Anybody know how to calculate what size fuel pump is required to make x Hp?? I know how to figure out the minimum required injector size to feed the beast but I'm not sure what size pump is required...

 

Calculate WOT gph requirement at operating pressure, then look at the pump specs and select one that is capable of delivering more fuel than the min. required amount @ WOT.

 

so say for 30lb injectors with 80% duty cycle and a rail pressure of 47psi figure out actual injector flow and multiply by # of injectors then convert to lph or gph? gas weights about 6.25lbs/gallon right?

 

Another route would to use the BSFC from a dyno. Without dyno figures, you could ASSUME a pessimistic, .5 BSFC. That means a half pound of fuel per horsepower, per hour.

RACE ON!!!

 

unless my math is all skewed-up that means a 600 Hp motor would only drink about 180 lph...(using 6.25 lbs fuel= 1 gallon & 1 gallon =3.785liters)...... if that is correct then why would anybody running a "streetable".... ( i know there are exceptions to this term here) Hi-Po motor ever need a fuel pump that caps this?? I mean if 600 Hp is fed by 180lph then why use a 255lph fuel pump? or even bigger???

 

I didn't check your math, but I assume it's correct. Probably the same reason people that can't take advantage of them use 1 3/4" headers when 1 5/8ths" would serve them better. "If some's good, more's better, and too much is just enough". There ARE some other factors with the fuel pump, however. Reserve capacity doesn't have the drawbacks, some other overboard mods do. The pump has to overcome the "G" forces of rocketing off the line in a drag situation. Pressure and capacity can partially make up for slightly under sized fuel lines. By the way, BSFC, stands for Brake Specific Fuel Consumption. You can verify what I said with your friendly, neighborhood, dyno operator.

RACE ON!!!

 

This makes me so crazy! my delima here is actually the fact that I could get a hi-volume replacement fuel pump to help power my new beast that is "rated" (by the manufacturer) for up to 450Hp... yet is advertising 255lph flow ratings... or another one from Bosch that is advertised to support over 500Hp and flows a rediculus 390lph....the price difference between the two pumps is $100!!
I expect to make at least 500 with my latest upgrades; mathematically the Hi-Vol pump should be more than sufficent but the manufacturer says it won't support my goals... WTF!?!?!

So let me hear them...all your opinions.....which pump? 255lph or the 390lph... is the difference worth the $$$$?

 

Check out my info. Check out the mfg's info. It may pay to ask them some questions. Maybe there is a factor or two that isn't apparent from the present info. Let us know.

RACE ON!!!

 

Electric pumps are rated by several factors, among which are:

Flow (output volume), Discharge Pressure (pump head), and Supply Voltage (batt volts needed
at the pump).


There are many technical criteria used to size pumps, but for discussion purposes you could take
GM's recent Corvette pump specs as a guide: GM pumps for MPFI appear to run in the neighborhood
of 10-12 GPH per 100 HP.* Thus to support 500 (real)HP for a NA small block you could ballpark
50-60 GPH at some pressure around 50 psig**.


If you consider the technical specs of the Walbro pumps on this site:
http://www.autoperformanceengineering.com/

You will see that the-
Walbro 255 l/hr pump (standard pressure) makes 53 GPH @ 50 psig & 12 v. / 62 GPH @ 50 psig & 13.5 v
Walbro 255 l/hr pump (high pressure) makes 54 GPH @ 50 psig & 12 v. / 65 GPH @ 50 psig & 13.5 v

(There is no reason to take manufacturer's specs seriously, but Walbro has a reputation for rating
their pumps honestly.)


I believe either Walbro pump can be fit to a Corvette tank, and the prices shown are about $100 for
the bare pump. The hi pressure pump appears to be in a reasonable capacity range for what you
have specified as your need, given a proper regard for installation details and rail pressure.

Note there is an 'LT1 Kit' listed among the products there that looks like a drop-in (excluding the
external wiring). Note too that after the pump is chosen, one also needs to consider the capacity of
the fuel lines & pressure regulator for the expected flow; as well as proper wiring and fuses for the
pump electrical supply. YMMV


HTH



*Here are some specs on GM stock pumps:
http://www.gnttype.org/techarea/fuelsystem/pmprate.html


**Pump discharge pressure is a significant variable because there will be pressure drop between
the pump outlet and the fuel injector rail at the engine. For some considerations on sizing the fuel
regulator & lines, check here:
http://www.gnttype.org/techarea/fuel...nearticle.html

 

Doctor J - great info and site... I knew my math wasn't off, guess I just needed some second check support. And you're RIGHT...don't believe everything you see advertised

So looks like the 255lpph pump for about $100 cheaper is the way run go...to sweet! I can tell my wife "I saved us $100 by getting this..."