will useing a fuel pump at its max duty cycle

ADRENLN · Dec 23, 2006

contribute to the pump burning out fast? still having fuel concerns about my future set up.

if i can get away the cobra set up now, when i add an intake it i will most likely have to change the fuel system.

ADRENLN · Dec 23, 2006

although, i wonder. arent there modded 03 cobras putting down like 700rwhp on the stock fuel system? not that i will be near 700rwhp, just wondering.

SaleenGT2001 · Dec 23, 2006

i would like to know also.

thomas91169 · Dec 23, 2006

I believe this is a Yes. I will go out on a limb and say that our fuel pumps are variable pressure since they are returnless style fuel systems, and pressure at the rail is controlled directly by the fuel pump, as compared to a return-style that the fuel pump is designed to operate at max all the time and the pressure at the rail is controlled by a in-line regulator. This is why the standard Walbro 255lph and a pressure regulator setup used by most cars in the modification tree wont work.

Cobras usually retrofit their stock fuel systems after 550whp, which is either the point of maxing out the stock eaton (ported by this time) and nitrous or after they install a KB/Whipple. I believe they step up to either Ford GT fuel pumps (Plural, cobras have twin in-tank pump setups), or the like.

Stan Weiss · Dec 24, 2006

I do not understand duty cycle here. Unlike a fuel injector the pump runs all the time. Because we have a return less system the pump speed will vary with engine RPM and load to meet the engine requirements. So as the RPM goes up it may wear a little more. Remember in a system with a regulator and return line the pump runs all the time and only has one speed.

the98stang · Dec 24, 2006

You don't want to run a pump at its max cycle rate. Eventually it will die.

Are you looking for a pump for your supercharger set up? If so, one GT pump with a BAP would support AT LEAST 550WHP.

thomas91169 · Dec 24, 2006

Stan Weiss said:
I do not understand duty cycle here. Unlike a fuel injector the pump runs all the time. Because we have a return less system the pump speed will vary with engine RPM and load to meet the engine requirements. So as the RPM goes up it may wear a little more. Remember in a system with a regulator and return line the pump runs all the time and only has one speed.

yes but hes talking about needing so much fuel hes maxing it out all times. though youll only max out the pump at WOT, at part throttle the pump will never have to run max. Youll know when youre maxing out the system, when your tuner has added as much fuel as possible and still its running lean or getting knock/predetonation.

btw you always want to keep injector duty cycles under 90% at WOT, if they are going over 100% IDC at WOT youre going to run into random in-consistencies in tuning.

LaserRed01GT · Dec 24, 2006

I agree with Stan, there is no such thing as a fuel pump duty cycle or cylce rate. On our cars the fuel rail pressure sensor will vary the voltage that is sent to the pump to raise or lower the rail pressure as the need for fuel increases or decreases. At part throttle or idle, the voltage sent to the pump is minimal. The only time the pump sees a significant voltage increase is under heavy load or WOT.

So unless you are driving up a big mountain both ways to work, or your foot never stays out of WOT, you cannot hurt the pump, even if it is not otherwise up to the task of satisfying the demands of the motor. The pumps are fuel cooled and they will only see a brief spike of voltage at your WOT blasts.

How much HP do you anticipate making at the crank?

jstreet0204 · Dec 24, 2006

On the newer return style systems there is a duty cycle for the fuel pump, and is one of the parameters that can be datalogged. 100% fuel pump duty cycle is when the fuel pump is kept at maximum voltage to maintain the desired fuel pressure.

ADRENLN · Dec 24, 2006

THANKS guys a lot of good info here. however, i still dont know if it matters or not. seems to be some disagreement here. i dont plan on running wot all the time, but will at least once every time i take the car out.

i plan on making between 500-530rwhp and what ever that equates to flywheel.

i was going to use the cobra pump and bap if i have too. will this be enough?

jstreet0204 · Dec 24, 2006

The problem with running it so close to 100% duty cycle isn't longevity, I don't think. The problem would be that you just don't have much of a safety margin in your fuel requirements. I am pretty sure you will be fine at that level with the cobra pumps and a bap at that hp level. Check in cobra forums though. Also check into the best way to wire the BAP. When I was running the BAP I had it wired per the instruction, and it burned out under WOT, which in turn blew my fuel pump fuse as well. I found out later there is a better way to wire them using some heavy guage wire and a relay.

LaserRed01GT · Dec 25, 2006

Jstreet is right about the fuel pump enhanced parameter. It's called Fuel Pump Monitor Duty Cycle and it has been around for most of the OBD-II Fords even on the returnless style cars. It gives you a percent of the target voltage as compared to the max voltage. But when I think of "duty cycle" I think injectors because they are measured in a percentage as well, but it is an observation of an on/off (switched) supplied current. Not a continuously varied voltage like the pumps.

Like jstreet pointed out it is not a question of pump longevity, but rather if your pump is capable of sustaining enough flow/pressure to satisfy your application within reasonable limits.

This seems to be the popular wiring kit people use with the BAP's:

BAP Wiring Upgrade Kit

will useing a fuel pump at its max duty cycle

ADRENLN

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SaleenGT2001

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thomas91169

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