Okay, I have a aeromotive a700 fuel pump.

I dont have the money for a fancy boost refenced fuel pump voltage controller. soooo..

I want to install a switch that allows me to run the pump at, say %65 of full flow.

I would hard wire the pump with the lower voltage and then just run full voltage through the switch and be able to turn it on when I want to really haul ***.

this will help keep from excessivly heating the fuel.
and it should be better for the pump.

what should I use to drop the voltage, and how much should I drop it??

 

just use a dimmer switch.. that will allow you to control the amount of voltage going to the pump...

just install a small lcd voltage meter so you know the amount of voltage.

 

yeh, but Im looking for a two step system, I dont want to have to **** with a ***, and look at a guage while im driving.

plus im looking for good reasons to add those cool Red covered switches to my dash.

 

Do you have any links to one of these "fancy boost refenced fuel pump voltage controllers" you speak of. Just curoius. Thanks.

 

^ also would like to see!

 

ok buy a 2 step switch...

on 1 of the throws wire in a resistor in "SERIES" to the pump. and that will lower the voltage going to the pump...

and on the other throw of the switch just wire it normally.

to figure out what size resistor would work.. just use this formula.. and variations of it... hope your good in algebra...

i could do it for u but im to lazy.

OHMS Law:
E=I * R

E=Voltage (volts)
I=Amps (amps)
R=Resistance (ohms)

An example of how this would be used for u
say you have 2 amps going to the pump

no you wire in a 4 ohm resistor in series so you get a voltage drop.

e=2*4
e=8

12-8= 4volts
4v would be the voltage goin to your pump..
12v is the power off your battery...

hope i wrote this so you under stand it

 

fuel pump controllers are available at summitracing.com

http://store.summitracing.com/partde...rt=AEI%2D16302

 

You can use a map sensor, op amp and relay to change the voltage going to the pump at a certain boost pressure.

 

I would think a variable resistor would be simple and do the job.

 

The "Cheap'n Cheerfull" option now

Get a 2-way switch and use the dimmer switch and LED gauge as already described.

Use the dimmer as the first setting, then use the second setting for the full voltage

 

you would only need a reostat if you wanted more than 1 setting...

such as low, medium, high

if not then a single resistor is all that is required

 

You could wire in as many variable resistors as you had switch capacity for. But to make it simple lets say you wanted 3 settings. A three position switch with two variable resistors (think of a simplified rheostat with less bulk and you have a variable resistor) Adjust one resistor so the pump runs at the minimal level you want and make it run off of the bottom leg of the switch.
Adjust the other resistor so it is where you feel a good mid level point is and attach it to the middle leg.
The third would be straight through voltage.

These are tiny and inexpensive, really inexpesive. You can get one of the mini project boxes at Radio Shack that come with the little circuit board and solder the whole thing up in 5 minutes. Have the wires to the switch and voltage input come though a rubber grommet. The box could fit anywhere.
Here is a pic of what an open version of the var resistors look like. They are tiny. It is hard to tell from tis pic but there is a place where you adjust resstance with a small flat tip screwdriver.

 

Are those variable resistors able to handle 30 amps? Also would a 120v dimmer switch for something like a chandelier work ok (like from home depot). My pump whining drives me crazy on long trips.

Also where could I get one of the lcd voltage readouts?

Thanks

 

Don't count on it. On either point. Try http://www.jameco.com or http://www.digikey.com

 

Oops, 30 amps
Not that much amperage without more electronics for these little guys. You could throw a power MOSFET into the circuit and run the VR off that so the MOSFET takes all the amperage.
There may be some fan switches that would be the simpliest way to handle that amperage. I am not sure of the amperage rating for a light dimmer switch but it would probably be a lot lower than a fan.
I had it in my head that the amperage range would be much lower for some dumb reason

 

Ok, just looked at Digikey for long enough to make my eyes cross. Here's the rheostat search page: http://www.digikey.com/scripts/us/dk...1&Cat=31917030

The only rheostat that could handle 30 amps (I picked 30 amps for a safety factor) is a 50w with about 3 ohms or less of resistance (RUS model). They look to be around at least $30-40 per, but digikey doesn't even sell them.

Another questions, does anyone know if current (amps) is constant? I'm curious because obviously if your current changes during load than that would affect your voltage based on the resistor soldered in.

Any idea on where to get an lcd panel for the voltage?

 

current is constant in a series circuit
votlage is not...

current is not consant in parrallel
voltage is

 

a dimmer will not run an inductive load like a motor. you will fry it after a while. whatever resistor you use has to be rated for the power dissipation you will be seeing. which at 20a 14v is 280 watts. 280w makes for a damn big resistor and no variable resisitor can handle that. i suggest using a stock fuel pump resistor from an FD or FC.

 

i can make a 2 stage, rpm Fully adjustable setup for $55 shipped. or 3 stage for $75 shipped.