Andy,
The PRESSURE RATING (PSI) on a pump is based on static pressure, and
that is the pressure the pump develops at zero flow. As soon as liquid
begins to flow, the pressure drops. The FLOW RATE (GPH) is the maximum
volume of fluid the pump can flow at a zero pressure drop. Since in the
real world all pumps see some level of resistance to flow, the actual
flow rate is lower than the rating. Some pumps come with a flow rate
curve which plots the flow rate as a function of back-pressure, Holley
rates their pumps at both zero and 5 psi.
There are many things that affect the true system flow rate including
tubing diameter, bends in the tubing, and filters. All these are
restrictions and slow the flow rate. In a carburetor-based system, the
pump feeds on a demand basis, when the carb floats open the needle
valve, fuel flows until the bowls are full. The float system is designed
to work at low pressures, 1 to 5 psi, so the pump needs to have a flow
rate that is capable of supplying enough fuel flow to keep the carb from
starving.
The SU that is OEM on the Tiger is barely adequate for the stock 260,
when you add horsepower the engine's demands can easily out-pace that
pump's ability to feed the system. I recommend looking at a high
performance pump that flows at least 80 GPH if you are running an engine
with over 200 hp. The Holley Red pump has worked well for me on a
variety of SBF applications including mild strokers. If you are running
track days and pushing over 300 hp then the next step beyond that pump
is recommended.
Bugz
-----Original Message-----
From: awtiger
Sent: Tuesday, August 02, 2011 11:59 PM
To: tigers@autox.team.net
Subject: [Tigers] Fuel pump flow rate question
Hey, guys:
Can any of you engineer/mathmetician types out there educate me on how
to figure how many gallons-per-hour a certain psi-rated fuel pump flows?
Specifically, I'm wondering how many GPH a 2 to 3 psi fuel pump would
flow.
Can anybody send me to school?
Thanks a million,
Andy Walker
Edmond, OK
B382001600LRXFE
TAC #740
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