I have recently upgraded the whole fuel stem from pump to injectors and back again Next step is the the fuel lines under the car I have heard guys say the return line is not large enough when on idle? My question is do I have to go to 10mm on feed and return? If feed as well, the pump has 8mm on pump side of pump- what is the advantages of larger lines if the outlet is smaller?
For the feed line resistance adds based on diameter x length, a single 8mm choke point creates less resistance than two meters at 8mm. This isn't always important but if you're operating in the upper ranges of the pressure the pump can support it'd be a good idea. For the return line it needs to be as big as the feed needs to be (it's not critical that they're the same size, just that both are large enough) or it'll add pressure at idle and your tune will end up all weird.
Not large enough (for what purpose) Pending the actual flow rate, fuel, use will determine if you need to look at larger lines. What rail and injectors? A -6 return is often more than enough
And obviously depends on what pump and what speed it is running at. On full speed at idle pressure will rise with my 485 pump. I run it at 30% at idle.
Awesome to hear fella's Thanks for your input and 2nd opinion!!!!! I decided on 8mm hard lines feed (not sure on the ID but same as stock) The pump (walbro 460ltr) has a smaller ID out the barb And 10mm return (not sure on the ID but similar material thickness as above) Fuel system: Walbro 460ltr/hr running full speed (no fuel pump reg) 8mm feed line 100-micron, 2,000 lb/hr Aeromotive Fuel Filter 8mm feed line 14mm 1300cc Bosch ID 8mm return line to Haltech Flex fuel sensor 10mm return line to tank
