Fuel Line and Fitting Discussion

[dsrace]

where i can see higher hp carb systems using a return line those aren't the majority of carb set systems or weren't i should say. even as you stated using a relay to cycle the pump for a return less FI system still uses the relay as a type of regulation system and can be done but what a pain and possibilities of gremlins are much greater imo. and i agree it makes no diff to injectors as they will open and close electronically w/wo a return line.  i wasn't referring to injectors, i was referring to the pump as it is a much higher psi as in 100 to 125 psi and flow than the standard 3 to 5 psi pumps used on the majority of carb systems. been reading some interesting info on pump amp ratings and draw. the 450 i purchased which i purchased because it's "advertised" as e85 compatible, states a 22 amp draw which turns out to be peak draw. there is differing info out there on this but basic principal is of course the faster the pump has to spin to maintain it's psi the higher the amp draw. enemy was using i believe the walbro 340 pump and was running short on fuel around 25 psi boost in his truck. after the change to the 450 he actually had to turn the inj's down because of the additional flow. imo length of fuel line plays a role in factoring it all. i will have 1/4 the length that truck has but once on e85 25 psi boost was the limit with that 340 lph pump, imo.

i have never seen or experienced an issue running next size smaller line on return either but if it was an issue it would be at idle or there abouts which is why i asked what instances he has seen an issue doing so.where i don't doubt his statement, I am wondering what poss factors.....again length of line imo plays a role in those factors, as well as fittings elbow etc etc. so if this was on trophy trucks or sand trucks and such with motors in the front and fuel cells on the back over the bumpers then longer lines and poss more fittings i.e. restrictions vs my one fitting at reg and straight line back to tank with a second fitting.

[fabr]

I have to get back to work ds and will respond more later but I think you have a couple misconceptions. in general we agree .

[dsrace]

not that this has any merrit to this discussion .....i ran clear fuel line on my turbo busa fuel system i purchased from speeway motors. i only did so as i wanted to watch for air bubbles. the interesting part was i saw none in the feed line nor the return line to the RR reg. however from the RR reg to the tank i always saw a few small one while running. i had no issues with that system so i never investigated why and chalked it up to the rcc's modified 12 to one reg but i did notice when we made the trek to st a that it was off by 3 psi at idle. i adjusted ( raised psi )and once home it was again off by 3 psi so i adjusted back down.  i was using the aem 320 lph in tank pump. which brings me to another question you commented on earlier fabbr.....you said it was/is believed that intank location was for cooling but infact it was for a better pick up location to ease strain of draw on inlet side of pump. the fuel running though it actually cools the pump. now your new desert set up you built the pump cradle for ...do those pumps sit at the bottom of the tank or half way down or such? i am sure you used that new mat in the bottom of the tank. i don't remember now if you went direct into the tank or a second tank for the pumps.

[fabr]

not that this has any merrit to this discussion .....i ran clear fuel line on my turbo busa fuel system i purchased from speeway motors. i only did so as i wanted to watch for air bubbles. the interesting part was i saw none in the feed line nor the return line to the RR reg. however from the RR reg to the tank i always saw a few small one while running. i had no issues with that system so i never investigated why and chalked it up to the rcc's modified 12 to one reg but i did notice when we made the trek to st a that it was off by 3 psi at idle. i adjusted ( raised psi )and once home it was again off by 3 psi so i adjusted back down.  i was using the aem 320 lph in tank pump. which brings me to another question you commented on earlier fabbr.....you said it was/is believed that intank location was for cooling but infact it was for a better pick up location to ease strain of draw on inlet side of pump. It is for both pump cooling and putting/keeping positive pressure on the fuel inlet to pump as opposed to the negative pressure that occurs by sucking fuel to an external pump. The negative pressure sucking fuel to the pump is what causes pump cavitation and/or vapor lock.the fuel running though it actually cools the pump. now your new desert set up you built the pump cradle for ...do those pumps sit at the bottom of the tank or half way down or such?As close to the bottom of tank as possible to keep the pump inlets under positive feed pressure as long as possible. i am sure you used that new mat in the bottom of the tank. i don't remember now if you went direct into the tank or a second tank for the pumps.No second tank. I did not use Holley Hydramat due to the $600 price for the size I would need to actually have the Hydramat do what it is supposed to do. At this time I am using the inlet filters as supplied with the pumps. .