Christian, did you have a Walbro setup before? What kind of fuel pressure were you seeing before? I still only have the 3/8" drawstraw running up to the Walbro pump and then to the pressure regulator, but after that, I ran 1/2" line all the way to my 2-micron filter and on to the dual pumps. With the stock Walbro springs, I see 15-16psi at idle and cruising, but it only drops to 14psi at WOT. Unfortunately I didn't have a fuel pressure guage when I just had the 3/8" line, so I can't compare. I think the 10-12psi you are seeing is sufficient fuel, I wonder how much higher your psi would stay if you just did a similar line swap like I did.

Jared

 

The friction loss / flow restriction in my set up is the 5/16" hard line and 03-04 style pick up...so the jump to 1/2" after the pump will not really help much...at all in my opinion. I cause I could run a fluid dynamics model on it and crunch some numbers...but I don't think it is needed.

I never ran dual pumps with the Walbro...I was told that it was a good idea to upsize the lift pump around 750 hp...which I am over now. A Walbro with a true 1/2" system might keep up...but I knew I had restrictions and I chose the "larger hammer" to pound more fuel through the same size hole...lol.

If I chose anything...I would swap to 1/2" from the tank to pump and keep 3/8" after till the cp3's. That is typical of an ideal set up...larger hose on the suction side...because thagt is where the pump is less effective...and has larger flow loss (study pump design...) and smaller on the pressurized side.


In my opinion...till I weld up a custom tank with a sump and a bottom draw...there is no effective 1/2" solution to a draw straw that does not have low fuel level problems. I like to eeek out every last mile of my tank...so that is not an option for me.

 

With you're setup I bet you're actually getting a pressure drop across the pump as the line size increases.

 

Wow, I really overkilled mine. 5/8 plastic DOT line with a 3/4in standpipe in the tank. It was free except for the brass so I guess its good.

 

Run 1/2" from the tank to the pump, then go 3/8" to the injection pumps, that makes some sense. My concern would be since the airdog is rated for 20psi measured in a 1/2" line....the pressure will increase if the diameter of the feed line changes...right.

 

I only got 13 psi at idle until I stretched the spring, now I get 17.5

 

I run the STOCK hard line from the raptor to the engine. 20psi @ idle, and 18wot.

Mike

 

The pressure will just have to be a little higher to flow the same...I would not worry about it.

 

Thats quite the question, is any of this necessary?


Ok I run it to and it keeps up with my TNT/Pressure great!

 

not sure I get your humor out of the question

 

the do make a 30psi kit also but you may already know that. on the pressure I would think it would be higher also in smaller line but im not fluid guru

 

1/2" line=good volume...for a guy like onetun I would say use the 1/2" line.
you can have 20psi all day long but if you lack the volume it's pointless to have the psi.
.02

 

I completely agree, everybody get caught up in PSI. Volume is what counts.

 

Guys...come on! They both matter. Plus...the return fuel at the CP3 has a maximum.

Every seen how much fuel squirts out of a 3/8" line with a 150 gph pump behind it????

Basically it supplys .625 gallons every 15 secs....or how about a 1/4 mile?

34 gallon tank / .625 gallons = 54.4 passes down the track....or 13.6 miles or 13.6 miles / 34 gallons = 0.4 mpg???????

Must have 5,000 hp...lol.

I must rambling...

 

your right they both do matter..but most seem to ONLY look at psi....and your also right that 3/8" will work for 90% of the people out there...but if you have some brand new 1/2" that came with your kit why not plumb it up???
it not like it's hard or will take all day!
and we all know Rob is looking for the very maximum of out his set-up up so why not just install the 1/2"?
you know christen...you changed out your walbro because it could not keep the volume up right? I assume you had great psi but the walbro is only a 85gph pump IIRC.
not try to argue just saying why not just put it on?