the calculation on 3/8" line, and then use two as suggested, you have more than the ideal setup for volume and pressure.

Which leads me to my next question - what is the problem that makes one feel they need to feed both ends of the case?

If you remove the restriction in the fuel inlet fitting at the rotary pump ie enlarge it from its approximatley 3/16" (size of the inverted flare) to almost 3/8" to match the supply line you would more than double fuel flow and should be able to supply more than enough fuel for 700 or so hp without all the convoluted dual fuel supply system stuff.

Or am I missing something here - does the rotary pump need the proposed high fuel bypass to cool the pump at high demand, or are you all sayin the pump is cavitating and losing pressure and these dual line systems are the bandaid?

Thoughts please

[DTanklage]

the stock inlet supplys the vane pump (<20)

the vane pump supplys the case (20-150?) (60-120?)

(see why i keep saying we need to install case press gage?)

the return comes out of the case

[JD730]

the vane pump supplys the case (20-150?) (60-120?)

(see why i keep saying we need to install case press gage?)

I wish I could give you some numbers right now. I only got case pressure gauge hooked up last night and now I have problems with one of my new EDM'd tips (also installed last night). After I get that straightened out I'll have some numbers. But I did see 120psi at higher rpms's last night.

[DTanklage]

what did you see at idle?

[JD730]

Around 40 I think, maybe 50, I'm not completely sure. I wasn't in the cab very long, had other problems to deal with.

[DTanklage]

In any other kinda race engine you figure out the fuel requirements in lbs per hour per projected hp, or gallons per minute if you will.

yes, and you need to do the same with this motor - and that includes any fuel that is returned via the 018 hole at the top of the case (if you leave the return intact) AND the fuel that returns via the injector rail return

this isnt a carburated gas motor - and everything the ve gets/produces is not injected into the combustion chamber

So if you only need by calculation 3/4 of a gallon in one minute, why would you be trying to be supplying 3 or 4 gallons per minute and bypassing most of it back to the tank?

who says you only need 3/4 of a gallon per minute?

Bigger line is NOT always better, and for our needs 3/4 inch would be rediculous in the extreme, if you could even keep pressure up in it.

you are totally lost - he is not talking about running 3/4 lines on the pressure side of the pump. he is talking about a 3/4 supply line to the lift pump. supply lines dont have pressure in them, they have vacuum. the larger the supply line the larger the volume avail for the lift pump. you can not install "too large" of a supply line

If you do the calculation on 3/8" line, and then use two as suggested, you have more than the ideal setup for volume and pressure.

who/where is it suggested that you use two 3/8" lines and how do you know what is ideal?

does the rotary pump need the proposed high fuel bypass to cool the pump at high demand

high demand or high output? i dont think the ve needs any fuel returned for cooling - let it push what ever it can to the injectors - and that aint a whole lot

If you remove the restriction in the fuel inlet fitting at the rotary pump ie enlarge it from its approximatley 3/16" (size of the inverted flare) to almost 3/8" to match the supply line you would more than double fuel flow and should be able to supply more than enough fuel for 700 or so hp without all the convoluted dual fuel supply system stuff.

you can not enlarge the inlet fitting to .375 id

not without enlarging the hole in the case first

the id of the threads in the factory hole is smaller than 375

how are you going to get a fitting to seal when there are no threads on the end of it?

Or am I missing something here

yes, like i said above, you are LOST

i was talking (in the psycho fuel system thread) about increasing case pressure - above and beyond what the rotory vane pump produces

[DTanklage]

Around 40 I think, maybe 50, I'm not completely sure. I wasn't in the cab very long, had other problems to deal with.

cool, now we have some hard numbers to work with

40-120

50-120

that is what i was expecting

now, i wonder what happens to output when you get case pressure to 240?

hehe

[DTanklage]

ps - do you now see why i dont think there is any reason to try to put 50 psi into the return? (once under boost)

50 psi to the vane pump inlet may be worth something tho...

[DTanklage]

pps - whats wrong with your new injectors?

[seeker1056]

Its obvious by the answer to my questions that fluid dynamics and pressure/flow vs engine demand are not a consideration or out of equation

So I will rephrase my question

What is the inherent issue with the ve pump that causes the need for all of this extra pressure and fuel return. I have got that the case pressure is dropping beyond acceptable limits but the question is why?

So how bout a technical answer to the issue?

As to the issue of the inlet fitting - getting almost 3/8" is easy when the line is soldered to a reamed fitting and a compression fitting used downstream for a disconnect.

[flashgordon]

hmmm

I think maybe this is going a little backwards

In any other kinda race engine you figure out the fuel requirements in lbs per hour per projected hp, or gallons per minute if you will.

So if you only need by calculation 3/4 of a gallon in one minute, why would you be trying to be supplying 3 or 4 gallons per minute and bypassing most of it back to the tank?

Bigger line is NOT always better, and for our needs 3/4 inch would be rediculous in the extreme, if you could even keep pressure up in it.

Fact is 1/2 inch is almost too big for the actual volumes required, from what I see in the posts from people who are actually makin big hp numbers.

Why - It takes one hell of a pump to make several gallons per minute flow and keep line pressure up.If you do the calculation on 3/8" line, and then use two as suggested, you have more than the ideal setup for volume and pressure.

Which leads me to my next question - what is the problem that makes one feel they need to feed both ends of the case?

If you remove the restriction in the fuel inlet fitting at the rotary pump ie enlarge it from its approximatley 3/16" (size of the inverted flare) to almost 3/8" to match the supply line you would more than double fuel flow and should be able to supply more than enough fuel for 700 or so hp without all the convoluted dual fuel supply system stuff.

Or am I missing something here - does the rotary pump need the proposed high fuel bypass to cool the pump at high demand, or are you all sayin the pump is cavitating and losing pressure and these dual line systems are the bandaid?

Thoughts please

For a tractor pulling truck, this my not be the case, but with A drag truck i agree with seeker1056. With a real fast drag truck, the inertia or weight of the fuel will want to go back to the fuel take on LAUNCH. the bigger the line the more weight.

The bigger the the suction line to the pump, the bigger the pump will need to be to over come the G-force of the fuel.
This could also cause caveatting too....Right.

Maybe this idea works? but there is a lot of "fuel weight" pulling the opposite direction on launch of the truck.
On a Dyno pull, None of this would come into play.


Flash.

[JD730]

pps - whats wrong with your new injectors?

One nozzle is not spraying right, its must be hung up or something, sprays like a water hose. Remember originally they were setup with pop pressure too high.

[Begle1]

So has anybody ever enlarged the stock inlet port? Are the passages in the pump any larger than the ~3/16" inlet port?