What is the stock pump good up to?

 

My best guess is 340 whp on a low reading Mustang Dyno to 375 whp on a higher reading dyno which seems to hover around 450 HP crank HP. See post 9 in this thread where AMS estimates the stock X pump supports around 350 whp:

https://www.evolutionm.net/forums/au...pump-test.html

With 43 psi base pressure running 27 PSI boost would push it to 70 psi and the stock pump drops off quicker at higher fuel pressures as flow demands increase (192 LPH vs 231 LPH @ 70 PSI). If you do the ratios a Walbro will flow at least 20-25% more fuel at the same pressure and is good for around 550 HP so a 450 HP at the crank seems like a reasonable max.

450 Crank HP is also right about where the stock injectors go 100% duty cycle which is around 650 cc assuming ".55 BSFC". I'm not sure what our Brake Specific Fuel Consumption is for our cars and if it is as high as .60 BSFC the the injectors might start giving out at 415 Crank HP.

I'm using http://www.deatschwerks.com/catalog/...alculators.php to calculate these numbers.

Personally once you are replacing the stock turbo it's a good time to upgrade the pump and injectors.