superheated fuel

Either way the P/pump requires 17 to 22 at Idle 38 to 42 during cruise. The return pressure normally is 14 to 15 psi.

Without these numbers all you will do is starve the pump.
Click to expand...

you speaking in regards to an engine with increased fuel consumption?



In my opinion you need pressure there to get the max amount of fuel into the plungers which also provides lubrication and cooling. Why else would the factory install a relief valve in the return port?
Click to expand...

that is true, but the pump also requires an adequate amount of bypass flow. without a pump that flows xx @ psi to match the increased regulator pressure, the actual bypass flow is decreased. Unless I am off base, this circulatory bypass is what actually cools the internals of the IP.

As far as the OFV being in the return - how would you build up pressure in the IP otherwise?
 
Hurley said:
that is true, but the pump also requires an adequate amount of bypass flow.
Click to expand...

Are you saying that a 180 gph lift pump isn't going to provide this even with the regulator set @ 40 psi? ( for cooling purposes )
 
oh hell missed that spec from the first post


adequate, indeed!
 
Hurley said:
you speaking in regards to an engine with increased fuel consumption?


Info given was mearly said to give a baseline in which to start from .

As always a person must determine what HP goal that he or she wants and build from there.


Even at 800HP a FASS or Air Dog with a supply of 45 to 50 psi is addiquate.
Click to expand...
 
^agreed, I was curious about the case of a bone stock truck that had much less operating pressure than what you had posted.


I would like to start a conversation discussing boost-referenced fuel pressure vs. set level. worthy for a new thread or keep it here?
 
I would say start a new thread .

My only opinion would be, why make it proportional.

Don't really see the theory behind it.
 
65fury said:
Well in my experience with low fuel pressure i have never once had my truck run any diffrerent..... whether my fuel pressure was at 2psi at WOT (which it has been there:doh:) or if it was at 40psi WOT. Before i made changes to my return valve thats how it was... when i raced or dynoed my fuel pressure would drop to almost 0psi!! but the truck never missed or ran any different.

Jason
Click to expand...

My dads truck had a really dirty fuel filter on it once. It is bone stock, so obviously its not requiring a lot of fuel. It wouldnt even go 70mph without missing and sputtering. My cousins truck also had a clogged fuel filter. Except it had laser cuts, DDP4's, 4k, etc and it was stuttering awful at WOT. Changing the filter(raising PSI) fixed both trucks.

Do what you want, It may work fine, but i dont see any reason to run that low of pressure personally. I agree that it needs pressure to get the fuel into the plungers.

Eric
 
Cummins Driver said:
My dads truck had a really dirty fuel filter on it once. It is bone stock, so obviously its not requiring a lot of fuel. It wouldnt even go 70mph without missing and sputtering. My cousins truck also had a clogged fuel filter. Except it had laser cuts, DDP4's, 4k, etc and it was stuttering awful at WOT. Changing the filter(raising PSI) fixed both trucks.

Do what you want, It may work fine, but i dont see any reason to run that low of pressure personally. I agree that it needs pressure to get the fuel into the plungers.

Eric
Click to expand...


Yes that would be an issue... but if there is no clog or restriction than low fuel pressure shouldnt cause it to studder... psi and volume are different... the reason my truck didnt studder is because i had enough volume, just a sloppy return spring:bang. Remember making 60psi on a stock turbo aint gonna make you any faster. A lower psi doesnt mean a lower volume of fuel. just my$.02 i personally runmy setup at 40psi at idle and it wont drop below 30psi under wot.


Jason
 
Also these pumps dont have a demand for fuel at idle. So there really is no reason to have 40psi at idle(which doesnt hurt it or help it), my truck is set that way cause i dont a have cool electric fuel pump with a boost ref on it:rockwoot:, but if you ask any pump shop they'll tell you that 5psi at idle is fine, it wont cause damage or lack of lube to the pump, as long as the pump has enough volume going to it, it'll be fine. as long as they have enough fuel in the "gally" for the plungers then its good. Again psi dont matter at idle.... its not using barley any fuel anyways.;)

Jason
 
Hurley said:
I would like to start a conversation discussing boost-referenced fuel pressure vs. set level. worthy for a new thread or keep it here?
Click to expand...

someone responded to your question and suggested you start a new thread.

did you?

thanks, don
 
MAXTORQ said:
My only opinion would be, why make it proportional?
Click to expand...

because i can:

fuelsystem033.jpg



you see, i already had the pump:

frtbummperandfasspumpmods006.jpg


you can clearly (well sort of) see it (or parts of it anyways) in the lower right corner of that pic

but it had a bad regulator

the ball that fass uses as the pressure relief valve was chipping:

frtbummperandfasspumpmods013.jpg




so i drilled out the hole that acts as the seat:

frtbummperandfasspumpmods003.jpg


and plugged it with a nitrous 1/16 npt pipe plug:

frtbummperandfasspumpmods016.jpg



then the pump became just that....a pump

needed a regulator and just happened to have this bypass reg laying around:

fuelsystem033.jpg



itsa boost compenstating bypass reg so why not run a hose off the afc and let it see boost:

fuelsystem030.jpg



this is the pump installed:

fuelsystem028.jpg


i need to make a bracket and redo it, cuz its too high still...


way higher than the sump:

fuelsystem025.jpg
 
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Maybe it will work ok? It could be that low pressure will be fine at high volume. I still think you would get more fuel into the pump with higher pressure at the same volume though. I would personally just regulate a good pump at 40psi, and call it good, but thats just me.
 
Cummins Driver said:
Maybe it will work ok?

I still think you would get more fuel into the pump with higher pressure at the same volume though.
Click to expand...

how you gonna do that?

they (pressure and volume) are inversly related

increase in pressure creates a decrease in volume
 
Cummins Driver said:
Maybe it will work ok? It could be that low pressure will be fine at high volume. I still think you would get more fuel into the pump with higher pressure at the same volume though. I would personally just regulate a good pump at 40psi, and call it good, but thats just me.
Click to expand...

Its like i stated before... volume and psi are different, and these injection pumps dont need 40psi at idle to run any better... making 70psi at idle or WOT wont make the truck run any different than 10psi at idle or WOT. The reason hes regulating the pump to a lower psi is to keep from over working the electric fuel pump(and possibly overheating the fuel). Since there is no reason to have his fuel pump running 40spi of fuel at idle... then why do it?

Jason
 
Hurley said:
is there really any concern with the fuel temperature increasing to undesirable levels?
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ummmm its possible.... don and i talked about it a few days ago, and basically he did the math on how much fuel would circulate through the entire system in 1hr and it was a quite a few times, i dont remember the specs he gave me, im sure he'll chime in and explain though.


jason
 
i dont know....thats why i started this thread

but it got all clutter up with the "it'll never work" from the nay sayers

lol
 
id say the calculations would be waaaaayyy overkill, hell, throw a thermocouple in the tank somewhere and monitor the temp if the concern remains
 
i was thinking more along the lines of throwing a tranny cooler in front of the 7100

not literally, but in relation to flow that is where i would put it
 
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