You pm me:
Originally Posted by friendly1_uk
Regardless, there are still a few options in fuel pumps. The ideal pump is the Walbro 190 lb/h HP fuel pump. HP stands for high pressure. It is important you get a HP unit if you plan on raising the fuel pressure levels past 90psi. The HP models can supply fuel up to 130psi. The standard 190 lb/h fuel pump is maxed at 90psi and the standard 255 lb/h pump is maxed at 80psi. The 190 HP unit will not only supply four 700cc injectors with enough flow to maintain 40-50psi in the fuel rail (enough for 400hp), but out flows the 255 HP model after 100psi.
im sorry pal, but not an ounce of that is true. look on the walbro site.
you also appear to advocate the use of the 190 hp when its struggling to meet delivery so much that it can no longer meet demand and the rail pressure drops below that set by the cars own fuel pressure regulator. that leans out number 4, a major cause of engine loss. fitting an equal pressure manifold (duel feed rail) will help, but is in no way an acceptable way of using a pump beyond its capability. its meant to have some reserve.
the 255 is fine. the problem is the cars own fuel pressure regulator cant return enough to the tank. it needs upgrading, not badly working around.
my response to you is:
No, i'm right.
When do i say, "use a pump beyond it's capability?"
The stock pump is perfectly suitable to flow enough fuel to support 305 BHP at 50psi.
it flows around 35 gal/hr. at 50psi.
35 gal/hr. converts to 210 lbs/hr (35 x 6) (gal/hr x 6 = lbs/hr)
210 lbs/hr x 80% DC / .55 BSFC = 305BHP
at 90psi however, the pump can only flow 5 gal/hr. or 43BHP.
5 x 6 = 35 x .8 / .55 = 43
Since I'm pretty sure you want to be able to flow
enough fuel to support a little more than 43 BHP while boosting, the ideal solution is using a HP model fuel pump, one that can support higher fuel pressures while using an FMU.
So we have two choices of Walbro; the 190 lb/hr or the 255 lb/hr.
The 255 HP can only flow enough fuel to about 100-110psi.
The 190 HP can flow the same to about 110-130psi.
At idle (35psi):
The 255 HP can support around 600 BHP at IDLE
The 190 HP can support around 400 BHP at idle
at 50psi (OEM FPR):
The 255 HP can support about 565 BHP
The 190 HP can support about 420 BHP
at 100psi (using FMU):
The 255 HP can support about 260 BHP
The 190 HP can support about.....260 BHP, weird!
Now, no sorry, the OEM FPR can return plenty of fuel, but at 35psi while idling, it shouldn't be trying to regulate flow for 600 Brake Horsepower, which is exactly why everyone who runs a 255 model complains. It overloads the FPR with too much fuel and raises your fuel pressure from 35psi to about 40-45psi. The 190 does not
So in your eyes, choosing a pump that gives no problems and supports plenty of fuel is the bandaid solution as opposed to running a 255 pump and replacing the OEM FPR to allow it to idle properly?
I guess I'm not crazy.
The 255 HP gives you absolutely no benefit when run at 100psi over the 190 HP, since they support about the exact same BHP.
The 190HP is cheaper.
The 190HP is the correct choice when using an FMU, 190 standard when using EMS.