phunk

I have had a customer hit 670rwhp maxed out on a single walbro 255 with gasoline. Pressure was falling hard, but it made the dyno pull. This was on a low compression VQ35DE. A stock compression VHR should in theory be able to go a little further. A pump alone does not determine your fuel quantity at the rail. Remove all sources of pressure drop and you will lower operating pressure at the pump, increasing the pumps output. That said, I do not recommend attempting that power out of a 255.

The restrictive sources of pressure drop along the system will increase pressure at the pump to maintain the same rail pressure. The higher the volume, the more drop the restrictions will generate, and the more pump pressure is required to maintain rail pressure. If you can get your fuel pressure at the pump to be the same as pressure in the rails at the volume of fuel you need, you will see maximum results from the pump.

There is no benefit to overpumping a car... it makes sense to use a pump that is just over your needs. Remember that a fuel pump is not like injectors in the sense that injectors are working harder the harder you work them... a fuel pump is working its hardest all the time, from engine idle to full power. So there is no harm in running the pump for all its worth, because the pump doesnt know any better. You only need a little extra pump for occasions where you might overboost or its nice and cold out and you make an extra 30-40hp. Generally I think that people over-pump a car simply because they dont know precisely how efficiently their build is going to use the fuel its given, so they go big to prevent having to go back in.

__________________