Since that other thread went downhill and got closed I’m posting the tech info I had here so it wasn’t wasted.
"JnJ made a good point about fuel pressure. Lots of people forget that positive fuel pressure reduces fuel pump flow. 200GPH at 0 psi is around 144 GPH at 4 bar which would be typical for a car running 1 bar of boost (with a manifold referenced FPR) on top of a standard 3 bar static pressure. At 2 bar of boost you’d be down around 125 GPH.
The fuel line size issue is somewhat up to debate since most cars fall between sizes, but here are some guidlines for EFI setups. The numbers don’t apply for carb’d cars running fuel pressures of 4-10 psi or so, which require larger lines for the same HP figures.
These figures are for gasoline folks. If you’re running methanol or some other fuel this goes right out the window.
-6 (3/8") fuel line is good for 500 HP on the outlet side of the pump, but you want -8 (1/2") for the suction side
-8 (1/2") fuel line is good for 900-1000 HP on the outlet side of the pump, but you want -10 (5/8") for the suction side
Yes people have made over 500 hp with lines smaller than -6, but that doesn’t mean it’s smart or safe. Remember different setups require different amounts of fuel to produce a given HP figure. I recommend switching to -6 for margin of safety if you’re around 450-500 hp, and I’d go to -8 above 650 HP or so. After that I’d switch to -10 around 1000 hp."
Again these are only guidelines. If you’re building something and want to know what fuel supplies you need I’m happy to help.
To add to this, remember that fuel pump flow changes with supply voltage. Find out what your system really produces and how much the pump flows at that voltage.
Good info, I have seen people squeeze what would be around 1200 flywheel HP out of a -8 AN line, but that was with around 75-80 psi of fuel pressure along with a big pump to keep up with that pressure & flow rate.
However when you are doing a fuel system the price of -8AN compared to -10AN is pennies per inch
Planned 450whp on awd tsi
Fuel Setup:
Fuel cell
-10an from cell to filter to pump
Aeromotive A1000 fuel pump
-8an from pump to filter to fuel rail
-8an from rail to regulator
Aeromotive Fuel Pressure Regulator
I am mostly doing this because the fuel tank is on its way out. I’m sure my current setup with meth injection would have been fine. Current setup- rewired walbro 255hp, new fuel filter, aeromotive fpr.
Gary I’d say -10 is overkill for 450whp, but knowing you i’m guessing you’re planning to go higher than that in the future.
Good data Matt. You can see that the Denso 310 pump gives you a touch more headroom than a wally 255, but only up to 22 psi. I’d switch up from a single Walbro or Denso 310lph around 500-550 hp. You can run twins or switch to an external above that. Again these are just guidelines and they depend on your setup. If you’re NA, you can go further than FI guys on the same pump due to BSFC and fuel pressure. Those running high boost require more pump capacity than those running low boost. Remember that as I mentioned above, fuel pump flow decreases as fuel pressure increases.
One nice thing about the Denso (for some people) is that it’s quiet. Many of you know that Walbros are a bit noisy. Also the Denso is OEM quality and they’re known to generally last longer than Walbros. However, they cost nearly 3 times as much, so most people stick with the Walbro.
As JnJ mentioned in the other thread, if you go to a big external pump, a pump controller is key to avoid fuel overheating and pump damage, especially for a street driven car which isn’t always at or near maximum effort. If you’re running twin Walbros or Densos, some engine management systems allow you to automatically kick on the secondary pump when certain conditions are met. For instance I’ve tuned cars which kicked the secondary pump on above a certain manifold pressure. This serves a similar purpose as the pump controller by pumping less fuel when it’s not needed. This decreases flow through the return system and excess recirculation.
