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-   -   help my fuel injector math (https://www.rx7club.com/single-turbo-rx-7s-23/help-my-fuel-injector-math-885661/)

Syritis 02-02-10 08:43 PM

help my fuel injector math
 
I'm just not sure how much fuel pressure loss to expect from the plumbing.
2(720) primary injectors
+2(1650) secondary injectors
=4800 cc/min
x 0.65 for injector duty
=3120 cc/min

now the walbro 255hp was measured at 4000cc/min at 55psi (40psi base+ 15psi boost)
can i really expect 880cc/min loss due to plumbing. cuz i'm leaning out at 7200rpm despite my fuel map having steady increase of fuel.
I'd tell you for sure that i'm running outta fuel pressure but the gauge is in the engine bay and it's kinda hard to see it while going really freakin fast.

also this car is mainly for track but i do daily drive it occasionally so most inline pumps are outta the question due to them burning up. the gas tank baffle won't fit a twin pump setup unless they are walbros, or i was contemplating the idea or having a walbro feed into the bosch 044 and run a higher output then either pump by itself. http://www.jayracing.com/index.php?main_page=faq

WaachBack 02-03-10 01:33 AM

It wont be a loss from plumbing, it will be a loss from fuel pressure at high rpm/boost.

What HP numbers are you wanting?

Syritis 02-03-10 06:14 PM

the walbro is measured at 4000cc/min @ 55psi but i'm only using 3120cc/min at 55psi, so how am i going lean if my fuel map has no change in fuel injector duration. a fuel pump will see higher pressure at the outlet then what is recorded at the FPR due to reduced ID of fittings or tight bends or fitting intersections but to have the walbro's output match my fuel consumption it would have to be seeing 80psi at it's outlet.
my fuel system is walbro in stock hanger > stock steel feed line > Aeromotive 35micron fuel filter >
http://photos-h.ak.fbcdn.net/photos-...06603_4519.jpg
> stock return line > gas tank
i have a hard time believing that this fuel system will cause an extra 25psi at the pump. unless the stock FD primary rail is that much of a restriction (side feed injectors)

I've got a conservative goal of 420-440hp but with higher boost maybe a final goal of 500hp.


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