lp ??

[Ace]

I'm pretty sure the stock 5/16" line is only really good for something less than around 300hp. Exactly how much less, dunno. But I do know that before I finished upgrading my fuel system (and the stock tank line was the last thing I did) I could always pull a pressure drop on the stock feed. By the time I had W/M injection and pushing 30lbs boost that drop was fairly significant, up to about a 5lb. drop from 15psi down to around 10lbs. WOT. This was even after the sender/pickup mod, with stock I/C injectors.

Now the fuel pressure guage never moves (maybe 1lb drop, probably just a pressure wave reaction) since going to 3/8" line throughout the system along with big filters.

[PToombs]

My fuel pressure drops from about 15 to 10 with the stock line. And that's with 370's and a bottomed out fuel screw. 388 hp. Not bad for a stock line in my opinion.

[DTanklage]

i was not referring to performance when i suggest it be replaced

i was talking about the condition of the line

the pump has to suck the fuel quite a ways before it compresses it

[Ace]

My fuel pressure drops from about 15 to 10 with the stock line. And that's with 370's and a bottomed out fuel screw. 388 hp. Not bad for a stock line in my opinion.

But for how long? I'll bet your EGT or speedometer is off the scale before it has time to actually run out of fuel.

[PToombs]

Welllllllll, The egt's are up pretty good and the speedo was kinda far gone. It was still climbing though!

I plan on upgrading to a 1/2" line this summer. I figure I'm pushing my luck with the age of the lines, like Don said. Plus, it has to be better for the pump with less draw to get fuel.

[DTanklage]

with larger lines there is not just more volume inside the line

there is also more weight

and if your truck leaves hard (accelerates) it creates g-forces

those g-forces are trying to pull the fuel away from the suction side of the pump

the larger (or longer) those lines are the more the g-forces effect the pumps ability to suck supply fuel

thats part of the reason behind a electric pump (vs a engine driven mechanical pump)

it can be mounted behind the tank so that the g-forces actually help supply fuel to the pump

tank

[PToombs]

What kinda G-forces do you get in a 16 second truck?

[DTanklage]

i dont know...

...but wouldnt it be a shame if you didnt have a 16 second truck pete?

but instead a thirteen second truck that was governed back to 16's

(by lack of fuel)

when my filter starts to get really bad (run your truck outta fuel once) i can totally feel the difference in performance. put a new filter in there and it flys again, same princible

tank

[Ace]

OK, couple things here, before we get too far off into fantasy land: Fuel is a liquid and it does not "compress." Fuel flow under pressure in a fuel line is not going to be measureably affected by G-force under acceleration in any vehicle that runs on land.

[DTanklage]

actually, even water can be compressed ever so slightly, but i am not gonna argue that point

not talking about the pressure side...talking about the suction side

[seeker1056]

Hey Ace - man you wanna tell that g-force one to the drag racers n the nascar boys - man thats funny
Tanklage has it correct

[Ace]

Suction - push, doesn't matter. It's a one-for-one zero sum game through the pump, because like you said, liquids don't compress. Nor do they expand. Much. A pump could cavitate and stop flowing due to blocked lines, sucking a rubber hose closed, but G-force? Maybe so, maybe not. Sounds more like the kind of force Darth Vader is dealing with, in this application.

So how many G's you pulling on launch with your truck there Seeker?

[DTanklage]

you grow til your about 25 then you start dying. you only have so many brain cells. some die ea day. once you close your mind you are done learning and with every day that goes by you are getting dumber

i try to keep an open mind even if what i am hearing sounds like bull. try to store it away until maybe one day i can apply it and find out for sure. and sometimes, just sometimes, i then find out that it was good info

thats how one learns

once you close your mind you are done learning....

and getting dumber every day

so try to keep an open mind

tank

[DoWhat?]

G-force seems like a moot point to me as long as the lp is supplying positive presure to the injection pump. But I'm just a puller, so I'll never leave the line hard enough to know...

[DTanklage]

well yea, its almost like running your truck on a dyno

(zero g-forces there)

but take the sled off of that thing, get it out of the dirt and on a concrete launch pad, and trust me...even a 16 second truck creates some g-force when accelerating. obviously the lower gear you are in the quicker it accelerates but my truck would pull enough g's even on the freeway for the pump to cavitate when i was running 1/2 line and a engine driven mechanical pump. where ones fuel tank is located has more to do with performance than many are aware of

tank