How much whp can you run with 42lbs injectors and a svt focus fuel pump?

 

42lb/h injectors, at 40 psi pressure drop, could support 570fwHP, 485 at the wheels, at 85% duty cycle running n/a (if you had the VE to do it--which with any 4.6L engine you will not).

Running boosted they would top out at 475fwHP, 405 at the wheels. Again at 40psi drop and 85% DC.

Both of these rule-of-thumb guesstimates assume the pump could deliver 48 gallons/hour; or 180 L/h at 40 psi. If you pump up the pressure (no pun intended) then the HP capacity rises by factor of:



According to this chart from Kenne Bell the Focus SVT pump can move 185 Lph at 60 psi. At 60 psi those Ford 42lb/h injectors become (60/42)^.5 = 50.2lb/h injectors. so using the same rule of thumb formulae as above we get 580rwHP running n/a (again, no way from a 4.6L engine), and 480rwHP with boost.

 

Some people report only seeing 400rwhp before maxing the SVTF pump. I wouldnt use an SVTF pump for over that personally. But as for injectors, I know of guys running over 450-480rwhp on stock 03 cobra 39lb injectors so the injectors have enough flow in them to probably make over 500rwhp, but the pump I'd say would be the limiting factor. New 5.0 supercharger kits come with 47lb injectors for making over 600rwhp.

 

Specifying injectors without also specifying the pressure drop across them is misleading--one can assume 40psi if we're talking about stock Ford fuel systems, or 43.5psi (3 bar) which is the industry standard pressure. However 80-100 psi are not unheard of with aftermarket return type systems and AFPRs.

At 100psi drop 24lb/h (rated at Ford's 40psi) injectors become 38lh/b injectors that could support 450fwHP.

On my '92 Miata I was pushing out 225rwHP with 260cc/m (24.7lb/h) injectors. At 43.5psi the best a 4-banger could make with 24.7lb/h injectors would be 137fwHP, but pump that fuel up to 125psi (Walbro HP 255lph pump)and they become 42lb/h injectors--good for 252fwHP.

They were flat our at 95% duty cycle, but they did it...

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BTW, it was a stock Mustang GT killer, the look on kid's faces when they just got their *** whipped by a 12 year old Miata was priceless...