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Stock fuel pump limitations????

  • Thread starter Thread starter v8only
  • Start date Start date Dec 26, 2006
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v8only

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Jul 3, 2003
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Dec 26, 2006
#1
  • Dec 26, 2006
  • #1
So i've been posting and talking around, and have come to the conclusion that my stock 88 lph(did I get that right?) fuel pump may not be enough for my gt40p heads, ported intake and bolt ons.

I've searched page after page, and found nothing on the limitations of the stock fuel pump. See I want to dyno it, however I can't do that until my mass air swap is complete, and a few other things I want to get out of the way.

In the mean time, I don't want to be running lean under WOT. Just wondering if anyone knows when to change up and when not to. The fuel pump in my tank now is near new from before the motor swap, but I'll swap it if I have to.
 

jrichker

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Dec 26, 2006
#2
  • Dec 26, 2006
  • #2
According to the magic Carfor calculator, the stock 88 LHP pump is good to 280 flywheel HP.

Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

304 HP x .85 = 258 HP
385 HP x .85 = 326 HP
480 HP x .85 = 408 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/ to get the calculators used in these examples.
 
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