me

 

Not at all. I understand, that is not the regulator i was referring to. I am going to bow out of this debate. I don't feel strongly one way or another i am just bored. Sorry to the op for all the clutter.

 

cool .. well then right here seems you agree with what i posted
.. and maybe half the people you looked at actually had it right

well then.. this isnt the OEM setup you was describing in your first post??
you do understand that in a 300 rwhp fuel setup there is less range between full power required flow and idle flows.. hence the problem is to some degree lesser because its not running a boost a pump revved up 044 to make 500
.. doesnt mean any of those with the system you described logged fuel pressure differential under all conditions now did it??
read the obviously knowledgeable google post,, take a moment to contemplate what he means when he describes the erratic fuel pressure issue and why that is

that is NOT going to be an issue in a drag car or race car kept at noise
.. it IS going to be an issue on a street car that sits for periods at only 40 hp worth of demand
.. but has 600hp worth of flow going circles into a restrictive return line

note again the post that calculates 90 % unrestricted flow.. and equal or larger size pipe to account for the factors like reynolds losses.. and hinting at swirlpot/ tank peculation backpressures..
note my numbers above .... realistic in this situ .. and see how much you are out of the 10% window......................................>

comeon people.. THINK


what we are dealing with is a system that can move 600 rwhp worth of fuel forwards
( 20 % over-design if you have half a clue )

that is idling.. in traffic.. using 40 rwhps worth......but has a return pipe smaller than the supply??. and the rail gets warm and the fuel hitting the tank is boiling making its own vapour pressure ?

 

look at this disclaimer on all the links there
.. if used with efi must use larger return line... if used with a1000 pump .. must use speed controller

// solid state pumps and modern EFI systems are not what is under discussion here

because of 100% variable speed control these can have a smaller return hose,, slow down the pump at idle and have no issue,, and speed up under hi demand
some OEM versions of this have no return..

with a 80/90s EFI system with wound pump and at best only two stage speed control ( and who keeps this when modding? ) this is not the case,, fuel system must be flowing at 20% over the FULL POWER demanded rate
.. when its only using 6% of that to idle.. as is likely in this case ..
then you NEED to be sure that the return line has same or larger diameter than supply




search also deadhead fuel system

,, search the variants..deadhead with kickback/bleed /pill return.. deadhead and bypass composite systems ( big on multicarb and nitrous engines )


understand also there is a technical distinction between
inlet, outlet and return

a bypass reg uses the terms inlet and return

a deadhead reg uses the terms inlet and outlets
..note especially where they have used the terms bypass reg ( all with the efi disclaimer )

and where they have used instead the term " reg with bypass "... that is no typo .. but deliberate misleading sales pitch

then you will understand what that third reg is all about

.. ps .. im not trying to knock you down mate,, but make the distinction between what is three fundamentally different fuel systems,, solid state speed controlled pump, dead head and bypass all have different reg requirements

 

What was the setup that you had problems with and what was the problem.

 

IMO, if you are using a smaller return line than the feed and are not having fuel pressure problems then the feed line is just too big for your fuel pump flow.


No, what that means is that you could get the same job done with a -6 feed line or even a -5 feed line.


The only way to truly know if your feed is too small is to measure the pressure at the pump and compare it to the system pressure at the regulator.

But, basic physics would dictate that if the feed and return lines are sized properly the return line would have to be at least equal in size of the feed line for proper pressure control in all situations.

 

how long is your day.. its 330 am here.. and i have 23 yrs worth ..
first time i guess would have been in 92.. doing one of the very first ever microtech installs.. first ever mistake,, and best lesson ever.. was getting fuel lines back to front..
start.. stop,, start.. stop... easy to do when both fuel pipes on the rails are same size
it was an rx4.. it was a 12at .... rx4s have little factory return line from a carb with no reg
.. then .. the very next day .. it drove 2200 kms to broome from perth. temps 42 C
about 800 km in
.. perc and flooding issue stopped it while slowing down through marble bar

.. till tank was vented,, car ( fuel system ) cooled down 4 hrs and all equalised

but that is just one example.. i really cant put as number on it,, just .. lots

... so here is an easy one for you,, i get it several times a year...

.... find someone with a weber carb and a genuine bypass fuel system

idle the car...

... partially pinch the return line .. tell me what happens on the reg gauge

..... now adjust up and down on the reg.. tell me what happens ..

try and adjust it back to the set point.. if you can.. if you cant.. leave at its lowest possible pressure setting

now release the restriction .. tell me what the pressure is now ////

or,, install all these same components in one rx4..
use the stock lines and a bypass reg,, what the minimum number you will set on the reg ?

bet it is higher than the minimum what it says on the reg packet...

and this is with only 150 HP flow differential between idle and load

i hope you go through the motions and see my point in action



enough now .. its 4am and i have a couple of turbos to build in the morning

 

go get some rest, what the heck are you doing up now anyway....

 

yes,, late.. marble bar is 800 km out from broome.. 1400 km from perth but you get the idea
.. and this is on a VL commie pump that is nothing more than a safe 250 rwhp pump at best

..and i expect a similar fuel use to idle a sequential 13b as to the old batch/ double fire 12at

that would have the car with a big fuel system in trouble much sooner
.. again the issue isnt so apparent to most till you slow down
though it may show up as a tune drift during cruise ..

 

was just playing around with numbers on the L&M engines fuel line calculator.

Very cool tool.

However what I am finding is that even with the Walbro F9000267 at Idle(43.5psi) which should be about 1.8333... gal/min the maximum pressure drop on a 3/8" line is about 3.8 psi

1/2" at the same flow is .81psi

These are about what I would have expected and clearly illustrates why you should run -8 or larger for feed

We are currently working on a build using -8 feed and -6 return And I don't expect it to be a problem. But in light of the info that has been shared on this thread I will certainly be doing more testing than I would have and be watching for any kind of problems

 

wow....thank you for all the info guys. I appreciate everything that has been posted. I always come back to this forum because there are very knowledgeable people with a lot of experience. Im not sure what im going to do just yet because im waiting to see if my borg warner can even keep up with the amount of fuel I plan to use. I do feel like I have learned a lot from reading all these post and I appreciate everyone's arguments. Im definitely going to go with a -8feed and undecided about the return....lol

-Danny-

 

Honestly you could be fine at 500whp if you ran a -6 feed and -6 return. -6 should be more than large enough to flow the fuel you're going to want/need, running a -8 feed will be overkill.

I went with a -8 feed, splitting to dual -6's (ran in parallel) to the fuel rails, with a -6 return under the theory of "better to have it and not need it, than need it and not have it". At the end of the day you'll be fine with a -8 feed and a -6 return, or a -6 feed and -6 return. I know bumpstart is gunna get a rage-boner by me saying that you'll be fine with the -8/-6, but the fact of the matter is that the -6 flows more than enough for an in-tank 044 whether it's at the front or the back..

The -8 lines and fittings will cost you more than the -6 lines and fittings.

 

Exactly what is clear about needing -8 line? Yes, larger line has lower pressure drop, -10 would have even lower than 0.81 psi, why isn't running -10 "clearly" the answer? As long as you're pump can overcome the pressure drop and maintain flow at that level, then the smaller line is completely satisfactory. Actually most pump outlets are sized for 3/8 inch diameter line.

 

personally, id run -8 and -8. do it once. in year to come at least you know you will have no limits on the fuel flow (once you upgrade pumps etc)

 

Saying that you should run -8 at those flow levels is only my opinion. To me the difference between 3.8psi drop and 0.8psi pressure drop makes it worthwhile.

Now is the difference of running -10 worth it? I don't think lowering the pressure drop to 0.27psi would really get you anything over the .8psi drop in the -8.

But in the end that is jmho

 

I am/ will be running the same size return as feed.... This is probably ideal to minimize unwanted pressure...

all I was saying is that the statement that this must always be the case is not always true...

if you look at many cases where bypass systems have smaller return than feed and work just fine

 

^ In the cases where the return is smaller the system will have some sort of pump speed control based on fueling requirements. Even the fd had a simple speed control system.

 

i had 2x 044s in tank(CJ hanger) and only upgraded the feed line and not return and i never had an issue. Return is not as pressurized

 

Basically if the pump can't flow more than the return line can flow with no pressure increase you are good... Correct me if I'm incorrect... But in this case your feel line could be 2x the size of your return with no adverse effects...